fMRI/MEG出版物

@article{Lee2013b,

title = {Auditory selective attention reveals preparatory activity in different cortical regions for selection based on source location and source pitch},

author = {Adrian K. C. Lee and Siddharth Rajaram and Jing Xia and Hari Bharadwaj and Eric D. Larson and Matti S. Hämäläinen and Barbara G. Shinn-Cunningham},

doi = {10.3389/fnins.2012.00190},

year  = {2013},

date = {2013-01-01},

journal = {Frontiers in Neuroscience},

volume = {6},

pages = {190},

abstract = {In order to extract information in a rich environment, we focus on different features that allow us to direct attention to whatever source is of interest. The cortical network deployed during spatial attention, especially in vision, is well characterized. For example, visuospatial attention engages a frontoparietal network including the frontal eye fields (FEFs), which modulate activity in visual sensory areas to enhance the representation of an attended visual object. However, relatively little is known about the neural circuitry controlling attention directed to non-spatial features, or to auditory objects or features (either spatial or non-spatial). Here, using combined magnetoencephalography (MEG) and anatomical information obtained from MRI, we contrasted cortical activity when observers attended to different auditory features given the same acoustic mixture of two simultaneous spoken digits. Leveraging the fine temporal resolution of MEG, we establish that activity in left FEF is enhanced both prior to and throughout the auditory stimulus when listeners direct auditory attention to target location compared to when they focus on target pitch. In contrast, activity in the left posterior superior temporal sulcus (STS), a region previously associated with auditory pitch categorization, is greater when listeners direct attention to target pitch rather than target location. This differential enhancement is only significant after observers are instructed which cue to attend, but before the acoustic stimuli begin. We therefore argue that left FEF participates more strongly in directing auditory spatial attention, while the left STS aids auditory object selection based on the non-spatial acoustic feature of pitch.},

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tppubtype = {article}

}

@article{Stephen2013,

title = {Differences in MEG gamma oscillatory power during performance of a prosaccade task in adolescents with FASD},

author = {Julia M. Stephen and Brian A. Coffman and David B. Stone and Piyadasa Kodituwakku},

doi = {10.3389/fnhum.2013.00900},

year  = {2013},

date = {2013-01-01},

journal = {Frontiers in Human Neuroscience},

volume = {7},

pages = {900},

abstract = {Fetal alcohol spectrum disorder (FASD) is characterized by a broad range of behavioral and cognitive deficits that impact the long-term quality of life for affected individuals. However, the underlying changes in brain structure and function associated with these cognitive impairments are not well-understood. Previous studies identified deficits in behavioral performance of prosaccade tasks in children with FASD. In this study, we investigated group differences in gamma oscillations during performance of a prosaccade task. We collected magnetoencephalography (MEG) data from 15 adolescents with FASD and 20 age-matched healthy controls (HC) with a mean age of 15.9 ± 0.4 years during performance of a prosaccade task. Eye movement was recorded and synchronized to the MEG data using an MEG compatible eye-tracker. The MEG data were analyzed relative to the onset of the visual saccade. Time-frequency analysis was performed using Fieldtrip with a focus on group differences in gamma-band oscillations. Following left target presentation, we identified four clusters over right frontal, right parietal, and left temporal/occipital cortex, with significantly different gamma-band (30-50 Hz) power between FASD and HC. Furthermore, visual M100 latencies described in Coffman etal. (2012) corresponded with increased gamma power over right central cortex in FASD only. Gamma-band differences were not identified for stimulus-averaged responses implying that these gamma-band differences were related to differences in saccade network functioning. These differences in gamma-band power may provide indications of atypical development of cortical networks in individuals with FASD.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Maloney2013,

title = {Human cortical and behavioral sensitivity to patterns of complex motion at eccentricity},

