EyeLink Clinical and Oculomotor Eye-Tracking Publications
EyeLink clinical and oculomotor research publications up until 2023 (with some early 2024s) are listed below by year. You can search the publications using keywords such as Saccadic Adaptation, Schizophrenia, Nystagmus, etc. You can also search for individual author names, and limit searches by year (choose the year then click the search button). If we missed any EyeLink clinical or oculomotor articles, please email us!
2017 |
Laura Vilkaitė; Norbert Schmitt Reading collocations in an L2: Do collocation processing benefits extend to non-adjacent collocations? Journal Article In: Applied Linguistics, no. 2013, pp. 1–27, 2017. @article{Vilkaite2017, Various studies have consistently shown that collocations are processed faster than matched control phrases, both in L1 and in L2. Most of these studies focused on adjacent collocations (e.g. provide information). However, research in corpus linguistics normally uses a span to identify collocations (e.g. plus or minus four words), and these non-adjacent collocations (e.g. provide some of the information) occur very frequently in language. Nevertheless, how they are processed is less established. A recent study on reading non-adjacent collocations seems to suggest similar processing advantages as for adjacent collocations (Vilkaite 2016), but this study was limited to the performance of native speakers (NSs). The present study addresses the question of whether advanced non-native speakers (NNSs) also show processing advantages for non-adjacent collocations as NSs do. Forty advanced NNSs of English read collocations in either adjacent or non-adjacent conditions, and their eye movements were recorded. Mixed-effects analysis of their eye movements was carried out. The results suggest that NNSs read adjacent collocations faster than non-formulaic controls, but this facilitation almost disappears for non-adjacent collocations. |
Xin Wang; Juan Wang; Jeffrey G. Malins In: Cognition, vol. 169, pp. 15–24, 2017. @article{Wang2017b, Although lexical tone is a highly prevalent phonetic cue in human languages, its role in bilingual spoken word recognition is not well understood. The present study investigates whether and how adult bilinguals, who use pitch contours to disambiguate lexical items in one language but not the other, access a tonal L1 when exclusively processing a non-tonal L2. Using the visual world paradigm, we show that Mandarin-English listeners automatically activated Mandarin translation equivalents of English target words such as ‘rain' (Mandarin ‘yu3'), and consequently were distracted by competitors whose segments and tones overlapped with the translations of English target words (‘feather', also ‘yu3' in Mandarin). Importantly, listeners were not distracted by competitors that overlapped with the translations of target words in all segments but not tone (‘fish'; Mandarin ‘yu2'), nor were they distracted by competitors that overlapped with the translations of target words in rime and tone (‘wheat', Mandarin ‘gu3'). These novel results demonstrate implicit access to L1 lexical representations through automatic/unconscious translation, as a result of cross-language top-down and/or lateral influence, and highlight the critical role of lexical tone activation in bilingual lexical access. |
Sarah J. White; Laura M. T. Lantz; Kevin B. Paterson Spontaneous rereading within sentences: Eye movement control and visual sampling Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 43, no. 2, pp. 395–413, 2017. @article{White2017, Three experiments examine the role of previously read text in sentence comprehension and the control of eye movements during spontaneous rereading. Spontaneous rereading begins with a regressive saccade and involves reinspection of previously read text. All 3 experiments employed the gaze-contingent change technique to modulate the availability of previously read text. In Experiment 1, previously read text was permanently masked either immediately to the left of the fixated word (beyond wordn) or more than 1 word to the left (beyond wordn-1). The results of Experiment 1 indicate that the availability of the word immediately to the left (wordn-1) is important for comprehension. Experiments 2 and 3 further explored the role of previously read text beyond wordn-1. In these studies, text beyond wordn-1 was replaced, retaining only word length information, or word length and shape information. Following a regression back within a sentence, meaningful text either reappeared or remained unavailable during rereading. The experiments show that the visual format of text beyond wordn-1 (the parafoveal postview) is important for triggering regressions. The results also indicate that, as least for more complex sentences, the availability of meaningful text is important in driving eye movement control during rereading. |
Veronica Whitford; Debra Titone The effects of word frequency and word predictability during first- and second-language paragraph reading in bilingual older and younger adults Journal Article In: Psychology and Aging, vol. 32, no. 2, pp. 158–177, 2017. @article{Whitford2017, We used eye movement measures of paragraph reading; varying in amount of current L2 experience. Our ke; across both early- and late-stage reading; word frequency effects were generally larger in ol; whereas word predictability effects were generally; across both age groups and both reading stages; word frequency effects were larger in the L2 than ; whereas word predictability effects were language-; graded differences in current L2 experience modula; but had no impact in older adults. Specifically; greater current L2 experience facilitated L2 word ; but impeded L1 word processing among younger adult; we draw 2 main conclusions. First; bilingual older adults experience changes in word-; potentially because lexical accessibility decrease; bilingual older adults experience changes in word-; potentially because lexical representations reach a functional ceiling over time. |
Douglas A. Ruff; Marlene R. Cohen A normalization model suggests that attention changes the weighting of inputs between visual areas Journal Article In: Proceedings of the National Academy of Sciences, vol. 114, no. 20, pp. E4085–E4094, 2017. @article{Ruff2017, Models of divisive normalization can explain the trial-averaged responses of neurons in sensory, association, and motor areas under a wide range of conditions, including how visual attention changes the gains of neurons in visual cortex. Attention, like other modulatory processes, is also associated with changes in the extent to which pairs of neurons share trial-to-trial variability. We showed recently that in addition to decreasing correlations between similarly tuned neurons within the same visual area, attention increases correlations between neurons in primary visual cortex (V1) and the middle temporal area (MT) and that an extension of a classic normalization model can account for this correlation increase. One of the benefits of having a descriptive model that can account for many physiological observations is that it can be used to probe the mechanisms underlying processes such as attention. Here, we use electrical microstimulation in V1 paired with recording in MT to provide causal evidence that the relationship between V1 and MT activity is nonlinear and is well described by divisive normalization. We then use the normalization model and recording and microstimulation experiments to show that the attention dependence of V1-MT correlations is better explained by a mechanism in which attention changes the weights of connections between V1 and MT than by a mechanism that modulates responses in either area. Our study shows that normalization can explain interactions between neurons in different areas and provides a framework for using multiarea recording and stimulation to probe the neural mechanisms underlying neuronal computations. |
Aldo Rustichini; Katherine E. Conen; Xinying Cai; Camillo Padoa-Schioppa Optimal coding and neuronal adaptation in economic decisions Journal Article In: Nature Communications, vol. 8, pp. 1208, 2017. @article{Rustichini2017, During economic decisions, offer value cells in orbitofrontal cortex (OFC) encode the values of offered goods. Furthermore, their tuning functions adapt to the range of values available in any given context. A fundamental and open question is whether range adaptation is behaviorally advantageous. Here we present a theory of optimal coding for economic decisions. We propose that the representation of offer values is optimal if it ensures maximal expected payoff. In this framework, we examine offer value cells in non-human primates. We show that their responses are quasi-linear even when optimal tuning functions are highly non-linear. Most importantly, we demonstrate that for linear tuning functions range adaptation maximizes the expected payoff. Thus value coding in OFC is functionally rigid (linear tuning) but parametrically plastic (range adaptation with optimal gain). Importantly, the benefit of range adaptation outweighs the cost of functional rigidity. While generally suboptimal, linear tuning may facilitate transitive choices. |
Philipp Schwedhelm; Daniel Baldauf; Stefan Treue Electrical stimulation of macaque lateral prefrontal cortex modulates oculomotor behavior indicative of a disruption of top-down attention Journal Article In: Scientific Reports, vol. 7, pp. 17715, 2017. @article{Schwedhelm2017, The lateral prefrontal cortex (lPFC) of primates is hypothesized to be heavily involved in decision-making and selective visual attention. Recent neurophysiological evidence suggests that information necessary for an orchestration of those high-level cognitive factors are indeed represented in the lPFC. However, we know little about the specific contribution of sub-networks within lPFC to the deployment of top-down influences that can be measured in extrastriate visual cortex. Here, we systematically applied electrical stimulations to areas 8Av and 45 of two macaque monkeys performing a concurrent goal-directed saccade task. Despite using currents well above saccadic thresholds of the directly adjacent Frontal Eye Fields (FEF), saccades were only rarely evoked by the stimulation. Instead, two types of behavioral effects were observed: Stimulations of caudal sites in 8Av (close to FEF) shortened or prolonged saccadic reaction times, depending on the task-instructed saccade, while rostral stimulations of 8Av/45 seem to affect the relative attentional weighting of saccade targets as well as saccadic reaction times. These results illuminate important differences in the causal involvement of different sub-networks within the lPFC and are most compatible with a stimulation-induced biasing of stimulus processing that accelerates the detection of saccade targets presented ipsilateral to stimulation through a disruption of contralaterally deployed top-down attention. |
Lenka Seillier; Corinna Lorenz; Katsuhisa Kawaguchi; Torben Ott; Andreas Nieder; Paria Pourriahi; Hendrikje Nienborg Serotonin decreases the gain of visual responses in awake macaque V1 Journal Article In: Journal of Neuroscience, vol. 37, no. 47, pp. 11390 –11405 Systems/Circuits, 2017. @article{Seillier2017, Serotonin, an important neuromodulator in the brain, is implicated in affective and cognitive functions. However, its role even for basic cortical processes is controversial. For example, in the mammalian primary visual cortex (V1), heterogenous serotonergic modulation has been observed in anesthetized animals. Here, we combined extracellular single-unit recordings with iontophoresis in awake animals. We examined the role of serotonin on well-defined tuning properties (orientation, spatial frequency, contrast, and size) in V1 of two male macaque monkeys. We find that in the awake macaque the modulatory effect of serotonin is surprisingly uniform: it causes a mainly multiplicative decrease of the visual responses and a slight increase in the stimulus-selective response latency. Moreover, serotonin neither systematically changes the selectivity or variability of the response, nor the interneuronal correlation unexplained by the stimulus ("noise-correlation"). The modulation by serotonin has qualitative similarities with that for a decrease in stimulus contrast, but differs quantitatively from decreasing contrast. It can be captured by a simple additive change to a threshold-linear spiking nonlinearity. Together, our results show that serotonin is well suited to control the response gain of neurons in V1 depending on the animal's behavioral or motivational context, complementing other known state-dependent gain-control mechanisms. |
Brianna J. Sleezer; Giuliana A. LoConte; Meghan D. Castagno; Benjamin Y. Hayden Neuronal responses support a role for orbitofrontal cortex in cognitive set reconfiguration Journal Article In: European Journal of Neuroscience, vol. 45, pp. 940–951, 2017. @article{Sleezer2017, We are often faced with the need to abandon no-longer beneficial rules and adopt new ones. This process, known as cognitive set reconfiguration, is a hallmark of executive control. Although cognitive functions like reconfiguration are most often associated with dorsal prefrontal structures, recent evidence suggests that the orbitofrontal cortex (OFC) may play an important role as well. We recorded the activity of OFC neurons while rhesus macaques performed an analogue of the Wisconsin Card Sorting Task that involved a trial and error stage. The OFC neurons demonstrated two types of switch-related activity, an early (switch-away) signal and a late (switch-to) signal, when the new task set was established. We also found a pattern of match modulation: a sig- nificant change in activity for the stimulus that matched the current perceptual rule (and would therefore be selected). These results extend our understanding of the executive functions of the OFC. They also allow us to directly compare the OFC with the complementary datasets we previously collected in the ventral (VS) and dorsal (DS) striatum. Although both effects are observed in all three areas, the timing of responses aligns the OFC more closely with DS than with VS. |
Courtney Turrin; Nicholas A. Fagan; Olga Dal Monte; Steve W. C. Chang Social resource foraging is guided by the principles of the Marginal Value Theorem Journal Article In: Scientific Reports, vol. 7, pp. 11274, 2017. @article{Turrin2017, Optimality principles guide how animals adapt to changing environments. During foraging for nonsocial resources such as food and water, species across taxa obey a strategy that maximizes resource harvest rate. However, it remains unknown whether foraging for social resources also obeys such a strategic principle. We investigated how primates forage for social information conveyed by conspecific facial expressions using the framework of optimal foraging theory. We found that the canonical principle of Marginal Value Theorem (MVT) also applies to social resources. Consistent with MVT, rhesus macaques (Macaca mulatta) spent more time foraging for social information when alternative sources of information were farther away compared to when they were closer by. A comparison of four models of patch-leaving behavior confirmed that the MVT framework provided the best fit to the observed foraging behavior. This analysis further demonstrated that patch-leaving decisions were not driven simply by the declining value of the images in the patch, but instead were dependent upon both the instantaneous social value intake rate and current time in the patch. |
Bram-Ernst Verhoef; John H. R. Maunsell Attention-related changes in correlated neuronal activity arise from normalization mechanisms Journal Article In: Nature Neuroscience, vol. 20, no. 7, pp. 969–977, 2017. @article{Verhoef2017, Attention is believed to enhance perception by altering the activity-level correlations between pairs of neurons. How attention changes neuronal activity correlations is unknown. Using multielectrodes in monkey visual cortex, we measured spike-count correlations when single or multiple stimuli were presented and when stimuli were attended or unattended. When stimuli were unattended, adding a suppressive, nonpreferred stimulus beside a preferred stimulus increased spike-count correlations between pairs of similarly tuned neurons but decreased spike-count correlations between pairs of oppositely tuned neurons. A stochastic normalization model containing populations of oppositely tuned, mutually suppressive neurons explains these changes and also explains why attention decreased or increased correlations: as an indirect consequence of attention-related changes in the inputs to normalization mechanisms. Our findings link normalization mechanisms to correlated neuronal activity and attention, showing that normalization mechanisms shape response correlations and that these correlations change when attention biases normalization mechanisms. |
Maya Zhe Wang; Benjamin Y. Hayden Reactivation of associative structure specific outcome responses during prospective evaluation in reward-based choices Journal Article In: Nature communications, vol. 8, pp. 15821, 2017. @article{Wang2017e, Before making a reward-based choice, we must evaluate each option. Some theories propose that prospective evaluation involves a reactivation of the neural response to the outcome. Others propose that it calls upon a response pattern that is specific to each underlying associative structure. We hypothesize that these views are reconcilable: during prospective evaluation, offers reactivate neural responses to outcomes that are unique to each associative structure; when the outcome occurs, this pattern is activated, simultaneously, with a general response to the reward. We recorded single-units from macaque orbitofrontal cortex (Area 13) in a riskless choice task with interleaved described and experienced offer trials. Here we report that neural activations to offers and their outcomes overlap, as do neural activations to the outcomes on the two trial types. Neural activations to experienced and described offers are unrelated even though they predict the same outcomes. Our reactivation theory parsimoniously explains these results. |
Brian J. White; David J. Berg; Janis Y. Y. Kan; Robert A. Marino; Laurent Itti; Douglas P. Munoz Superior colliculus neurons encode a visual saliency map during free viewing of natural dynamic video Journal Article In: Nature Communications, vol. 8, pp. 14263, 2017. @article{White2017b, Models of visual attention postulate the existence of a saliency map whose function is to guide attention and gaze to the most conspicuous regions in a visual scene. Although cortical representations of saliency have been reported, there is mounting evidence for a subcortical saliency mechanism, which pre-dates the evolution of neocortex. Here, we conduct a strong test of the saliency hypothesis by comparing the output of a well-established computational saliency model with the activation of neurons in the primate superior colliculus (SC), a midbrain structure associated with attention and gaze, while monkeys watched video of natural scenes. We find that the activity of SC superficial visual-layer neurons (SCs), specifically, is well-predicted by the model. This saliency representation is unlikely to be inherited from fronto-parietal cortices, which do not project to SCs, but may be computed in SCs and relayed to other areas via tectothalamic pathways. |
