EyeLink fMRI / MEG Publications
All EyeLink fMRI and MEG research publications (with concurrent eye tracking) up until 2021 (with some early 2022s) are listed below by year. You can search the publications using keywords such as Visual Cortex, Neural Plasticity, MEG, etc. You can also search for individual author names. If we missed any EyeLink fMRI or MEG articles, please email us!
Charles R. Marshall; Christopher J. D. Hardy; Lucy L. Russell; Rebecca L. Bond; Harri Sivasathiaseelan; Caroline Greaves; Katrina M. Moore; Jennifer L. Agustus; Janneke E. P. Leeuwen; Stephen J. Wastling; Jonathan D. Rohrer; James M. Kilner; Jason D. Warren
In: Brain, vol. 142, no. 9, pp. 2873–2887, 2019.
Impaired processing of emotional signals is a core feature of frontotemporal dementia syndromes, but the underlying neural mechanisms have proved challenging to characterize and measure. Progress in this field may depend on detecting functional changes in the working brain, and disentangling components of emotion processing that include sensory decoding, emotion categorization and emotional contagion. We addressed this using functional MRI of naturalistic, dynamic facial emotion processing with concurrent indices of autonomic arousal, in a cohort of patients representing all major frontotemporal dementia syndromes relative to healthy age-matched individuals. Seventeen patients with behavioural variant frontotemporal dementia [four female; mean (standard deviation) age 64.8 (6.8) years], 12 with semantic variant primary progressive aphasia [four female; 66.9 (7.0) years], nine with non-fluent variant primary progressive aphasia [five female; 67.4 (8.1) years] and 22 healthy controls [12 female; 68.6 (6.8) years] passively viewed videos of universal facial expressions during functional MRI acquisition, with simultaneous heart rate and pupillometric recordings; emotion identification accuracy was assessed in a post-scan behavioural task. Relative to healthy controls, patient groups showed significant impairments (analysis of variance models, all P 5 0.05) of facial emotion identification (all syndromes) and cardiac (all syndromes) and pupillary (non-fluent variant only) reactivity. Group-level functional neuroanatomical changes were assessed using statistical parametric mapping, thresholded at P 5 0.05 after correction for multiple comparisons over the whole brain or within pre-specified regions of interest. In response to viewing facial expressions, all participant groups showed comparable activation of primary visual cortex while patient groups showed differential hypo-activation of fusiform and posterior temporo-occipital junctional cortices. Bi-hemispheric, syndrome-specific activations predicting facial emotion identification performance were identified (behavioural variant, anterior insula and caudate; semantic variant, anterior temporal cortex; non-fluent variant, frontal operculum). The semantic and non-fluent variant groups additionally showed complex profiles of central parasympathetic and sympathetic autonomic involvement that overlapped signatures of emotional visual and categorization processing and extended (in the non-fluent group) to brainstem effector pathways. These findings open a window on the functional cerebral mechanisms underpinning complex socio-emotional phenotypes of frontotemporal dementia, with implications for novel physiological biomarker development.
Timothy H. Muller; Rogier B. Mars; Timothy E. Behrens; Jill X. O'Reilly
Control of entropy in neural models of environmental state Journal Article
In: eLife, vol. 8, pp. 1–30, 2019.
Humans and animals construct internal models of their environment in order to select appropriate courses of action. The representation of uncertainty about the current state of the environment is a key feature of these models that controls the rate of learning as well as directly affecting choice behaviour. To maintain flexibility, given that uncertainty naturally decreases over time, most theoretical inference models include a dedicated mechanism to drive up model uncertainty. Here we probe the long-standing hypothesis that noradrenaline is involved in determining the uncertainty, or entropy, and thus flexibility, of neural models. Pupil diameter, which indexes neuromodulatory state including noradrenaline release, predicted increases (but not decreases) in entropy in a neural state model encoded in human medial orbitofrontal cortex, as measured using multivariate functional MRI. Activity in anterior cingulate cortex predicted pupil diameter. These results provide evidence for top-down, neuromodulatory control of entropy in neural state models.
Jonathan F. O'rawe; Anna S. Huang; Daniel N. Klein; Hoi-Chung Leung
In: Neuropsychologia, vol. 127, pp. 158–170, 2019.
Visual processing in the primate brain is highly organized along the ventral visual pathway, although it is still unclear how categorical selectivity emerges in this system. While many theories have attempted to explain the pattern of visual specialization within the ventral occipital and temporal areas, the biased connectivity hypothesis provides a framework which postulates extrinsic connectivity as a potential mechanism in shaping the development of category selectivity. As the posterior parietal cortex plays a central role in visual attention, we examined whether the pattern of parietal connectivity with the face and scene processing regions is closely linked with the functional properties of these two visually selective networks in a cohort of 60 children ages 9 to 12. Functionally localized face and scene selective regions were used in deriving each visual network's resting-state functional connectivity. The children's face and scene processing networks appeared to show a weak network segregation during resting state, which was confirmed when compared to that of a group of gender and handedness matched adults. Parietal regions of these children showed differential connectivity with the face and scene networks, and the extent of this differential parietal-visual connectivity predicted individual differences in the degree of segregation between the two visual networks, which in turn predicted individual differences in visual perception performance. Finally, the pattern of parietal connectivity with the face processing network also predicted the foci of face-related activation in the right fusiform gyrus across children. These findings provide evidence that extrinsic connectivity with regions such as the posterior parietal cortex may have important implications in the development of specialized visual processing networks.
Eduard Ort; Johannes J. Fahrenfort; Reshanne Reeder; Stefan Pollmann; Christian N. L. Olivers
In: NeuroImage, vol. 202, pp. 116133, 2019.
Cognitive control can involve proactive (preparatory) and reactive (corrective) mechanisms. Using a gaze-contingent eye tracking paradigm combined with fMRI, we investigated the involvement of these different modes of control and their underlying neural networks, when switching between different targets in multiple-target search. Participants simultaneously searched for two possible targets presented among distractors, and selected one of them. In one condition, only one of the targets was available in each display, so that the choice was imposed, and reactive control would be required. In the other condition, both targets were present, giving observers free choice over target selection, and allowing for proactive control. Switch costs emerged only when targets were imposed and not when target selection was free. We found differential levels of activity in the frontoparietal control network depending on whether target switches were free or imposed. Furthermore, we observed core regions of the default mode network to be active during target repetitions, indicating reduced control on these trials. Free and imposed switches jointly activated parietal and posterior frontal cortices, while free switches additionally activated anterior frontal cortices. These findings highlight unique contributions of proactive and reactive control during visual search.
Abhijit Rajan; Sreenivasan Meyyappan; Harrison Walker; Immanuel Babu; Henry Samuel; Zhenhong Hu; Mingzhou Ding
In: Cortex, vol. 117, pp. 77–88, 2019.
When performing a demanding cognitive task, internal distraction in the form of task-irrelevant thoughts and mind wandering can shift our attention away from the task, negatively affecting task performance. Behaviorally, individuals with higher executive function indexed by higher working memory capacity (WMC) exhibit less mind wandering during cognitive tasks, but the underlying neural mechanisms are unknown. To address this problem, we recorded functional magnetic resonance imaging (fMRI) data from subjects performing a cued visual attention task, and assessed their WMC in a separate experiment. Applying machine learning and time-series analysis techniques, we showed that (1) higher WMC individuals experienced lower internal distraction through stronger suppression of posterior cingulate cortex (PCC) activity, (2) higher WMC individuals had better neural representations of attended information as evidenced by higher multivoxel decoding accuracy of cue-related activities in the dorsal attention network (DAN), (3) the positive relationship between WMC and DAN decoding accuracy was mediated by suppression of PCC activity, (4) the dorsal anterior cingulate (dACC) was a source of top-down signals that regulate PCC activity as evidenced by the negative association between Granger-causal influence dACC/PCC and PCC activity levels, and (5) higher WMC individuals exhibiting stronger dACC/PCC Granger-causal influence. These results shed light on the neural mechanisms underlying the executive suppression of internal distraction in tasks requiring externally oriented attention and provide an explanation of the individual differences in such suppression.
Birgit Rauchbauer; Bruno Nazarian; Morgane Bourhis; Magalie Ochs; Laurent Prévot; Thierry Chaminade
In: Philosophical Transactions of the Royal Society B: Biological Sciences, vol. 374, pp. 1–8, 2019.
We present a novel functional magnetic resonance imaging paradigm for second-person neuroscience. The paradigm compares a human social interaction (human-human interaction, HHI) to an interaction with a conversational robot (human-robot interaction, HRI). The social interaction consists of 1 min blocks of live bidirectional discussion between the scanned participant and the human or robot agent. A final sample of 21 participants is included in the corpus comprising physiological (blood oxygen level-dependent, respiration and peripheral blood flow) and behavioural (recorded speech from all interlocutors, eye tracking from the scanned participant, face recording of the human and robot agents) data. Here, we present the first analysis of this corpus, contrasting neural activity between HHI and HRI. We hypothesized that independently of differences in behaviour between interactions with the human and robot agent, neural markers of mentalizing (temporoparietal junction (TPJ) and medial prefrontal cortex) and social motivation (hypothalamus and amygdala) would only be active in HHI. Results confirmed significantly increased response associated with HHI in the TPJ, hypothalamus and amygdala, but not in the medial prefrontal cortex. Future analysis of this corpus will include fine-grained characterization of verbal and non-verbal behaviours recorded during the interaction to investigate their neural correlates.
Ryan V. Raut; Anish Mitra; Abraham Z. Snyder; Marcus E. Raichle
In: NeuroImage, vol. 194, pp. 211–227, 2019.
Accumulating evidence indicates that resting-state functional magnetic resonance imaging (rsfMRI) signals correspond to propagating electrophysiological infra-slow activity (<0.1 Hz). Thus, pairwise correlations (zero-lag functional connectivity (FC)) and temporal delays among regional rsfMRI signals provide useful, complementary descriptions of spatiotemporal structure in infra-slow activity. However, the slow nature of fMRI signals implies that practical scan durations cannot provide sufficient independent temporal samples to stabilize either of these measures. Here, we examine factors affecting sampling variability in both time delay estimation (TDE) and FC. Although both TDE and FC accuracy are highly sensitive to data quantity, we use surrogate fMRI time series to study how the former is additionally related to the magnitude of a given pairwise correlation and, to a lesser extent, the temporal sampling rate. These contingencies are further explored in real data comprising 30-min rsfMRI scans, where sampling error (i.e., limited accuracy owing to insufficient data quantity) emerges as a significant but underappreciated challenge to FC and, even more so, to TDE. Exclusion of high-motion epochs exacerbates sampling error; thus, both sides of the bias-variance (or data quality-quantity) tradeoff associated with data exclusion should be considered when analyzing rsfMRI data. Finally, we present strategies for TDE in motion-corrupted data, for characterizing sampling error in TDE and FC, and for mitigating the influence of sampling error on lag-based analyses.
Jim D. Herring; Sophie Esterer; Tom R. Marshall; Ole Jensen; Til O. Bergmann
In: NeuroImage, vol. 184, pp. 440–449, 2019.
Low frequency oscillations such as alpha (8–12 Hz) are hypothesized to rhythmically gate sensory processing, reflected by 40–100 Hz gamma band activity, via the mechanism of pulsed inhibition. We applied transcranial alternating current stimulation (TACS) at individual alpha frequency (IAF) and flanking frequencies (IAF-4 Hz, IAF+4 Hz) to the occipital cortex of healthy human volunteers during concurrent magnetoencephalography (MEG), while participants performed a visual detection task inducing strong gamma-band responses. Occipital (but not retinal) TACS phasically suppressed stimulus-induced gamma oscillations in the visual cortex and impaired target detection, with stronger phase-to-amplitude coupling predicting behavioral impairments. Retinal control TACS ruled out retino-thalamo-cortical entrainment resulting from (subthreshold) retinal stimulation. All TACS frequencies tested were effective, suggesting that visual gamma-band responses can be modulated by a range of low frequency oscillations. We propose that TACS-induced membrane potential modulations mimic the rhythmic change in cortical excitability by which spontaneous low frequency oscillations may eventually exert their impact when gating sensory processing via pulsed inhibition.
Erik L Meijs; Pim Mostert; Heleen A. Slagter; Floris P. Lange; Simon Gaal
In: Neuroscience of Consciousness, vol. 5, no. 1, pp. 1–12, 2019.
Subjective experience can be influenced by top-down factors, such as expectations and stimulus relevance. Recently, it has been shown that expectations can enhance the likelihood that a stimulus is consciously reported, but the neural mechanisms supporting this enhancement are still unclear. We manipulated stimulus expectations within the attentional blink (AB) paradigm using letters and combined visual psychophysics with magnetoencephalographic (MEG) recordings to investigate whether prior expectations may enhance conscious access by sharpening stimulus-specific neural representations. We further explored how stimulus-specific neural activity patterns are affected by the factors expectation, stimulus relevance and conscious report. First, we show that valid expectations about the identity of an upcoming stimulus increase the likelihood that it is consciously reported. Second, using a series of multivariate decoding analyses, we show that the identity of letters presented in and out of the AB can be reliably decoded from MEG data. Third, we show that early sensory stimulus-specific neural representations are similar for reported and missed target letters in the AB task (active report required) and an oddball task in which the letter was clearly presented but its identity was task-irrelevant. However, later sustained and stable stimulus-specific representations were uniquely observed when target letters were consciously reported (decision-dependent signal). Fourth, we show that global pre-stimulus neural activity biased perceptual decisions for a ‘seen' response. Fifth and last, no evidence was obtained for the sharpening of sensory representations by top-down expectations. We discuss these findings in light of emerging models of perception and conscious report highlighting the role of expectations and stimulus relevance.
Sebastian Michelmann; Bernhard P. Staresina; Howard Bowman; Simon Hanslmayr
In: Nature Human Behaviour, vol. 3, no. 2, pp. 143–154, 2019.
Remembering information from continuous past episodes is a complex task 1 . On the one hand, we must be able to recall events in a highly accurate way, often including exact timings. On the other hand, we can ignore irrelevant details and skip to events of interest. Here, we track continuous episodes consisting of different subevents as they are recalled from memory. In behavioural and magnetoencephalography data, we show that memory replay is temporally compressed and proceeds in a forward direction. Neural replay is characterized by the reinstatement of temporal patterns from encoding 2,3 . These fragments of activity reappear on a compressed timescale. Herein, the replay of subevents takes longer than the transition from one subevent to another. This identifies episodic memory replay as a dynamic process in which participants replay fragments of fine-grained temporal patterns and are able to skip flexibly across subevents.
Judith Nicolas; Aline Bompas; Romain Bouet; Olivier Sillan; Eric Koun; Christian Urquizar; Aurélie Bidet-Caulet; Denis Pélisson
In: Cerebral Cortex, vol. 29, no. 9, pp. 3606–3617, 2019.
Attention and saccadic adaptation (SA) are critical components of visual perception, the former enhancing sensory processing of selected objects, the latter maintaining the eye movements accuracy toward them. Recent studies propelled the hypothesis of a tight functional coupling between these mechanisms, possibly due to shared neural substrates. Here, we used magnetoencephalography to investigate for the first time the neurophysiological bases of this coupling and of SA per se. We compared visual discrimination performance of 12 healthy subjects before and after SA. Eye movements and magnetic signals were recorded continuously. Analyses focused on gamma band activity (GBA) during the pretarget period of the discrimination and the saccadic tasks. We found that GBA increases after SA. This increase was found in the right hemisphere for both postadaptation saccadic and discrimination tasks. For the latter, GBA also increased in the left hemisphere. We conclude that oculomotor plasticity involves GBA modulation within an extended neural network which persists after SA, suggesting a possible role of gamma oscillations in the coupling between SA and attention.
Elena V. Orekhova; Tatiana A. Stroganova; Justin F. Schneiderman; Sebastian Lundström; Bushra Riaz; Darko Sarovic; Olga V. Sysoeva; Georg Brant; Christopher Gillberg; Nouchine Hadjikhani
In: Human Brain Mapping, vol. 40, no. 5, pp. 1583–1593, 2019.
Gamma oscillations facilitate information processing by shaping the excitatory input/output of neuronal populations. Recent studies in humans and nonhuman primates have shown that strong excitatory drive to the visual cortex leads to suppression of induced gamma oscillations, which may reflect inhibitory-based gain control of network excitation. The efficiency of the gain control measured through gamma oscillations may in turn affect sensory sensitivity in everyday life. To test this prediction, we assessed the link between self-reported sensitivity and changes in magneto-encephalographic gamma oscillations as a function of motion velocity of high-contrast visual gratings. The induced gamma oscillations increased in frequency and decreased in power with increasing stimulation intensity. As expected, weaker suppression of the gamma response correlated with sensory hypersensitivity. Robustness of this result was confirmed by its replication in the two samples: neurotypical subjects and people with autism, who had generally elevated sensory sensitivity. We conclude that intensity-related suppression of gamma response is a promising biomarker of homeostatic control of the excitation–inhibition balance in the visual cortex.