author = {Ryan T. Maloney and Tamara L. Watson and Colin W. G. Clifford},

doi = {10.1016/j.otc.2017.11.015},

year  = {2013},

date = {2013-01-01},

journal = {Journal of Neurophysiology},

volume = {110},

number = {11},

pages = {2545–2556},

abstract = {Complex patterns of image motion (contracting, expanding, rotating, and spiraling fields) are important in the coordination of visually guided behaviors. Whereas specialized detectors in monkey visual cortex show selectivity for particular patterns of complex motion, their representation in human visual cortex remains unclear. In the present study, functional magnetic resonance imaging (fMRI) was used to investigate the sensitivity of functionally defined regions of human visual cortex to parametrically modulated complex motion trajectories, coupled with complementary psychophysical testing. A unique stimulus design made it possible to disambiguate the neural responses and psychophysical sensitivity to complex motions per se from the distribution of local motions relative to the fovea, which are known to enhance cortical activity when presented radial to fixation. This involved presenting several small, separate motion fields in the periphery in a manner that distinguished them from global optic flow patterns. The patterns were morphed through complex motion space in a systematic time-locked fashion when presented in the scanner. Anisotropies were observed in the fMRI signal, marked by an enhanced response to expanding vs. contracting fields, even in early visual cortex. Anisotropies in the psychophysical sensitivity measures followed a similar pattern that was correlated with activity in areas hV4, V5/MT, and MST. This represents the first systematic examination of complex motion perception at both a behavioral and neural level in human observers. The characteristic processing anisotropy revealed in both data sets can inform models of complex motion processing, particularly with respect to computations performed in early visual cortex.},

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pubstate = {published},

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}

@article{Preston2013,

title = {Neural representations of contextual guidance in visual search of real-world scenes},

author = {Tim J. Preston and Fei Guo and Koel Das and Barry Giesbrecht and Miguel P. Eckstein},

doi = {10.1523/JNEUROSCI.5840-12.2013},

year  = {2013},

date = {2013-01-01},

journal = {Journal of Neuroscience},

volume = {33},

number = {18},

pages = {7846–7855},

abstract = {Exploiting scene context and object– object co-occurrence is critical in guiding eye movements and facilitating visual search, yet the mediating neural mechanisms are unknown. We used functional magnetic resonance imaging while observers searched for target objects in scenes and used multivariate pattern analyses (MVPA) to show that the lateral occipital complex (LOC) can predict the coarse spatial location of observers' expectations about the likely location of 213 different targets absent from the scenes. In addition, we found weaker but significant representations of context location in an area related to the orienting of attention (intraparietal sulcus, IPS) as well as a region related to scene processing (retrosplenial cortex, RSC). Importantly, the degree of agreement among 100 independent raters about the likely location to contain a target object in a scene correlated with LOC's ability to predict the contextual location while weaker but significant effects were found in IPS, RSC, the human motion area, and early visual areas (V1, V3v). When contextual information was made irrelevant to observers' behavioral task, the MVPA analysis of LOC and the other areas' activity ceased to predict the location of context. Thus, our findings suggest that the likely locations of targets in scenes are represented in various visual areas with LOC playing a key role in contextual guidance during visual search of objects in real scenes.},

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}

@article{Song2013c,

title = {Effective connectivity within human primary visual cortex predicts interindividual diversity in illusory perception},

author = {Chen Song and D. Samuel Schwarzkopf and Antoine Lutti and Baojuan Li and Ryota Kanai and Geraint Rees},