Brian J. White; Janis Y. Y. Kan; Ron Levy; Laurent Itti; Douglas P. Munoz Superior colliculus encodes visual saliency before the primary visual cortex Journal Article In: Proceedings of the National Academy of Sciences, vol. 114, no. 35, pp. 9451–9456, 2017. @article{White2017c, Models of visual attention postulate the existence of a bottom-up saliency map that is formed early in the visual processing stream. Although studies have reported evidence of a saliency map in various cortical brain areas, determining the contribution of phylogenetically older pathways is crucial to understanding its origin. Here, we compared saliency coding from neurons in two early gateways into the visual system: the primary visual cortex (V1) and the evolutionarily older superior colliculus (SC). We found that, while the response latency to visual stimulus onset was earlier for V1 neurons than superior colliculus superficial visual-layer neurons (SCs), the saliency representation emerged earlier in SCs than in V1. Because the dominant input to the SCs arises from V1, these relative timings are consistent with the hypothesis that SCs neurons pool the inputs from multiple V1 neurons to form a feature-agnostic saliency map, which may then be relayed to other brain areas. |
Niklas Wilming; Tim C. Kietzmann; Megan Jutras; Cheng Xue; Stefan Treue; Elizabeth A. Buffalo; Peter König Differential contribution of low- and high-level image content to eye movements in monkeys and humans Journal Article In: Cerebral Cortex, vol. 27, no. 1, pp. 279–293, 2017. @article{Wilming2017, Oculomotor selection exerts a fundamental impact on our experience of the environment. To better understand the underlying principles, researchers typically rely on behavioral data from humans, and electrophysiological recordings in macaque monkeys. This approach rests on the assumption that the same selection processes are at play in both species. To test this assumption, we compared the viewing behavior of 106 humans and 11 macaques in an unconstrained free-viewing task. Our data-driven clustering analyses revealed distinct human and macaque clusters, indicating species-specific selection strategies. Yet, cross-species predictions were found to be above chance, indicating some level of shared behavior. Analyses relying on computational models of visual saliency indicate that such cross-species commonalities in free viewing are largely due to similar low-level selection mechanisms, with only a small contribution by shared higher level selection mechanisms and with consistent viewing behavior of monkeys being a subset of the consistent viewing behavior of humans. |
Jacob L. Yates; Il Memming Park; Leor N. Katz; Jonathan W. Pillow; Alexander C. Huk Functional dissection of signal and noise in MT and LIP during decision-making Journal Article In: Nature Neuroscience, vol. 20, no. 9, pp. 1285–1292, 2017. @article{Yates2017, During perceptual decision-making, responses in the middle temporal (MT) and lateral intraparietal (LIP) areas appear to map onto theoretically defined quantities, with MT representing instantaneous motion evidence and LIP reflecting the accumulated evidence. However, several aspects of the transformation between the two areas have not been empirically tested. We therefore performed multistage systems identification analyses of the simultaneous activity of MT and LIP during individual decisions. We found that monkeys based their choices on evidence presented in early epochs of the motion stimulus and that substantial early weighting of motion was present in MT responses. LIP responses recapitulated MT early weighting and contained a choice-dependent buildup that was distinguishable from motion integration. Furthermore, trial-by-trial variability in LIP did not depend on MT activity. These results identify important deviations from idealizations of MT and LIP and motivate inquiry into sensorimotor computations that may intervene between MT and LIP. |
Kitty Z. Xu; Brian A. Anderson; Erik E. Emeric; Anthony W. Sali; Veit Stuphorn; Steven Yantis; Susan M. Courtney Neural basis of cognitive control over movement inhibition: Human fMRI and primate electrophysiology evidence Journal Article In: Neuron, vol. 96, no. 6, pp. 1447–1458.e6, 2017. @article{Xu2017, Executive control involves the ability to flexibly inhibit or change an action when it is contextually inappropriate. Using the complimentary techniques of human fMRI and monkey electrophysiology in a context-dependent stop signal task, we found a functional double dissociation between the right ventrolateral prefrontal cortex (rVLPFC) and the bi-lateral frontal eye field (FEF). Different regions of rVLPFC were associated with context-based signal meaning versus intention to inhibit a response, while FEF activity corresponded to success or failure of the response inhibition regardless of the stimulus response mapping or the context. These results were validated by electrophysiological recordings in rVLPFC and FEF from one monkey. Inhibition of a planned behavior is therefore likely not governed by a single brain system as had been previously proposed, but instead depends on two distinct neural processes involving different sub-regions of the rVLPFC and their interactions with other motor-related brain regions. Xu et al. present a rare combination of complementary evidence from human fMRI and primate neurophysiology, demonstrating that response inhibition is not directly accomplished by the rVLPFC, but instead requires multiple, distinct rVLPFC networks involving attention and contextual stimulus interpretation. |
David L. Barack; Steve W. C. Chang; Michael L. Platt Posterior cingulate neurons dynamically signal decisions to disengage during foraging Journal Article In: Neuron, vol. 96, no. 2, pp. 339–347.e5, 2017. @article{Barack2017, Foraging for resources is a fundamental behavior balancing systematic search and strategic disengagement. The foraging behavior of primates is especially complex and requires long-term memory, value comparison, strategic planning, and decision-making. Here we provide evidence from two different foraging tasks that neurons in primate posterior cingulate cortex (PCC) signal decision salience during foraging to motivate disengagement from the current strategy. In our foraging tasks, salience refers to the difference between decision thresholds and the net harvested reward. Salience signals were stronger in poor foraging contexts than rich ones, suggesting low harvest rates recruit mechanisms in PCC that regulate strategic disengagement and exploration during foraging. Barack et al. report that foraging salience motivated strategic disengagement in two distinct tasks. Posterior cingulate neurons preferentially signaled salience and forecast divergent choices when reward rates were low, suggesting a role in the strategic control of behavior. |
Charles B. Beaman; Sarah L. Eagleman; Valentin Dragoi Sensory coding accuracy and perceptual performance are improved during the desynchronized cortical state Journal Article In: Nature Communications, vol. 8, pp. 1308, 2017. @article{Beaman2017, Cortical activity changes continuously during the course of the day. At a global scale, population activity varies between the ‘synchronized' state during sleep and ‘desynchronized' state during waking. However, whether local fluctuations in population synchrony during wakefulness modulate the accuracy of sensory encoding and behavioral performance is poorly understood. Here, we show that populations of cells in monkey visual cortex exhibit rapid fluctuations in synchrony ranging from desynchronized responses, indicative of high alertness, to highly synchronized responses. These fluctuations are local and control the trial variability in population coding accuracy and behavioral performance in a discrimination task. When local population activity is desynchronized, the correlated variability between neurons is reduced, and network and behavioral performance are enhanced. These findings demonstrate that the structure of variability in local cortical populations is not noise but rather controls how sensory information is optimally integrated with ongoing processes to guide network coding and behavior. |
Joachim Bellet; Chih-Yang Chen; Ziad M. Hafed Sequential hemifield gating of alpha and beta behavioral performance oscillations after microsaccades Journal Article In: Journal of Neurophysiology, vol. 118, pp. 2789–2805, 2017. @article{Bellet2017, Microsaccades are tiny saccades that occur during gaze fixation. Even though visual processing has been shown to be strongly modulated close to the time of microsaccades, both at central and peripheral eccentricities, it is not clear how these eye movements might influence longer term fluctuations in brain activity and behavior. Here we found that visual processing is significantly affected and, in a rhythmic manner, even several hundreds of milliseconds after a microsaccade. Human visual detection efficiency, as measured by reaction time, exhibited coherent rhythmic oscillations in the ? - and ? -frequency bands for up to ~650–700 ms after a microsaccade. Surprisingly, the oscillations were sequentially pulsed across visual hemifields relative to microsaccade direction, first occurring in the same hemifield as the movement vector for ~400 ms and then the opposite. Such pulsing also affected perceptual detection performance. Our results suggest that visual processing is subject to long-lasting oscillations that are phase locked to microsaccade generation, and that these oscillations are dependent on microsaccade direction. |
Kelly R. Bullock; Florian Pieper; Adam J. Sachs; Julio C. Martinez-Trujillo Visual and presaccadic activity in area 8Ar of the macaque monkey lateral prefrontal cortex Journal Article In: Journal of Neurophysiology, vol. 118, no. 1, pp. 15–28, 2017. @article{Bullock2017, Common trends observed in many visual and oculomotor-related cortical areas include retinotopically organized receptive and movement fields exhibiting a Gaussian shape and increasing size with eccentricity. These trends are demonstrated in the frontal eye fields (FEF), many visual areas, and the superior colliculus (SC), but have not been thoroughly characterized in prearcuate area 8Ar of the prefrontal cortex. This is important since area 8Ar, located anterior to the FEF, is more cytoarchitectonically similar to prefrontal areas than premotor areas. Here we recorded the responses of 166 neurons in area 8Ar of two male macaques while the animals made visually guided saccades to a peripheral sine-wave grating stimulus positioned at one of 40 possible locations (8 angles along 5 eccentricities). To characterize the neurons' receptive and movement fields, we fit a bivariate Gaussian model to the baseline-subtracted average firing rate during stimulus presentation (early and late visual epoch) and prior to saccade onset (presaccadic epoch). 121/166 neurons showed spatially selective visual and presaccadic responses. Of the visually selective neurons, 76% preferred the contralateral visual hemifield, whereas 24% preferred the ipsilateral hemifield. The angular width of visual and movement-related fields scaled positively with increasing eccentricity. Moreover, responses of neurons with visual receptive fields were modulated by target contrast exhibiting sigmoid tuning curves that resemble those of visual neurons in upstream areas such as MT and V4. Finally, we found that neurons with receptive fields at similar spatial locations were clustered within the area; however, this organization did not appear retinotopic. |
Jason L. Chan; Michael J. Koval; Kevin D. Johnston; Stefan Everling Neural correlates for task switching in the macaque superior colliculus Journal Article In: Journal of Neurophysiology, vol. 118, pp. 2156–2170, 2017. @article{Chan2017, Successful task switching requires a network of brain areas to select, maintain, implement, and execute the appropriate task. Although frontoparietal brain areas are thought to play a critical role in task switching by selecting and encoding task rules and exerting top-down control, how brain areas closer to the execution of tasks participate in task switching is unclear. The superior colliculus (SC) integrates information from various brain areas to generate saccades and is likely influenced by task switching. Here, we investigated switch costs in nonhuman primates and their neural correlates in the activity of SC saccade-related neurons in monkeys performing cued, randomly interleaved pro- and anti-saccade trials. We predicted that behavioral switch costs would be associated with differential modulations of SC activity in trials on which the task was switched vs. repeated, with activity on the current trial resembling that associated with the task set of the previous trial when a switch occurred. We observed both error rate and reaction time switch costs and changes in the discharge rate and timing of activity in SC neurons between switch and repeat trials. These changes were present later in the task only after fixation on the cue stimuli but before saccade onset. These results further establish switch costs in macaque monkeys and suggest that SC activity is modulated by task-switching processes in a manner inconsistent with the concept of task set inertia. |
Benjamin W. Corrigan; Roberto A. Gulli; Guillaume Doucet; Julio C. Martinez-Trujillo Characterizing eye movement behaviors and kinematics of non-human primates during virtual navigation tasks Journal Article In: Journal of Vision, vol. 17, no. 12, pp. 1–22, 2017. @article{Corrigan2017, Virtual environments (VE) allow testing complex behaviors in naturalistic settings by combining highly controlled visual stimuli with spatial navigation and other cognitive tasks. They also allow for the recording of eye movements using high-precision eye tracking techniques, which is important in electrophysiological studies examining the response properties of neurons in visual areas of nonhuman primates. However, during virtual navigation, the pattern of retinal stimulation can be highly dynamic which may influence eye movements. Here we examine whether and how eye movement patterns change as a function of dynamic visual stimulation during virtual navigation tasks, relative to standard oculomotor tasks. We trained two rhesus macaques to use a joystick to navigate in a VE to complete two tasks. To contrast VE behavior with classic measurements, the monkeys also performed a simple Cued Saccade task. We used a robust algorithm for rapid classification of saccades, fixations, and smooth pursuits. We then analyzed the kinematics of saccades during all tasks, and specifically during different phases of the VE tasks. We found that fixation to smooth pursuit ratios were smaller in VE tasks (4:5) compared to the Cued Saccade task (7:1), reflecting a more intensive use of smooth pursuit to foveate targets in VE than in a standard visually guided saccade task or during spontaneous fixations. Saccades made to rewarded targets (exploitation) tended to have increased peak velocities compared to saccades made to unrewarded objects (exploration). VE exploitation saccades were 6% slower than saccades to discrete targets in the Cued Saccade task. Virtual environments represent a technological advance in experimental design for nonhuman primates. Here we provide a framework to study the ways that eye movements change between and within static and dynamic displays. |
Olga Dal Monte; Matthew Piva; Kevin M. Anderson; Marios Tringides; Avram J. Holmes; Steve W. C. Chang Oxytocin under opioid antagonism leads to supralinear enhancement of social attention Journal Article In: Proceedings of the National Academy of Sciences, vol. 114, no. 20, pp. 5247–5252, 2017. @article{DalMonte2017, To provide new preclinical evidence toward improving the efficacy of oxytocin (OT) in treating social dysfunction, we tested the benefit of administering OT under simultaneously induced opioid antagonism during dyadic gaze interactions in monkeys. OT coadministered with a μ-opioid receptor antagonist, naloxone, invoked a supralinear enhancement of prolonged and selective social attention, producing a stronger effect than the summed effects of each administered separately. These effects were consistently observed when averaging over entire sessions, as well as specifically following events of particular social importance, including mutual eye contact and mutual reward receipt. Furthermore, attention to various facial regions was differentially modulated depending on social context. Using the Allen Institute's transcriptional atlas, we further established the colocalization of μ-opioid and κ-opioid receptor genes and OT genes at the OT-releasing sites in the human brain. These data across monkeys and humans support a regulatory relationship between the OT and opioid systems and suggest that administering OT under opioid antagonism may boost the therapeutic efficacy of OT for enhancing social cognition. |
Nicholas K. DeWind; Jiyun Peng; Andrew Luo; Elizabeth M. Brannon; Michael L. Platt Pharmacological inactivation does not support a unique causal role for intraparietal sulcus in the discrimination of visual number Journal Article In: PLoS ONE, vol. 12, no. 12, pp. e0188820, 2017. @article{DeWind2017, The "number sense" describes the intuitive ability to quantify without counting. Single neu-ron recordings in non-human primates and functional imaging in humans suggest the intra-parietal sulcus is an important neuroanatomical locus of numerical estimation. Other lines of inquiry implicate the IPS in numerous other functions, including attention and decision mak-ing. Here we provide a direct test of whether IPS has functional specificity for numerosity judgments. We used muscimol to reversibly and independently inactivate the ventral and lat-eral intraparietal areas in two monkeys performing a numerical discrimination task and a color discrimination task, roughly equilibrated for difficulty. Inactivation of either area caused parallel impairments in both tasks and no evidence of a selective deficit in numerical pro-cessing. These findings do not support a causal role for the IPS in numerical discrimination, except insofar as it also has a role in the discrimination of color. We discuss our findings in light of several alternative hypotheses of IPS function, including a role in orienting responses, a general cognitive role in attention and decision making processes and a more specific role in ordinal comparison that encompasses both number and color judgments. |
Kacie Dougherty; Michele A. Cox; Taihei Ninomiya; David A. Leopold; Alexander Maier Ongoing alpha activity in V1 regulates visually driven spiking responses Journal Article In: Cerebral Cortex, vol. 27, no. 2, pp. 1113–1124, 2017. @article{Dougherty2017, The interlaminar connections in the primate primary visual cortex (V1) are well described, as is the presence of ongoing alpha-range (7-14 Hz) fluctuations in this area. Less well understood is how these interlaminar connections and ongoing fluctuations contribute to the regulation of visual spiking responses. Here, we investigate the relationship between alpha fluctuations and spiking responses to visual stimuli across cortical layers. Using laminar probes in macaque V1, we show that neural firing couples with the phase of alpha fluctuations, and that magnitude of this coupling is particularly pronounced during visual stimulation. The strongest modulation of spiking activity was observed in layers 2/3. Alpha-spike coupling and current source density analysis pointed to an infragranular origin of the alpha fluctuations. Taken together, these results indicate that ongoing infragranular alpha-range fluctuations in V1 play a role in regulating columnar visual activity. |