Davide Paoletti; Christoph Braun; Elisabeth Julie Vargo; Wieske Zoest
In: European Journal of Neuroscience, vol. 49, pp. 137–149, 2019.
Previous behavioural studies have accrued evidence that response time plays a critical role in determining whether selection is influenced by stimulus saliency or target template. In the present work, we investigated to what extent the variations in timing and consequent oculomotor controls are influenced by spontaneous variations in pre-stimulus alpha oscillations. We recorded simultaneously brain activity using magnetoencephalography (MEG) and eye movements while participants performed a visual search task. Our results show that slower saccadic reaction times were predicted by an overall stronger alpha power in the 500 ms time window preceding the stimulus onset, while weaker alpha power was a signature of faster responses. When looking separately at performance for fast and slow responses, we found evidence for two specific sources of alpha activity predicting correct versus incorrect responses. When saccades were quickly elicited, errors were predicted by stronger alpha activity in posterior areas, comprising the angular gyrus in the temporal-parietal junction (TPJ) and possibly the lateral intraparietal area (LIP). Instead, when participants were slower in responding, an increase of alpha power in frontal eye fields (FEF), supplementary eye fields (SEF) and dorsolateral pre-frontal cortex (DLPFC) predicted erroneous saccades. In other words, oculomotor accuracy in fast responses was predicted by alpha power differences in more posterior areas, while the accuracy in slow responses was predicted by alpha power differences in frontal areas, in line with the idea that these areas may be differentially related to stimulus-driven and goal-driven control of selection.
Thomas Parr; M. Berk Mirza; Hayriye Cagnan; Karl J. Friston
Dynamic causal modelling of active vision Journal Article
In: Journal of Neuroscience, vol. 39, no. 32, pp. 6265–6275, 2019.
In this paper, we draw from recent theoretical work on active perception, which suggests that the brain makes use of an internal (i.e., generative) model to make inferences about the causes of sensations. This view treats visual sensations as consequent on action (i.e., saccades) and implies that visual percepts must be actively constructed via a sequence ofeye movements. Oculomotor control calls on a distributed set ofbrain sources that includes the dorsal and ventral frontoparietal (attention) networks.Weargue that connections from the frontal eye fields to ventral parietal sources represent the mapping from “where”, fixation location to information derived from “what” representations in the ventral visual stream. During scene construction, this mapping must be learned, putatively through changes in the effective connectivityofthese synapses. Here,wetest the hypothesis that the couplingbetweenthe dorsal frontal cortexand the right temporoparietal cortex is modulated during saccadic interrogation ofa simple visual scene. Using dynamic causal modeling for magnetoencephalography with (male and female) human participants, we assess the evidence for changes in effective connectivity by comparing models that allow for this modulation with models that do not. We find strong evidence for modulation of connections between the two attention networks; namely, a disinhibition ofthe ventral network by its dorsal counterpart.
Ella Podvalny; Matthew W. Flounders; Leana E. King; Tom Holroyd; Biyu J. He
In: Nature Communications, vol. 10, pp. 3910, 2019.
Vision relies on both specific knowledge of visual attributes, such as object categories, and general brain states, such as those reflecting arousal. We hypothesized that these phenomena independently influence recognition of forthcoming stimuli through distinct processes reflected in spontaneous neural activity. Here, we recorded magnetoencephalographic (MEG) activity in participants (N = 24) who viewed images of objects presented at recognition threshold. Using multivariate analysis applied to sensor-level activity patterns recorded before stimulus presentation, we identified two neural processes influencing subsequent subjective recognition: a general process, which disregards stimulus category and correlates with pupil size, and a specific process, which facilitates category-specific recognition. The two processes are doubly-dissociable: the general process correlates with changes in criterion but not in sensitivity, whereas the specific process correlates with changes in sensitivity but not in criterion. Our findings reveal distinct mechanisms of how spontaneous neural activity influences perception and provide a framework to integrate previous findings.
Tzvetan Popov; Bart Gips; Sabine Kastner; Ole Jensen
In: Human Brain Mapping, vol. 40, no. 15, pp. 4432–4440, 2019.
Alpha oscillations are strongly modulated by spatial attention. To what extent, the generators of cortical alpha oscillations are spatially distributed and have selectivity that can be related to retinotopic organization is a matter of continuous scientific debate. In the present report, neuromagnetic activity was quantified by means of spatial location tuning functions from 30 participants engaged in a visuospatial attention task. A cue presented briefly in one of 16 locations directing covert spatial attention resulted in a robust modulation of posterior alpha oscillations. The distribution of the alpha sources approximated the retinotopic organization of the human visual system known from hemodynamic studies. Better performance in terms of target identification was associated with a more spatially constrained alpha modulation. The present findings demonstrate that the generators of posterior alpha oscillations are retinotopically organized when modulated by spatial attention.
Silvan C. Quax; Nadine Dijkstra; Mariel J. Staveren; Sander E. Bosch; Marcel A. J. Gerven
In: NeuroImage, vol. 195, pp. 444–453, 2019.
Eye movements are an integral part of human perception, but can induce artifacts in many magneto-encephalography (MEG) and electroencephalography (EEG) studies. For this reason, investigators try to minimize eye movements and remove these artifacts from their data using different techniques. When these artifacts are not purely random, but consistent regarding certain stimuli or conditions, the possibility arises that eye movements are actually inducing effects in the MEG signal. It remains unclear how much of an influence eye movements can have on observed effects in MEG, since most MEG studies lack a control analysis to verify whether an effect found in the MEG signal is induced by eye movements. Here, we find that we can decode stimulus location from eye movements in two different stages of a working memory match-to-sample task that encompass different areas of research typically done with MEG. This means that the observed MEG effect might be (partly) due to eye movements instead of any true neural correlate. We suggest how to check for eye movement effects in the data and make suggestions on how to minimize eye movement artifacts from occurring in the first place.
Romain Quentin; Jean Rémi King; Etienne Sallard; Nathan Fishman; Ryan Thompson; Ethan R. Buch; Leonardo G. Cohen
In: Journal of Neuroscience, vol. 39, no. 19, pp. 3728–3740, 2019.
Working memory is our ability to select and temporarily hold information as needed for complex cognitive operations. The temporal dynamics of sustained and transient neural activity supporting the selection and holding of memory content is not known. To address this problem, we recorded magnetoencephalography in healthy participants performing a retro-cue working memory task in which the selection rule and the memory content varied independently. Multivariate decoding and source analyses showed that selecting the memory content relies on prefrontal and parieto-occipital persistent oscillatory neural activity. By contrast, the memory content was reactivated in a distributed occipitotemporal posterior network, preceding the working memory decision and in a different format than during the visual encoding. These results identify a neural signature of content selection and characterize differentiated spatiotemporal constraints for subprocesses of working memory.
Mats W. J. Es; Jan-Mathijs Schoffelen
In: NeuroImage, vol. 186, pp. 703–712, 2019.
The efficiency of neuronal information transfer in activated brain networks may affect behavioral performance. Gamma-band synchronization has been proposed to be a mechanism that facilitates neuronal processing of behaviorally relevant stimuli. In line with this, it has been shown that strong gamma-band activity in visual cortical areas leads to faster responses to a visual go cue. We investigated whether there are directly observable consequences of trial-by-trial fluctuations in non-invasively observed gamma-band activity on the neuronal response. Specifically, we hypothesized that the amplitude of the visual evoked response to a go cue can be predicted by gamma power in the visual system, in the window preceding the evoked response. Thirty-three human subjects (22 female) performed a visual speeded response task while their magnetoencephalogram (MEG) was recorded. The participants had to respond to a pattern reversal of a concentric moving grating. We estimated single trial stimulus-induced visual cortical gamma power, and correlated this with the estimated single trial amplitude of the most prominent event-related field (ERF) peak within the first 100 ms after the pattern reversal. In parieto-occipital cortical areas, the amplitude of the ERF correlated positively with gamma power, and correlated negatively with reaction times. No effects were observed for the alpha and beta frequency bands, despite clear stimulus onset induced modulation at those frequencies. These results support a mechanistic model, in which gamma-band synchronization enhances the neuronal gain to relevant visual input, thus leading to more efficient downstream processing and to faster responses.
Rasmus M. Birn; Alexander K. Converse; Abigail Z. Rajala; Andrew L. Alexander; Walter F. Block; Alan B. McMillan; Bradley T. Christian; Caitlynn N. Filla; Dhanabalan Murali; Samuel A. Hurley; Rick L. Jenison; Luis C. Populin
In: Journal of Neuroscience, vol. 39, no. 8, pp. 1436–1444, 2019.
Dopamine (DA) levels in the striatum are increased by many therapeutic drugs, such as methylphenidate (MPH), which also alters behavioral and cognitive functions thought to be controlled by the PFC dose-dependently. We linked DA changes and functional connectivity (FC) using simultaneous [18F]fallypride PET and resting-state fMRI in awake male rhesus monkeys after oral administration of various doses of MPH. We found a negative correlation between [18F]fallypride nondisplaceable binding potential (BPND) and MPH dose in the head of the caudate (hCd), demonstrating increased extracellular DA resulting from MPH administration. The decreased BPND was negatively correlated with FC between the hCd and the PFC. Subsequent voxelwise analyses revealed negative correlations with FC between the hCd and the dorsolateral PFC, hippocampus, and precuneus. These results, showing that MPH-induced changes in DA levels in the hCd predict resting-state FC, shed light on a mechanism by which changes in striatal DA could influence function in the PFC.
Ilona M. Bloem; Sam Ling
In: Nature Communications, vol. 10, pp. 5660, 2019.
Although attention is known to increase the gain of visuocortical responses, its underlying neural computations remain unclear. Here, we use fMRI to test the hypothesis that a neural population's ability to be modulated by attention is dependent on divisive normalization. To do so, we leverage the feature-tuned properties of normalization and find that visuocortical responses to stimuli sharing features normalize each other more strongly. Comparing these normalization measures to measures of attentional modulation, we demonstrate that subpopulations which exhibit stronger normalization also exhibit larger attentional benefits. In a converging experiment, we reveal that attentional benefits are greatest when a subpopulation is forced into a state of stronger normalization. Taken together, these results suggest that the degree to which a subpopulation exhibits normalization plays a role in dictating its potential for attentional benefits.
Rodrigo M. Braga; Koene R. A. Van Dijk; Jonathan R. Polimeni; Mark C. Eldaief; Randy L. Buckner
In: Journal of Neurophysiology, vol. 121, no. 4, pp. 1513–1534, 2019.
Examination of large-scale distributed networks within the individual reveals details of cortical network organization that are absent in group-averaged studies. One recent discovery is that a distributed transmodal network, often referred to as the “default network,” comprises two closely interdigitated networks, only one of which is coupled to posterior parahippocampal cortex. Not all studies of individuals have identified the same networks, and questions remain about the degree to which the two networks are separate, particularly within regions hypothesized to be interconnected hubs. In this study we replicate the observation of network separation across analytical (seed-based connectivity and parcellation) and data projection (volume and surface) methods in two individuals each scanned 31 times. Additionally, three individuals were examined with highresolution (7T; 1.35 mm) functional magnetic resonance imaging to gain further insight into the anatomical details. The two networks were identified with separate regions localized to adjacent portions of the cortical ribbon, sometimes inside the same sulcus. Midline regions previously implicated as hubs revealed near complete spatial separation of the two networks, displaying a complex spatial topography in the posterior cingulate and precuneus. The network coupled to parahippocampal cortex also revealed a separate region directly within the hippocampus, at or near the subiculum. These collective results support that the default network is composed of at least two spatially juxtaposed networks. Fine spatial details and juxtapositions of the two networks can be identified within individuals at high resolution, providing insight into the network organization of association cortex and placing further constraints on interpretation of group-averaged neuroimaging data.
Benjamin T. Carter; Brent Foster; Nathan M. Muncy; Steven G. Luke
In: NeuroImage, vol. 189, pp. 224–240, 2019.
The ability to make predictions is thought to facilitate language processing. During language comprehension such predictions appear to occur at multiple levels of linguistic representations (i.e. semantic, syntactic and lexical). The neural mechanisms that define the network sensitive to linguistic predictability have yet to be adequately defined. The purpose of the present study was to explore the neural network underlying predictability during the normal reading of connected text. Predictability values for different linguistic information were obtained from a pre-existing text corpus. Forty-one subjects underwent simultaneous eye-tracking and fMRI scans while reading these select paragraphs. Lexical, semantic, and syntactic predictability measures were then correlated with functional activation associated with fixation onset on the individual words. Activation patterns showed both positive and negative correlations to lexical, semantic, and syntactic predictabilities. Conjunction analysis revealed regions specific to or shared between each type of predictability. The regions associated with the different predictability measures were largely separate. Results suggest that most linguistic predictions are graded in nature, activating components of the existing language system. A number of regions were also found to be uniquely associated with full lexical predictability, most notably the anterior temporal lobe and the inferior posterior temporal cortex.
Joao Castelhano; Isabel C. Duarte; Carlos Ferreira; Joao Duraes; Henrique Madeira; Miguel Castelo-Branco
In: Brain Imaging and Behavior, vol. 13, no. 3, pp. 623–637, 2019.
Software programming is a complex and relatively recent human activity, involving the integration of mathematical, recursive thinking and language processing. The neural correlates of this recent human activity are still poorly understood. Error monitoring during this type of task, requiring the integration of language, logical symbol manipulation and other mathematical skills, is particularly challenging. We therefore aimed to investigate the neural correlates of decision-making during source code understanding and mental manipulation in professional participants with high expertise. The present fMRI study directly addressed error monitoring during source code comprehension, expert bug detection and decision-making. We used C code, which triggers the same sort of processing irrespective of the native language of the programmer. We discovered a distinct role for the insula in bug monitoring and detection and a novel connectivity pattern that goes beyond the expected activation pattern evoked by source code understanding in semantic language and mathematical processing regions. Importantly, insula activity levels were critically related to the quality of error detection, involving intuition, as signalled by reported initial bug suspicion, prior to final decision and bug detection. Activity in this salience network (SN) region evoked by bug suspicion was predictive of bug detection precision, suggesting that it encodes the quality of the behavioral evidence. Connectivity analysis provided evidence for top-down circuit “reutilization” stemming from anterior cingulate cortex (BA32), a core region in the SN that evolved for complex error monitoring such as required for this type of recent human activity. Cingulate (BA32) and anterolateral (BA10) frontal regions causally modulated decision processes in the insula, which in turn was related to activity of math processing regions in early parietal cortex. In other words, earlier brain regions used during evolution for other functions seem to be reutilized in a top-down manner for a new complex function, in an analogous manner as described for other cultural creations such as reading and literacy.
Alexandra E. D'Agostino; David Kattan; Turhan Canli
An fMRI study of loneliness in younger and older adults Journal Article
In: Social Neuroscience, vol. 14, no. 2, pp. 136–148, 2019.
Loneliness, the subjective experience of social isolation, may reflect, in part, underlying neural processing of social signals. Aging may exacerbate loneliness due to decreased social networks and increased social isolation, or it may reduce loneliness due to preferential attentional processing of positive information and increased interactions with emotionally close partners. Here, we conducted a functional magnetic resonance imaging (fMRI) study of loneliness in younger (N = 50, 26 female, M age = 20.4) and older (N = 49, 30 female, M age = 62.9) adults. Compared to younger adults, older adults were less lonely and dwelled longer on faces, regardless of valence. Previous studies in younger adults found that loneliness was negatively correlated with ventral striatal (VS) activation to pleasant social pictures of strangers yet positively correlated with VS activation to faces of close others. In the present study, we observed no association between loneliness and VS activation to social pictures of strangers in either age group. Further, unlike previous studies, we observed no association between social network size and amygdala activation to social stimuli. Additional research is needed to examine the effect of loneliness and social network size on neural processing of different dimensions of social stimuli.
Abdurahman S. Elkhetali; Leland L. Fleming; Ryan J. Vaden; Rodolphe Nenert; Jane E. Mendle; Kristina M. Visscher
In: NeuroImage, vol. 184, pp. 790–800, 2019.