doi = {10.1523/JNEUROSCI.4201-12.2013},

year  = {2013},

date = {2013-01-01},

journal = {Journal of Neuroscience},

volume = {33},

number = {48},

pages = {18781–18791},

abstract = {Visual perception depends strongly on spatial context. A classic example is the tilt illusion where the perceived orientation of a central stimulus differs from its physical orientation when surrounded by tilted spatial contexts. Here we show that such contextual modulation of orientation perception exhibits trait-like interindividual diversity that correlates with interindividual differences in effective connectivity within human primary visual cortex. We found that the degree to which spatial contexts induced illusory orientation perception, namely, the magnitude of the tilt illusion, varied across healthy human adults in a trait-like fashion independent of stimulus size or contrast. Parallel to contextual modulation of orientation perception, the presence of spatial contexts affected effective connectivity within human primary visual cortex between peripheral and foveal representations that responded to spatial context and central stimulus, respectively. Importantly, this effective connectivity from peripheral to foveal primary visual cortex correlated with interindividual differences in the magnitude of the tilt illusion. Moreover, this correlation with illusion perception was observed for effective connectivity under tilted contextual stimulation but not for that under iso-oriented contextual stimulation, suggesting that it reflected the impact of orientation-dependent intra-areal connections. Our findings revealed an interindividual correlation between intra-areal connectivity within primary visual cortex and contextual influence on orientation perception. This neurophysiological-perceptual link provides empirical evidence for theoretical proposals that intra-areal connections in early visual cortices are involved in contextual modulation of visual perception.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Tark2013,

title = {Deciding where to look based on visual, auditory, and semantic information},

author = {Kyeong Jin Tark and Clayton E. Curtis},

doi = {10.1016/j.brainres.2013.06.002},

year  = {2013},

date = {2013-01-01},

journal = {Brain Research},

volume = {1525},

pages = {26–38},

publisher = {Elsevier},

abstract = {Neurons in the dorsal frontal and parietal cortex are thought to transform incoming visual signals into the spatial goals of saccades, a process known as target selection. Here, we used functional magnetic resonance imaging (fMRI) to test how target selection may generalize beyond visual transformations when auditory and semantic information is used for selection. We compared activity in the frontal and parietal cortex when subjects made visually, aurally, and semantically guided saccades to one of four differently colored dots. Selection was based on a visual cue (i.e., one of the dots blinked), an auditory cue (i.e., a white noise burst was emitted at one of the dots' location), or a semantic cue (i.e., the color of one of the dots was spoken). Although neural responses in frontal and parietal cortex were robust, they were non-specific with regard to the type of information used for target selection. Decoders, however, trained on the patterns of activity in the intraparietal sulcus could classify both the type of cue used for target selection and the direction of the saccade. Therefore, we find evidence that the posterior parietal cortex is involved in transforming multimodal inputs into general spatial representations that can be used to guide saccades.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Visser2013,

title = {Neural pattern similarity predicts long-term fear memory},

author = {Renée M. Visser and H. Steven Scholte and Tinka Beemsterboer and Merel Kindt},

doi = {10.1038/nn.3345},

year  = {2013},

date = {2013-01-01},

journal = {Nature Neuroscience},

volume = {16},

number = {4},

pages = {388–390},

publisher = {Nature Publishing Group},

abstract = {Although certain changes in the brain may reflect fear learning, there are no known markers that indicate whether an aversive experience will develop into fear memory. We examined the moment-to-moment dynamics of human fear learning by applying multi-voxel pattern analysis to single-trial blood oxygen level–dependent magnetic resonance imaging data. We found that the long-term behavioral expression of fear memory could be predicted from neural patterns at the time of learning.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Zeki2013,

title = {Functional specialization and generalization for grouping of stimuli based on colour and motion},

author = {Semir Zeki and Jonathan Stutters},

doi = {10.1016/j.neuroimage.2013.02.001},

year  = {2013},

date = {2013-01-01},

journal = {NeuroImage},

volume = {73},

pages = {156–166},

publisher = {Elsevier Inc.},

abstract = {This study was undertaken to learn whether the principle of functional specialization that is evident at the level of the prestriate visual cortex extends to areas that are involved in grouping visual stimuli according to attribute, and specifically according to colour and motion. Subjects viewed, in an fMRI scanner, visual stimuli composed of moving dots, which could be either coloured or achromatic; in some stimuli the moving coloured dots were randomly distributed or moved in random directions; in others, some of the moving dots were grouped together according to colour or to direction of motion, with the number of groupings varying from 1 to 3. Increased activation was observed in area V4 in response to colour grouping and in V5 in response to motion grouping while both groupings led to activity in separate though contiguous compartments within the intraparietal cortex. The activity in all the above areas was parametrically related to the number of groupings, as was the prominent activity in Crus I of the cerebellum where the activity resulting from the two types of grouping overlapped. This suggests (a) that, the specialized visual areas of the prestriate cortex have functions beyond the processing of visual signals according to attribute, namely that of grouping signals according to colour (V4) or motion (V5); (b) that the functional separation evident in visual cortical areas devoted to motion and colour, respectively, is maintained at the level of parietal cortex, at least as far as grouping according to attribute is concerned; and (c) that, by contrast, this grouping-related functional segregation is not maintained at the level of the cerebellum.},