R. Becket Ebitz; Tirin Moore Selective modulation of the pupil light reflex by microstimulation of prefrontal cortex Journal Article In: Journal of Neuroscience, vol. 37, no. 19, pp. 5008–5018, 2017. @article{Ebitz2017, The prefrontal cortex (PFC) is thought to flexibly regulate sensorimotor responses, perhaps through modulating activity in other circuits. However, the scope of that control remains unknown: it remains unclear whether the PFC can modulate basic reflexes. One canonical example of a central reflex is the pupil light reflex (PLR): the automatic constriction of the pupil in response to luminance increments. Unlike pupil size, which depends on the interaction of multiple physiological and neuromodulatory influences, the PLR reflects the action of a simple brainstem circuit. However, emerging behavioral evidence suggests that the PLR may be modulated by cognitive processes. Although the neural basis of these modulations remains unknown, one possible source is the PFC, particularly the frontal eye field (FEF), an area of the PFC implicated in the control of attention. We show that microstimulation of the rhesus macaque FEF alters the magnitude of the PLR in a spatially specific manner. FEF microstimulation enhanced the PLR to probes presented within the stimulated visual field, but suppressed the PLR to probes at nonoverlapping locations. The spatial specificity of this effect parallels the effect of FEF stimulation on attention and suggests that FEF is capable of modulating visuomotor transformations performed at a lower level than was previously known. These results provide evidence of the selective regulation of a basic brainstem reflex by the PFC. |
Hongwei Fan; Xiaochuan Pan; Rubin Wang; Masamichi Sakagami Differences in reward processing between putative cell types in primate prefrontal cortex Journal Article In: PLoS ONE, vol. 12, no. 12, pp. e0189771, 2017. @article{Fan2017a, Single-unit studies in monkeys have demonstrated that neurons in the prefrontal cortex predict the reward type, reward amount or reward availability associated with a stimulus. To examine contributions of pyramidal cells and interneurons in reward processing, single-unit activity was extracellularly recorded in prefrontal cortices of four monkeys performing a reward prediction task. Based on their shapes of spike waveforms, prefrontal neurons were classified into broad-spike and narrow-spike units that represented putative pyramidal cells and interneurons, respectively. We mainly observed that narrow-spike neurons showed higher firing rates but less bursty discharges than did broad-spike neurons. Both narrow-spike and broad-spike cells selectively responded to the stimulus, reward and their interaction, and the proportions of each type of selective neurons were similar between the two cell classes. Moreover, the two types of cells displayed equal reliability of reward or stimulus discrimination. Furthermore, we found that broad-spike and narrow-spike cells showed distinct mechanisms for encoding reward or stimulus information. Broad-spike neurons raised their firing rate relative to the baseline rate to represent the preferred reward or stimulus information, whereas narrow-spike neurons inhibited their firing rate lower than the baseline rate to encode the non-preferred reward or stimulus information. Our results suggest that narrow-spike and broad-spike cells were equally involved in reward and stimulus processing in the prefrontal cortex. They utilized a binary strategy to complementarily represent reward or stimulus information, which was consistent with the task structure in which the monkeys were required to remember two reward conditions and two visual stimuli. |
Amber M. Fyall; Yasmine El-Shamayleh; Hannah Choi; Eric Shea-Brown; Anitha Pasupathy Dynamic representation of partially occluded objects in primate prefrontal and visual cortex Journal Article In: eLife, vol. 6, pp. 1–25, 2017. @article{Fyall2017, Successful recognition of partially occluded objects is presumed to involve dynamic interactions between brain areas responsible for vision and cognition, but neurophysiological evidence for the involvement of feedback signals is lacking. Here, we demonstrate that neurons in the ventrolateral prefrontal cortex (vlPFC) of monkeys performing a shape discrimination task respond more strongly to occluded than unoccluded stimuli. In contrast, neurons in visual area V4 respond more strongly to unoccluded stimuli. Analyses of V4 response dynamics reveal that many neurons exhibit two transient response peaks, the second of which emerges after vlPFC response onset and displays stronger selectivity for occluded shapes. We replicate these findings using a model of V4/vlPFC interactions in which occlusion-sensitive vlPFC neurons feed back to shape- selective V4 neurons, thereby enhancing V4 responses and selectivity to occluded shapes. These results reveal how signals from frontal and visual cortex could interact to facilitate object recognition under occlusion. |
Diego A. Gutnisky; Charles B. Beaman; Sergio E. Lew; Valentin Dragoi Spontaneous fluctuations in visual cortical responses influence population coding accuracy Journal Article In: Cerebral Cortex, vol. 27, no. 2, pp. 1409–1427, 2017. @article{Gutnisky2017, Information processing in the cerebral cortex depends not only on the nature of incoming stimuli, but also on the state of neuronal networks at the time of stimulation. That is, the same stimulus will be processed differently depending on the neuronal context in which it is received. A major factor that could influence neuronal context is the background, or ongoing neuronal activity before stimulation. In visual cortex, ongoing activity is known to play a critical role in the development of local circuits, yet whether it influences the coding of visual features in adult cortex is unclear. Here, we investigate whether and how the information encoded by individual neurons and populations in primary visual cortex (V1) depends on the ongoing activity before stimulus presentation. We report that when individual neurons are in a "low" prestimulus state, they have a higher capacity to discriminate stimulus features, such as orientation, despite their reduction in evoked responses. By measuring the distribution of prestimulus activity across a population of neurons, we found that network discrimination accuracy is improved in the low prestimulus state. Thus, the distribution of ongoing activity states across the network creates an "internal context" that dynamically filters incoming stimuli to modulate the accuracy of sensory coding. The modulation of stimulus coding by ongoing activity state is consistent with recurrent network models in which ongoing activity dynamically controls the balanced background excitation and inhibition to individual neurons. |
Diego A. Gutnisky; Charles Beaman; Sergio E. Lew; Valentin Dragoi Cortical response states for enhanced sensory discrimination Journal Article In: eLife, vol. 6, pp. 1–23, 2017. @article{Gutnisky2017a, Brain activity during wakefulness is characterized by rapid fluctuations in neuronal responses. Whether these fluctuations play any role in modulating the accuracy of behavioral responses is poorly understood. Here, we investigated whether and how trial changes in the population response impact sensory coding in monkey V1 and perceptual performance. Although the responses of individual neurons varied widely across trials, many cells tended to covary with the local population. When population activity was in a 'low' state, neurons had lower evoked responses and correlated variability, yet higher probability to predict perceptual accuracy. The impact of firing rate fluctuations on network and perceptual accuracy was strongest 200-ms before stimulus presentation, and it greatly diminished when the number of cells used to measure the state of the population was decreased. These findings indicate that enhanced perceptual discrimination occurs when population activity is in a 'silent' response mode in which neurons increase information extraction. |
Gerald Hahn; Adrian Ponce-Alvarez; Cyril Monier; Giacomo Benvenuti; Arvind Kumar; Frédéric Chavane; Gustavo Deco; Yves Frégnac Spontaneous cortical activity is transiently poised close to criticality Journal Article In: PLoS Computational Biology, vol. 13, no. 5, pp. e1005543, 2017. @article{Hahn2017, Brain activity displays a large repertoire of dynamics across the sleep-wake cycle and even during anesthesia. It was suggested that criticality could serve as a unifying principle underlying the diversity of dynamics. This view has been supported by the observation of spontaneous bursts of cortical activity with scale-invariant sizes and durations, known as neuronal avalanches, in recordings of mesoscopic cortical signals. However, the existence of neuronal avalanches in spiking activity has been equivocal with studies reporting both its presence and absence. Here, we show that signs of criticality in spiking activity can change between synchronized and desynchronized cortical states. We analyzed the spontaneous activity in the primary visual cortex of the anesthetized cat and the awake monkey, and found that neuronal avalanches and thermodynamic indicators of criticality strongly depend on collective synchrony among neurons, LFP fluctuations, and behavioral state. We found that synchronized states are associated to criticality, large dynamical repertoire and prolonged epochs of eye closure, while desynchronized states are associated to sub-criticality, reduced dynamical repertoire, and eyes open conditions. Our results show that criticality in cortical dynamics is not stationary, but fluctuates during anesthesia and between different vigilance states. |
S. A. Hassani; Mariann Oemisch; M. Balcarras; Stephanie Westendorff; S. Ardid; M. A. Meer; P. Tiesinga; T. Womelsdorf In: Scientific Reports, vol. 7, pp. 40606, 2017. @article{Hassani2017, Noradrenaline is believed to support cognitive flexibility through the alpha 2A noradrenergic receptor (a2A-NAR) acting in prefrontal cortex. Enhanced flexibility has been inferred from improved working memory with the a2A-NA agonist Guanfacine. But it has been unclear whether Guanfacine improves specific attention and learning mechanisms beyond working memory, and whether the drug effects can be formalized computationally to allow single subject predictions. We tested and confirmed these suggestions in a case study with a healthy nonhuman primate performing a feature-based reversal learning task evaluating performance using Bayesian and Reinforcement learning models. In an initial dose-testing phase we found a Guanfacine dose that increased performance accuracy, decreased distractibility and improved learning. In a second experimental phase using only that dose we examined the faster feature-based reversal learning with Guanfacine with single-subject computational modeling. Parameter estimation suggested that improved learning is not accounted for by varying a single reinforcement learning mechanism, but by changing the set of parameter values to higher learning rates and stronger suppression of non-chosen over chosen feature information. These findings provide an important starting point for developing nonhuman primate models to discern the synaptic mechanisms of attention and learning functions within the context of a computational neuropsychiatry framework. |
James P. Herman; Richard J. Krauzlis Color-change detection activity in the primate superior colliculus Journal Article In: eNeuro, vol. 4, no. 2, pp. 1–16, 2017. @article{Herman2017, The primate superior colliculus (SC) is a midbrain structure that participates in the control of spatial attention. Previous studies examining the role of the SC in attention have mostly used luminance-based visual features (e.g., motion, contrast) as the stimuli and saccadic eye movements as the behavioral response, both of which are known to modulate the activity of SC neurons. To explore the limits of the SC's involvement in the control of spatial attention, we recorded SC neuronal activity during a task using color, a visual feature dimension not traditionally associated with the SC, and required monkeys to detect threshold-level changes in the saturation of a cued stimulus by releasing a joystick during maintained fixation. Using this color-based spatial attention task, we found substantial cue-related modulation in all categories of visually responsive neurons in the intermediate layers of the SC. Notably, near-threshold changes in color saturation, both increases and decreases, evoked phasic bursts of activity with magnitudes as large as those evoked by stimulus onset. This change-detection activity had two distinctive features: activity for hits was larger than for misses, and the timing of change-detection activity accounted for 67% of joystick release latency, even though it preceded the release by at least 200 ms. We conclude that during attention tasks, SC activity denotes the behavioral relevance of the stimulus regardless of feature dimension and that phasic event-related SC activity is suitable to guide the selection of manual responses as well as saccadic eye movements. |
Markus A. Hietanen; Nicholas S. C. Price; Shaun L. Cloherty; Kostas Hadjidimitrakis; Michael R. Ibbotson Long-term sensorimotor adaptation in the ocular following system of primates Journal Article In: PLoS ONE, vol. 12, no. 12, pp. e0189030, 2017. @article{Hietanen2017, The sudden movement of a wide-field image leads to a reflexive eye tracking response referred to as short-latency ocular following. If the image motion occurs soon after a saccade the initial speed of the ocular following is enhanced, a phenomenon known as post-saccadic enhancement. We show in macaque monkeys that repeated exposure to the same stimulus regime over a period of months leads to progressive increases in the initial speeds of ocular following. The improvement in tracking speed occurs for ocular following with and without a prior saccade. As a result of the improvement in ocular following speeds, the influence of post-saccadic enhancement wanes with increasing levels of training. The improvement in ocular following speed following repeated exposure to the same oculomotor task represents a novel form of sensori-motor learning in the context of a reflexive movement. |
Guilhem Ibos; David J. Freedman Sequential sensory and decision processing in posterior parietal cortex Journal Article In: eLife, vol. 6, pp. 1–19, 2017. @article{Ibos2017, <p>Decisions about the behavioral significance of sensory stimuli often require comparing sensory inference of what we are looking at to internal models of what we are looking for. Here, we test how neuronal selectivity for visual features is transformed into decision-related signals in posterior parietal cortex (area LIP). Monkeys performed a visual matching task that required them to detect target stimuli composed of conjunctions of color and motion-direction. Neuronal recordings from area LIP revealed two main findings. First, the sequential processing of visual features and the selection of target-stimuli suggest that LIP is involved in transforming sensory information into decision-related signals. Second, the patterns of color and motion selectivity and their impact on decision-related encoding suggest that LIP plays a role in detecting target stimuli by comparing bottom-up sensory inputs (what the monkeys were looking at) and top-down cognitive encoding inputs (what the monkeys were looking for).</p> |
Nan Jia; Scott L. Brincat; Andrés F. Salazar-Gómez; Mikhail Panko; Frank H. Guenther; Earl K. Miller Decoding of intended saccade direction in an oculomotor brain-computer interface Journal Article In: Journal of Neural Engineering, vol. 14, no. 4, pp. 1–13, 2017. @article{Jia2017a, OBJECTIVE: To date, invasive brain-computer interface (BCI) research has largely focused on replacing lost limb functions using signals from of hand/arm areas of motor cortex. However, the oculomotor system may be better suited to BCI applications involving rapid serial selection from spatial targets, such as choosing from a set of possible words displayed on a computer screen in an augmentative and alternative communication (AAC) application. Here we aimed to demonstrate the feasibility of a BCI utilizing the oculomotor system. APPROACH: We developed a chronic intracortical BCI in monkeys to decode intended saccadic eye movement direction using activity from multiple frontal cortical areas. MAIN RESULTS: Intended saccade direction could be decoded in real time with high accuracy, particularly at contralateral locations. Accurate decoding was evident even at the beginning of the BCI session; no extensive BCI experience was necessary. High-frequency (80-500 Hz) local field potential magnitude provided the best performance, even over spiking activity, thus simplifying future BCI applications. Most of the information came from the frontal and supplementary eye fields, with relatively little contribution from dorsolateral prefrontal cortex. SIGNIFICANCE: Our results support the feasibility of high-accuracy intracortical oculomotor BCIs that require little or no practice to operate and may be ideally suited for 'point and click' computer operation as used in most current AAC systems. |
Yoshinao Kajikawa; John F. Smiley; Charles E. Schroeder Primary generators of visually evoked field potentials recorded in the macaque auditory cortex Journal Article In: Journal of Neuroscience, vol. 37, no. 42, pp. 10139–10153, 2017. @article{Kajikawa2017, Prior studies have reported “local” field potential (LFP) responses to faces in the macaque auditory cortex and have suggested that such face-LFPs may be substrates of audiovisual integration. However, although field potentials (FPs) may reflect the synaptic currents of neurons near the recording electrode, due to the use of a distant reference electrode, they often reflect those of synaptic activity occurring in distant sites as well. Thus, FP recordings within a given brain region (e.g., auditory cortex) may be “contaminated” by activity generated elsewhere in the brain. To determine whether face responses are indeed generated within macaque auditory cortex, we recorded FPs and concomitant multiunit activity with linear array multielectrodes across auditory cortex in three macaques (one female), and applied current source density (CSD) analysis to the laminar FP profile. CSD analysis revealed no appreciable local generator contribution to the visual FP in auditory cortex, although we did note an increase in the amplitude of visual FP with cortical depth, suggesting that their generators are located below auditory cortex. In the underlying inferotemporal cortex, we found polarity inversions of the main visual FP components accompanied by robust CSD responses and large-amplitude multiunit activity. These results indicate that face-evoked FP responses in auditory cortex are not generated locally but are volume-conducted from other face-responsive regions. In broader terms, our results underscore the caution that, unless far-field contamination is removed, LFPs in general may reflect such “far-field” activity, in addition to, or in absence of, local synaptic responses. |
Kohitij Kar; Jacob Duijnhouwer; Bart Krekelberg Transcranial alternating current stimulation attenuates neuronal adaptation Journal Article In: Journal of Neuroscience, vol. 37, no. 9, pp. 2325–2335, 2017. @article{Kar2017, We previously showed that brief application of 2 mA (peak-to-peak) transcranial currents alternating at 10 Hz significantly reduces motion adaptation in humans. This is but one of many behavioral studies showing that weak currents applied to the scalp modulate neural processing. Transcranial stimulation has been shown to improve perception, learning, and a range of clinical symptoms. Few studies, however, have measured the neural consequences of transcranial current stimulation. We capitalized on the strong link between motion perception and neural activity in the middle temporal (MT) area of the macaque monkey to study the neural mechanisms that underlie the behavioral consequences of transcranial alternating current stimulation. First, we observed that 2 mA currents generated substantial intracranial fields, which were much stronger in the stimulated hemisphere (0.12 V/m) than on the opposite side of the brain (0.03 V/m). Second, we found that brief application of transcranial alternating current stimulation at 10 Hz reduced spike-frequency adaptation of MT neurons and led to a broadband increase in the power spectrum of local field potentials. Together, these findings provide a direct demonstration that weak electric fields applied to the scalp significantly affect neural processing in the primate brain and that this includes a hitherto unknown mechanism that attenuates sensory adaptation. |