The human brain has the ability to process identical information differently depending on the task. In order to perform a given task, the brain must select and react to the appropriate stimuli while ignoring other irrelevant stimuli. The dynamic nature of environmental stimuli and behavioral intentions requires an equally dynamic set of responses within the brain. Collectively, these responses act to set up and maintain states needed to perform a given task. However, the mechanisms that allow for setting up and maintaining a task state are not fully understood. Prior evidence suggests that one possible mechanism for maintaining a task state may be through altering 'background connectivity,' connectivity that exists independently of the trials of a task. Although previous studies have suggested that background connectivity contributes to a task state, these studies have typically not controlled for stimulus characteristics, or have focused primarily on relationships among areas involved with visual sensory processing. In the present study we examined background connectivity during tasks involving both visual and auditory stimuli. We examined the connectivity profiles of both visual and auditory sensory cortex that allow for selection of task-relevant stimuli, demonstrating the existence of a potentially universal pattern of background connectivity underlying attention to a stimulus. Participants were presented with simultaneous auditory and visual stimuli and were instructed to respond to only one, while ignoring the other. Using functional MRI, we observed task-based modulation of the background connectivity profile for both the auditory and visual cortex to certain brain regions. There was an increase in background connectivity between the task-relevant sensory cortex and control areas in the frontal cortex. This increase in synchrony when receiving the task-relevant stimulus as compared to the task irrelevant stimulus may be maintaining paths for passing information within the cortex. These task-based modulations of connectivity occur independently of stimuli and could be one way the brain sets up and maintains a task state.
Magdalena Fafrowicz; Bartosz Bohaterewicz; Anna Ceglarek; Monika Cichocka; Koryna Lewandowska; Barbara Sikora-Wachowicz; Halszka Oginska; Anna Beres; Justyna Olszewska; Tadeusz Marek
In: Frontiers in Human Neuroscience, vol. 13, pp. 288, 2019.
Human performance, alertness, and most biological functions express rhythmic fluctuations across a 24-h-period. This phenomenon is believed to originate from differences in both circadian and homeostatic sleep-wake regulatory processes. Interactions between these processes result in time-of-day modulations of behavioral performance as well as brain activity patterns. Although the basic mechanism of the 24-h clock is conserved across evolution, there are interindividual differences in the timing of sleep-wake cycles, subjective alertness and functioning throughout the day. The study of circadian typology differences has increased during the last few years, especially research on extreme chronotypes, which provide a unique way to investigate the effects of sleep-wake regulation on cerebral mechanisms. Using functional magnetic resonance imaging (fMRI), we assessed the influence of chronotype and time-of-day on resting-state functional connectivity. Twenty-nine extreme morning- and 34 evening-type participants underwent two fMRI sessions: about 1 h after wake-up time (morning) and about 10 h after wake-up time (evening), scheduled according to their declared habitual sleep-wake pattern on a regular working day. Analysis of obtained neuroimaging data disclosed only an effect of time of day on resting-state functional connectivity; there were different patterns of functional connectivity between morning (MS) and evening (ES) sessions. The results of our study showed no differences between extreme morning-type and evening-type individuals. We demonstrate that circadian and homeostatic influences on the resting-state functional connectivity have a universal character, unaffected by circadian typology.
Jesse Gomez; Alexis Drain; Brianna Jeska; Vaidehi S. Natu; Michael Barnett; Kalanit Grill-Spector
In: NeuroImage, vol. 188, pp. 59–69, 2019.
Human visual cortex encompasses more than a dozen visual field maps across three major processing streams. One of these streams is the lateral visual stream, which extends from V1 to lateral-occipital (LO) and temporal-occipital (TO) visual field maps and plays a prominent role in shape as well as motion perception. However, it is unknown if and how population receptive fields (pRFs) in the lateral visual stream develop from childhood to adulthood, and what impact this development may have on spatial coding. Here, we used functional magnetic resonance imaging and pRF modeling in school-age children and adults to investigate the development of the lateral visual stream. Our data reveal four main findings: 1) The topographic organization of eccentricity and polar angle maps of the lateral stream is stable after age five. 2) In both age groups there is a reliable relationship between eccentricity map transitions and cortical folding: the middle occipital gyrus predicts the transition between the peripheral representation of LO and TO maps. 3) pRFs in LO and TO maps undergo differential development from childhood to adulthood, resulting in increasing coverage of the central visual field in LO and of the peripheral visual field in TO. 4) Model-based decoding shows that the consequence of pRF and visual field coverage development is improved spatial decoding from LO and TO distributed responses in adults vs. children. Together, these results explicate both the development and topography of the lateral visual stream. Our data show that the general structural-functional organization is laid out early in development, but fine-scale properties, such as pRF distribution across the visual field and consequently, spatial precision, become fine-tuned across childhood development. These findings advance understanding of the development of the human visual system from childhood to adulthood and provide an essential foundation for understanding developmental deficits.
Joseph C. Griffis; Nicholas V. Metcalf; Maurizio Corbetta; Gordon L. Shulman
In: Cell Reports, vol. 28, no. 10, pp. 2527–2540, 2019.
Stroke causes focal brain lesions that disrupt functional connectivity (FC), a measure of activity synchronization, throughout distributed brain networks. It is often assumed that FC disruptions reflect damage to specific cortical regions. However, an alternative explanation is that they reflect the structural disconnection (SDC) of white matter pathways. Here, we compare these explanations using data from 114 stroke patients. Across multiple analyses, we find that SDC measures outperform focal damage measures, including damage to putative critical cortical regions, for explaining FC disruptions associated with stroke. We also identify a core mode of structure-function covariation that links the severity of interhemispheric SDCs to widespread FC disruptions across patients and that correlates with deficits in multiple behavioral domains. We conclude that a lesion's impact on the structural connectome is what determines its impact on FC and that interhemispheric SDCs may play a particularly important role in mediating FC disruptions after stroke.
E. A. Allen; E. Damaraju; T. Eichele; L. Wu; V. D. Calhoun
EEG signatures of dynamic functional network connectivity states Journal Article
In: Brain Topography, vol. 31, no. 1, pp. 101–116, 2018.
The human brain operates by dynamically mod- ulating different neural populations to enable goal directed behavior. The synchrony or lack thereof between different brain regions is thought to correspond to observed functional connectivity dynamics in resting state brain imaging data. In a large sample of healthy human adult subjects and utilizing a sliding windowed correlation method on functional imaging data, earlier we demonstrated the presence of seven distinct functional connectivity states/patterns between different brain networks that reliably occur across time and subjects. Whether these connectivity states correspond to meaningful electrophysiological signatures was not clear. In this study, using a dataset with concurrent EEG and resting state functional imaging data acquired during eyes open and eyes closed states, we demonstrate the replicability of previous findings in an independent sample, and identify EEG spectral signatures associated with these functional network connectivity changes. Eyes open and eyes closed conditions show common and different connectivity patterns that are associated with distinct EEG spectral signatures. Certain connectivity states are more prevalent in the eyes open case and some occur only in eyes closed state. Both conditions exhibit a state of increased thalamo-cortical anticorrelation associated with reduced EEG spec- tral alpha power and increased delta and theta power possi- bly reflecting drowsiness. This state occurs more frequently in the eyes closed state. In summary, we find a link between dynamic connectivity in fMRI data and concurrently collected EEG data, including a large effect of vigilance on functional connectivity. As demonstrated with EEG and fMRI, the stationarity of connectivity cannot be assumed, even for relatively short periods.
Noah C. Benson; Keith W. Jamison; Michael J. Arcaro; An T. Vu; Matthew F. Glasser; Timothy S. Coalson; David C. Van Essen; Essa Yacoub; Kamil Ugurbil; Jonathan Winawer; Kendrick N. Kay
In: Journal of Vision, vol. 18, no. 13, pp. 1–22, 2018.
About a quarter of human cerebral cortex is dedicated mainly to visual processing. The large-scale spatial organization of visual cortex can be measured with functional magnetic resonance imaging (fMRI) while subjects view spatially modulated visual stimuli, also known as ‘‘retinotopic mapping.'' One of the datasets collected by the Human Connectome Project involved ultra high-field (7 Tesla) fMRI retinotopic mapping in 181 healthy young adults (1.6-mm resolution), yielding the largest freely available collection of retinotopy data. Here, we describe the experimental paradigm and the results of model-based analysis of the fMRI data. These results provide estimates of population receptive field position and size. Our analyses include both results from individual subjects as well as results obtained by averaging fMRI time series across subjects at each cortical and subcortical location and then fitting models. Both the group-average and individual-subject results reveal robust signals across much of the brain, including occipital, temporal, parietal, and frontal cortex as well as subcortical areas. The group-average results agree well with previously published parcellations of visual areas. In addition, split-half analyses show strong within-subject reliability, further demonstrating the high quality of the data. We make publicly available the analysis results for individual subjects and the group avera ge, as well as associated stimuli and analysis code. These resources provide an opportunity for studying fine-scale individual variability in cortical and subcortical organization and the properties of high-resolution fMRI. In addition, they provide a set of observations that can be compared with other Human Connectome Project measures acquired in these same participants.
Daniel K. Bjornn; Bonnie Brinton Anderson; Anthony Vance; Jeffrey L. Jenkins; C. Brock Kirwan
In: MIS Quarterly, vol. 42, no. 2, pp. 355–380, 2018.
Research in the fields of information systems and human-computer interaction has shown that habituation— decreased response to repeated stimulation—is a serious threat to the effectiveness of security warnings. Although habituation is a neurobiological phenomenon that develops over time, past studies have only examined this problem cross-sectionally. Further, past studies have not examined how habituation influences actual security warning adherence in the field. For these reasons, the full extent of the problem of habituation is unknown. We address these gaps by conducting two complementary longitudinal experiments. First, we performed an experiment collecting fMRI and eye-tracking data simultaneously to directly measure habituation to security warnings as it develops in the brain over a five-day workweek. Our results show not only a general decline of participants' attention to warnings over time but also that attention recovers at least partially between workdays without exposure to the warnings. Further, we found that updating the appearance of a warning— that is, a polymorphic design—substantially reduced habituation of attention. Second, we performed a three-week field experiment in which users were naturally exposed to privacy permis-sion warnings as they installed apps on their mobile devices. Consistent with our fMRI results, users' warning adherence substantially decreased over the three weeks. However, for users who received polymorphic permis-sion warnings, adherence dropped at a substantially lower rate and remained high after three weeks, compared to users who received standard warnings. Together, these findings provide the most complete view yet of the problem of habituation to security warnings and demonstrate that polymorphic warnings can substantially improve adherence.
Johannes Bloechle; Stefan Huber; Elise Klein; Julia Bahnmueller; Korbinian Moeller; Johannes Rennig
In: NeuroImage, vol. 181, pp. 359–369, 2018.
Recent neuroimaging studies identified posterior regions in the temporal and parietal lobes as neuro-functional correlates of subitizing and global Gestalt perception. Beyond notable overlap on a neuronal level both mechanisms are remarkably similar on a behavioral level representing both a specific form of visual top-down processing where single elements are integrated into a superordinate entity. In the present study, we investigated whether subitizing draws on principles of global Gestalt perception enabling rapid top-down processes of visual quantification. We designed two functional neuroimaging experiments: a task identifying voxels responding to global Gestalt stimuli in posterior temporo-parietal brain regions and a visual quantification task on dot patterns with magnitudes within and outside the subitizing range. We hypothesized that voxels activated in global Gestalt perception should respond stronger to dot patterns within than those outside the subitizing range. The results confirmed this prediction for left-hemispheric posterior temporo-parietal brain areas. Additionally, we trained a classifier with response patterns from global Gestalt perception to predict neural responses of visual quantification. With this approach we were able to classify from TPJ Gestalt ROIs of both hemispheres whether a trial requiring subitizing was processed. The present study demonstrates that mechanisms of subitizing seem to build on processes of high-level visual perception.
Johannes Bloechle; Stefan Huber; Elise Klein; Julia Bahnmueller; Johannes Rennig; Korbinian Moeller; Julia F. Huber
In: Frontiers in Human Neuroscience, vol. 12, pp. 54, 2018.
Performance in visual quantification tasks shows two characteristic patterns as a function of set size. A precise subitizing process for small sets (up to four) was contrasted with an approximate estimation process for larger sets. The spatial arrangement of elements in a set also influences visual quantification performance, with frequently perceived arrangements (e.g., dice patterns) being faster enumerated than random arrangements. Neuropsychological and imaging studies identified the intraparietal sulcus (IPS), as key brain area for quantification, both within and above the subitizing range. However, it is not yet clear if and how set size and spatial arrangement of elements in a set modulate IPS activity during quantification. In an fMRI study, participants enumerated briefly presented dot patterns with random, canonical or dice arrangement within and above the subitizing range. We evaluated how activity amplitude and pattern in the IPS were influenced by size and spatial arrangement of a set. We found a discontinuity in the amplitude of IPS response between subitizing and estimation range, with steep activity increase for sets exceeding four elements. In the estimation range, random dot arrangements elicited stronger IPS response than canonical arrangements which in turn elicited stronger response than dice arrangements. Furthermore, IPS activity patterns differed systematically between arrangements. We found a signature in the IPS response for a transition between subitizing and estimation processes during quantification. Differences in amplitude and pattern of IPS activity for different spatial arrangements indicated a more precise representation of non-symbolic numerical magnitude for dice and canonical than for random arrangements. These findings challenge the idea of an abstract coding of numerosity in the IPS even within a single notation.
Michael B. Bone; Marie St-Laurent; Christa Dang; Douglas A. McQuiggan; Jennifer D. Ryan; Bradley R. Buchsbaum; Jennifer D. Ryan; Christa Dang; Michael B. Bone; Marie St-Laurent
In: Cerebral Cortex, vol. 29, no. 3, pp. 1075–1089, 2018.
Half a century ago, Donald Hebb posited that mental imagery is a constructive process that emulates perception. Specifically, Hebb claimed that visual imagery results from the reactivation of neural activity associated with viewing images. He also argued that neural reactivation and imagery benefit from the re-enactment of eye movement patterns that first occurred at viewing (fixation reinstatement). To investigate these claims, we applied multivariate pattern analyses to functional MRI (fMRI) and eye-tracking data collected while healthy human participants repeatedly viewed and visualized complex images. We observed that the specificity of neural reactivation correlated positively with vivid imagery and with memory for stimulus image details. Moreover, neural reactivation correlated positively with fixation reinstatement, meaning that image-specific eye movements accompanied image-specific patterns of brain activity during visualization. These findings support the conception of mental imagery as a simulation of perception, and provide evidence of the supportive role of eye-movement in neural reactivation.
James A. Brissenden; Sean M. Tobyne; David E. Osher; Emily J. Levin; Mark A. Halko; David C. Somers
In: Current Biology, vol. 28, pp. 3364–3372, 2018.
Substantial portions of the cerebellum appear to support non-motor functions; however, previous investigations of cerebellar involvement in cognition have revealed only a coarse degree of specificity. Although somatotopic maps have been observed within cerebellum, similar precision within corticocerebellar networks supporting non-motor functions has not previously been reported. Here, we find that human cerebellar lobule VIIb/VIIIa differentially codes key aspects of visuospatial cognition. Ipsilateral visuospatial representations were observed during both a visual working memory and an attentionally demanding visual receptive field-mapping fMRI task paradigm. Moreover, within lobule VIIb/VIIIa, we observed a functional dissociation between spatial coding and visual working memory processing. Visuospatial representations were found in the dorsomedial portion of lobule VIIb/VIIIa, and load dependent visual working memory processing was shifted ventrolaterally. A similar functional gradient for spatial versus load processing was found in posterior parietal cortex. This cerebral cortical organization was well predicted by functional connectivity with spatial and load regions of cerebellar lobule VIIb/VIIIa. Collectively, our findings indicate that recruitment by visuospatial attentional functions within cerebellar lobule VIIb/VIIIa is highly specific. Furthermore, the topographic arrangement of these functions is mirrored in frontal and parietal cortex. These findings motivate a closer examination of cortico-cerebellar functional specialization across a broad range of cognitive domains.
Rotem Broday-Dvir; Shany Grossman; Edna Furman-Haran; Rafael Malach
In: NeuroImage, vol. 171, pp. 84–98, 2018.