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}

@article{Brown2013,

title = {The functional anatomy of attention: A DCM study},

author = {Harriet R. Brown and Karl J. Friston},

doi = {10.3389/fnhum.2013.00784},

year  = {2013},

date = {2013-01-01},

journal = {Frontiers in Human Neuroscience},

volume = {7},

pages = {784},

abstract = {Recent formulations of attention—in terms of predictive coding—associate attentional gain with the expected precision of sensory information. Formal models of the Posner paradigm suggest that validity effects can be explained in a principled (Bayes optimal) fashion in terms of a cue-dependent setting of precision or gain on the sensory channels reporting anticipated target locations, which is updated selectively by invalid targets. This normative model is equipped with a biologically plausible process theory in the form of predictive coding, where precision is encoded by the gain of superficial pyramidal cells reporting prediction error. We used dynamic causal modeling to assess the evidence in magnetoencephalographic responses for cue-dependent and top-down updating of superficial pyramidal cell gain. Bayesian model comparison suggested that it is almost certain that differences in superficial pyramidal cells gain—and its top-down modulation—contribute to observed responses; and we could be more than 80% certain that anticipatory effects on post-synaptic gain are limited to visual (extrastriate) sources. These empirical results speak to the role of attention in optimizing perceptual inference and its formulation in terms of predictive coding.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Capilla2013,

title = {The early spatio-temporal correlates and task independence of cerebral voice processing studied with MEG},

author = {Almudena Capilla and Pascal Belin and Joachim Gross},

doi = {10.1093/cercor/bhs119},

year  = {2013},

date = {2013-01-01},

journal = {Cerebral Cortex},

volume = {23},

number = {6},

pages = {1388–1395},

abstract = {Functional magnetic resonance imaging studies have repeatedly provided evidence for temporal voice areas (TVAs) with particular sensitivity to human voices along bilateral mid/anterior superior temporal sulci and superior temporal gyri (STS/STG). In contrast, electrophysiological studies of the spatio-temporal correlates of cerebral voice processing have yielded contradictory results, finding the earliest correlates either at ∼300-400 ms, or earlier at ∼200 ms ("fronto-temporal positivity to voice", FTPV). These contradictory results are likely the consequence of different stimulus sets and attentional demands. Here, we recorded magnetoencephalography activity while participants listened to diverse types of vocal and non-vocal sounds and performed different tasks varying in attentional demands. Our results confirm the existence of an early voice-preferential magnetic response (FTPVm, the magnetic counterpart of the FTPV) peaking at about 220 ms and distinguishing between vocal and non-vocal sounds as early as 150 ms after stimulus onset. The sources underlying the FTPVm were localized along bilateral mid-STS/STG, largely overlapping with the TVAs. The FTPVm was consistently observed across different stimulus subcategories, including speech and non-speech vocal sounds, and across different tasks. These results demonstrate the early, largely automatic recruitment of focal, voice-selective cerebral mechanisms with a time-course comparable to that of face processing.},