Steffen Klingenhoefer; Bart Krekelberg Perisaccadic visual perception Journal Article In: Journal of Vision, vol. 17, no. 9, pp. 1–14, 2017. @article{Klingenhoefer2017, Primates use frequent, rapid eye movements to sample their visual environment. This is a fruitful strategy to make the best use of the highly sensitive foveal part of the retina, but it requires neural mechanisms to bind the rapidly changing visual input into a single, stable percept. Studies investigating these neural mechanisms have typically assumed that perisaccadic perception in nonhuman primates matches that of humans. We tested this assumption by performing identical experiments in human and nonhuman primates. Our data confirm that perisaccadic visual perception of macaques and humans is qualitatively similar. Specifically, we found a reduction in detectability and mislocalization of targets presented at the time of saccades. We also found substantial differences between human and nonhuman primates. Notably, in nonhuman primates, localization that requires knowledge of eye position was less precise, nonhuman primates detected fewer perisaccadic stimuli, and perisaccadic compression was not towards the saccade target. The qualitative similarities between species support the view that the nonhuman primate is ideally suited to study aspects of brain function-such as those relying on foveal vision-that are uniquely developed in primates. The quantitative differences, however, demonstrate the need for a reassessment of the models purportedly linking neural response changes at the time of saccades with the behavioral phenomena of perisaccadic reduction of detectability and mislocalization. |
Adrian Staub; Brian W. Dillon; Charles Clifton The matrix verb as a source of comprehension difficulty in object relative sentences Journal Article In: Cognitive Science, vol. 41, pp. 1353–1376, 2017. @article{Staub2017, Two experiments used eyetracking during reading to examine the processing of the matrix verb following object and subject relative clauses. The experiments show that the processing of the matrix verb following an object relative is indeed slowed compared to the processing of the same verb following a subject relative. However, this difficulty is entirely eliminated if additional material intervenes between the object gap and the matrix verb. An explanation in terms of spillover processing is ruled out, suggesting that it is the gap-matrix verb sequence that is itself responsible for the difficulty. We consider two accounts of this difficulty, one emphasizing the potential difficulty of rapidly switching between the sentential subject's thematic or syntactic role in the embedded clause and its role in the matrix clause, and one emphasizing the potential difficulty of performing two demanding memory retrievals in rapid succession. The present experiments also closely replicate the previous findings from eyetracking that the noun phrase and the verb within an object relative are both loci of processing difficulty, but that the former induces substantially greater difficulty. |
Allison A. Steen-Baker; Shukhan Ng; Brennan R. Payne; Carolyn J. Anderson; Kara D. Federmeier; Elizabeth A. L. Stine-Morrow The effects of context on processing words during sentence reading among adults varying in age and literacy skill Journal Article In: Psychology and Aging, vol. 32, no. 5, pp. 460–472, 2017. @article{SteenBaker2017, The facilitation of word processing by sentence context reflects the interaction between the build-up of message-level semantics and lexical processing. Yet, little is known about how this effect varies through adulthood as a function of reading skill. In this study, Participants 18-64 years old with a range of literacy competence read simple sentences as their eye movements were monitored. We manipulated the predictability of a sentence-final target word, operationalized as cloze probability. First fixation durations showed an interaction between age and literacy skill, decreasing with age among more skilled readers but increasing among less skilled readers. This pattern suggests that age-related slowing may impact reading when not buffered by skill, but with continued practice, automatization of reading can continue to develop in adulthood. In absolute terms, readers were sensitive to predictability, regardless of age or literacy, in both early and later measures. Older readers showed differential contextual sensitivity in regression patterns, effects not moderated by literacy skill. Finally, comprehension performance increased with age and literacy skill, but performance among less skilled readers was especially reduced when predictability was low, suggesting that low-literacy adults (regardless of age) struggle when creating mental representations under weaker semantic constraints. Collectively, these findings suggest that aging readers (regardless of reading skill) are more sensitive to context for meaning-integration processes; that less skilled adult readers (regardless of age) depend more on a constrained semantic representation for comprehension; and that the capacity for literacy engagement enables continued development of efficient lexical processing in adult reading development. |
Anastasia Stoops; Kiel Christianson Parafoveal processing of inflectional morphology on Russian nouns Journal Article In: Journal of Cognitive Psychology, vol. 29, no. 6, pp. 653–669, 2017. @article{Stoops2017, The present study investigated whether inflectional morphology on Russian nouns is processed parafoveally during silent reading. The boundary-change paradigm [Rayner, K. (1975). The perceptual span and peripheral cues in reading. Cognitive Psychology, 7, 65–81] was used to examine parafoveal processing of nominal case markings of Russian nouns. The results yielded preview cost for morphologically related preview in gaze duration (vs. an identical baseline) and in total time (TT) (vs. a non-word baseline) and preview benefit in regressions out of the target word. The contribution of the study is two-fold. First this is the first demonstration that bound nominal inflectional morphemes are processed parafoveally in a language with linear concatenated morphology (Russian). Second the observed preview effects suggest that parafoveal preview of a morphologically related word was processed fully in the parafovea and interfered with the integration of the target word into the syntactic structure of the sentence. |
Yuichi Suzuki Validity of new measures of implicit knowledge: Distinguishing implicit knowledge from automatized explicit knowledge Journal Article In: Applied Psycholinguistics, vol. 38, no. 5, pp. 1229–1261, 2017. @article{Suzuki2017, <p>Accumulating evidence suggests that time-pressured form-focused tasks like grammaticality judgment tests (GJTs) can measure second language (L2) implicit knowledge. The current paper, however, proposes that these tasks draw on automatized explicit knowledge. A battery of six grammar tests was designed to distinguish automatized explicit knowledge and implicit knowledge. While three time-pressured form-focused tasks (an auditory GJT, a visual GJT, and a fill in the blank test) were hypothesized to measure automatized explicit knowledge, three real-time comprehension tasks (a visual-world task, a word-monitoring task, and a self-paced reading task) were hypothesized to measure implicit knowledge. One hundred advanced L2 Japanese learners with first language Chinese residing in Japan took all six tests. Confirmatory factor analysis and multitrait-multimethod analysis provided an array of evidence supporting that these tests assessed two types of linguistic knowledge separately with little influence from the method effects. The results analyzed separately by length of residence in Japan (a proxy for the amount of naturalistic L2 exposure) showed that learners with longer residence in Japan can draw on implicit knowledge in the real-time comprehension tasks with more stability than those with shorter residence. These findings indicate the potential of finely tuned real-time comprehension tasks as measures of implicit knowledge.</p> |
Yuichi Suzuki; Robert DeKeyser The interface of explicit and implicit knowledge in a second language: Insights from individual differences in cognitive aptitudes Journal Article In: Language Learning, vol. 67, no. 4, pp. 747–790, 2017. @article{Suzuki2017a, Recent research has called for the use offine-grained measures that distinguish implicit knowledge from automatized explicit knowledge. In the current study, such measures were used to determine how the two systems interact in a naturalistic second language (L2) acquisition context. One hundred advanced L2 speakers ofJapanese living in Japan were assessed using tests of automatized explicit knowledge and implicit knowledge, along with tests of phonological short-term memory and aptitude tests for explicit and implicit learning. Structural equation modeling demonstrated that aptitude for explicit learning significantly predicted acquisition of automatized explicit knowledge, and automatized explicit knowledge significantly predicted acquisition of implicit knowledge. The effects of implicit learning aptitude and phonological short-term memory on This acquisition of automatized explicit knowledge and implicit knowledge were limited. These findings provide the first empirical evidence that automatized explicit knowledge, which develops through explicit learning mechanisms, may impact the acquisition of implicit knowledge. |
Malathi Thothathiri; Daniel G. Evans; Sonali Poudel Verb bias and verb-specific competition effects on sentence production Journal Article In: PLoS ONE, vol. 12, no. 7, pp. e0180580, 2017. @article{Thothathiri2017, How do speakers choose between structural options for expressing a given meaning? Overall preference for some structures over others as well as prior statistical association between specific verbs and sentence structures (“verb bias”) are known to broadly influence language use. However, the effects of prior statistical experience on the planning and execution of utterances and the mechanisms that facilitate structural choice for verbs with different biases have not been fully explored. In this study, we manipulated verb bias for English double-object (DO) and prepositional-object (PO) dative structures: some verbs appeared solely in the DO structure (DO-only), others solely in PO (PO-only) and yet others equally in both (Equi). Structural choices during subsequent free-choice sentence production revealed the expected dispreference for DO overall but critically also a reliable linear trend in DO production that was consistent with verb bias (DO-only > Equi > PO-only). Going beyond the general verb bias effect, three results suggested that Equi verbs, which were associated equally with the two structures, engendered verb-specific competition and required additional resources for choosing the dispreferred DO structure. First, DO production with Equi verbs but not the other verbs correlated with participants' inhibition ability. Second, utterance duration prior to the choice of a DO structure showed a quadratic trend (DO-only < Equi > PO-only) with the longest durations for Equi verbs. Third, eye movements consistent with reimagining the event also showed a quadratic trend (DO-only < Equi > PO-only) prior to choosing DO, suggesting that participants used such recall particularly for Equi verbs. Together, these analyses of structural choices, utterance durations, eye movements and individual differences in executive functions shed light on the effects of verb bias and verb-specific competition on sentence production and the role of different executive functions in choosing between sentence structures. |
Melissa Troyer; Arielle Borovsky Maternal socioeconomic status influences the range of expectations during language comprehension in adulthood Journal Article In: Cognitive Science, vol. 41, no. 6, pp. 1405–1433, 2017. @article{Troyer2017, In infancy, maternal socioeconomic status (SES) is associated with real-time language processing skills, but whether or not (and if so, how) this relationship carries into adulthood is unknown. We explored the effects of maternal SES in college-aged adults on eye-tracked, spoken sentence comprehension tasks using the visual world paradigm. When sentences ended in highly plausible, expected target nouns (Exp. 1), higher SES was associated with a greater likelihood of considering alternative endings related to the action of the sentence. Moreover, for unexpected sentence endings (Exp. 2), individuals from higher SES backgrounds were sensitive to whether the ending was action-related (plausible) or unrelated (implausible), showing a benefit for plausible endings. Individuals from lower SES backgrounds did not show this advantage. This suggests maternal SES can influence the dynamics of sentence processing even in adulthood, with consequences for processing unexpected content. These findings highlight the importance of early lexical experience for adult language skills. |
Cara Tsang; Craig G. Chambers; Mindaugas Mozuraitis Compounds, competition, and incremental word identification in spoken Cantonese Journal Article In: Language, Cognition and Neuroscience, vol. 32, no. 1, pp. 69–81, 2017. @article{Tsang2017, The majority of words in Cantonese are compounds, which seems likely to burden the process of identifying words in running speech. Cantonese is also a stress-timed language, which reduces the potential for durational contrasts to distinguish embedded constituents from self-standing words. The current study demonstrates the challenge of identifying words in spoken Cantonese. As a compound unfolds, listeners are more likely to consider an onset-embedded constituent as the intended word than the actual word they are hearing – a result that seems poorly adapted to the prevalence of compounds. However, the results also show these challenges are offset by sentence-based cues, such as those provided by noun classifiers. This occurs despite variability in classifier-noun pairings and the fact that adult speakers often show incomplete mastery of these pairings. Together the results demonstrate how even highly biased cases of lexical competition are overcome by sentence-level constraints that may be only moderate in strength. |
Damon Tutunjian; Fredrik Heinat; Eva Klingvall; Anna-Lena Wiklund Processing relative clause extractions in Swedish Journal Article In: Frontiers in Psychology, vol. 8, pp. 2118, 2017. @article{Tutunjian2017, Relative clauses are considered strong islands for extraction across languages. Swedish comprises a well-known exception, allegedly allowing extraction from relative clauses (RCE), raising the possibility that island constraints may be subject to "deep variation" between languages. One alternative is that such exceptions are only illusory and represent "surface variation" attributable to independently motivated syntactic properties. Yet, to date, no surface account has proven tenable for Swedish RCEs. The present study uses eyetracking while reading to test whether the apparent acceptability of Swedish RCEs has any processing correlates at the point of filler integration compared to uncontroversial strong island violations. Experiment 1 tests RCE against licit that-clause extraction (TCE), illicit extraction from a non-restrictive RC island (NRCE), and an intransitive control. For this, RCE was found to pattern similarly to TCE at the point of integration in early measures, but between TCE and NRCE in total durations. Experiment 2 uses RCE and extraction from a subject NP island (SRCE) to test the hypothesis that only non-islands will show effects of implausible filler-verb dependencies. RCE showed sensitivity to the plausibility manipulation across measures at the first potential point of filler integration, whereas such effects were limited to late measures for SRCE. In addition, structural facilitation was seen across measures for RCE relative to SRCE. We propose that our results are compatible with RCEs being licit weak island extractions in Swedish, and that the overall picture speaks in favor of a surface rather than a deep variation approach to the lack of island effects in Swedish RCEs. |
Jorge R. Valdés Kroff; Paola E. Dussias; Chip Gerfen; Lauren Perrotti; María Teresa Bajo Experience with code-switching modulates the use of grammatical gender during sentence processing Journal Article In: Linguistic Approaches to Bilingualism, vol. 7, no. 2, pp. 163–198, 2017. @article{ValdesKroff2017, Using code-switching as a tool to illustrate how language experience modulates comprehension, the visual world paradigm was employed to examine the extent to which gender-marked Spanish determiners facilitate upcoming target nouns in a group of Spanish-English bilingual code-switchers. The first experiment tested target Spanish nouns embedded in a carrier phrase (Experiment 1b) and included a control Spanish monolingual group (Experiment 1a). The second set of experiments included critical trials in which participants heard code-switches from Spanish determiners into English nouns (e.g., la house) either in a fixed carrier phrase (Experiment 2a) or in variable and complex sentences (Experiment 2b). Across the experiments, bilinguals revealed an asymmetric gender effect in processing, showing facilitation only for feminine target items. These results reflect the asymmetric use of gender in the production of code-switched speech. The extension of the asymmetric effect into Spanish (Experiment 1b) underscores the permeability between language modes in bilingual code-switchers. |
Maya Yablonski; Uri Polat; Yoram S. Bonneh; Michal Ben-Shachar Microsaccades are sensitive to word structure: A novel approach to study language processing Journal Article In: Scientific Reports, vol. 7, pp. 3999, 2017. @article{Yablonski2017, Microsaccades are miniature eye movements that occur involuntarily during fixation. They are typically inhibited following stimulus onset and are released from inhibition about 300 ms post-stimulus. Microsaccade-inhibition is modulated by low level features of visual stimuli, but it is currently unknown whether they are sensitive to higher level, abstract linguistic properties. To address this question, we measured the timing of microsaccades while subjects were presented with written Hebrew words and pronounceable nonwords (pseudowords). We manipulated the underlying structure of pseudowords such that half of them contained real roots while the other half contained invented roots. Importantly, orthographic similarity to real words was equated between the two conditions. Microsaccade onset was significantly slower following real-root compared to invented-root stimuli. Similar results were obtained when considering post-stimulus delay of eye blinks. Moreover, microsaccade-delay was positively and significantly correlated with measures of real-word similarity. These findings demonstrate, for the first time, sensitivity of microsaccades to linguistic structure. Because microsaccades are involuntary and can be measured in the absence of overt response, our results provide initial evidence that they can be used as a novel physiological measure in the study of language processes in healthy and clinical populations. |
Toshiyuki Yamada; Manabu Arai; Yuki Hirose Unforced revision in processing relative clause association ambiguity in Japanese: Evidence against revision as last resort Journal Article In: Journal of Psycholinguistic Research, vol. 46, no. 3, pp. 661–714, 2017. @article{Yamada2017, The current study tackles a long standing question of whether comprehenders perform structural revision when it is not forced by grammar or not. Using an eye-tracking reading paradigm, we addressed this issue by making use of global structural ambiguity in Japanese. Our results show that comprehenders initially associate a relative clause with the first potential head noun and that they revise this analysis when the second noun is lexico-semantically possible as the relative clause head, but do not when it is impossible. The results are incompatible with the Revision as Last Resort hypothesis. Instead, they support the parsing with unforced revision that is immediately sensitive to lexical properties. We argue that our results cannot be accounted for by serial modular processing models but that they can be explained by ranked-parallel interactive processing models. Furthermore, we propose that head-finality is a key factor involved in the availability of unforced revision. |