In the absence of a task, the human brain enters a mode of slow spontaneous fluctuations. A fundamental, unresolved question is whether these fluctuations are ongoing and thus persist during task engagement, or alternatively, are quenched and replaced by task-related activations. Here, we examined this issue in the human visual cortex, using fMRI. Participants were asked to either perform a recognition task of randomly appearing face and non-face targets (attended condition) or watch them passively (unattended condition). Importantly, in approximately half of the trials, all sensory stimuli were absent. Our results show that even in the absence of stimuli, spontaneous fluctuations were suppressed by attention. The effect occurred in early visual cortex as well as in fronto-parietal attention network regions. During unattended trials, the activity fluctuations were negatively linked to pupil diameter, arguing against attentional fluctuations as underlying the effect. The results demonstrate that spontaneous fluctuations do not remain unchanged with task performance, but are rather modulated according to behavioral and cognitive demands.
Daniel Carey; Francesco Caprini; Micah Allen; Antoine Lutti; Nikolaus Weiskopf; Geraint Rees; Martina F. Callaghan; Frederic Dick
In: NeuroImage, vol. 182, pp. 429–440, 2018.
Measuring the structural composition of the cortex is critical to understanding typical development, yet few investigations in humans have charted markers in vivo that are sensitive to tissue microstructural attributes. Here, we used a well-validated quantitative MR protocol to measure four parameters (R1, MT, R2* PD*) that differ in their sensitivity to facets of the tissue microstructural environment (R1, MT: myelin, macromolecular content; R2*: myelin, paramagnetic ions, i.e., iron; PD*: free water content). Mapping these parameters across cortical regions in a young adult cohort (18–39 years
Natalie Caspari; John T. Arsenault; Rik Vandenberghe; Wim Vanduffel
In: Cerebral Cortex, vol. 28, no. 6, pp. 2085–2099, 2018.
We continually shift our attention between items in the visual environment. These attention shifts are usually based on task relevance (top-down) or the saliency of a sudden, unexpected stimulus (bottom-up), and are typically followed by goal-directed actions. It could be argued that any species that can covertly shift its focus of attention will rely on similar, evolutionarily conserved neural substrates for processing such shift-signals. To address this possibility, we performed comparative fMRI experiments in humans and monkeys, combining traditional, and novel, data-driven analytical approaches. Specifically, we examined correspondences between monkey and human brain areas activated during covert attention shifts. When " shift " events were compared with " stay " events, the medial (superior) parietal lobe (mSPL) and inferior parietal lobes showed similar shift sensitivities across species, whereas frontal activations were stronger in monkeys. To identify, in a data-driven manner, monkey regions that corresponded with human shift-selective SPL, we used a novel interspecies beta-correlation strategy whereby task-related beta-values were correlated across voxels or regions-of-interest in the 2 species. Monkey medial parietal areas V6/V6A most consistently correlated with shift-selective human mSPL. Our results indicate that both species recruit corresponding, evolutionarily conserved regions within the medial superior parietal lobe for shifting spatial attention.
Marshall A. Dalton; Peter Zeidman; Cornelia McCormick; Eleanor A. Maguire
In: Journal of Neuroscience, vol. 38, no. 38, pp. 8146–8159, 2018.
The hippocampus is known to be important for a range of cognitive functions including episodic memory, spatial navigation and future-thinking. Wide agreement on the exact nature of its contribution has proved elusive, with some theories emphasising associative processes and another proposing that scene construction is its primary role. To directly compare these accounts of hippocampal function in human males and females, we devised a novel mental imagery paradigm where different tasks were closely matched for associative processing and mental construction, but either did or did not evoke scene representations, and we combined this with high resolution functional MRI. The results were striking in showing that differentiable parts of the hippocampus, along with distinct cortical regions, were recruited for scene construction or non-scene-evoking associative processing. The contrasting patterns of neural engagement could not be accounted for by differences in eye movements, mnemonic processing or the phenomenology of mental imagery. These results inform conceptual debates in the field by showing that the hippocampus does not seem to favour one type of process over another; it is not a story of exclusivity. Rather, there may be different circuits within the hippocampus, each associated with different cortical inputs, which become engaged depending on the nature of the stimuli and the task at hand. Overall, our findings emphasise the importance of considering the hippocampus as a heterogeneous structure, and that a focus on characterising how specific portions of the hippocampus interact with other brain regions may promote a better understanding of its role in cognition.
Michelle I. C. Haan; Sonja Wel; Renée M. Visser; H. Steven Scholte; Guido A. Wingen; Merel Kind
In: Scientific Reports, vol. 8, pp. 14552, 2018.
Even though human fear-conditioning involves affective learning as well as expectancy learning, most studies assess only one of the two distinct processes. Commonly used read-outs of associative fear learning are the fear-potentiated startle reflex (FPS), pupil dilation and US-expectancy ratings. FPS is thought to reflect the affective aspect of fear learning, while pupil dilation reflects a general arousal response. However, in order to measure FPS, aversively loud acoustic probes are presented during conditioning, which might in itself exert an effect on fear learning. Here we tested the effect of startle probes on fear learning by comparing brain activation (fMRI), pupil dilation and US-expectancy ratings with and without acoustic startle probes within subjects. Regardless of startle probes, fear conditioning resulted in enhanced dACC, insula and ventral striatum activation. Interaction analyses showed that startle probes diminished differential pupil dilation between CS+ and CS− due to increased pupil responses to CS−. A trend significant interaction effect was observed for US-expectancy and amygdala activation. Startle probes affect differential fear learning by impeding safety learning, as measured with pupil dilation, a read-out of the cognitive component of fear learning. However, we observed no significant effect of acoustic startle probes on other measures of fear learning.
Benjamin De Haas; D. Samuel Schwarzkopf
In: Scientific Reports, vol. 8, pp. 611, 2018.
Early visual cortex responds to illusory contours in which abutting lines or collinear edges imply the presence of an occluding surface, as well as to occluded parts of an object. Here we used functional magnetic resonance imaging (fMRI) and population receptive field (pRF) analysis to map retinotopic responses in early visual cortex using bar stimuli defined by illusory contours, occluded parts of a bar, or subtle luminance contrast. All conditions produced retinotopic responses in early visual field maps even though signal-to-noise ratios were very low. We found that signal-to-noise ratios and coherence with independent high-contrast mapping data increased from V1 to V2 to V3. Moreover, we found no differences of signal-to-noise ratios or pRF sizes between the low-contrast luminance and illusion conditions. We propose that all three conditions mapped spatial attention to the bar location rather than activations specifically related to illusory contours or occlusion.
Katharina Dobs; Johannes Schultz; Isabelle Bülthoff; Justin L. Gardner
In: NeuroImage, vol. 172, pp. 689–702, 2018.
What cortical mechanisms allow humans to easily discern the expression or identity of a face? Subjects detected changes in expression or identity of a stream of dynamic faces while we measured BOLD responses from topographically and functionally defined areas throughout the visual hierarchy. Responses in dorsal areas increased during the expression task, whereas responses in ventral areas increased during the identity task, consistent with previous studies. Similar to ventral areas, early visual areas showed increased activity during the identity task. If visual responses are weighted by perceptual mechanisms according to their magnitude, these increased responses would lead to improved attentional selection of the task-appropriate facial aspect. Alternatively, increased responses could be a signature of a sensitivity enhancement mechanism that improves representations of the attended facial aspect. Consistent with the latter sensitivity enhancement mechanism, attending to expression led to enhanced decoding of exemplars of expression both in early visual and dorsal areas relative to attending identity. Similarly, decoding identity exemplars when attending to identity was improved in dorsal and ventral areas. We conclude that attending to expression or identity of dynamic faces is associated with increased selectivity in representations consistent with sensitivity enhancement.
Laura Dugué; Elisha P. Merriam; David J. Heeger; Marisa Carrasco
In: Cerebral Cortex, vol. 28, no. 7, pp. 2375–2390, 2018.
The temporo-parietal junction (TPJ) has been associated with various cognitive and social functions, and is critical for attentional reorienting. Attention affects early visual processing. Neuroimaging studies dealing with such processes have thus far concentrated on striate and extrastriate areas. Here, we investigated whether attention orienting or reorienting modulate activity in visually driven TPJ subregions. For each observer we identified 3 visually responsive subregions within TPJ: 2 bilateral (vTPJ ant and vTPJ post) and 1 right lateralized (vTPJ cent). Cortical activity in these subregions was measured using fMRI while observers performed a 2-alternative forced-choice orientation discrimination task. Covert spatial endogenous (voluntary) or exogenous (involuntary) attention was manipulated using either a central or a peripheral cue with task, stimuli and observers constant. Both endogenous and exogenous attention increased activity for invalidly cued trials in right vTPJ post ; only endogenous attention increased activity for invalidly cued trials in left vTPJ post and in right vTPJ cent ; and neither type of attention modulated either right or left vTPJ ant . These results demonstrate that vTPJ post and vTPJ cent mediate the reorientation of covert attention to task relevant stimuli, thus playing a critical role in visual attention. These findings reveal a differential reorienting cortical response after observers' attention has been oriented to a given location voluntarily or involuntarily.
Katherine Duncan; Bradley B. Doll; Nathaniel D. Daw; Daphna Shohamy
In: Neuron, vol. 98, no. 3, pp. 645–657.e6, 2018.
People often perceive configurations rather than the elements they comprise, a bias that may emerge because configurations often predict outcomes. But how does the brain learn to associate configurations with outcomes and how does this learning differ from learning about individual elements? We combined behavior, reinforcement learning models, and functional imaging to understand how people learn to associate configurations of cues with outcomes. We found that configural learning depended on the relative predictive strength of elements versus configurations and was related to both the strength of BOLD activity and patterns of BOLD activity in the hippocampus. Configural learning was further related to functional connectivity between the hippocampus and nucleus accumbens. Moreover, configural learning was associated with flexible knowledge about associations and differential eye movements during choice. Together, this suggests that configural learning is associated with a distinct computational, cognitive, and neural profile that is well suited to support flexible and adaptive behavior. Duncan et al. investigate how people learn to predict outcomes using cue configurations. They show that configural learning is characterized by unique computational, behavioral, and neural signatures, including hippocampal activity, interactions between the hippocampus and striatum, and enhanced flexible knowledge.
Kathleen A. Garrison; Stephanie S. O'malley; Ralitza Gueorguieva; Suchitra Krishnan-Sarin
In: Drug and Alcohol Dependence, vol. 186, pp. 233–241, 2018.
Background: E-cigarettes are sold in flavors such as "skittles," "strawberrylicious," and "juicy fruit," and no restrictions are in place on marketing e-cigarettes to youth. Sweets/fruits depicted in e-cigarette advertisements may increase their appeal to youth and interfere with health warnings. This study tested a brain biomarker of product preference for sweet/fruit versus tobacco flavor e-cigarettes, and whether advertising for flavors interfered with warning labels. Methods: Participants (N = 26) were college-age young adults who had tried an e-cigarette and were susceptible to future e-cigarette use. They viewed advertisements in fMRI for sweet/fruit and tobacco flavor e-cigarettes, menthol and regular cigarettes, and control images of sweets/fruits/mints with no tobacco product. Cue-reactivity was measured in the nucleus accumbens, a brain biomarker of product preference. Advertisements randomly contained warning labels, and recognition of health warnings was tested post-scan. Visual attention was measured using eye-tracking. Results: There was a significant effect of e-cigarette condition (sweet/tobacco/control) on nucleus accumbens activity, that was not found for cigarette condition (menthol/regular/control). Nucleus accumbens activity was greater for sweet/fruit versus tobacco flavor e-cigarette advertisements and did not differ compared with control images of sweets and fruits. Greater nucleus accumbens activity was correlated with poorer memory for health warnings. Conclusions: These and exploratory eye-tracking findings suggest that advertising for sweet/fruit flavors may increase positive associations with e-cigarettes and/or override negative associations with tobacco, and interfere with health warnings, suggesting that one way to reduce the appeal of e-cigarettes to youth and educate youth about e-cigarette health risks is to regulate advertising for flavors.
Detre A. Godinez; Daniel S. Lumian; Tanisha Crosby-Attipoe; Ana M. Bedacarratz; Paree Zarolia; Kateri McRae
In: NeuroImage, vol. 166, pp. 239–246, 2018.
Previous studies have demonstrated that imitating a face can be relatively automatic and reflexive. In contrast, opposing facial expressions may require engaging flexible, cognitive control. However, few studies have examined the degree to which imitation and opposition of facial movements recruit overlapping and distinct neural regions. Furthermore, little work has examined whether opposition and imitation of facial movements differ between emotional and averted eye gaze facial expressions. This study utilized a novel task with 40 participants to compare passive viewing, imitation and opposition of emotional faces looking forward and neutral faces with averted eye gaze [(3: Look, Imitate, Oppose) x (2: Emotion, Averted Eye)]. Imitation and opposition of both types of facial movements elicited overlapping activation in frontal, premotor, superior temporal and anterior intraparietal regions. These regions are recruited during cognitive control, face processing and mirroring tasks. For both emotional and averted eye gaze photos, opposition engaged the superior frontal gyrus, superior temporal sulcus and the anterior intraparietal sulcus to a greater extent compared to imitation. Finally, stimulus type and instruction interacted, such that for the eye gaze condition only, greater activation was observed in the dorsal anterior cingulate (dACC) during opposition compared to imitation, while no significant dACC differences were observed for the emotional expression conditions, which instead showed significantly greater activation in the middle and frontal pole. Overall these results showed significant overlap between imitation and opposition, as well as increased activation of these regions to generate an opposing facial movement relative to imitating.
Alain Guillaume; Jason R. Fuller; Riju Srimal; Clayton E. Curtis
Cortico-cerebellar network involved in saccade adaptation Journal Article
In: Journal of Neurophysiology, vol. 120, no. 5, pp. 2583–2594, 2018.
Saccade adaptation is the learning process that en- sures that vision and saccades remain calibrated. The central nervous system network involved in these adaptive processes remains unclear because of difficulties in isolating the learning process from the correlated visual and motor processes. Here we imaged the human brain during a novel saccade adaptation paradigm that allowed us to isolate neural signals involved in learning independent of the changes in the amplitude of corrective saccades usually correlated with adap- tation. We show that the changes in activation in the ipsiversive cerebellar vermis that track adaptation are not driven by the changes in corrective saccades and thus provide critical supporting evidence for previous findings. Similarly, we find that activation in the dorso- medial wall of the contraversive precuneus mirrors the pattern found in the cerebellum. Finally, we identify dorsolateral and dorsomedial cortical areas in the frontal and parietal lobes that encode the retinal errors following inaccurate saccades used to drive recalibration. To- gether, these data identify a distributed network of cerebellar and cortical areas and their specific roles in oculomotor learning.
Michelle G. Hall; Claire K. Naughtin; Jason B. Mattingley; Paul E. Dux
In: NeuroImage, vol. 173, pp. 351–360, 2018.
Incidental learning affords a behavioural advantage when sensory information matches regularities that have previously been encountered. Previous studies have taken a focused approach by probing the involvement of specific candidate brain regions underlying incidentally acquired memory representations, as well as expectation effects on early sensory representations. Here, we investigated the broader extent of the brain's sensitivity to violations and fulfilments of expectations, using an incidental learning paradigm in which the contingencies between target locations and target identities were manipulated without participants' overt knowledge. Multivariate analysis of functional magnetic resonance imaging data was applied to compare the consistency of neural activity for visual events that the contingency manipulation rendered likely versus unlikely. We observed widespread sensitivity to expectations across frontal, temporal, occipital, and sub-cortical areas. These activation clusters showed distinct response profiles, such that some regions displayed more reliable activation patterns under fulfilled expectations, whereas others showed more reliable patterns when expectations were violated. These findings reveal that expectations affect multiple stages of information processing during visual decision making, rather than early sensory processing stages alone.
Michael P. Harms; Leah H. Somerville; Beau M. Ances; Jesper Andersson; Deanna M. Barch; Matteo Bastiani; Susan Y. Bookheimer; Timothy B. Brown; Randy L. Buckner; Gregory C. Burgess; Timothy S. Coalson; Michael A. Chappell; Mirella Dapretto; Gwenaëlle Douaud; Bruce Fischl; Matthew F. Glasser; Douglas N. Greve; Cynthia Hodge; Keith W. Jamison; Saad Jbabdi; Sridhar Kandala; Xiufeng Li; Ross W. Mair; Silvia Mangia; Daniel Marcus; Daniele Mascali; Steen Moeller; Thomas E. Nichols; Emma C. Robinson; David H. Salat; Stephen M. Smith; Stamatios N. Sotiropoulos; Melissa Terpstra; Kathleen M. Thomas; M. Dylan Tisdall; Kamil Ugurbil; Andre Kouwe; Roger P. Woods; Lilla Zöllei; David C. Van Essen; Essa Yacoub
In: NeuroImage, vol. 183, pp. 972–984, 2018.