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pubstate = {published},

tppubtype = {article}

}

@article{Coffman2013,

title = {Primary visual response (M100) delays in adolescents with FASD as measured with MEG},

author = {Brian A. Coffman and Piyadasa Kodituwakku and Elizabeth L. Kodituwakku and Lucinda Romero and Nirupama Muniswamy Sharadamma and David Stone and Julia M. Stephen},

doi = {10.1002/hbm.22110},

year  = {2013},

date = {2013-01-01},

journal = {Human Brain Mapping},

volume = {34},

number = {11},

pages = {2852–2862},

abstract = {Fetal alcohol spectrum disorders (FASD) are debilitating, with effects of prenatal alcohol exposure persisting into adolescence and adulthood. Complete characterization of FASD is crucial for the development of diagnostic tools and intervention techniques to decrease the high cost to individual families and society of this disorder. In this experiment, we investigated visual system deficits in adolescents (12-21 years) diagnosed with an FASD by measuring the latency of patients' primary visual M100 responses using MEG. We hypothesized that patients with FASD would demonstrate delayed primary visual responses compared to controls. M100 latencies were assessed both for FASD patients and age-matched healthy controls for stimuli presented at the fovea (central stimulus) and at the periphery (peripheral stimuli; left or right of the central stimulus) in a saccade task requiring participants to direct their attention and gaze to these stimuli. Source modeling was performed on visual responses to the central and peripheral stimuli and the latency of the first prominent peak (M100) in the occipital source timecourse was identified. The peak latency of the M100 responses were delayed in FASD patients for both stimulus types (central and peripheral), but the difference in latency of primary visual responses to central vs. peripheral stimuli was significant only in FASD patients, indicating that, while FASD patients' visual systems are impaired in general, this impairment is more pronounced in the periphery. These results suggest that basic sensory deficits in this population may contribute to sensorimotor integration deficits described previously in this disorder.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{GuitartMasip2013,

title = {Synchronization of medial temporal lobe and prefrontal rhythms in human decision making},

author = {M. Guitart-Masip and G. R. Barnes and A. Horner and Markus Bauer and Raymond J. Dolan and E. Duzel},

doi = {10.1523/JNEUROSCI.2573-12.2013},

year  = {2013},

date = {2013-01-01},

journal = {Journal of Neuroscience},

volume = {33},

number = {2},

pages = {442–451},

abstract = {Optimal decision making requires that we integrate mnemonic information regarding previous decisions with value signals that entail likely rewards and punishments. The fact that memory and value signals appear to be coded by segregated brain regions, the hippocampus in the case of memory and sectors of prefrontal cortex in the case of value, raises the question as to how they are integrated during human decision making. Using magnetoencephalography to study healthy human participants, we show increased theta oscillations over frontal and temporal sensors during nonspatial decisions based on memories from previous trials. Using source reconstruction we found that the medial temporal lobe (MTL), in a location compatible with the anterior hippocampus, and the anterior cingulate cortex in the medial wall of the frontal lobe are the source of this increased theta power. Moreover, we observed a correlation between theta power in the MTL source and behavioral performance in decision making, supporting a role for MTL theta oscillations in decision-making performance. These MTL theta oscillations were synchronized with several prefrontal sources, including lateral superior frontal gyrus, dorsal anterior cingulate gyrus, and medial frontopolar cortex. There was no relationship between the strength of synchronization and the expected value of choices. Our results indicate a mnemonic guidance of human decision making, beyond anticipation of expected reward, is supported by hippocampal-prefrontal theta synchronization.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Faivre2012a,

title = {Nonconscious emotional processing involves distinct neural pathways for pictures and videos},

author = {Nathan Faivre and Sylvain Charron and Paul Roux and Stephane Lehericy and Sid Kouider},