Panpan Yao; Baoguo Chen Cross-linguistic differences affect late Chinese-English learners on-line processing of English tense and aspect Journal Article In: International Journal of Bilingualism, vol. 21, no. 3, pp. 268–290, 2017. @article{Yao2017, Aims: The present study aimed to explore how varied cross-linguistic differences affect late Chinese-English learners' on-line processing of tense and aspect in English. Methodology: We used the self-paced reading task (Experiment 1) and the eye-tracking technique (Experiment 2) to test the above question. Data and analysis: Reading times in Experiment 1 and first-fixation duration, and gaze time in Experiment 2 in four interested positions were analysed in R by ANOVAs and t-tests. Findings: Both high-and low-proficiency participants showed their sensitivity to the violation of progressive, which is nearly congruent between English and Chinese. Only high-proficiency participants were sensitive to the violation of past tense, which is similar but not congruent between Chinese and English. With regard to present third person singular, which is incongruent between Chinese and English, high-proficiency participants also showed their sensitivity to its violation; however, this sensitivity is only detected by the eye-tracking method (Experiment 2). These results suggested that cross-linguistic differences affect late second language learners' on-line processing of English tense and aspect. Originality: To the best of our knowledge, this study is the first one exploring varied cross-linguistic differences' influence on late Chinese-English learners' on-line processing of tense and aspect in English. Significance: Our results provide new evidence to support the Performance Deficit Account. |
Menahem Yeari; Marja Oudega; Paul W. Broek The effect of highlighting on processing and memory of central and peripheral text information: evidence from eye movements Journal Article In: Journal of Research in Reading, vol. 40, no. 4, pp. 365–383, 2017. @article{Yeari2017, The present study investigated the effect of text highlighting on online processing and memory of central and peripheral information. We compared processing time (using eye-tracking methodology) and recall of central and peripheral information for three types of highlighting: (a) highlighting of central information, (b) highlighting of pe-ripheral information and (c) no highlighting. Results indicate that highlighting central information decreased the amount of rereading of peripheral information, whereas highlighting peripheral information increased the amount of rereading of peripheral information. Processing and recall of central information did not differ across highlighting conditions but were higher than the processing and recall of peripheral information (i.e., centrality effects). These findings suggest that highlighting influ-ences processing of text but that this influence occurs after initial processing, interacts with centrality and is strongest for text information that is relatively peripheral to the overall coherence and meaning of the text. Proficient readers apparently selectively process and store central information regardless of what is highlighted in the text. |
Miao-Hsuan Yen; Ying-Tien Wu In: Computers in Human Behavior, vol. 75, pp. 14–24, 2017. @article{Yen2017, With an online reading context, this study aimed to investigate whether university students' informal reasoning ability and disposition (indicated by counterargument construction) could reduce or even reverse “myside bias” in reading relevant webpages regarding a controversial issue. Also, the association of students' online reading patterns with their progress in counterargument construction and changes in attitude extremity was examined in this study. The participants were sixty-four university students. They were asked to read eight relevant webpages freely (eye movement recorded) and to express their personal opinions about building nuclear power plants. These webpages were edited from various aspects regarding this controversial issue, with half of them presenting supporting and opposing information respectively. Before and after reading the webpages, the participants' counterargument construction performance and attitude extremity toward the controversial issue were assessed. This study revealed that participants who could construct successful counterarguments in the pre-test tended to pay more attention to other-side than to myside webpages. For their counterparts, it was found that those who spent more time viewing other-side webpages either progressed in counterargument construction or neutralized their attitude in the post-test. With different methodology, this study also provides convergent evidences that myside bias was associated with attitude polarization. |
Wei Yi; Shiyi Lu; Guojie Ma Frequency, contingency and online processing of multiword sequences: An eye-tracking study Journal Article In: Second Language Research, vol. 33, no. 4, pp. 519–549, 2017. @article{Yi2017, Frequency and contingency are two primary statistical factors that drive the acquisition and processing of language. This study explores the role of phrasal frequency and contingency (the co- occurrence probability/statistical association of the constituent words in multiword sequences) during online processing of multiword sequences. Meanwhile, it also examines language users' sensitivity to the two types of statistical information. Using the eye-tracking paradigm, native and advanced nonnative speakers of Chinese were instructed to read 80 disyllabic two-word Chinese adverbial sequences embedded in sentence contexts. Eye movements of the participants were recorded using both early and late measures. Mixed-effects modeling revealed that both phrasal frequency and contingency influenced the processing of the adverbial sequences; however, they were likely to function in different time windows. In addition, both native and nonnative speakers were sensitive to the phrasal frequency and contingency of the sequences, though their degrees of such sensitivity differed. Our findings suggest that adult language learners retain the statistical learning ability in second language acquisition and they may share a general statistical learning mechanism with native speakers when processing multiword sequences. |
Lili Yu; Qiaoming Zhang; Caspian Priest; Erik D. Reichle; Heather Sheridan Character-complexity effects in Chinese reading and visual search: A comparison and theoretical implications Journal Article In: Quarterly Journal of Experimental Psychology, vol. 71, no. 1, pp. 140–151, 2017. @article{Yu2017b, Three eye-movement experiments were conducted to examine how the complexity of characters in Chinese words (i.e., number of strokes per character) influences their processing and eye-movement behaviour. In Experiment 1, English speakers with no significant knowledge of Chinese searched for specific low-, medium-, and high-complexity target characters in a multi-page narrative containing characters of varying complexity (3–16 strokes). Fixation durations and skipping rates were influenced by the visual complexity of both the target characters and the characters being searched even though participants had no knowledge of Chinese. In Experiment 2, native Chinese speakers performed the same character-search task, and a similar pattern of results was observed. Finally, in Experiment 3, a second sample of native Chinese speakers read the same text used in Experiments 1 and 2, with text characters again exhibiting complexity effects. These results collectively suggest that character-complexity effects on eye movements may not be due to lexical processing per se but may instead reflect whatever visual processing is required to know whether or not a character corresponds to an episodically represented target. The theoretical implications of this for our understanding of normal reading are discussed. |
Matthew R. Krause; Theodoros P. Zanos; Bennett A. Csorba; Praveen K. Pilly; Jaehoon Choe; Matthew E. Phillips; Abhishek Datta; Christopher C. Pack Transcranial direct current stimulation facilitates associative learning and alters functional connectivity in the primate brain Journal Article In: Current Biology, vol. 27, no. 20, pp. 3086–3096, 2017. @article{Krause2017, There has been growing interest in transcranial direct current stimulation (tDCS), a non-invasive technique purported to modulate neural activity via weak, externally applied electric fields. Although some promising preliminary data have been reported for applications ranging from stroke rehabilitation to cognitive enhancement, little is known about how tDCS affects the human brain, and some studies have concluded that it may have no effect at all. Here, we describe a macaque model of tDCS that allows us to simultaneously examine the effects of tDCS on brain activity and behavior. We find that applying tDCS to right prefrontal cortex improves monkeys' performance on an associative learning task. While firing rates do not change within the targeted area, tDCS does induce large low-frequency oscillations in the underlying tissue. These oscillations alter functional connectivity, both locally and between distant brain areas, and these long-range changes correlate with tDCS's effects on behavior. Together, these results are consistent with the idea that tDCS leads to widespread changes in brain activity and suggest that it may be a valuable method for cheaply and non-invasively altering functional connectivity in humans. Krause et al. test transcranial direct current stimulation (tDCS) in a realistic non-human primate model. Stimulation of prefrontal cortex (PFC) improved animals' associative learning while altering coherence between PFC and sensory areas. Their data suggest that tDCS may act by altering long-range connectivity between PFC and other brain areas. |
Matthew L. Leavitt; Florian Pieper; Adam J. Sachs; Julio C. Martinez-Trujillo Correlated variability modifies working memory fidelity in primate prefrontal neuronal ensembles Journal Article In: Proceedings of the National Academy of Sciences, vol. 114, no. 12, pp. E2494–E2503, 2017. @article{Leavitt2017a, Neurons in the primate lateral prefrontal cortex (LPFC) encode working memory (WM) representations via sustained firing, a phenomenon hypothesized to arise from recurrent dynamics within ensembles of interconnected neurons. Here, we tested this hypothesis by using microelectrode arrays to examine spike count correlations (rsc) in LPFC neuronal ensembles during a spatial WM task. We found a pattern of pairwise rsc during WM maintenance indicative of stronger coupling between similarly tuned neurons and increased inhibition between dissimilarly tuned neurons. We then used a linear decoder to quantify the effects of the high-dimensional rsc structure on information coding in the neuronal ensembles. We found that the rsc structure could facilitate or impair coding, depending on the size of the ensemble and tuning properties of its constituent neurons. A simple optimization procedure demonstrated that near-maximum decoding performance could be achieved using a relatively small number of neurons. These WM- optimized subensembles were more signal correlation (rsignal)- diverse and anatomically dispersed than predicted by the statistics of the full recorded population of neurons, and they often con- tained neurons that were poorly WM-selective, yet enhanced cod- ing fidelity by shaping the ensemble's rsc structure. We observed a pattern of rsc between LPFC neurons indicative of recurrent dynamics as a mechanism for WM-related activity and that the rsc structure can increase the fidelity ofWM representations. Thus, WM coding in LPFC neuronal ensembles arises from a complex synergy between single neuron coding properties and multidimensional, ensemble-level phenomena. |
Jeyeon Lee; Hoseok Choi; Seho Lee; Baek Hwan Cho; Kyoung-ha Ahn; In Young Kim; Kyoung-Min Lee; Dong-Pyo Jang Decoding saccadic directions using epidural ECoG in non-human primates Journal Article In: Journal of Korean Medical Science, vol. 32, no. 8, pp. 1243–1250, 2017. @article{Lee2017, A brain-computer interface (BCI) can be used to restore some communication as an alternative interface for patients suffering from locked-in syndrome. However, most BCI systems are based on SSVEP, P300, or motor imagery, and a diversity of BCI protocols would be needed for various types of patients. In this paper, we trained the choice saccade (CS) task in 2 non-human primate monkeys and recorded the brain signal using an epidural electrocorticogram (eECoG) to predict eye movement direction. We successfully predicted the direction of the upcoming eye movement using a support vector machine (SVM) with the brain signals after the directional cue onset and before the saccade execution. The mean accuracies were 80% for 2 directions and 43% for 4 directions. We also quantified the spatial-spectro-temporal contribution ratio using SVM recursive feature elimination (RFE). The channels over the frontal eye field (FEF), supplementary eye field (SEF), and superior parietal lobule (SPL) area were dominantly used for classification. The α-band in the spectral domain and the time bins just after the directional cue onset and just before the saccadic execution were mainly useful for prediction. A saccade based BCI paradigm can be projected in the 2D space, and will hopefully provide an intuitive and convenient communication platform for users. |
Roman F. Loonis; Scott L. Brincat; Evan G. Antzoulatos; Earl K. Miller A meta-analysis suggests different neural correlates for implicit and explicit learning Journal Article In: Neuron, vol. 96, no. 2, pp. 521–534.e7, 2017. @article{Loonis2017, A meta-analysis of non-human primates performing three different tasks (Object-Match, Category-Match, and Category-Saccade associations) revealed signatures of explicit and implicit learning. Performance improved equally following correct and error trials in the Match (explicit) tasks, but it improved more after correct trials in the Saccade (implicit) task, a signature of explicit versus implicit learning. Likewise, error-related negativity, a marker for error processing, was greater in the Match (explicit) tasks. All tasks showed an increase in alpha/beta (10–30 Hz) synchrony after correct choices. However, only the implicit task showed an increase in theta (3–7 Hz) synchrony after correct choices that decreased with learning. In contrast, in the explicit tasks, alpha/beta synchrony increased with learning and decreased thereafter. Our results suggest that explicit versus implicit learning engages different neural mechanisms that rely on different patterns of oscillatory synchrony. Loonis et al. find that explicit and implicit learning use feedback about correct choices versus errors differently. Implicit learning relies more on theta synchrony (3–7 Hz) while explicit learning relies on alpha/beta synchrony (10–30 Hz). |
Nicolas Y. Masse; Jonathan M. Hodnefield; David J. Freedman Mnemonic encoding and cortical organization in parietal and prefrontal cortices Journal Article In: Journal of Neuroscience, vol. 37, no. 25, pp. 6098–6112, 2017. @article{Masse2017, Persistent activity within the frontoparietal network is consistently observed during tasks that require working memory. However, the neural circuit mechanisms underlying persistent neuronal encoding within this network remain unresolved. Here, we ask how neural circuits support persistent activity by examining population recordings from posterior parietal (PPC) and prefrontal (PFC) cortices in two male monkeys that performed spatial and motion direction-based tasks that required working memory. While spatially selective persistent activity was observed in both areas, robust selective persistent activity for motion direction was only observed in PFC. Crucially, we find that this difference between mnemonic encoding in PPC and PFC is associated with the presence offunctional clustering: PPC and PFC neurons up to ~700 μm apart preferred similar spatial locations, and PFC neurons up to ~700 μm apart preferred similar motion directions. In contrast, motion-direction tuning similarity between nearby PPC neurons was much weaker and decayed rapidly beyond ~200 μm. We also observed a similar association between persistent activity and functional clustering in trained recurrent neural network models embedded with a columnar topology. These results suggest that functional clustering facilitates mnemonic encoding of sensory information. |
Diego Mendoza-Halliday; Julio C. Martinez-Trujillo Neuronal population coding of perceived and memorized visual features in the lateral prefrontal cortex Journal Article In: Nature Communications, vol. 8, pp. 15471, 2017. @article{MendozaHalliday2017, The primate lateral prefrontal cortex (LPFC) encodes visual stimulus features while they are perceived and while they are maintained in working memory. However, it remains unclear whether perceived and memorized features are encoded by the same or different neurons and population activity patterns. Here we record LPFC neuronal activity while monkeys perceive the motion direction of a stimulus that remains visually available, or memorize the direction if the stimulus disappears. We find neurons with a wide variety of combinations of coding strength for perceived and memorized directions: some neurons encode both to similar degrees while others preferentially or exclusively encode either one. Reading out the combined activity of all neurons, a machine-learning algorithm reliably decode the motion direction and determine whether it is perceived or memorized. Our results indicate that a functionally diverse population of LPFC neurons provides a substrate for discriminating between perceptual and mnemonic representations of visual features. |
Soo Hyun Park; Brian E. Russ; David B. T. McMahon; Kenji W. Koyano; Rebecca A. Berman; David A. Leopold Functional subpopulations of neurons in a macaque face patch revealed by single-unit fMRI mapping Journal Article In: Neuron, vol. 95, no. 4, pp. 971–981.e5, 2017. @article{Park2017, Neurons within fMRI-defined face patches of the macaque brain exhibit shared categorical responses to flashed images but diverge in their responses under more natural viewing conditions. Here we investigate functional diversity among neurons in the anterior fundus (AF) face patch, combining whole-brain fMRI with longitudinal single-unit recordings in a local population (<1 mm3). For each cell, we computed a whole-brain correlation map based on its shared time course with voxels throughout the brain during naturalistic movie viewing. Based on this mapping, neighboring neurons showed markedly different affiliation with distant visually responsive areas and fell coarsely into subpopulations. Of these, only one subpopulation (∼16% of neurons) yielded similar correlation maps to the local fMRI signal. The results employ the readout of large-scale fMRI networks and, by indicating multiple functional domains within a single voxel, present a new view of functional diversity within a local neural population. |