The Human Connectome Projects in Development (HCP-D) and Aging (HCP-A) are two large-scale brain imaging studies that will extend the recently completed HCP Young-Adult (HCP-YA) project to nearly the full lifespan, collecting structural, resting-state fMRI, task-fMRI, diffusion, and perfusion MRI in participants from 5 to 100+ years of age. HCP-D is enrolling 1300+ healthy children, adolescents, and young adults (ages 5–21), and HCP-A is enrolling 1200+ healthy adults (ages 36–100+), with each study collecting longitudinal data in a subset of individuals at particular age ranges. The imaging protocols of the HCP-D and HCP-A studies are very similar, differing primarily in the selection of different task-fMRI paradigms. We strove to harmonize the imaging protocol to the greatest extent feasible with the completed HCP-YA (1200+ participants, aged 22–35), but some imaging-related changes were motivated or necessitated by hardware changes, the need to reduce the total amount of scanning per participant, and/or the additional challenges of working with young and elderly populations. Here, we provide an overview of the common HCP-D/A imaging protocol including data and rationales for protocol decisions and changes relative to HCP-YA. The result will be a large, rich, multi-modal, and freely available set of consistently acquired data for use by the scientific community to investigate and define normative developmental and aging related changes in the healthy human brain.
John M. Henderson; Wonil Choi; Steven G. Luke; Joseph Schmidt
In: Quarterly Journal of Experimental Psychology, vol. 71, no. 1, pp. 314–323, 2018.
Reading requires integration of language and cognitive processes with attention and eye movement control. Individuals differ in their reading ability, but little is known about the neurocognitive processes associated with these individual differences. To investigate this issue, we combined eyetracking and functional magnetic resonance imaging (fMRI), simultaneously recording eye movements and blood oxygen level dependent (BOLD) activity while subjects read text passages. We found that the variability and skew of fixation duration distributions across individuals, as assessed by ex-Gaussian analyses, decreased with increasing neural activity in regions associated with the cortical eye movement control network (left frontal eye fields [FEF], left intraparietal sulcus [IPS] , left inferior frontal gyrus [IFG] and right IFG). The results suggest that individual differences in fixation duration during reading are related to underlying neurocognitive processes associated with the eye movement control system and its relationship to language processing. The results also show that eye movements and fMRI can be combined to investigate the neural correlates of individual differences in natural reading.
Nora A. Herweg; Tobias Sommer; Nico Bunzeck
In: Journal of Neuroscience, vol. 38, no. 3, pp. 745–754, 2018.
The striatum is a central part of the dopaminergic mesolimbic system and contributes both to the encoding and retrieval of long-term memories. In this regard, the co-occurrence of striatal novelty and retrieval success effects in independent studies underlines the structure's double duty and suggests dynamic contextual adaptation. To test this hypothesis and further investigate the underlying mechanisms ofencoding and retrieval dynamics, human subjects viewed pre-familiarized scene images intermixed with new scenes and classified them as indoor versus outdoor (encoding task) or old versus new (retrieval task), while fMRI and eye tracking data were recorded. Subsequently, subjects performed a final recognition task. As hypothesized, striatal activity and pupil size reflected task- conditional salience ofold and new stimuli, but, unexpectedly, this effect was not reflected in the substantia nigra and ventral tegmental area (SN/VTA), medial temporal lobe, or subsequent memory performance. Instead, subsequent memory generally benefitted from retrieval, an effect possibly driven by task difficulty and activity in a network including different parts ofthe striatum and SN/VTA. Our findings extend memory models of encoding and retrieval dynamics by pinpointing a specific contextual factor that differentially modulates the functional properties ofthe mesolimbic system.
Michael Jigo; Mengyuan Gong; Taosheng Liu
In: eNeuro, vol. 5, no. 1, pp. 1–15, 2018.
Studies of feature-based attention have associated activity in a dorsal frontoparietal network with putative attentional priority signals. Yet, how this neural activity mediates attentional selection and whether it guides behavior are fundamental questions that require investigation. We reasoned that endogenous fluctuations in the quality of attentional priority should influence task performance. Human subjects detected a speed increment while viewing clockwise (CW) or counterclockwise (CCW) motion (baseline task) or while attending to either direction amid distracters (attention task). In an fMRI experiment, direction-specific neural pattern similarity between the baseline task and the attention task revealed a higher level of similarity for correct than incorrect trials in frontoparietal regions. Using transcranial magnetic stimulation (TMS), we disrupted posterior parietal cortex (PPC) and found a selective deficit in the attention task, but not in the baseline task, demonstrating the necessity of this cortical area during feature-based attention. These results reveal that frontoparietal areas maintain attentional priority that facilitates successful behavioral selection.
Janne Kauttonen; Yevhen Hlushchuk; Iiro P. Jääskeläinen; Pia Tikka
In: NeuroImage, vol. 172, pp. 313–325, 2018.
How does the human brain recall and connect relevant memories with unfolding events? To study this, we presented 25 healthy subjects, during functional magnetic resonance imaging, the movie ‘Memento' (director C. Nolan). In this movie, scenes are presented in chronologically reverse order with certain scenes briefly overlapping previously presented scenes. Such overlapping “key-frames” serve as effective memory cues for the viewers, prompting recall of relevant memories of the previously seen scene and connecting them with the concurrent scene. We hypothesized that these repeating key-frames serve as immediate recall cues and would facilitate reconstruction of the story piece-by-piece. The chronological version of Memento, shown in a separate experiment for another group of subjects, served as a control condition. Using multivariate event-related pattern analysis method and representational similarity analysis, focal fingerprint patterns of hemodynamic activity were found to emerge during presentation of key-frame scenes. This effect was present in higher-order cortical network with regions including precuneus, angular gyrus, cingulate gyrus, as well as lateral, superior, and middle frontal gyri within frontal poles. This network was right hemispheric dominant. These distributed patterns of brain activity appear to underlie ability to recall relevant memories and connect them with ongoing events, i.e., “what goes with what” in a complex story. Given the real-life likeness of cinematic experience, these results provide new insight into how the human brain recalls, given proper cues, relevant memories to facilitate understanding and prediction of everyday life events.
Derek Kellar; Sharlene Newman; Franco Pestilli; Hu Cheng; Nicholas L. Port
In: NeuroImage: Clinical, vol. 18, pp. 413–424, 2018.
Objectives: Though sub-concussive impacts are common during contact sports, there is little consensus whether repeat blows affect brain function. Using a “lifetime exposure” rather than acute exposure approach, we examined oculomotor performance and brain activation among collegiate football players and two control groups. Our analysis examined whether there are group differences in eye movement behavioral performance and in brain activation during smooth pursuit. Methods: Data from 21 off-season Division I football “starters” were compared with a) 19 collegiate cross-country runners, and b) 11 non-athlete college students who were SES matched to the football player group (total N = 51). Visual smooth pursuit was performed while undergoing fMRI imaging via a 3 Tesla scanner. Smooth pursuit eye movements to three stimulus difficulty levels were measured with regard to RMS error, gain, and lag. Results: No meaningful differences were found for any of the standard analyses used to assess smooth pursuit eye movements. For fMRI, greater activation was seen in the oculomotor region of the cerebellar vermis and areas of the FEF for football players as compared to either control group, who did not differ on any measure. Conclusion: Greater cerebellar activity among football players while performing an oculomotor task could indicate that they are working harder to compensate for some subtle, long-term subconcussive deficits. Alternatively, top athletes in a sport requiring high visual motor skill could have more of their cerebellum and FEF devoted to oculomotor task performance regardless of subconcussive history. Overall, these results provide little firm support for an effect of accumulated subconcussion exposure on brain function.
Stephanie J. Larcombe; Christopher Kennard; Holly Bridge
In: Human Brain Mapping, vol. 39, no. 1, pp. 145–156, 2018.
Repeated practice of a specific task can improve visual performance, but the neural mechanisms underlying this improvement in performance are not yet well understood. Here we trained healthy partici- pants on a visual motion task daily for 5 days in one visual hemifield. Before and after training, we used functional magnetic resonance imaging (fMRI) to measure the change in neural activity. We also imaged a control group of participants on two occasions who did not receive any task training. While in the MRI scanner, all participants completed the motion task in the trained and untrained visual hemifields sepa- rately. Following training, participants improved their ability to discriminate motion direction in the trained hemifield and, to a lesser extent, in the untrained hemifield. The amount of task learning correlated positively with the change in activity in the medial superior temporal (MST) area. MST is the anterior por- tion of the human motion complex (hMT1). MST changes were localized to the hemisphere contralateral to the region of the visual field, where perceptual training was delivered. Visual areas V2 and V3a showed an increase in activity between the first and second scan in the training group, but this was not correlated with performance. The contralateral anterior hippocampus and bilateral dorsolateral prefrontal cortex (DLPFC) and frontal pole showed changes in neural activity that also correlated with the amount of task learning. These findings emphasize the importance of MST in perceptual learning of a visual motion task.
Zhong-Xu Liu; Kelly Shen; Rosanna K. Olsen; Jennifer D. Ryan
In: Neuropsychologia, vol. 119, pp. 81–91, 2018.
Deciphering the mechanisms underlying age-related memory declines remains an important goal in cognitive neuroscience. Recently, we observed that visual sampling behavior predicted activity within the hippocampus, a region critical for memory. In younger adults, increases in the number of gaze fixations were associated with increases in hippocampal activity (Liu et al., 2017). This finding suggests a close coupling between the oculomotor and memory system. However, the extent to which this coupling is altered with aging has not been investigated. In this study, we gave older adults the same face processing task used in Liu et al. (2017) and compared their visual exploration behavior and neural activation in the hippocampus and the fusiform face area (FFA) to those of younger adults. Compared to younger adults, older adults showed an increase in visual exploration as indexed by the number of gaze fixations. However, the relationship between visual exploration and neural responses in the hippocampus and FFA was weaker than that of younger adults. Older adults also showed weaker responses to novel faces and a smaller repetition suppression effect in the hippocampus and FFA compared to younger adults. All together, this study provides novel evidence that the capacity to bind visually sampled information, in real-time, into coherent representations along the ventral visual stream and the medial temporal lobe declines with aging.
Kep Kee Loh; Fadila Hadj-Bouziane; Michael Petrides; Emmanuel Procyk; Céline Amiez
In: Frontiers in Neuroscience, vol. 11, pp. 753, 2018.
According to contemporary views, the lateral frontal cortex is organized along a rostro-caudal functional axis with increasingly complex cognitive/behavioral control implemented rostrally, and increasingly detailed motor control implemented caudally. Whether the medial frontal cortex follows the same organization remains to be elucidated. To address this issue, the functional connectivity of the 3 cingulate motor areas (CMAs) in the human brain with the lateral frontal cortex was investigated. First, the CMAs and their representations of hand, tongue, and eye movements were mapped via task-related functional magnetic resonance imaging (fMRI). Second, using resting-state fMRI, their functional connectivity with lateral prefrontal and lateral motor cortical regions of interest (ROIs) were examined. Importantly, the above analyses were conducted at the single-subject level to account for variability in individual cingulate morphology. The results demonstrated a rostro-caudal functional organization of the CMAs in the human brain that parallels that in the lateral frontal cortex: the rostral CMA has stronger functional connectivity with prefrontal regions and weaker connectivity with motor regions; conversely, the more caudal CMAs have weaker prefrontal and stronger motor connectivity. Connectivity patterns of the hand, tongue and eye representations within the CMAs are consistent with that of their parent CMAs. The parallel rostral-to-caudal functional organization observed in the medial and lateral frontal cortex could likely contribute to different hierarchies of cognitive-motor control.
Scott Marek; Joshua S. Siegel; Evan M. Gordon; Ryan V. Raut; Caterina Gratton; Dillan J. Newbold; Mario Ortega; Timothy O. Laumann; Babatunde Adeyemo; Derek B. Miller; Annie Zheng; Katherine C. Lopez; Jeffrey J. Berg; Rebecca S. Coalson; Annie L. Nguyen; Donna Dierker; Andrew N. Van; Catherine R. Hoyt; Kathleen B. McDermott; Scott A. Norris; Joshua S. Shimony; Abraham Z. Snyder; Steven M. Nelson; Deanna M. Barch; Bradley L. Schlaggar; Marcus E. Raichle; Steven E. Petersen; Deanna J. Greene; Nico U. F. Dosenbach
In: Neuron, vol. 100, no. 4, pp. 977–993.e7, 2018.
Cerebellar functional networks are topographically individual-specific. Cerebellar intrinsic fMRI signals lag those in cortex by 100–400 ms. The frontoparietal control network is greatly overrepresented (>2-fold), suggesting that the cerebellum is important for the adaptive control of the brain's cognitive processes.
Rachel Millin; Tamar Kolodny; Anastasia V. Flevaris; Alexander M. Kale; Michael Paul Schallmo; Jennifer Gerdts; Raphael A. Bernier; Scott Murray
Reduced auditory cortical adaptation in autism spectrum disorder Journal Article
In: eLife, vol. 7, pp. 1–15, 2018.
<p>Adaptation is a fundamental property of cortical neurons and has been suggested to be altered in individuals with autism spectrum disorder (ASD). We used fMRI to measure adaptation induced by repeated audio-visual stimulation in early sensory cortical areas in individuals with ASD and neurotypical (NT) controls. The initial transient responses were equivalent between groups in both visual and auditory cortices and when stimulation occurred with fixed-interval and randomized-interval timing. However, in auditory but not visual cortex, the post-transient sustained response was greater in individuals with ASD than NT controls in the fixed-interval timing condition, reflecting reduced adaptation. Further, individual differences in the sustained response in auditory cortex correlated with ASD symptom severity. These findings are consistent with hypotheses that ASD is associated with increased neural responsiveness but that responsiveness differences only manifest after repeated stimulation, are specific to the temporal pattern of stimulation, and are confined to specific cortical regions.</p>
Olga Mishulina; Olga Skripko; Anastasia Korosteleva
In: Procedia Computer Science, vol. 123, pp. 328–333, 2018.
The connection between cognitive processes and the movement of the human eye during the reading and retelling the text is investigated. A series of experiments were performed, in which people with normal speech, people with stuttering and in the treatment stage of stuttering took part. The results of the experiment were fixed by the eye tracker and the functional magnetic resonance tomograph. The statistical processing of the tracking data was performed, which discovered stable differences of fixation duration in groups of participants when performing test tasks.
Christoph Naegeli; Thomas Zeffiro; Marco Piccirelli; Assia Jaillard; Anina Weilenmann; Katayun Hassanpour; Matthis Schick; Michael Rufer; Scott P. Orr; Christoph Mueller-Pfeiffer
In: Biological Psychiatry, vol. 83, no. 3, pp. 254–262, 2018.
Background: Patients with posttraumatic stress disorder (PTSD) are hyperresponsive to unexpected or potentially threatening environmental stimuli. Research in lower animals and humans suggests that sensitization of the locus coeruleus–norepinephrine system may underlie behavioral and autonomic hyperresponsiveness in PTSD. However, direct evidence linking locus coeruleus system hyperactivity to PTSD hyperresponsiveness is sparse. Methods: Psychophysiological recording and functional magnetic resonance imaging were used during passive listening to brief, 95-dB sound pressure level, white noise bursts presented intermittently to determine whether behavioral and autonomic hyperresponsiveness to sudden sounds in PTSD is associated with locus coeruleus hyperresponsiveness. Results: Participants with PTSD (n = 28) showed more eye-blink reflexes and larger heart rate, skin conductance, and pupil area responses to loud sounds (multivariate p =.007) compared with trauma-exposed participants without PTSD (n = 26). PTSD participants exhibited larger responses in locus coeruleus (t = 2.60, region of interest familywise error corrected), intraparietal sulcus, caudal dorsal premotor cortex, and cerebellar lobule VI (t ≥ 4.18, whole-brain familywise error corrected). Caudal dorsal premotor cortex activity was associated with both psychophysiological response magnitude and levels of exaggerated startle responses in daily life in PTSD participants (t ≥ 4.39, whole-brain familywise error corrected). Conclusions: Behavioral and autonomic hyperresponsiveness in PTSD may arise from a hyperactive alerting/orienting system in which processes related to attention and motor preparation localized to lateral premotor cortex, intraparietal sulcus, and posterior superior cerebellar cortex are modulated by atypically high phasic noradrenergic influences originating in the locus coeruleus.
Vaidehi S. Natu; Jesse Gomez; Kalanit Grill-Spector; Brianna Jeska; Michael Barnett
In: Nature Communications, vol. 9, pp. 788, 2018.