doi = {10.1016/j.neuropsychologia.2012.10.025},

year  = {2012},

date = {2012-01-01},

journal = {Neuropsychologia},

volume = {50},

pages = {3736–3744},

abstract = {Facial expressions are known to impact observers' behavior, even when they are not consciously identifiable. Relying on visual crowding, a perceptual phenomenon whereby peripheral faces become undiscriminable, we show that participants exposed to happy vs. neutral crowded faces rated the pleasantness of subsequent neutral targets accordingly to the facial expression's valence. Using functional magnetic resonance imaging (fMRI) along with psychophysiological interaction analysis, we investigated the neural determinants of this nonconscious preference bias, either induced by static (i.e., pictures) or dynamic (i.e., videos) facial expressions. We found that while static expressions activated primarily the ventral visual pathway (including task-related functional connectivity between the fusiform face area and the amygdala), dynamic expressions triggered the dorsal visual pathway (i.e., posterior partietal cortex) and the substantia innominata, a structure that is contiguous with the dorsal amygdala. As temporal cues are known to improve the processing of visible facial expressions, the absence of ventral activation we observed with crowded videos questions the capacity to integrate facial features and facial motions without awareness. Nevertheless, both static and dynamic facial expressions activated the hippocampus and the orbitofrontal cortex, suggesting that nonconscious preference judgments may arise from the evaluation of emotional context and the computation of aesthetic evaluation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Guerin2012,

title = {Retrieval failure contributes to gist-based false recognition},

author = {Scott A. Guerin and Clifford A. Robbins and Adrian W. Gilmore and Daniel L. Schacter},

doi = {10.1016/j.jml.2011.07.002},

year  = {2012},

date = {2012-01-01},

journal = {Journal of Memory and Language},

volume = {66},

number = {1},

pages = {68–78},

publisher = {Elsevier Inc.},

abstract = {People often falsely recognize items that are similar to previously encountered items. This robust memory error is referred to as gist-based false recognition. A widely held view is that this error occurs because the details fade rapidly from our memory. Contrary to this view, an initial experiment revealed that, following the same encoding conditions that produce high rates of gist-based false recognition, participants overwhelmingly chose the correct target rather than its related foil when given the option to do so. A second experiment showed that this result is due to increased access to stored details provided by reinstatement of the originally encoded photograph, rather than to increased attention to the details. Collectively, these results suggest that details needed for accurate recognition are, to a large extent, still stored in memory and that a critical factor determining whether false recognition will occur is whether these details can be accessed during retrieval.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Guo2012,

title = {Feature-independent neural coding of target detection during search of natural scenes},

author = {Fei Guo and Tim J. Preston and Koel Das and Barry Giesbrecht and Miguel P. Eckstein},

doi = {10.1523/JNEUROSCI.5876-11.2012},

year  = {2012},

date = {2012-01-01},

journal = {Journal of Neuroscience},

volume = {32},

number = {28},

pages = {9499–9510},

abstract = {Visual search requires humans to detect a great variety of target objects in scenes cluttered by other objects or the natural environment. It is unknown whether there is a general purpose neural detection mechanism in the brain that codes the presence of a wide variety of categories of objects embedded in natural scenes. We provide evidence for a feature-independent coding mechanism for detecting behaviorally relevant targets in natural scenes in the dorsal frontoparietal network. Pattern classifiers using single-trial fMRI responses in the dorsal frontoparietal network reliably predicted the presence of 368 different target objects and also the observer's choices. Other vision-related areas such as the primary visual cortex, lateral occipital complex, the parahippocampal, and the fusiform gyri did not predict target presence, while high-level association areas related to general purpose decision making, including the dorsolateral prefrontal cortex and anterior cingulate, did. Activity in the intraparietal sulcus, a main area in the dorsal frontoparietal network, correlated with observers' decision confidence and with the task difficulty of individual images. These results cannot be explained by physical differences across images or eye movements. Thus, the dorsal frontoparietal network detects behaviorally relevant targets in natural scenes independent of their defining visual features and may be the human analog of the priority map in monkey lateral intraparietal cortex.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jerde2012,

title = {Prioritized maps of space in human frontoparietal cortex},

author = {Trenton A. Jerde and Elisha P. Merriam and Adam C. Riggall and James H. Hedges and Clayton E. Curtis},