Aishwarya Parthasarathy; Roger Herikstad; Jit Hon Bong; Felipe Salvador Medina; Camilo Libedinsky; Shih-Cheng Yen Mixed selectivity morphs population codes in prefrontal cortex Journal Article In: Nature Neuroscience, vol. 20, no. 12, pp. 1770–1779, 2017. @article{Parthasarathy2017, The prefrontal cortex plays an important role in the maintenance of working memory, as evidenced by studies using microelectrode recordings 1, lesions 2, inactivation 3, micro-stimulation 4, 5, and functional neuroimaging 6. Furthermore, the pre-frontal cortex suppresses task-irrelevant stimuli, or distractors 3, 7, 8. This has led to the notion that the prefrontal cortex plays a central role in the maintenance of working memory and the suppression of distractors, which are cornerstones of executive processing. Individual neurons in the lateral prefrontal cortex (LPFC; Brodmann area 46) show selective, sustained activity during the delay period of working memory and only as long as the memory is maintained 1,9,10. Populations of LPFC neurons form a stable memory code during the delay period of a working memory task 11. Distractors are thought to be suppressed in the LPFC, since it responds less to distractors than to task-relevant stimuli 3, 7, 8. Notably, sustained activity of LPFC neurons persists even after distractors are presented 3, 10. Thus, it is reasonable to hypothesize that the stable code observed during the delay period persists after a distractor is presented, forming a persistent code throughout the memory period. Recent studies have shown that the LPFC hosts an abundance of neurons with mixed selectivity 12-19. These cells encode multiple parameters of the task simultaneously, such as sensory stimuli, task rule, or motor response. In particular, neurons with nonlinear mixed selectivity (NMS) are thought to play a key role in the encoding of information 18, 20. In the context of a working memory task with interfering distractors, mixed selectivity could lead to a change in code after the distractor is presented. Thus, it is also reasonable to hypothesize that the code does not persist throughout the memory period but rather that it is flexible, with the ability to adapt to new task contingencies, such as the presentation of a distractor. Here we found that the LPFC morphs its code, as the latter hypothesis predicts , while the frontal eye fields (FEF) maintain a stable code, in agreement with the former hypothesis. Results Two monkeys were trained to perform a delayed saccade task (Fig. 1a). Overall performance of both animals was higher than 75% correct (Fig. 1b). We recorded a total of 256 neurons from the LPFC (144 from Monkey A and 112 from Monkey B; the positions of the implanted electrode arrays are shown in red in Fig. 1c) and 137 neurons from the FEF (125 from Monkey A and 12 from Monkey B; electrode arrays are shown in blue in Fig. 1c) while the animals performed the task. Of the neurons recorded, more than 40% displayed selectiv-ity to target location in at least one stage during the trial (Fig. 1d). Examples of the responses of an LPFC and an FEF neuron are shown in Supplementary Fig. 1a,b. To quantify the magnitude of this selec-tivity, we computed the percentage of explained variance (PEV) for spatial selectivity in each neuron. The average PEVs across significant neurons (Methods) are shown in Fig. 1d. In the LPFC, we observed that target information in selective cells (n = 107, 42% of the LPFC population) increased during the target presentation period and remained stable throughout the rest of the trial (Fig. 1d). In addition, in Supplementary Fig. 1c, we show that the distractor information was much lower in these same neurons during the Delay 2 period (P < 0.001, Hedges' g = 23.99). A previous study found a sharp decrease in target information following distractor presentation , together with an increase of distractor information 21. Our results, however, did not replicate these observations. Rather, we found that target information remained stable, and distractor information stayed close to baseline throughout the trial (Supplementary Fig. 1c). This difference may reflect the simpler nature of our task and the comparatively lower behavioral saliency of the distractor we used. It may also reflect differences in the ways different types of information are encoded; perhaps the working memory code for numerosity in LPFC is more susceptible to distractors than the code for spatial locations. In contrast, in the FEF we observed The prefrontal cortex maintains working memory information in the presence of distracting stimuli. It has long been thought that sustained activity in individual neurons or groups of neurons was responsible for maintaining information in the form of a persistent, stable code. Here we show that, upon the presentation of a distractor, information in the lateral prefrontal cortex was reorganized into a different pattern of activity to create a morphed stable code without losing information. In contrast, the code in the frontal eye fields persisted across different delay periods but exhibited substantial instability and information loss after the presentation of a distractor. We found that neurons with mixed-selective responses were necessary and sufficient for the morphing of code and that these neurons were more abundant in the lateral prefrontal cortex than the frontal eye fields. This suggests that mixed selectivity provides populations with code-morphing capability, a property that may underlie cognitive flexibility. |
Tyler R. Peel; Suryadeep Dash; Stephen G. Lomber; Brian D. Corneil Frontal eye field inactivation diminishes superior colliculus activity, but delayed saccadic accumulation governs reaction time increases Journal Article In: Journal of Neuroscience, vol. 37, no. 48, pp. 11715–11730, 2017. @article{Peel2017, Stochastic accumulator models provide a comprehensive framework for how neural activity could produce behavior. Neural activity within the frontal eye fields (FEFs) and intermediate layers of the superior colliculus (iSC) support such models for saccade initiation by relating variations in saccade reaction time (SRT) to variations in such parameters as baseline, rate of accumulation of activity, and threshold. Here, by recording iSC activity during reversible cryogenic inactivation of the FEF in four male nonhuman primates, we causally tested which parameter(s) best explains concomitant increases in SRT. While FEF inactivation decreased all aspects of ipsilesional iSC activity, decreases in accumulation rate and threshold poorly predicted accompanying increases in SRT. Instead, SRT increases best correlated with delays in the onset of saccade-related accumulation. We conclude that FEF signals govern the onset of saccade-related accumulation within the iSC, and that the onset of accumulation is a relevant parameter for stochastic accumulation models of saccade initiation. |
Joel Reithler; Judith C. Peters; Rainer Goebel In: NeuroImage, vol. 152, pp. 551–562, 2017. @article{Reithler2017, Visual scenes are initially processed via segregated neural pathways dedicated to either of the two visual hemifields. Although higher-order visual areas are generally believed to utilize invariant object representations (abstracted away from features such as stimulus position), recent findings suggest they retain more spatial information than previously thought. Here, we assessed the nature of such higher-order object representations in human cortex using high-resolution fMRI at 7T, supported by corroborative 3T data. We show that multi-voxel activation patterns in both the contra- and ipsilateral hemisphere can be exploited to successfully classify the object category of unilaterally presented stimuli. Moreover, robustly identified rank order-based response profiles demonstrated a strong contralateral bias which frequently outweighed object category preferences. Finally, we contrasted different combinatorial operations to predict the responses during bilateral stimulation conditions based on responses to their constituent unilateral elements. Results favored a max operation predominantly reflecting the contralateral stimuli. The current findings extend previous work by showing that configuration-dependent modulations in higher-order visual cortex responses as observed in single unit activity have a counterpart in human neural population coding. They furthermore corroborate the emerging view that position coding is a fundamental functional characteristic of ventral visual stream processing. |
Huixia Zhou; Sonja Rossi; Juan Li; Huanhuan Liu; Ran Chen; Baoguo Chen Effects of working memory capacity in processing wh-extractions: Eye-movement evidence from Chinese–English bilinguals Journal Article In: Journal of Research in Reading, vol. 40, no. 4, pp. 420–438, 2017. @article{Zhou2017a, By using the eye-tracking method, the present study explores whether working memory capacity assessed via the second language (L2) reading span (L2WMC) as well as the operational span task (OSPAN) affects the processing of subject-extraction and object-extraction in Chinese–English bilinguals. Results showed that L2WMC has no effects on the grammatical judgement accuracies, the first fixation duration, gaze duration, go-past times and total fixation duration of the critical regions in wh-extractions. In contrast, OSPAN influences the first fixation duration and go-past times of the critical regions in wh-extractions. Specifically, in region 1, (e.g., Who do you think loved the comedian [region 1] with [region 2] all his heart [subject-extraction]? versus Who do you think the comedian loved [region 1] with [region 2] all his heart? [object-extraction] ), participants with high OSPAN were much slower than those with low OSPAN in their first fixation duration in reading subject-extractions, whereas there were no differences between participants with different OSPANs in reading object-extractions. In region 2, participants with high OSPAN were much faster than those with low OSPAN in their go-past times of object-extractions. These results indicated that individual differences in OSPAN rather than in L2WMC more strongly affect processing of wh-extractions. Thus, OSPAN results to be more suitable to explore the influences of working memory while processing L2 sentences with complex syntax, at least for intermediate proficient bilinguals. Results of the study also provide further support for the Capacity Theory of Comprehension. |
Yaser Merrikhi; Kelsey Clark; Eddy Albarran; Mohammadbagher Parsa; Marc Zirnsak; Tirin Moore; Behrad Noudoost Spatial working memory alters the efficacy of input to visual cortex Journal Article In: Nature Communications, vol. 8, pp. 15041, 2017. @article{Merrikhi2017, Prefrontal cortex modulates sensory signals in extrastriate visual cortex, in part via its direct projections from the frontal eye field (FEF), an area involved in selective attention. We find that working memory-related activity is a dominant signal within FEF input to visual cortex. Although this signal alone does not evoke spiking responses in areas V4 and MT during memory, the gain of visual responses in these areas increases, and neuronal receptive fields expand and shift towards the remembered location, improving the stimulus representation by neuronal populations. These results provide a basis for enhancing the representation of working memory targets and implicate persistent FEF activity as a basis for the interdependence of working memory and selective attention. |
Juri Minxha; Clayton Mosher; Jeremiah K. Morrow; Adam N. Mamelak; Ralph Adolphs; Katalin M. Gothard; Ueli Rutishauser Fixations gate species-specific responses to free viewing of faces in the human and macaque amygdala Journal Article In: Cell Reports, vol. 18, no. 4, pp. 878–891, 2017. @article{Minxha2017, Neurons in the primate amygdala respond prominently to faces. This implicates the amygdala in the processing of socially significant stimuli, yet its contribution to social perception remains poorly understood. We evaluated the representation of faces in the primate amygdala during naturalistic conditions by recording from both human and macaque amygdala neurons during free viewing of identical arrays of images with concurrent eye tracking. Neurons responded to faces only when they were fixated, suggesting that neuronal activity was gated by visual attention. Further experiments in humans utilizing covert attention confirmed this hypothesis. In both species, the majority of face-selective neurons preferred faces of conspecifics, a bias also seen behaviorally in first fixation preferences. Response latencies, relative to fixation onset, were shortest for conspecific-selective neurons and were ∼100 ms shorter in monkeys compared to humans. This argues that attention to faces gates amygdala responses, which in turn prioritize species-typical information for further processing. |
Ilya E. Monosov Anterior cingulate is a source of valence-specific information about value and uncertainty Journal Article In: Nature Communications, vol. 8, pp. 134, 2017. @article{Monosov2017, Anterior cingulate cortex (ACC) is thought to control a wide range of reward, punishment, and uncertainty-related behaviors. However, how it does so is unclear. Here, in a Pavlovian procedure in which monkeys displayed a diverse repertoire of reward-related, punishment-related, and uncertainty-related behaviors, we show that many ACC-neurons represent expected value and uncertainty in a valence-specific manner, signaling value or uncertainty predictions about either rewards or punishments. Other ACC-neurons signal prediction information about rewards and punishments by displaying excitation to both (rather than excitation to one and inhibition to the other). This diversity in valence representations may support the role of ACC in many behavioral states that are either enhanced by reward and punishment (e.g., vigilance) or specific to either reward or punishment (e.g., approach and avoidance). Also, this first demonstration of punishment-uncertainty signals in the brain suggests that ACC could be a target for the treatment of uncertainty-related disorders of mood. |
Sujaya Neupane; Daniel Guitton; Christopher C. Pack Coherent alpha oscillations link current and future receptive fields during saccades Journal Article In: Proceedings of the National Academy of Sciences, vol. 114, no. 29, pp. E5979–E5985, 2017. @article{Neupane2017, Oscillations are ubiquitous in the brain, and they can powerfully influence neural coding. In particular, when oscillations at distinct sites are coherent, they provide a means of gating the flow of neural signals between different cortical regions. Coherent oscillations also occur within individual brain regions, although the purpose of this coherence is not well understood. Here, we report that within a single brain region, coherent alpha oscillations link stimulus representations as they change in space and time. Specifically, in primate cortical area V4, alpha coherence links sites that encode the retinal location of a visual stimulus before and after a saccade. These coherence changes exhibit properties similar to those of receptive field remapping, a phenomenon in which individual neurons change their receptive fields according to the metrics of each saccade. In particular, alpha coherence, like remapping, is highly dependent on the saccade vector and the spatial arrangement of current and future receptive fields. Moreover, although visual stimulation plays a modulatory role, it is neither necessary nor sufficient to elicit alpha coherence. Indeed, a similar pattern of coherence is observed even when saccades are made in darkness. Together, these results show that the pattern of alpha coherence across the retinotopic map in V4 matches many of the properties of receptive field remapping. Thus, oscillatory coherence might play a role in constructing the stable representation of visual space that is an essential aspect of conscious perception. |
James E. Niemeyer; Michael A. Paradiso Contrast sensitivity, V1 neural activity, and natural vision Journal Article In: Journal of Neurophysiology, vol. 117, no. 2, pp. 492–508, 2017. @article{Niemeyer2017, Contrast sensitivity is fundamental to natural visual processing and an important tool for characterizing both visual function and clinical disorders. We simultaneously measured contrast sensitivity and neural contrast response functions and compared measurements in common laboratory conditions with naturalistic conditions. In typical experiments, a subject holds fixation and a stimulus is flashed on, whereas in natural vision, saccades bring stimuli into view. Motivated by our previous V1 findings, we tested the hypothesis that perceptual contrast sensitivity is lower in natural vision and that this effect is associated with corresponding changes in V1 activity. We found that contrast sensitivity and V1 activity are correlated and that the relationship is similar in laboratory and naturalistic paradigms. However, in the more natural situation, contrast sensitivity is reduced up to 25% compared with that in a standard fixation paradigm, particularly at lower spatial frequencies, and this effect correlates with significant reductions in V1 responses. Our data suggest that these reductions in natural vision result from fast adaptation on one fixation that lowers the response on a subsequent fixation. This is the first demonstration of rapid, naturalimage adaptation that carries across saccades, a process that appears to constantly influence visual sensitivity in natural vision. NEW & NOTEWORTHY Visual sensitivity and activity in brain area V1 were studied in a paradigm that included saccadic eye movements and natural visual input. V1 responses and contrast sensitivity were significantly reduced compared with results in common laboratory paradigms. The parallel neural and perceptual effects of eye movements and stimulus complexity appear to be due to a form of rapid adaptation that carries across saccades. |
Jordi Aguila; F. Javier Cudeiro; Casto Rivadulla In: Cerebral Cortex, vol. 27, no. 6, pp. 3331–3345, 2017. @article{Aguila2017, In awake monkeys, we used repetitive transcranial magnetic stimulation (rTMS) to focally inactivate visual cortex while measuring the responsiveness of parvocellular lateral geniculate nucleus (LGN) neurons. Effects were noted in 64/75 neurons, and could be divided into 2 main groups: (1) for 39 neurons, visual responsiveness decreased and visual latency increased without apparent shift in receptive field (RF) position and (2) a second group (n = 25, 33% of the recorded cells) whose excitability was not compromised, but whose RF position shifted an average of 4.5°. This change is related to the retinotopic correspondence observed between the recorded thalamic area and the affected cortical zone. The effect of inactivation for this group of neurons was compatible with silencing the original retinal drive and unmasking a second latent retinal drive onto the studied neuron. These results indicate novel and remarkable dynamics in thalamocortical circuitry that force us to reassess constraints on retinogeniculate transmission. |
Habiba Azab; Benjamin Y. Hayden Correlates of decisional dynamics in the dorsal anterior cingulate cortex Journal Article In: PLoS Biology, vol. 15, no. 11, pp. e2003091, 2017. @article{Azab2017, We hypothesized that during binary economic choice, decision makers use the first option they attend as a default to which they compare the second. To test this idea, we recorded activity of neurons in the dorsal anterior cingulate cortex (dACC) of macaques choosing between gambles presented asynchronously. We find that ensemble encoding of the value of the first offer includes both choice-dependent and choice-independent aspects, as if reflecting a partial decision. That is, its responses are neither entirely pre- nor post-decisional. In contrast, coding of the value of the second offer is entirely decision dependent (i.e., post-decisional). This result holds even when offer-value encodings are compared within the same time period. Additionally, we see no evidence for 2 pools of neurons linked to the 2 offers; instead, all comparison appears to occur within a single functionally homogenous pool of task-selective neurons. These observations suggest that economic choices reflect a context-dependent evaluation of attended options. Moreover, they raise the possibility that value representations reflect, to some extent, a tentative commitment to a choice. |