Receptive fields (RFs) processing information in restricted parts of the visual field are a key property of visual system neurons. However, how RFs develop in humans is unknown. Using fMRI and population receptive field (pRF) modeling in children and adults, we determine where and how pRFs develop across the ventral visual stream. Here we report that pRF properties in visual field maps, from the first visual area, V1, through the first ventro-occipital area, VO1, are adult-like by age 5. However, pRF properties in face-selective and character- selective regions develop into adulthood, increasing the foveal coverage bias for faces in the right hemisphere and words in the left hemisphere. Eye-tracking indicates that pRF changes are related to changing fixation patterns on words and faces across development. These findings suggest a link between face and word viewing behavior and the differential development of pRFs across visual cortex, potentially due to competition on foveal coverage.
Matthias Nau; Tobias Navarro Schröder; Jacob L. S. Bellmund; Christian F. Doeller
In: Nature Neuroscience, vol. 21, no. 2, pp. 188–190, 2018.
Entorhinal grid cells map the local environment, but their involvement beyond spatial navigation remains elusive. We examined human functional MRI responses during a highly controlled visual tracking task and show that entorhinal cortex exhibited a sixfold rotationally symmetric signal encoding gaze direction. Our results provide evidence for a grid-like entorhinal code for visual space and suggest a more general role of the entorhinal grid system in coding information along continuous dimensions.
Claire K. Naughtin; Jason B. Mattingley; Angela D. Bender; Paul E. Dux
In: Cortex, vol. 99, pp. 45–54, 2018.
To isolate a visual stimulus as a unique object with a specific spatial location and time of occurrence, it is necessary to first register (individuate) the stimulus as a distinct perceptual entity. Recent investigations into the neural substrates of object individuation have suggested it is subserved by a distributed neural network, but previous manipulations of individuation load have introduced extraneous visual confounds, which might have yielded ambiguous findings, particularly in early cortical areas. Furthermore, while it has been assumed that selective attention is required for object individuation, there is no definitive evidence on the brain regions recruited for attended and ignored objects. Here we addressed these issues by combining functional magnetic resonance imaging (fMRI) with a novel object-enumeration paradigm in which to-be-individuated objects were defined by illusory contours, such that the physical elements of the display remained constant across individuation conditions. Multi-voxel pattern analyses revealed that attended objects modulated patterns of activity in early visual cortex, as well as frontal and parietal brain areas, as a function of object-individuation load. These findings suggest that object indi-viduation recruits both early and later cortical areas, consistent with theoretical accounts proposing that this operation acts at the junction of feed-forward and feedback processing stages in visual analysis. We also found dissociations between brain regions involved in individuation of attended and unattended objects, suggesting that voluntary spatial attention influences the brain regions recruited for this process.
Akitoshi Ogawa; Atsushi Ueshima; Keigo Inukai; Tatsuya Kameda
In: Scientific Reports, vol. 8, pp. 12857, 2018.
Risky decision making for others is ubiquitous in our societies. Whereas financial decision making for oneself induces strong concern about the worst outcome (maximin concern) as well as the expected value, behavioral and neural characteristics of decision making for others are less well understood. We conducted behavioral and functional magnetic resonance imaging (fMRI) experiments to examine the neurocognitive underpinnings of risky decisions for an anonymous other, using decisions for self as a benchmark. We show that, although the maximin concern affected both types of decisions equally strongly, decision making for others recruited a more risk-neutral computational mechanism than decision making for self. Specifically, participants exhibited more balanced information search when choosing a risky option for others. Activity of right temporoparietal junction (rTPJ, associated with cognitive perspective taking) was parametrically modulated by options' expected values in decisions for others, and by the minimum amounts in decisions for self. Furthermore, individual differences in self-reported empathic concern modified these attentional and neural processes. Overall, these results indicate that the typical maximin concern is attenuated in a risk-neutral direction in decisions for others as compared to self. We conjecture that, given others' diverse preferences, deciding as a neutral party may cognitively recruit such risk-neutrality.
Tanya Orlov; Ehud Zohary
In: Journal of Neuroscience, vol. 38, no. 3, pp. 659–678, 2018.
We typically recognize visual objects, by utilizing the spatial layout of their parts, simultaneously present on the retina. Thus, shape extraction is based on integration of the relevant retinal information over space. The lateral occipital complex (LOC) can faithfully represent shape in such conditions. However, sometimes, integration over time is required to determine object shape. To study shape extraction through temporal integration of successive partial-shape views, we presented human participants (both men and women) with artificial shapes that moved behind a narrow vertical or horizontal slit. Only a tiny fraction of the shape was visible at any instant, at the sameretinal location. Yet, observers perceived a coherent whole shape instead of a jumbled pattern.Using fMRI and multivoxel-pattern analysis we searched for brain regions that encode temporally-integrated shape identity. We further required that the representation of shape should be invariant to changes in the slit-orientation. We show that slit-invariant shape information is most accurate in LOC. Importantly, the slit-invariant shape representations matched the conventional whole-shape representations assessed during full-image runs. Moreover, when the same slit-dependent shape-slivers were shuffled, thereby preventing their spatiotemporal integration, slit-invariant shape information was dramatically reduced. The slit-invariant representation of the various shapes also mirrored the structure of shape perceptual space, as assessed by perceptual similarity-judgment tests. Thus, LOC is likely to mediate temporal integration of slit-dependent shape-views, generating a slit-invariant whole-shape percept. These findings provide strong evidence for a global encoding of shape in LOC, regardless of integration processes required to generate the shape percept.
Alexandra Papadopoulos; Francesco Sforazzini; Gary F. Egan; Sharna D. Jamadar
In: Human Brain Mapping, vol. 39, no. 1, pp. 354–368, 2018.
Object-based visuospatial transformation is important for the ability to interact with the world and the people and objects within it. In this preliminary investigation, we hypothesized that object-based visuospatial transformation is a unitary process invoked regardless of current context and is localized to the intraparietal sulcus. Participants (n = 14) performed both antisaccade and mental rotation tasks while scanned using fMRI. A statistical conjunction confirmed that both tasks activated the intraparietal sulcus. Statistical parametric anatomical mapping determined that the statistical conjunction was localized to intraparietal sulcus subregions hIP2 and hIP3. A Gaussian naive Bayes classifier confirmed that the conjunction in region hIP3 was indistinguishable between tasks. The results provide evidence that object-based visuospatial transformation is a domain-general process that is invoked regardless of current context. Our results are consistent with the modular model of the posterior parietal cortex and the distinct cytoarchitectonic, structural, and functional connectivity profiles of the subregions in the intraparietal sulcus.
Andrew S. Persichetti; Daniel D. Dilks
In: Journal of Neuroscience, vol. 38, no. 48, pp. 10295–10304, 2018.
When entering an environment, we can use the present visual information from the scene to either recognize the kind ofplace it is (e.g., a kitchen or a bedroom) or navigate through it. Here we directly test the hypothesis that these two processes, what we call “scene categorization” and “visually-guided navigation”, are supported by dissociable neural systems. Specifically, we manipulated task demands by asking human participants (male and female) to perform a scene categorization, visually-guided navigation, and baseline task on images of scenes, and measured both the average univariate responses and multivariate spatial pattern of responses within two scene-selective cortical regions, the parahippocampal place area (PPA) and occipital place area (OPA), hypothesized to be separably involved in scene categorization and visually-guided navigation, respectively. As predicted, in the univariate analysis, PPA responded significantly more during the categorization task than during both the navigation and baseline tasks, whereas OPA showed the complete opposite pattern. Similarly, in the multivariate analysis, a linear support vector machine achieved above-chance classification for the categorization task, but not the navigation task in PPA. By contrast, above-chance classification was achieved for both the navigation and categorization tasks in OPA. However, above-chance classification for both tasks was also found in early visual cortex and hence not specific to OPA, suggesting that the spatial patterns of responses in OPA are merely inherited from early vision, and thus may be epiphenomenal to behavior. Together, these results are evidence for dissociable neural systems involved in recognizing places and navigating through them.
Eliska Prochazkova; Luisa Prochazkova; Michael Rojek Giffin; H. Steven Scholte; Carsten K. W. De Dreu; Mariska E. Kret
Pupil mimicry promotes trust through the theory-of-mind network Journal Article
In: Proceedings of the National Academy of Sciences, vol. 115, no. 31, pp. E7265–E7274, 2018.
The human eye can provide powerful insights into the emotions and intentions of others; however, how pupillary changes influence observers' behavior remains largely unknown. The present fMRI–pupillometry study revealed that when the pupils of interacting partners synchronously dilate, trust is promoted, which suggests that pupil mimicry affiliates people. Here we provide evidence that pupil mimicry modulates trust decisions through the activation of the theory-of-mind network (precuneus, temporo-parietal junction, superior temporal sulcus, and medial prefrontal cortex). This network was recruited during pupil-dilation mimicry compared with interactions without mimicry or compared with pupil-constriction mimicry. Furthermore, the level of theory-of-mind engagement was proportional to individual's susceptibility to pupil-dilation mimicry. These data reveal a fundamental mechanism by which an individual's pupils trigger neurophysiological responses within an observer: when interacting partners synchronously dilate their pupils, humans come to feel reflections of the inner states of others, which fosters trust formation.
Masih Rahmati; Golbarg T. Saber; Clayton E. Curtis
Population dynamics of early visual cortex during working memory Journal Article
In: Journal of Cognitive Neuroscience, vol. 30, no. 2, pp. 219–233, 2018.
Although the content of working memory (WM) can be decoded from the spatial patterns of brain activity in early visual cortex, how populations encode WM representations remains unclear.Here, we address this limitation by using a model-based approach that reconstructs the feature encoded by population activity measured with fMRI. Using this approach, we could successfully reconstruct the locations of memory-guided saccade goals based on the pattern of activity in visual cortex during a memory delay. We could reconstruct the saccade goal even when we dissociated the visual stimulus from the saccade goal using a memory-guided antisaccade procedure. By comparing the spatiotemporal population dynamics, we find that the representations in visual cortex are stable but can also evolve from a representation of a remembered visual stimulus to a prospective goal. Moreover, because the representation of the antisaccade goal cannot be the result of bottom–up visual stimulation, it must be evoked by top–down signals presumably originating from frontal and/ or parietal cortex. Indeed, we find that trial-by-trial fluctuations in delay period activity in frontal and parietal cortex correlate with the precision with which our model reconstructed the maintained saccade goal based on the pattern of activity in visual cortex. Therefore, the population dynamics in visual cortex encode WM representations, and these representations can be sculpted by top–down signals from frontal and parietal cortex.
Ignacio Rebollo; Anne-Dominique Devauchelle; Benoît Béranger; Catherine Tallon-Baudry
In: eLife, vol. 7, pp. 1–25, 2018.
Resting-state networks offer a unique window into the brain's functional architecture, but their characterization remains limited to instantaneous connectivity thus far. Here, we describe a novel resting-state network based on the delayed connectivity between the brain and the slow electrical rhythm (0.05 Hz) generated in the stomach. The gastric network cuts across classical resting-state networks with partial overlap with autonomic regulation areas. This network is composed of regions with convergent functional properties involved in mapping bodily space through touch, action or vision, as well as mapping external space in bodily coordinates. The network is characterized by a precise temporal sequence of activations within a gastric cycle, beginning with somato-motor cortices and ending with the extrastriate body area and dorsal precuneus. Our results demonstrate that canonical resting-state networks based on instantaneous connectivity represent only one of the possible partitions of the brain into coherent networks based on temporal dynamics.
Johannes Rennig; Michael S. Beauchamp
In: NeuroImage, vol. 183, pp. 25–36, 2018.
During face-to-face communication, the mouth of the talker is informative about speech content, while the eyes of the talker convey other information, such as gaze location. Viewers most often fixate either the mouth or the eyes of the talker's face, presumably allowing them to sample these different sources of information. To study the neural correlates of this process, healthy humans freely viewed talking faces while brain activity was measured with BOLD fMRI and eye movements were recorded with a video-based eye tracker. Post hoc trial sorting was used to divide the data into trials in which participants fixated the mouth of the talker and trials in which they fixated the eyes. Although the audiovisual stimulus was identical, the two trials types evoked differing responses in subregions of the posterior superior temporal sulcus (pSTS). The anterior pSTS preferred trials in which participants fixated the mouth of the talker while the posterior pSTS preferred fixations on the eye of the talker. A second fMRI experiment demonstrated that anterior pSTS responded more strongly to auditory and audiovisual speech than posterior pSTS eye-preferring regions. These results provide evidence for functional specialization within the pSTS under more realistic viewing and stimulus conditions than in previous neuroimaging studies.
Maya L. Rosen; Chantal E. Stern; Kathryn J. Devaney; David C. Somers
In: Cerebral Cortex, vol. 28, no. 8, pp. 2935–2947, 2018.
Long-term memory (LTM) helps to efficiently direct and deploy the scarce resources of the attentional system; however, the neural substrates that support LTM-guidance of visual attention are not well understood. Here, we present results from fMRI experiments that demonstrate that cortical and subcortical regions of a network defined by resting-state functional connectivity are selectively recruited for LTM-guided attention, relative to a similarly demanding stimulus-guided attention paradigm that lacks memory retrieval and relative to a memory retrieval paradigm that lacks covert deployment of attention. Memory-guided visuospatial attention recruited posterior callosal sulcus, posterior precuneus, and lateral intraparietal sulcus bilaterally. Additionally, 3 subcortical regions defined by intrinsic functional connectivity were recruited: the caudate head, mediodorsal thalamus, and cerebellar lobule VI/Crus I. Although the broad resting-state network to which these nodes belong has been referred to as a cognitive control network, the posterior cortical regions activated in the present study are not typically identified with supporting standard cognitive control tasks. We propose that these regions form a Memory-Attention Network that is recruited for processes that integrate mnemonic and stimulus-based representations to guide attention. These findings may have important implications for understanding the mechanisms by which memory retrieval influences attentional deployment.
Ricky R. Savjani; Sucharit Katyal; Elizabeth Halfen; Jung Hwan Kim; David Ress
In: NeuroImage, vol. 171, pp. 199–208, 2018.
The superior colliculus (SC) is a layered midbrain structure involved in directing both head and eye movements and coordinating visual attention. Although a retinotopic organization for the mediation of saccadic eye-movements has been shown in monkey SC, in human SC the topography of saccades has not been confirmed. Here, a novel experimental paradigm was performed by five participants (one female) while high-resolution (1.2-mm) functional magnetic resonance imaging was used to measure activity evoked by saccadic eye movements within human SC. Results provide three critical observations about the topography of the SC: (1) saccades along the superior-inferior visual axis are mapped across the medial-lateral anatomy of the SC; (2) the saccadic eye-movement representation is in register with the retinotopic organization of visual stimulation; and (3) activity evoked by saccades occurs deeper within SC than that evoked by visual stimulation. These approaches lay the foundation for studying the organization of human subcortical – and enhanced cortical mapping – of eye-movement mechanisms.
Max Schneider; Laura Leuchs; Michael Czisch; Philipp G. Sämann; Victor I. Spoormaker
In: NeuroImage, vol. 178, pp. 11–22, 2018.
The reward system may provide an interesting intermediate phenotype for anhedonia in affective disorders. Reward anticipation is characterized by an increase in arousal, and previous studies have linked the anterior cingulate cortex (ACC) to arousal responses such as dilation of the pupil. Here, we examined pupil dynamics during a reward anticipation task in forty-six healthy human subjects and evaluated its neural correlates using functional magnetic resonance imaging (fMRI). Pupil size showed a strong increase during monetary reward anticipation, a moderate increase during verbal reward anticipation and a decrease during control trials. For fMRI analyses, average pupil size and pupil change were computed in 1-s time bins during the anticipation phase. Activity in the ventral striatum was inversely related to the pupil size time course, indicating an early onset of activation and a role in reward prediction processing. Pupil dilations were linked to increased activity in the salience network (dorsal ACC and bilateral insula), which likely triggers an increase in arousal to enhance task performance. Finally, increased pupil size preceding the required motor response was associated with activity in the ventral attention network. In sum, pupillometry provides an effective tool for disentangling different phases of reward anticipation, with relevance for affective symptomatology.
Oleg Solopchuk; Moustapha Sebti; Céline Bouvy; Charles-Etienne Benoit; Thibault Warlop; Anne Jeanjean; Alexandre Zénon
In: Scientific Reports, vol. 8, pp. 12381, 2018.