doi = {10.1523/JNEUROSCI.3810-12.2012},

year  = {2012},

date = {2012-01-01},

journal = {Journal of Neuroscience},

volume = {32},

number = {48},

pages = {17382–17390},

abstract = {Priority maps are theorized to be composed of large populations of neurons organized topographically into a map of gaze-centered space whose activity spatially tags salient and behaviorally relevant information. Here, we identified four priority map candidates along human posterior intraparietal sulcus (IPS0-IPS3) and two along the precentral sulcus (PCS) that contained reliable retinotopically organized maps of contralateral visual space. Persistent activity increased from posterior-to-anterior IPS areas and from inferior-to-superior PCS areas during the maintenance of a working memory representation, the maintenance of covert attention, and the maintenance of a saccade plan. Moreover, decoders trained to predict the locations on one task (e.g., working memory) cross-predicted the locations on other tasks (e.g., attention) in superior PCS and IPS2, suggesting that these patterns of maintenance activity may be interchangeable across the tasks. Such properties make these two areas in frontal and parietal cortex viable priority map candidates.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Josipovic2012,

title = {Influence of meditation on anti-correlated networks in the brain},

author = {Zoran Josipovic and Ilan Dinstein and Jochen Weber and David J. Heeger},

doi = {10.3389/fnhum.2011.00183},

year  = {2012},

date = {2012-01-01},

journal = {Frontiers in Human Neuroscience},

volume = {5},

pages = {183},

abstract = {Human experiences can be broadly divided into those that are external and related to interaction with the environment, and experiences that are internal and self-related. The cerebral cortex appears to be divided into two corresponding systems: an "extrinsic" system composed of brain areas that respond more to external stimuli and tasks and an "intrinsic" system composed of brain areas that respond less to external stimuli and tasks. These two broad brain systems seem to compete with each other, such that their activity levels over time is usually anti-correlated, even when subjects are "at rest" and not performing any task. This study used meditation as an experimental manipulation to test whether this competition (anti-correlation) can be modulated by cognitive strategy. Participants either fixated without meditation (fixation), or engaged in non-dual awareness (NDA) or focused attention (FA) meditations. We computed inter-area correlations ("functional connectivity") between pairs of brain regions within each system, and between the entire extrinsic and intrinsic systems. Anti-correlation between extrinsic vs. intrinsic systems was stronger during FA meditation and weaker during NDA meditation in comparison to fixation (without mediation). However, correlation between areas within each system did not change across conditions. These results suggest that the anti-correlation found between extrinsic and intrinsic systems is not an immutable property of brain organization and that practicing different forms of meditation can modulate this gross functional organization in profoundly different ways.},

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pubstate = {published},

tppubtype = {article}

}

@article{Freeman2011a,

title = {Orientation decoding depends on maps, not columns},

author = {Jeremy Freeman and G. J. Brouwer and David J. Heeger and Elisha P. Merriam},

doi = {10.1523/JNEUROSCI.5160-10.2011},

year  = {2011},

date = {2011-01-01},

journal = {Journal of Neuroscience},

volume = {31},

number = {13},

pages = {4792–4804},

abstract = {The representation of orientation in primary visual cortex (V1) has been examined at a fine spatial scale corresponding to the columnar architecture. We present functional magnetic resonance imaging (fMRI) measurements providing evidence for a topographic map of orientation preference in human V1 at a much coarser scale, in register with the angular-position component of the retinotopic map of V1. This coarse-scale orientation map provides a parsimonious explanation for why multivariate pattern analysis methods succeed in decoding stimulus orientation from fMRI measurements, challenging the widely held assumption that decoding results reflect sampling of spatial irregularities in the fine-scale columnar architecture. Decoding stimulus attributes and cognitive states from fMRI measurements has proven useful for a number of applications, but our results demonstrate that the interpretation cannot assume decoding reflects or exploits columnar organization.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kluge2011,

title = {Plasticity of human auditory-evoked fields induced by shock conditioning and contingency reversal},

author = {Christian Kluge and Markus Bauer and Alexander P. Leff and Hans-Jochen Heinze and Raymond J. Dolan and Jon Driver and Alexander Paul},