Sahand Babapoor-Farrokhran; Martin Vinck; Thilo Womelsdorf; Stefan Everling Theta and beta synchrony coordinate frontal eye fields and anterior cingulate cortex during sensorimotor mapping Journal Article In: Nature Communications, vol. 8, pp. 13967, 2017. @article{BabapoorFarrokhran2017, The frontal eye fields (FEFs) and the anterior cingulate cortex (ACC) are commonly coacti- vated for cognitive saccade tasks, but whether this joined activation indexes coordinated activity underlying successful guidance of sensorimotor mapping is unknown. Here we test whether ACC and FEF circuits coordinate through phase synchronization of local field potential and neural spiking activity in macaque monkeys performing memory-guided and pro- and anti-saccades. We find that FEF and ACC showed prominent synchronization at a 3–9 Hz theta and a 12–30 Hz beta frequency band during the delay and preparation periods with a strong Granger-causal influence from ACC to FEF. The strength of theta- and beta- band coherence between ACC and FEF but not variations in power predict correct task performance. Taken together, the results support a role of ACC in cognitive control of fron- toparietal networks and suggest that narrow-band theta and to some extent beta rhythmic activity indexes the coordination of relevant information during periods of enhanced control demands. |
Bob McMurray; Ashley Farris-Trimble; Hannah Rigler Waiting for lexical access: Cochlear implants or severely degraded input lead listeners to process speech less incrementally Journal Article In: Cognition, vol. 169, pp. 147–164, 2017. @article{McMurray2017, Spoken language unfolds over time. Consequently, there are brief periods of ambiguity, when incomplete input can match many possible words. Typical listeners solve this problem by immediately activating multiple candidates which compete for recognition. In two experiments using the visual world paradigm, we examined real-time lexical competition in prelingually deaf cochlear implant (CI) users, and normal hearing (NH) adults listening to severely degraded speech. In Experiment 1, adolescent CI users and NH controls matched spoken words to arrays of pictures including pictures of the target word and phonological competitors. Eye-movements to each referent were monitored as a measure of how strongly that candidate was considered over time. Relative to NH controls, CI users showed a large delay in fixating any object, less competition from onset competitors (e.g., sandwich after hearing sandal), and increased competition from rhyme competitors (e.g., candle after hearing sandal). Experiment 2 observed the same pattern with NH listeners hearing highly degraded speech. These studies suggests that in contrast to all prior studies of word recognition in typical listeners, listeners recognizing words in severely degraded conditions can exhibit a substantively different pattern of dynamics, waiting to begin lexical access until substantial information has accumulated. |
Jinger Pan; Ming Yan; Jochen Laubrock Perceptual span in oral reading: The case of Chinese Journal Article In: Scientific Studies of Reading, vol. 21, no. 3, pp. 254–263, 2017. @article{Pan2017, The present study explores the perceptual span, that is, the physical extent of the area from which useful visual information is obtained during a single fixation, during oral reading of Chinese sentences. Characters outside a window of legible text were replaced by visually similar characters. Results show that the influence of window size on the perceptual span was consistent across different fixation and oculomotor measures. To maintain normal reading behavior when reading aloud, it was necessary to have information provided from three characters to the right of the fixation. Together with findings from previous research, our findings suggest that the physical size of the perceptual span is smaller when reading aloud than in silent reading. This is in agreement with previous studies in English, suggesting that the mechanisms causing the reduced span in oral reading have a common base that generalizes across languages and writing systems. |
Adam J. Parker; Julie A. Kirkby; Timothy J. Slattery Predictability effects during reading in the absence of parafoveal preview Journal Article In: Journal of Cognitive Psychology, vol. 29, no. 8, pp. 902–911, 2017. @article{Parker2017, The predictability of upcoming words facilitates both spoken and written language comprehension. One interesting difference between these language modalities is that readers' routinely have access to upcoming words in parafoveal vision while listeners must wait for each fleeting word from a speaker. Despite readers' potential glimpse into the future, it is not clear if and how this bottom-up information aids top-down prediction. The current study manipulated the predictability of target words and their location on a line of text. Targets were located in the middle of the line (preview available) or as the first word on a new line (preview unavailable). This represents an innovative method for manipulating parafoveal preview which utilises return sweeps to deny access to parafoveal preview of target words without the use of invalid previews. The study is the first to demonstrate gaze duration word predictability effects in the absence of parafoveal preview. |
Dan Parker; Colin Phillips Reflexive attraction in comprehension is selective Journal Article In: Journal of Memory and Language, vol. 94, pp. 272–290, 2017. @article{Parker2017a, Many studies have shown that attraction effects are consistently found for linguistic dependencies like subject-verb agreement, e.g., The key to the cabinets are on the table. However, not all dependencies are equally susceptible to attraction. A parade case involves reflexive-antecedent dependencies, which rarely show attraction effects. The contrast between agreement and reflexives with respect to attraction has motivated various proposals regarding the memory architecture for the parser, including the use of qualitatively different access mechanisms or the selective use of morphological features as retrieval cues for different dependencies. In this paper, we show how to systematically induce attraction effects for reflexives in three eye-tracking experiments. Furthermore, we show based on computational simulations that it is possible to derive both the presence and absence of reflexive attraction from the same retrieval mechanism, based on the ACT-R architecture. We then propose an account of why agreement and reflexives are differentially susceptible to attraction, based on the predictability of the dependency. |
Manuel Perea; Eva Rosa; Ana Marcet Where is the locus of the lowercase advantage during sentence reading? Journal Article In: Acta Psychologica, vol. 177, pp. 30–35, 2017. @article{Perea2017, While most models of visual word identification and reading posit that a word's visual codes are rapidly transformed onto case-invariant representations (i.e., table and TABLE would equally activate the word unit corresponding to “table”), a number of experiments have shown a lowercase advantage in various word identification and reading tasks. In the present experiment, we examined the locus of this lowercase advantage by comparing the pattern of eye movements when reading sentences in lowercase vs. uppercase. Each sentence contained a target word that was high or low in word-frequency. Overall, results showed faster reading times for lowercase than for uppercase sentences. More important, while the word-frequency effect was sizeable in the first-fixation durations on the target word, the lowercase advantage only arose in the gaze durations (i.e., the sum of durations of first-pass fixations on the target word, including refixations). Furthermore, we found an effect of word-frequency, but not of letter case, in the first-fixation duration on target words with multiple first-pass fixations. Taken together, these findings suggest that the lowercase advantage reflects operations that do not occur in the initial contact with the lexical entries. |
Pilar Piñar; Matthew T. Carlson; Jill P. Morford; Paola E. Dussias Bilingual deaf readers' use of semantic and syntactic cues in the processing of English relative clauses Journal Article In: Bilingualism: Language and Cognition, vol. 20, no. 5, pp. 980–998, 2017. @article{Pinar2017, Eye fixation measures were used to examine English relative clause processing by adult ASL-English bilingual deaf readers. Participants processed subject relative clauses faster than object relative clauses, but expected animacy cues eliminated processing difficulty in object relative clauses. This brings into question previous claims that deaf readers' sentence processing strategies are qualitatively different from those of hearing English native speakers. Measures of English comprehension predicted reading speed, but not differences in syntactic processing. However, a trend for ASL self-ratings to predict the ability to handle syntactic complexity approached significance. Results suggest a need to explore how objective ASL proficiency measures might provide insights into deaf readers' ability to exploit syntactic cues in English. |
Joshua D. Pratt; Scott B. Stevenson; Harold E. Bedell Scotoma visibility and reading rate with bilateral central scotomas Journal Article In: Optometry and Vision Science, vol. 94, no. 3, pp. 279–284, 2017. @article{Pratt2017, PURPOSE: In this experiment, we tested whether perceptually delineating the scotoma location and border with a gaze contingent polygon overlay improves reading speed and reading eye movements in patients with bilateral central scotomas. METHODS: Eight patients with age-related macular degeneration and bilateral central scotomas read aloud MNRead style sentences with their preferred eye. Eye movement signals from an EyeLink II eyetracker were used to create a gaze contingent display in which a polygon overlay delineating the area of the patient's scotoma was superimposed on the text during 18 of the 42 trials. Blocks of six trials with the superimposed polygon were alternated with blocks of six trials without the polygon. Reading speed and reading eye movements were assessed before and after the subjects practiced reading with the polygon overlay. RESULTS: All of the subjects but one showed an increase in reading speed. A paired-samples t-test for the group as a whole revealed a statistically significant increase in reading speed of 0.075 ± 0.060 (SD) log wpm after reading with the superimposed polygon. Individual subjects demonstrated significant changes in reading eye movements, with the greatest number of subjects demonstrating a shift in the average vertical fixation locus. Across subjects, there was no significant difference between the initial and final reading eye movements in terms of saccades per second, average fixation duration, average amplitude of saccades, or proportion of non-horizontal saccades. CONCLUSIONS: The improvement in reading speed (0.075 log wpm or 19%) over the short experimental session for the majority of subjects indicates that making the scotoma location more visible is potentially beneficial for improving reading speed in patients with bilateral central scotomas. Additional research to examine the efficacy of more extended training with this paradigm is warranted. |
Timothy R. Jordan; Victoria A. McGowan; Stoyan Kurtev; Kevin B. Paterson In: Frontiers in Psychology, vol. 8, pp. 807, 2017. @article{Jordan2017, Printed words are complex visual stimuli containing a range of different spatial frequencies, and several studies have suggested that various spatial frequencies are effective for skilled adult reading. But while it is well known that the area of text from which information is acquired during reading extends to the left and right of each fixation, the effectiveness of spatial frequencies falling each side of fixation has yet to be determined. To investigate this issue, we used a spatial frequency adaptation of the gaze-contingent moving-window paradigm in which sentences were shown to skilled adult readers either entirely as normal or filtered to contain only low, medium, or high spatial frequencies except for a window of normal text around each point of fixation. Windows replaced filtered text either symmetrically 1 character to the left and right of each fixated character, or asymmetrically, 1 character to the left and 7 or 13 to the right, or 1 character to the right and 7 or 13 to the left. Reading times and eye-movement measures showed that reading performance for sentences presented entirely as normal generally changed very little with filtered displays when windows extended to the right but was often disrupted when windows extended to the left. However, asymmetrical windows affected performance on both sides of fixation. Indeed, increasing the leftward extent of windows from 7 to 13 characters produced decreases in both reading times and fixation durations, suggesting that reading was influenced by the spatial frequency content of leftward areas of text some considerable distance from fixation. Overall, the findings show that while a range of different spatial frequencies can be used by skilled adult readers, the effectiveness of spatial frequencies differs for text on each side of central vision, and may reflect different roles played by these two areas of text during reading. |
Barbara J. Juhasz; Rebecca L. Johnson; Jennifer Brewer An investigation into the processing of lexicalized English blend words: Evidence from lexical decisions and eye movements during reading Journal Article In: Journal of Psycholinguistic Research, vol. 46, no. 2, pp. 281–294, 2017. @article{Juhasz2017, New words enter the language through several word formation processes [see Simonini (Engl J 55:752-757, 1966)]. One such process, blending, occurs when two source words are combined to represent a new concept (e.g., SMOG, BRUNCH, BLOG, and INFOMERCIAL). While there have been examinations of the structure of blends [see Gries (Linguistics 42:639-667, 2004) and Lehrer (Am Speech 73:3-28, 1998)], relatively little attention has been given to how lexicalized blends are recognized and if this process differs from other types of words. In the present study, blend words were matched to non-blend control words on length, familiarity, and frequency. Two tasks were used to examine blend processing: lexical decision and sentence reading. The results demonstrated that blend words were processed differently than non-blend control words. However, the nature of the effect varied as a function of task demands. Blends were recognized slower than control words in the lexical decision task but received shorter fixation durations when embedded in sentences. |
Krista R. Kelly; Reed M. Jost; Angie De La Cruz; Lori Dao; Cynthia L. Beauchamp; David R. Stager; Eileen E. Birch Slow reading in children with anisometropic amblyopia is associated with fixation instability and increased saccades Journal Article In: Journal of AAPOS, vol. 21, no. 6, pp. 447–451, 2017. @article{Kelly2017, Background: Previous studies show slow reading in strabismic amblyopia. We recently identified amblyopia, not strabismus, as the key factor in slow reading in children. No studies have focused on reading in amblyopic children without strabismus. We examined reading in anisometropic children and evaluated whether slow reading was associated with ocular motor dysfunction in children with amblyopia. Methods: Anisometropic children (7-12 years) with or without amblyopia were compared to age-similar normal controls. Children silently read a grade-appropriate paragraph during binocular viewing. Reading rate (words/min), number of forward and regressive saccades (per 100 words) and fixation duration were recorded with the ReadAlyzer. Binocular fixation instability was also evaluated (EyeLink 1000). Results: Amblyopic anisometropic children read more slowly (n = 25; mean with standard deviation, 149 ± 42 words/min) than nonamblyopic anisometropic children (n = 15; 196 ± 80 words/min; P = 0.024) and controls (n = 25; 191 ± 65 words/min; P = 0.020). Nonamblyopic anisometropic children read at a comparable rate to controls (P = 0.81). Slow reading in amblyopic anisometropic children was correlated with increased forward saccades (r = −0.84, P < 0.001), increased regressive saccades (r = −0.85, P < 0.001), and fellow eye instability during binocular viewing (r = −0.52 |
Azizuddin Khan; Otto Loberg; Jarkko Hautala On the eye movement control of changing reading direction for a single word: The case of reading numerals in Urdu Journal Article In: Journal of Psycholinguistic Research, vol. 46, no. 5, pp. 1273–1283, 2017. @article{Khan2017, Typically orthographies are consistent in terms of reading direction, i.e. from left-to-right or right-to-left. However, some are bidirectional, i.e., certain parts of the text, (such as numerals in Urdu), are read against the default reading direction. Such sudden changes in reading direction may challenge the reader in many ways, at the level of planning of saccadic eye movements, changing the direction of attention, word recognition processes and cognitive reading strategies. The present study attempts to understand how readers achieve such sudden changes in reading direction at the level of eye movements and conscious cognitive reading strategies. Urdu readers reported employing a two-stage strategy for reading numerals by first counting the number of digits during right-to-left fixations, and only then forming numeric representation during left-to-right fixations. Eye movement findings were aligned with this strategy usage, as long numerals were often read with deliberate forward-and-backward fixation sequences. In these sequences fixations preceding saccades to default reading direction were shorter than against it, suggesting that different cognitive processes such as counting and formation of numeric representation were involved in fixations preceding left- and right-directed saccades. Finally, the change against the default reading direction was preceded by highly inflated fixation duration, pinpointing the oculomotor, attentional and cognitive demands in executing sudden changes in reading direction. |
Ying-Yee Kong; Alexandra Jesse Low-frequency fine-structure cues allow for the online use of lexical stress during spoken-word recognition in spectrally degraded speech Journal Article In: The Journal of the Acoustical Society of America, vol. 141, no. 1, pp. 373–382, 2017. @article{Kong2017, English listeners use suprasegmental cues to lexical stress during spoken-word recognition. Prosodic cues are, however, less salient in spectrally degraded speech, as provided by cochlear implants. The present study examined how spectral degradation with and without low-frequency fine-structure information affects normal-hearing listeners' ability to benefit from suprasegmental cues to lexical stress in online spoken-word recognition. To simulate electric hearing, an eight-channel vocoder spectrally degraded the stimuli while preserving temporal envelope information. Additional lowpass-filtered speech was presented to the opposite ear to simulate bimodal hearing. Using a visual world paradigm, listeners' eye fixations to four printed words (target, competitor, two distractors) were tracked, while hearing a word. The target and competitor overlapped segmentally in their first two syllables but mismatched suprasegmentally in their first syllables, as the initial syllable received primary stress in one word and secondary stress in the other (e.g., "'admiral," "'admi'ration"). In the vocoder-only condition, listeners were unable to use lexical stress to recognize targets before segmental information disambiguated them from competitors. With additional lowpass-filtered speech, however, listeners efficiently processed prosodic information to speed up online word recognition. Low-frequency fine-structure cues in simulated bimodal hearing allowed listeners to benefit from suprasegmental cues to lexical stress during word recognition. |