Fatigue is a frequent complaint among healthy population and one of the earliest and most debilitating symptoms in Parkinson's disease (PD). Earlier studies have examined the role of dopamine and serotonin in pathogenesis of fatigue, but the plausible role of noradrenalin (NA) remains underexplored. We investigated the relationship between fatigue in Parkinsonian patients and the extent of degeneration of Locus Coeruleus (LC), the main source of NA in the brain. We quantified LC and Substantia Nigra (SN) atrophy using neuromelanin-sensitive imaging, analyzed with a novel, fully automated algorithm. We also assessed patients' fatigue, depression, sleep disturbance and vigilance. We found that LC degeneration correlated with the levels of depression and vigilance but not with fatigue, while fatigue correlated weakly with atrophy of SN. These results indicate that LC degeneration in Parkinson's disease is unlikely to cause fatigue, but may be involved in mood and vigilance alterations.
Chen Song; Geraint Rees
In: NeuroImage, vol. 175, pp. 80–90, 2018.
The integration of inputs across the entire visual field into a single conscious experience is fundamental to human visual perception. This integrated nature of visual experience is illustrated by contextual illusions such as the tilt illusion, in which the perceived orientation of a central grating appears tilted away from its physical orientation, due to the modulation by a surrounding grating with a different orientation. Here we investigated the relative contribution of local, intra-hemispheric and global, inter-hemispheric integration mechanisms to perception of the tilt illusion. We used Dynamic Causal Modelling of fMRI signals to estimate effective connectivity in human early visual cortices (V1, V2, V3) during bilateral presentation of a tilt illusion stimulus. Our analysis revealed that neural responses associated with the tilt illusion were modulated by intra- rather than inter-hemispheric connectivity. Crucially, across participants, intra-hemispheric connectivity in V1 correlated with the magnitude of the tilt illusion, while no such correlation was observed for V1 inter-hemispheric connectivity, or V2, V3 connectivity. Moreover, when the illusion stimulus was presented unilaterally rather than bilaterally, the illusion magnitude did not change. Together our findings suggest that perception of the tilt illusion reflects an intra-hemispheric integration mechanism. This is in contrast to the existing literature, which suggests inter-hemispheric modulation of neural activity as early as V1. This discrepancy with our findings may reflect the diversity and complexity of integration mechanisms involved in visual processing and visual perception.
Teresa Sousa; Alexandre Sayal; João V. Duarte; Gabriel N. Costa; Ricardo Martins; Miguel Castelo-Branco
In: NeuroImage, vol. 179, pp. 540–547, 2018.
Visual adaptation describes the processes by which the visual system alters its operating properties in response to changes in the environment. It is one of the mechanisms controlling visual perceptual bistability – when two perceptual solutions are available – by controlling the duration of each percept. Moving plaids are an example of such ambiguity. They can be perceived as two surfaces sliding incoherently over each other or as a single coherent surface. Here, we investigated, using fMRI, whether activity in the human motion complex (hMT+), a region tightly related to the perceptual integration of visual motion, is modulated by distinct forms of visual adaptation to coherent or incoherent perception of moving plaids. Our hypothesis is that exposure to global coherent or incoherent moving stimuli leads to different levels of measurable adaptation, reflected in hMT+ activity. We found that the strength of the measured visual adaptation effect depended on whether subjects integrated (coherent percept) or segregated (incoherent percept) surface motion signals. Visual motion adaptation was significant both for coherent motion and globally incoherent surface motion. Although not as strong as to the coherent percept, visual adaptation due to the incoherent percept also affects hMT+. This shows that adaptation can contribute to regulate percept duration during visual bistability, with distinct weights, depending on the type of percept. Our findings suggest a link between bistability and adaptation mechanisms, both due to coherent and incoherent motion percepts, but in an asymmetric manner. These asymmetric adaptation weights have strong implications in models of perceptual decision and may explain asymmetry of perceptual interpretation periods.
Maria Steffens; C. Neumann; Anna-Maria Kasparbauer; B. Becker; Bernd Weber; Mitul A. Mehta; R. Hurlemann; Ulrich Ettinger
Effects of ketamine on brain function during response inhibition Journal Article
In: Psychopharmacology, vol. 235, no. 12, pp. 3559–3571, 2018.
Introduction The uncompetitive N-methyl-D-aspartate (NMDA) receptor (NMDAR) antagonist ketamine has been proposed to model symptoms ofpsychosis. Inhibitory deficits in the schizophrenia spectrumhave been reliably reported using the antisaccade task. Interestingly, although similar antisaccade deficits have been reported following ketamine in non-human primates, ketamine-induced deficits have not been observed in healthy human volunteers. Methods To investigate the effects of ketamine on brain function during an antisaccade task, we conducted a double-blind, placebo-controlled, within-subjects study on n = 15 healthy males. We measured the blood oxygen level dependent (BOLD) response and eye movements during a mixed antisaccade/prosaccade task while participants received a subanesthetic dose of intravenous ketamine (target plasma level 100 ng/ml) on one occasion and placebo on the other occasion. Results While ketamine significantly increased self-ratings of psychosis-like experiences, it did not induce antisaccade or prosaccade performance deficits. At the level of BOLD, we observed an interaction between treatment and task condition in somatosensory cortex, suggesting recruitment of additional neural resources in the antisaccade condition under NMDAR blockage. Discussion Given the robust evidence ofantisaccade deficits in schizophrenia spectrum populations, the current findings suggest that ketamine may not mimic all features ofpsychosis at the dose used in this study. Our findings underline the importance of a more detailed research to further understand and define effects of NMDAR hypofunction on human brain function and behavior, with a view to applying ketamine administration as a model system of psychosis. Future studies with varying doses will be of importance in this context.
Daniel Marten Es; Jan Theeuwes; Tomas Knapen
In: eLife, vol. 7, pp. 1–28, 2018.
Spatial attention changes the sampling of visual space. Behavioral studies suggest that feature-based attention modulates this resampling to optimize the attended feature's sampling. We investigate this hypothesis by estimating spatial sampling in visual cortex while independently varying both feature-based and spatial attention. Our results show that spatial and feature-based attention interacted: resampling of visual space depended on both the attended location and feature (color vs. temporal frequency). This interaction occurred similarly throughout visual cortex, regardless of an area's overall feature preference. However, the interaction did depend on spatial sampling properties of voxels that prefer the attended feature. These findings are parsimoniously explained by variations in the precision of an attentional gain field. Our results demonstrate that the deployment of spatial attention is tailored to the spatial sampling properties of units that are sensitive to the attended feature.
Koen Lith; Dick Johan Veltman; Moran Daniel Cohn; Louise Else Pape; Marieke Eleonora Akker-Nijdam; Amanda Wilhelmina Geertruida Loon; Pierre Bet; Guido Alexander Wingen; Wim Brink; Theo Doreleijers; Arne Popma
In: Journal of the American Academy of Child and Adolescent Psychiatry, vol. 57, no. 12, pp. 934–943, 2018.
Objective: Although the neural underpinnings of antisocial behavior have been studied extensively, research on pharmacologic interventions targeting specific neural mechanisms remains sparse. Hypoactivity of the amygdala and ventromedial prefrontal cortex (vmPFC) has been reported in antisocial adolescents, which could account for deficits in fear learning (amygdala) and impairments in decision making (vmPFC), respectively. Limited clinical research suggests positive effects of methylphenidate, a dopamine agonist, on antisocial behavior in adolescents. Dopamine is a key neurotransmitter involved in amygdala and vmPFC functioning. The objective of this study was to investigate whether methylphenidate targets dysfunctions in these brain areas in adolescents with antisocial behavior. Method: A group of 42 clinical referred male adolescents (14–17 years old) with a disruptive behavior disorder performed a fear learning/reversal paradigm in a randomized double-blinded placebo-controlled pharmacologic functional magnetic resonance imaging study. Participants with disruptive behavior disorder were randomized to receive a single dose of methylphenidate 0.3 to 0.4 mg/kg (n = 22) or placebo (n = 20) and were compared with 21 matched healthy controls not receiving medication. Results: In a region-of-interest analysis of functional magnetic resonance imaging data during fear learning, the placebo group showed hyporeactivity of the amygdala compared with healthy controls, whereas amygdala reactivity was normalized in the methylphenidate group. There were no group differences in vmPFC reactivity during fear reversal learning. Whole-brain analyses showed no group differences. Conclusion: These findings suggest that methylphenidate is a promising pharmacologic intervention for youth antisocial behavior that could restore amygdala functioning.
Anouk Mariette Loon; Katya Olmos-Solis; Johannes J. Fahrenfort; Christian N. L. Olivers
In: eLife, vol. 7, pp. 1–25, 2018.
Adaptive behavior requires the separation of current from future goals in working memory. We used fMRI of object-selective cortex to determine the representational (dis)similarities of memory representations serving current and prospective perceptual tasks. Participants remembered an object drawn from three possible categories as the target for one of two consecutive visual search tasks. A cue indicated whether the target object should be looked for first (currently relevant), second (prospectively relevant), or if it could be forgotten (irrelevant). Prior to the first search, representations of current, prospective and irrelevant objects were similar, with strongest decoding for current representations compared to prospective (Experiment 1) and irrelevant (Experiment 2). Remarkably, during the first search, prospective representations could also be decoded, but revealed anti-correlated voxel patterns compared to currently relevant representations of the same category. We propose that the brain separates current from prospective memories within the same neuronal ensembles through opposite representational patterns.
Maryam Vaziri-Pashkam; JohnMark Taylor; Yaoda Xu
In: Journal of Cognitive Neuroscience, vol. 31, no. 1, pp. 49–63, 2018.
Primate ventral and dorsal visual pathways both contain visual object representations. Dorsal regions receive more input from magnocellular system while ventral regions receive inputs from both magnocellular and parvocellular systems. Due to potential differences in the spatial sensitivites of man- ocellular and parvocellular systems, object representations in ventral and dorsal regions may differ in how they represent visual input from different spatial scales. To test this prediction, we asked observers to view blocks of images from six object catego- ries, shown in full spectrum, high spatial frequency (SF), or low SF. We found robust object category decoding in all SF conditions as well as SF decoding in nearly all the early visual, ventral, and dorsal regions examined. Cross-SF decoding further revealed that object category representations in all regions exhibited sub- stantial tolerance across the SF components. No difference between ventral and dorsal regions was found in their preference for the different SF components. Further comparisons revealed that, whereas differences in the SF component separated object category representations in early visual areas, such a separation was much smaller in downstream ventral and dorsal regions. In those regions, variations among the object categories played a more significant role in shaping the visual representational structures. Our findings show that ventral and dorsal regions are sim- ilar in how they represent visual input from different spatial scales and argue against a dissociation of these regions based on differential sensitivity to different SFs.
Regine Zopf; Marina Butko; Alexandra Woolgar; Mark A. Williams; Anina N. Rich
In: Cortex, vol. 106, pp. 132–150, 2018.
When interacting with objects, we have to represent their location relative to our bodies. To facilitate bodily reactions, location may be encoded in the brain not just with respect to the retina (retinotopic reference frame), but also in relation to the head, trunk or arm (collectively spatiotopic reference frames). While spatiotopic reference frames for location encoding can be found in brain areas for action planning, such as parietal areas, there is debate about the existence of spatiotopic reference frames in higher-level occipitotemporal visual areas. In an extensive multi-voxel pattern analysis (MVPA) fMRI study using faces, headless bodies and scenes stimuli, Golomb and Kanwisher (2012) did not find evidence for spatiotopic reference frames in shape-selective occipitotemporal cortex. This finding is important for theories of how stimulus location is encoded in the brain. It is possible, however, that their failure to find spatiotopic reference frames is related to their stimuli: we typically do not manipulate faces, headless bodies or scenes. It is plausible that we only represent body-centred location when viewing objects that are typically manipulated. Here, we tested for object location encoding in shape-selective occipitotemporal cortex using manipulable object stimuli (balls and cups) in a MVPA fMRI study. We employed Bayesian analyses to determine sample size and evaluate the sensitivity of our data to test the hypothesis that location can be encoded in a spatiotopic reference frame in shape-selective occipitotemporal cortex over the null hypothesis of no spatiotopic location encoding. We found strong evidence for retinotopic location encoding consistent with previous findings that retinotopic reference frames are common neural representations of object location. In contrast, when testing for spatiotopic encoding, we found evidence that object location information for small manipulable objects is not decodable in relation to the body in shape-selective occipitotemporal cortex. Post-hoc exploratory analyses suggested that spatiotopic aspects might modulate retinotopic location encoding.
Iske Bakker-Marshall; Atsuko Takashima; Jan-Mathijs Schoffelen; Janet G. Hell; Gabriele Janzen; James M. McQueen
In: Journal of Cognitive Neuroscience, vol. 30, no. 5, pp. 621–633, 2018.
Like many other types of memory formation, novel word learning benefits from an offline consolidation period after the initial encoding phase. A previous EEG study has shown that retrieval of novel words elicited more word-like-induced electrophysiological brain activity in the theta band after consolidation [Bakker, I., Takashima, A., van Hell, J. G., Janzen, G., & McQueen, J. M. Changes in theta and beta oscillations as signatures of novel word consolidation. Journal of Cognitive Neuroscience, 27, 1286–1297, 2015]. This suggests that theta-band oscillations play a role in lexicalization, but it has not been demonstrated that this effect is directly caused by the formation of lexical representations. This study used magnetoencephalography to localize the theta consolidation effect to the left posterior middle temporal gyrus (pMTG), a region known to be involved in lexical storage. Both untrained novel words and words learned immediately before test elicited lower theta power during retrieval than existing words in this region. After a 24-hr consolidation period, the difference between novel and existing words decreased significantly, most strongly in the left pMTG. The magnitude of the decrease after consolidation correlated with an increase in behavioral competition effects between novel words and existing words with similar spelling, reflecting functional integration into the mental lexicon. These results thus provide new evidence that consolidation aids the development of lexical representations mediated by the left pMTG. Theta synchronizationmay enable lexical access by facilitating the simultaneous activation of distributed semantic, phonological, and orthographic representations that are bound together in the pMTG.
Eran Eldar; Gyung Jin Bae; Zeb Kurth-Nelson; Peter Dayan; Raymond J. Dolan
In: Nature Human Behaviour, vol. 2, no. 9, pp. 670–681, 2018.
When confronted with complex inputs consisting of multiple elements, humans use various strategies to integrate the elements quickly and accurately. For instance, accuracy may or over be improved by processing elements one at a time1–4 extended periods5–8 ; speed can increase if the internal rep- resentation of elements is accelerated9,10 . However, little is known about how humans actually approach these challenges because behavioural findings can be accounted for by mul- tiple alternative process models11 and neuroimaging investi-gations typically rely on haemodynamic signals that change too slowly. Consequently, to uncover the fast neural dynamics that support information integration, we decoded magnetoencephalographic signals that were recorded as human subjects performed a complex decision task. Our findings reveal three sources of individual differences in the temporal structure of the integration process—sequential representation, partial reinstatement and early computation—each having a dissociable effect on how subjects handled problem complexity and temporal constraints. Our findings shed new light on the structure and influence of self-determined neural integration processes.
Wei He; Blake W. Johnson
In: Developmental Cognitive Neuroscience, vol. 30, pp. 13–22, 2018.
Electrophysiological studies of adults indicate that brain activity is enhanced during viewing of repeated faces, at a latency of about 250 ms after the onset of the face (M250/N250). The present study aimed to determine if this effect was also present in preschool-aged children, whose brain activity was measured in a custom-sized pediatric MEG system. The results showed that, unlike adults, face repetition did not show any significant modulation of M250 amplitude in children; however children's M250 latencies were significantly faster for repeated than non-repeated faces. Dynamic causal modelling (DCM) of the M250 in both age groups tested the effects of face repetition within the core face network including the occipital face area (OFA), the fusiform face area (FFA), and the superior temporal sulcus (STS). DCM revealed that repetition of identical faces altered both forward and backward connections in children and adults; however the modulations involved inputs to both FFA and OFA in adults but only to OFA in children. These findings suggest that the amplitude-insensitivity of the immature M250 may be due to a weaker connection between the FFA and lower visual areas.
Simone G. Heideman; Gustavo Rohenkohl; Joshua J. Chauvin; Clare E. Palmer; Freek Ede; Anna C. Nobre
In: NeuroImage, vol. 178, pp. 46–56, 2018.