doi = {10.1073/pnas.1016124108},

year  = {2011},

date = {2011-01-01},

journal = {Proceedings of the National Academy of Sciences},

volume = {108},

number = {30},

pages = {12545–12550},

abstract = {We used magnetoencephalography (MEG) to assess plasticity of human auditory cortex induced by classical conditioning and contingency reversal. Participants listened to random sequences of high or low tones. A first baseline phase presented these without further associations. In phase 2, one of the frequencies (CS(+)) was paired with shock on half its occurrences, whereas the other frequency (CS(-)) was not. In phase 3, the contingency assigning CS(+) and CS(-) was reversed. Conditioned pupil dilation was observed in phase 2 but extinguished in phase 3. MEG revealed that, during phase-2 initial conditioning, the P1m, N1m, and P2m auditory components, measured from sensors over auditory temporal cortex, came to distinguish between CS(+) and CS(-). After contingency reversal in phase 3, the later P2m component rapidly reversed its selectivity (unlike the pupil response) but the earlier P1m did not, whereas N1m showed some new learning but not reversal. These results confirm plasticity of human auditory responses due to classical conditioning, but go further in revealing distinct constraints on different levels of the auditory hierarchy. The later P2m component can reverse affiliation immediately in accord with an updated expectancy after contingency reversal, whereas the earlier auditory components cannot. These findings indicate distinct cognitive and emotional influences on auditory processing.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Herrmann2010,

title = {When size matters: Attention affects performance by contrast or response gain},

author = {Katrin Herrmann and Leila Montaser-Kouhsari and Marisa Carrasco and David J. Heeger},

doi = {10.1038/nn.2669},

year  = {2010},

date = {2010-01-01},

journal = {Nature Neuroscience},

volume = {13},

number = {12},

pages = {1554–1561},

publisher = {Nature Publishing Group},

abstract = {Covert attention, the selective processing of visual information in the absence of eye movements, improves behavioral performance. Here, we show that attention, both exogenous (involuntary) and endogenous (voluntary), can affect performance by contrast or response gain changes, depending on the stimulus size and the relative size of the attention field. These two variables were manipulated in a cueing task while varying stimulus contrast. We observed a change in behavioral performance consonant with a change in contrast gain for small stimuli paired with spatial uncertainty, but a change in response gain for large stimuli presented at one location (no uncertainty) and surrounded by irrelevant flanking distracters. A complementary neuroimaging experiment revealed that observers' attention field was wider with than without spatial uncertainty. Our results support key predictions of the normalization model of attention, and reconcile previous, seemingly contradictory, findings on the effects of visual attention. Introduction},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kourtzi2005,

title = {Distributed neural plasticity for shape learning in the human visual cortex},

author = {Zoe Kourtzi and Lisa R. Betts and Pegah Sarkheil and Andrew E. Welchman},

doi = {10.1371/journal.pbio.0030204},

year  = {2005},

date = {2005-01-01},

journal = {PLoS Biology},

volume = {3},

number = {7},

pages = {1317–1327},

abstract = {Expertise in recognizing objects in cluttered scenes is a critical skill for our interactions in complex environments and is thought to develop with learning. However, the neural implementation of object learning across stages of visual analysis in the human brain remains largely unknown. Using combined psychophysics and functional magnetic resonance imaging (fMRI), we show a link between shape-specific learning in cluttered scenes and distributed neuronal plasticity in the human visual cortex. We report stronger fMRI responses for trained than untrained shapes across early and higher visual areas when observers learned to detect low-salience shapes in noisy backgrounds. However, training with high-salience pop-out targets resulted in lower fMRI responses for trained than untrained shapes in higher occipitotemporal areas. These findings suggest that learning of camouflaged shapes is mediated by increasing neural sensitivity across visual areas to bolster target segmentation and feature integration. In contrast, learning of prominent pop-out shapes is mediated by associations at higher occipitotemporal areas that support sparser coding of the critical features for target recognition. We propose that the human brain learns novel objects in complex scenes by reorganizing shape processing across visual areas, while taking advantage of natural image correlations that determine the distinctiveness of target shapes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}