Arnout W. Koornneef; Iris Mulders Can we ‘read' the eye-movement patterns of readers? Unraveling the relationship between reading profiles and processing strategies Journal Article In: Journal of Psycholinguistic Research, vol. 46, no. 1, pp. 39–56, 2017. @article{Koornneef2017, In an eye-tracking experiment we examined the risky reading hypothesis, in which long saccades and many regressions are considered to be indicative of a proactive reading style (Rayner et al. in Psychol Aging 21(3):448, 2006; Psychol Aging 24(3):755, 2009). We did so by presenting short texts-that confirmed or disconfirmed verb-based implicit causality expectations-to two types of readers: proactive readers (long saccades, many regressions) and conservative readers (short saccades, few regressions). Whereas proactive readers used implicit causality information to predict upcoming referents, and slowed down immediately when they encountered a pronoun that was inconsistent with these verb-based expectations, the conservative readers slowed down much later in the sentence. These findings were consistent with the predictions of the risky reading hypothesis and as such presented novel evidence for the general idea that the eye-movement profile of readers reveals valuable information about their processing strategy. |
Daniel Schmidtke; Kazunaga Matsuki; Victor Kuperman Surviving blind decomposition: A distributional analysis of the time-course of complex word recognition Journal Article In: Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 43, no. 11, pp. 1793–1820, 2017. @article{Schmidtke2017, The current study addresses a discrepancy in the psycholinguistic literature about the chronology of information processing during the visual recognition of morphologically complex words. Form-then-meaning accounts of complex word recognition claim that morphemes are processed as units of form prior to any influence of their meanings, whereas form-and-meaning models posit that recognition of complex word forms involves the simultaneous access of morphological and semantic information. The study reported here addresses this theoretical discrepancy by applying a nonparametric distributional technique of survival analysis (Reingold & Sheridan, 2014) to 2 behavioral measures of complex word processing. Across 7 experiments reported here, this technique is employed to estimate the point in time at which orthographic, morphological, and semantic variables exert their earliest discernible influence on lexical decision RTs and eye movement fixation durations. Contrary to form-then-meaning predictions, Experiments 1–4 reveal that surface frequency is the earliest lexical variable to exert a demonstrable influence on lexical decision RTs for English and Dutch derived words (e.g., badness; bad ⫹ ness), English pseudoderived words (e.g., wander; wand ⫹ er) and morphologically simple control words (e.g., ballad; ball ⫹ ad). Furthermore, for derived word processing across lexical decision and eye-tracking paradigms (Experiments 1–2; 5–7), semantic effects emerge early in the time-course of word recognition, and their effects either precede or emerge simultaneously with morphological effects. These results are not consistent with the premises of the form-then-meaning view of complex word recognition, but are convergent with a form-and-meaning account of complex word recognition. |
Merel C. J. Scholman; Hannah Rohde; Vera Demberg “On the one hand” as a cue to anticipate upcoming discourse structure Journal Article In: Journal of Memory and Language, vol. 97, pp. 47–60, 2017. @article{Scholman2017, Research has shown that people anticipate upcoming linguistic content, but most work to date has focused on relatively short-range expectation-driven processes within the current sentence or between adjacent sentences. We use the discourse marker On the one hand to test whether comprehenders maintain expectations regarding upcoming content in discourse representations that span multiple sentences. Three experiments show that comprehenders anticipate more than just On the other hand; rather, they keep track of embedded constituents and establish non-local dependencies. Our results show that comprehenders disprefer a subsequent contrast marked with On the other hand when a passage has already provided intervening content that establishes an appropriate contrast with On the one hand. Furthermore, comprehenders maintain their expectation for an upcoming contrast across intervening material, even if the embedded constituent itself contains contrast. The results are taken to support expectation-driven models of processing in which comprehenders posit and maintain structural representations of discourse structure. |
Petra B. Schumacher; Leah Roberts; Juhani Järvikivi Agentivity drives real-time pronoun resolution: Evidence from German er and der Journal Article In: Lingua, vol. 185, pp. 25–41, 2017. @article{Schumacher2017, We report two experiments on the referential resolution of the German subject pronoun er and the demonstrative der (‘he'). Using the visual world eye-tracking paradigm, we examined the effects of grammatical role, thematic role and the information status of potential referents in the antecedent clause operationalized by word-order (canonical/non-canonical), in the context of active–accusative verbs (Exp. 1) and dative-experiencer verbs (Exp. 2). In information-structurally neutral contexts, er prefers the proto-agent and der the proto-patient. This suggests that agentivity is a better predictor for pronoun resolution than subjecthood or sentence topic as previously proposed. It further supports the claim that agentivity is a core property of language processing and it more generally substantiates the proposal from cognitive sciences that agentivity represents core knowledge of the human attentional system. With non-canonical antecedent clauses, because they lack alignment of prominence features, interpretive preferences become less stable, indicating that multiple cues are involved in pronoun resolution. The data further suggest that the demonstrative pronoun elicits more reliable interpretive biases than the personal pronoun. |
Florian Schwarz; Sonja Tiemann Presupposition projection in online processing Journal Article In: Journal of Semantics, vol. 34, no. 1, pp. 61–106, 2017. @article{Schwarz2017, A central aspect of language comprehension is that hearers integrate incoming lin- guistic content both with the rest of the current sentence and the larger discourse con- text. Presuppositions crucially interact with both intra- and inter-sentential context in intricate ways, which makes their study especially useful in this regard. We present a series of experiments investigating the time-course of interpreting presuppositions in online comprehension and the impact that so-called presupposition projection has on this in cases where presuppositions appear in embedded environments. We find im- mediate delays in eye tracking reading times when the presupposition of German wieder (‘again') is not supported by the context, but only for unembedded occur- rences of wieder . Further evidence from a rating experiment and a stops-making- sense study supports our interpretation of this result to the effect that global presup- positions of embedded presupposition triggers are not immediately available in pro- cessing. A second reading time experiment explores the effects of embedding further by providing presuppositional support in different locations in contexts with a more complex structure involving conditionals. We find longer reading times when the sup- port is more distant, measured in terms of the number of projection steps posited by Discourse Representation Theory (DRT). Altogether, the results suggest that presup- position projection is a cognitively effortful process, and are thus consistent with the- oretical accounts that reflect this in terms of the complexity of the representations involved in the different types of contexts, while other accounts that are more neutral in this regard need to be supplemented by additional assumptions or alternative ex- planations for the observed effects. On the more general level of discourse processing models, these results suggest that there is even more structure relevant to cognitive processes at a level between the surface representation and the purely semantic level (e.g. the commonly assumed level of a text-base) than previously assumed. |
Wei Shen; Qingqing Qu; Aiping Ni; Junyi Zhou; Xingshan Li The time course of morphological processing during spoken word recognition in Chinese Journal Article In: Psychonomic Bulletin & Review, vol. 24, no. 6, pp. 1957–1963, 2017. @article{Shen2017, We investigated the time course of morphological processing during spoken word recognition using the printed-word paradigm. Chinese participants were asked to listen to a spoken disyllabic compound word while simultaneously viewing a printed-word display. Each visual display consisted of three printed words: a semantic associate of the first constituent of the compound word (morphemic competitor), a semantic associate of the whole compound word (whole-word competitor), and an unrelated word (distractor). Participants were directed to detect whether the spoken target word was on the visual display. Results indicated that both the morphemic and whole-word competitors attracted more fixations than the distractor. More importantly, the morphemic competitor began to diverge from the distractor immediately at the acoustic offset of the first constituent, which was earlier than the whole-word competitor. These results suggest that lexical access to the auditory word is incremental and morphological processing (i.e., semantic access to the first constituent) that occurs at an early processing stage before access to the representation of the whole word in Chinese. |
Susana Silva; Filomena Inácio; Vasiliki Folia; Karl Magnus Petersson Eye movements in implicit artificial grammar learning Journal Article In: Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 43, no. 9, pp. 1387–1402, 2017. @article{Silva2017, Artificial grammar learning (AGL) has been probed with forced-choice behavioral tests (active tests). Recent attempts to probe the outcomes of learning (implicitly acquired knowledge) with eye-movement responses (passive tests) have shown null results. However, these latter studies have not tested for sensitivity effects, for example, increased eye movements on a printed violation. In this study, we tested for sensitivity effects in AGL tests with (Experiment 1) and without (Experiment 2) concurrent active tests (preference- and grammaticality classification) in an eye-tracking experiment. Eye movements discriminated between sequence types in passive tests and more so in active tests. The eye-movement profile did not differ between preference and grammaticality classification, and it resembled sensitivity effects commonly observed in natural syntax processing. Our findings show that the outcomes of implicit structured sequence learning can be characterized in eye tracking. More specifically, whole trial measures (dwell time, number of fixations) showed robust AGL effects, whereas first-pass measures (first-fixation duration) did not. Furthermore, our findings strengthen the link between artificial and natural syntax processing, and they shed light on the factors that determine performance differences in preference and grammaticality classification tests. |
Alastair C. Smith; Padraic Monaghan; Falk Huettig The multimodal nature of spoken word processing in the visual world: Testing the predictions of alternative models of multimodal integration Journal Article In: Journal of Memory and Language, vol. 93, pp. 276–303, 2017. @article{Smith2017, Ambiguity in natural language is ubiquitous, yet spoken communication is effective due to integration of information carried in the speech signal with information available in the surrounding multimodal landscape. Language mediated visual attention requires visual and linguistic information integration and has thus been used to examine properties of the architecture supporting multimodal processing during spoken language comprehension. In this paper we test predictions generated by alternative models of this multimodal system. A model (TRACE) in which multimodal information is combined at the point of the lexical representations of words generated predictions of a stronger effect of phonological rhyme relative to semantic and visual information on gaze behaviour, whereas a model in which sub-lexical information can interact across modalities (MIM) predicted a greater influence of visual and semantic information, compared to phonological rhyme. Two visual world experiments designed to test these predictions offer support for sub-lexical multimodal interaction during online language processing. |
Joshua Snell; Martijn Meeter; Jonathan Grainger Evidence for simultaneous syntactic processing of multiple words during reading Journal Article In: PLoS ONE, vol. 12, no. 3, pp. e0173720, 2017. @article{Snell2017, A hotly debated issue in reading research concerns the extent to which readers process parafoveal words, and how parafoveal information might influence foveal word recognition. We investigated syntactic word processing both in sentence reading and in reading isolated foveal words when these were flanked by parafoveal words. In Experiment 1 we found a syntactic parafoveal preview benefit in sentence reading, meaning that fixation durations on target words were decreased when there was a syntactically congruent preview word at the target location (n) during the fixation on the pre-target (n-1). In Experiment 2 we used a flanker paradigm in which participants had to classify foveal target words as either noun or verb, when those targets were flanked by syntactically congruent or incongruent words (stimulus on-time 170 ms). Lower response times and error rates in the congruent condition suggested that higher-order (syntactic) information can be integrated across foveal and parafoveal words. Although higher-order parafoveal-on-foveal effects have been elusive in sentence reading, results from our flanker paradigm show that the reading system can extract higher-order information from multiple words in a single glance. We propose a model of reading to account for the present findings. |
Joshua Snell; Françoise Vitu; Jonathan Grainger Integration of parafoveal orthographic information during foveal word reading: Beyond the sub-lexical level? Journal Article In: Quarterly Journal of Experimental Psychology, vol. 70, no. 10, pp. 1984–1996, 2017. @article{Snell2017a, Prior research has shown that processing of a given target word is facilitated by the simultaneous presentation of orthographically related stimuli in the parafovea. Here we investigate the nature of such spatial integration processes by presenting orthographic neighbours of target words in the parafovea, considering that neighbours have been shown to inhibit, rather than facilitate, recognition of target words in foveal masked priming research. In Experiment 1, we used the gaze-contingent boundary paradigm to manipulate the parafoveal information subjects received while they fixated a target word within a sentence. In Experiment 2, we used the Flanking Letters Lexical Decision paradigm to manipulate parafoveal information while subjects read isolated words. Parafoveal words were either a higher-frequency orthographic neighbour of targets words (e.g., blue-blur) or a high-frequency unrelated word (e.g., hand-blur). We found that parafoveal orthographic neighbours facilitated, rather than inhibited, processing of the target. Thus, the present findings provide further evidence that orthographic information is integrated across multiple words and suggest that either the integration process does not enable simultaneous access to those words' lexical representations, or that lexical representations activated by spatially distinct stimuli do not compete for recognition. |
Iya Khelm Price; Jeffrey Witzel Sources of relative clause processing difficulty: Evidence from Russian Journal Article In: Journal of Memory and Language, vol. 97, pp. 208–244, 2017. @article{Price2017a, This study investigates the sources of processing difficulty in complex sentences involving relative clauses (RCs). Self-paced reading and eye tracking were used to test the comprehension of Russian subject-and object-extracted RCs (SRCs and ORCs) that had the same word-order configuration, but different noun phrase (NP) types (full NPs vs. pronouns) in the embedded clause. In both SRCs and ORCs, this NP intervened between the modified noun and the RC verb. A corpus analysis and acceptability rating experiment indicated different frequency/preference profiles for this word order depending on RC type and embedded NP type. In line with these profiles, processing difficulty was revealed early in the embedded clause for less frequent/dispreferred constructions. Later in the embedded clause, the processing of the RC verb was comparable for both SRCs and ORCs when the same number of NP arguments was available for integration. While there were no indications of an ORC penalty at or after this verb, late-stage comprehension difficulty was found for full-NP ORCs, but not for their pronominal counterparts, suggesting that similarity-based interference in combination with ORC structure influences the overall comprehension of these sentences. Taken together, these findings support a hybrid model under which independent sources of processing difficulty affect different stages of RC comprehension. |
Silvia Primativo; Jamie Reilly; Sebastian J. Crutch Abstract conceptual feature ratings predict gaze within written word arrays: Evidence from a visual wor(l)d paradigm Journal Article In: Cognitive Science, vol. 41, no. 3, pp. 659–685, 2017. @article{Primativo2017a, The Abstract Conceptual Feature (ACF) framework predicts that word meaning is represented within a high-dimensional semantic space bounded by weighted contributions of perceptual, affective, and encyclopedic information. The ACF, like latent semantic analysis, is amenable to distance metrics between any two words. We applied predictions of the ACF framework to abstract words using eyetracking via an adaptation of the classical "visual word paradigm" (VWP). Healthy adults (n = 20) selected the lexical item most related to a probe word in a 4-item written word array comprising the target and three distractors. The relation between the probe and each of the four words was determined using the semantic distance metrics derived from ACF ratings. Eye movement data indicated that the word that was most semantically related to the probe received more and longer fixations relative to distractors. Importantly, in sets where participants did not provide an overt behavioral response, the fixation rates were nonetheless significantly higher for targets than distractors, closely resembling trials where an expected response was given. Furthermore, ACF ratings which are based on individual words predicted eye fixation metrics of probe-target similarity at least as well as latent semantic analysis ratings which are based on word co-occurrence. The results provide further validation of Euclidean distance metrics derived from ACF ratings as a measure of one facet of the semantic relatedness of abstract words and suggest that they represent a reasonable approximation of the organization of abstract conceptual space. The data are also compatible with the broad notion that multiple sources of information (not restricted to sensorimotor and emotion information) shape the organization of abstract concepts. While the adapted "VWP" is potentially a more metacognitive task than the classical visual world paradigm, we argue that it offers potential utility for studying abstract word comprehension. |