Spatial and temporal expectations act synergistically to facilitate visual perception. In the current study, we sought to investigate the anticipatory oscillatory markers of combined spatial-temporal orienting and to test whether these decline with ageing. We examined anticipatory neural dynamics associated with joint spatial-temporal orienting of attention using magnetoencephalography (MEG) in both younger and older adults. Participants performed a cued covert spatial-temporal orienting task requiring the discrimination of a visual target. Cues indicated both where and when targets would appear. In both age groups, valid spatial-temporal cues significantly enhanced perceptual sensitivity and reduced reaction times. In the MEG data, the main effect of spatial orienting was the lateralised anticipatory modulation of posterior alpha and beta oscillations. In contrast to previous reports, this modulation was not attenuated in older adults; instead it was even more pronounced. The main effect of temporal orienting was a bilateral suppression of posterior alpha and beta oscillations. This effect was restricted to younger adults. Our results also revealed a striking interaction between anticipatory spatial and temporal orienting in the gamma-band (60–75 Hz). When considering both age groups separately, this effect was only clearly evident and only survived statistical evaluation in the older adults. Together, these observations provide several new insights into the neural dynamics supporting separate as well as combined effects of spatial and temporal orienting of attention, and suggest that different neural dynamics associated with attentional orienting appear differentially sensitive to ageing.
Simone G. Heideman; Freek Ede; Anna C. Nobre
In: European Journal of Neuroscience, vol. 48, no. 8, pp. 2684–2695, 2018.
Performance improves when participants respond to events that are structured in repeating sequences, suggesting that learning can lead to proactive anticipatory preparation. Whereas most sequence-learning studies have emphasised spatial structure, most sequences also contain a prominent temporal structure. We used MEG to investigate spatial and temporal anticipatory neural dynamics in a modified serial reaction time (SRT) task. Performance and brain activity were compared between blocks with learned spatial-temporal sequences and blocks with new sequences. After confirming a strong behavioural benefit of spatial-temporal predictability, we show lateralisation of beta oscillations in anticipation of the response associated with the upcoming target location and show that this also aligns to the expected timing of these forthcoming events. This effect was found both when comparing between repeated (learned) and new (unlearned) sequences, as well as when comparing targets that were expected after short vs. long intervals within the repeated (learned) sequence. Our findings suggest that learning of spatial-temporal structure leads to proactive and dynamic modulation of motor cortical excitability in anticipation of both the location and timing of events that are relevant to guide action.
Simone G. Heideman; Freek Ede; Anna C. Nobre
In: Neuroscience, vol. 389, pp. 74–84, 2018.
In daily life, temporal expectations may derive from incidental learning of recurring patterns of intervals. We investigated the incidental acquisition and utilisation of combined temporal-ordinal (spatial/effector) structure in complex visual-motor sequences using a modified version of a serial reaction time (SRT) task. In this task, not only the series of targets/responses, but also the series of intervals between subsequent targets was repeated across multiple presentations of the same sequence. Each participant completed three sessions. In the first session, only the repeating sequence was presented. During the second and third session, occasional probe blocks were presented, where a new (unlearned) spatial-temporal sequence was introduced. We first confirm that participants not only got faster over time, but that they were slower and less accurate during probe blocks, indicating that they incidentally learned the sequence structure. Having established a robust behavioural benefit induced by the repeating spatial-temporal sequence, we next addressed our central hypothesis that implicit temporal orienting (evoked by the learned temporal structure) would have the largest influence on performance for targets following short (as opposed to longer) intervals between temporally structured sequence elements, paralleling classical observations in tasks using explicit temporal cues. We found that indeed, reaction time differences between new and repeated sequences were largest for the short interval, compared to the medium and long intervals, and that this was the case, even when comparing late blocks (where the repeated sequence had been incidentally learned), to early blocks (where this sequence was still unfamiliar). We conclude that incidentally acquired temporal expectations that follow a sequential structure can have a robust facilitatory influence on visually-guided behavioural responses and that, like more explicit forms of temporal orienting, this effect is most pronounced for sequence elements that are expected at short inter-element intervals.
Carina Kelbsch; Archana Jalligampala; Torsten Strasser; Paul Richter; Katarina Stingl; Christoph Braun; Daniel L. Rathbun; Eberhart Zrenner; Helmut Wilhelm; Barbara Wilhelm; Tobias Peters; Krunoslav Stingl
In: Experimental Eye Research, vol. 176, pp. 210–218, 2018.
The purpose was to evaluate retinal function by measuring pupillary responses to sinusoidal transcorneal electrostimulation in healthy young human subjects. This work also translates data from analogous in vitro experiments and connects it to the pupillary responses obtained in human experiments. 14 healthy human subjects participated (4 males, 10 females); for the in vitro experiments, two male healthy mouse retinas (adult wild-type C57B/6J) were used. Pupillary responses to sinusoidal transcorneal electrostimulation of varying stimulus carrier frequencies (10, 20 Hz; envelope frequency constantly kept at 1.2 Hz) and intensities (10, 20, 50 $mu$A) were recorded and compared with those obtained with light stimulation (1.2 Hz sinusoidal blue, red light). A strong correlation between the sinusoidal stimulation (electrical as well as light) and the pupillary sinusoidal response was found. The difference between the lag of electrical and light stimulation allowed the estimation of an intensity threshold for pupillary responses to transcorneal electrostimulation (mean ± SD: 30 ± 10 $mu$A (10 Hz); 38 ± 10 $mu$A (20 Hz)). A comparison between the results of the two stimulation frequencies showed a not statistically significant smaller lag for 10 Hz (10 Hz: 633 ± 90 ms; 20 Hz: 725 ± 178 ms; 50 $mu$A intensity). Analogous in vitro experiments on murine retinas indicated a selective stimulation of photoreceptors and bipolar cells (lower frequencies) and retinal ganglion cells (higher frequencies) and lower stimulation thresholds for the retinal network with sinusoidal compared to pulsatile stimulation – emphasizing that sinu- soidal waveforms are well-suited to our purposes. We demonstrate that pupillary responses to sinusoidal transcorneal electrostimulation are measurable as an objective marker in healthy young subjects, even at very low stimulus intensities. By using this unique approach, we unveil the potential for an estimation of the in- dividual intensity threshold and a selective activation of different retinal cell types in humans by varying the stimulation frequency. This technique may have broad clinical utility as well as specific relevance in the monitoring of patients with hereditary retinal disorders, especially as implemented in study protocols for novel therapies, e.g. retinal prostheses or gene therapies.
Eline R. Kupers; Helena X. Wang; Kaoru Amano; Kendrick N. Kay; David J. Heeger; Jonathan Winawer
In: PLoS ONE, vol. 13, no. 3, pp. e0193107, 2018.
Currently, non-invasive methods for studying the human brain do not routinely and reliably measure spike-rate-dependent signals, independent of responses such as hemodynamic coupling (fMRI) and subthreshold neuronal synchrony (oscillations and event-related potentials). In contrast, invasive methods-microelectrode recordings and electrocorticography (ECoG)-have recently measured broadband power elevation in field potentials ($sim$50-200 Hz) as a proxy for locally averaged spike rates. Here, we sought to detect and quantify stimulus-related broadband responses using magnetoencephalography (MEG). Extracranial measurements like MEG and EEG have multiple global noise sources and relatively low signal-to-noise ratios; moreover high frequency artifacts from eye movements can be confounded with stimulus design and mistaken for signals originating from brain activity. For these reasons, we developed an automated denoising technique that helps reveal the broadband signal of interest. Subjects viewed 12-Hz contrast-reversing patterns in the left, right, or bilateral visual field. Sensor time series were separated into evoked (12-Hz amplitude) and broadband components (60-150 Hz). In all subjects, denoised broadband responses were reliably measured in sensors over occipital cortex, even in trials without microsaccades. The broadband pattern was stimulus-dependent, with greater power contralateral to the stimulus. Because we obtain reliable broadband estimates with short experiments ($sim$20 minutes), and with sufficient signal-to-noise to distinguish responses to different stimuli, we conclude that MEG broadband signals, denoised with our method, offer a practical, non-invasive means for characterizing spike-rate-dependent neural activity for addressing scientific questions about human brain function.
Mariya E. Manahova; Pim Mostert; Peter Kok; Jan-Mathijs Schoffelen; Floris P. Lange
In: Journal of Cognitive Neuroscience, vol. 30, no. 9, pp. 1366–1377, 2018.
Prior knowledge about the visual world can change how a visual stimulus is processed. Two forms of prior knowledge are often distinguished: stimulus familiarity (i.e., whether a stimulus has been seen before) and stimulus expectation (i.e., whether a stimulus is expected to occur, based on the context). Neurophysiological studies in monkeys have shown suppression of spiking activity both for expected and for familiar items in object-selective inferotemporal cortex. It is an open question, however, if and how these types of knowledge interact in their modulatory effects on the sensory response. To address this issue and to examine whether previous findings generalize to noninvasively measured neural activity in humans, we separately manipulated stimulus familiarity and expectation while noninvasively recording human brain activity using magnetoencephalography. We observed independent suppression of neural activity by familiarity and expectation, specifically in the lateral occipital complex, the putative human homologue of monkey inferotemporal cortex. Familiarity also led to sharpened response dynamics, which was predominantly observed in early visual cortex. Together, these results show that distinct types of sensory knowledge jointly determine the amount of neural resources dedicated to object processing in the visual ventral stream.
Pim Mostert; Anke Marit Albers; Loek Brinkman; Larisa Todorova; Peter Kok; Floris P. Lange
In: eNeuro, vol. 5, no. 4, pp. 1–14, 2018.
A relatively new analysis technique, known as neural decoding or multivariate pattern analysis (MVPA), has become increasingly popular for cognitive neuroimaging studies over recent years. These techniques promise to uncover the representational contents of neural signals, as well as the underlying code and the dynamic profile thereof. A field in which these techniques have led to novel insights in particular is that of visual working memory (VWM). In the present study, we subjected human volunteers to a combined VWM/imagery task while recording their neural signals using magnetoencephalography (MEG). We applied multivariate decoding analyses to uncover the temporal profile underlying the neural representations of the memorized item. Analysis of gaze position however revealed that our results were contaminated by systematic eye movements, suggesting that the MEG decoding results from our originally planned analyses were confounded. In addition to the eye movement analyses, we also present the original analyses to highlight how these might have readily led to invalid conclusions. Finally, we demonstrate a potential remedy, whereby we train the decoders on a functional localizer that was specifically designed to target bottom-up sensory signals and as such avoids eye movements. We conclude by arguing for more awareness of the potentially pervasive and ubiquitous effects of eye movement-related confounds.
Pim Mostert; Sander Bosch; Nadine Dijkstra; Marcel A. J. Gerven; Floris P. Lange
In: eLife, vol. 7, pp. 1–16, 2018.
Visual perception and imagery rely on similar representations in the visual cortex. During perception, visual activity is characterized by distinct processing stages, but the temporal dynamics underlying imagery remain unclear. Here, we investigated the dynamics of visual imagery in human participants using magnetoencephalography. Firstly, we show that, compared to perception, imagery decoding becomes significant later and representations at the start of imagery already overlap with later time points. This suggests that during imagery, the entire visual representation is activated at once or that there are large differences in the timing of imagery between trials. Secondly, we found consistent overlap between imagery and perceptual processing around 160 ms and from 300 ms after stimulus onset. This indicates that the N170 gets reactivated during imagery and that imagery does not rely on early perceptual representations. Together, these results provide important insights for our understanding of the neural mechanisms of visual imagery.
Elena V. Orekhova; Olga V. Sysoeva; Justin F. Schneiderman; Sebastian Lundström; Ilia A. Galuta; Dzerasa E. Goiaeva; Andrey O. Prokofyev; Bushra Riaz; Courtney Keeler; Nouchine Hadjikhani; Christopher Gillberg; Tatiana A. Stroganova
In: Scientific Reports, vol. 8, pp. 8451, 2018.
Gamma-band oscillations arise from the interplay between neural excitation (E) and inhibition (I) and may provide a non-invasive window into the state of cortical circuitry. A bell-shaped modulation of gamma response power by increasing the intensity of sensory input was observed in animals and is thought to reflect neural gain control. Here we sought to find a similar input-output relationship in humans with MEG via modulating the intensity of a visual stimulation by changing the velocity/ temporal-frequency of visual motion. In the first experiment, adult participants observed static and moving gratings. The frequency of the MEG gamma response monotonically increased with motion velocity whereas power followed a bell-shape. In the second experiment, on a large group of children and adults, we found that despite drastic developmental changes in frequency and power of gamma oscillations, the relative suppression at high motion velocities was scaled to the same range of values across the life-span. In light of animal and modeling studies, the modulation of gamma power and frequency at high stimulation intensities characterizes the capacity of inhibitory neurons to counterbalance increasing excitation in visual networks. Gamma suppression may thus provide a non- invasive measure of inhibitory-based gain control in the healthy and diseased brain.
Hyojin Park; Robin A. A. Ince; Philippe G. Schyns; Gregor Thut; Joachim Gross
In: PLoS Biology, vol. 16, no. 8, pp. e2006558, 2018.
Integration of multimodal sensory information is fundamental to many aspects of human behavior, but the neural mechanisms underlying these processes remain mysterious. For example, during face-to-face communication, we know that the brain integrates dynamic auditory and visual inputs, but we do not yet understand where and how such integration mechanisms support speech comprehension. Here, we quantify representational interactions between dynamic audio and visual speech signals and show that different brain regions exhibit different types of representational interaction. With a novel information theoretic measure, we found that theta (3-7 Hz) oscillations in the posterior superior temporal gyrus/sulcus (pSTG/S) represent auditory and visual inputs redundantly (i.e., represent common features of the two), whereas the same oscillations in left motor and inferior temporal cortex represent the inputs synergistically (i.e., the instantaneous relationship between audio and visual inputs is also represented). Importantly, redundant coding in the left pSTG/S and synergistic coding in the left motor cortex predict behavior-i.e., speech comprehension performance. Our findings therefore demonstrate that processes classically described as integration can have different statistical properties and may reflect distinct mechanisms that occur in different brain regions to support audiovisual speech comprehension.
Thomas Pfeffer; Arthur Ervin Avramiea; Guido Nolte; Andreas K. Engel; Klaus Linkenkaer-Hansen; Tobias H. Donner
In: PLoS Biology, vol. 16, no. 2, pp. e2003453, 2018.
The ascending modulatory systems of the brain stem are powerful regulators of global brain state. Disturbances of these systems are implicated in several major neuropsychiatric disorders. Yet, how these systems interact with specific neural computations in the cerebral cortex to shape perception, cognition, and behavior remains poorly understood. Here, we probed into the effect of two such systems, the catecholaminergic (dopaminergic and noradrenergic) and cholinergic systems, on an important aspect of cortical computation: its intrinsic variability. To this end, we combined placebo-controlled pharmacological intervention in humans, recordings of cortical population activity using magnetoencephalography (MEG), and psychophysical measurements of the perception of ambiguous visual input. A low-dose catecholaminergic, but not cholinergic, manipulation altered the rate of spontaneous perceptual fluctuations as well as the temporal structure of “scale-free” population activity of large swaths of the visual and parietal cortices. Computational analyses indicate that both effects were consistent with an increase in excitatory relative to inhibitory activity in the cortical areas underlying visual perceptual inference. We propose that catecholamines regulate the variability of perception and cognition through dynamically changing the cortical excitation–inhibition ratio. The combined readout of fluctuations in perception and cortical activity we established here may prove useful as an efficient and easily accessible marker of altered cortical computation in neuropsychiatric disorders.
K. Seeliger; Matthias Fritsche; U. Güçlü; S. Schoenmakers; J. M. Schoffelen; S. E. Bosch; Marcel A. J. Gerven
In: NeuroImage, vol. 180, pp. 253–266, 2018.
Representations learned by deep convolutional neural networks (CNNs) for object recognition are a widely investigated model of the processing hierarchy in the human visual system. Using functional magnetic resonance imaging, CNN representations of visual stimuli have previously been shown to correspond to processing stages in the ventral and dorsal streams of the visual system. Whether this correspondence between models and brain signals also holds for activity acquired at high temporal resolution has been explored less exhaustively. Here, we addressed this question by combining CNN-based encoding models with magnetoencephalography (MEG). Human participants passively viewed 1,000 images of objects while MEG signals were acquired. We modelled their high temporal resolution source-reconstructed cortical activity with CNNs, and observed a feed-forward sweep across the visual hierarchy between 75 and 200 ms after stimulus onset. This spatiotemporal cascade was captured by the network layer representations, where the increasingly abstract stimulus representation in the hierarchical network model was reflected in different parts of the visual cortex, following the visual ventral stream. We further validated the accuracy of our encoding model by decoding stimulus identity in a left-out validation set of viewed objects, achieving state-of-the-art decoding accuracy.