Publications by authors named "Mark A Pinsk"

25 Publications

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Neural Basis of Biased Competition in Development: Sensory Competition in Visual Cortex of School-Aged Children.

Cereb Cortex 2021 Feb 10. Epub 2021 Feb 10.

Department of Psychology and Princeton Neuroscience Institute, Princeton University, Princeton, NJ 08544, USA.

The fundamental receptive field (RF) architecture in human visual cortex becomes adult-like by age 5. However, visuo-spatial functions continue to develop until teenage years. This suggests that, despite the early maturation of the RF structure, functional interactions within and across RFs may mature slowly. Here, we used fMRI to investigate functional interactions among multiple stimuli in the visual cortex of school children (ages 8 to 12) in the context of biased competition theory. In the adult visual system, multiple objects presented in the same visual field compete for neural representation. These competitive interactions occur at the level of the RF and are therefore closely linked to the RF architecture. Like in adults, we found suppression of evoked responses in children's visual cortex when multiple stimuli were presented simultaneously. Such suppression effects were modulated by the spatial distance between the stimuli as a function of RF size across the visual system. Our findings suggest that basic competitive interactions in the visual cortex of children above age 8 operate in an adult-like manner, with subtle differences in early visual areas and area MT. Our study establishes a paradigm and provides baseline data to investigate the neural basis of visuo-spatial processing in typical and atypical development.
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http://dx.doi.org/10.1093/cercor/bhab009DOI Listing
February 2021

Large-scale resculpting of cortical circuits in children after surgical resection.

Sci Rep 2020 12 9;10(1):21589. Epub 2020 Dec 9.

Department of Psychology and Neuroscience Institute, Carnegie Mellon University, Pittsburgh, USA.

Despite the relative successes in the surgical treatment of pharmacoresistant epilepsy, there is rather little research on the neural (re)organization that potentially subserves behavioral compensation. Here, we examined the post-surgical functional connectivity (FC) in children and adolescents who have undergone unilateral cortical resection and, yet, display remarkably normal behavior. Conventionally, FC has been investigated in terms of the mean correlation of the BOLD time courses extracted from different brain regions. Here, we demonstrated the value of segregating the voxel-wise relationships into mutually exclusive populations that were either positively or negatively correlated. While, relative to controls, the positive correlations were largely normal, negative correlations among networks were increased. Together, our results point to reorganization in the contralesional hemisphere, possibly suggesting competition for cortical territory due to the demand for representation of function. Conceivably, the ubiquitous negative correlations enable the differentiation of function in the reduced cortical volume following a unilateral resection.
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http://dx.doi.org/10.1038/s41598-020-78394-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7725819PMC
December 2020

Distinct auditory and visual tool regions with multisensory response properties in human parietal cortex.

Prog Neurobiol 2020 12 21;195:101889. Epub 2020 Jul 21.

Princeton Neuroscience Institute, Princeton University, Princeton, NJ 08544, USA; Department of Psychology, Princeton University, Princeton, NJ 08544, USA. Electronic address:

Left parietal cortex has been associated with the human-specific ability of sophisticated tool use. Yet, it is unclear how tool information is represented across senses. Here, we compared auditory and visual tool-specific activations within healthy human subjects to probe the relation of tool-specific networks, uni- and multisensory response properties, and functional and structural connectivity using functional and diffusion-weighted MRI. In each subject, we identified an auditory tool network with regions in left anterior inferior parietal cortex (aud-aIPL), bilateral posterior lateral sulcus, and left inferior precentral sulcus, and a visual tool network with regions in left aIPL (vis-aIPL) and bilateral inferior temporal gyrus. Aud-aIPL was largely separate and anterior/inferior from vis-aIPL, with varying degrees of overlap across subjects. Both regions displayed a strong preference for tools versus other stimuli presented within the same modality. Despite their modality preference, aud-aIPL and vis-aIPL and a region in left inferior precentral sulcus displayed multisensory response properties, as revealed in multivariate analyses. Thus, two largely separate tool networks are engaged by the visual and auditory modalities with nodes in parietal and prefrontal cortex potentially integrating information across senses. The diversification of tool processing in human parietal cortex underpins its critical role in complex object processing.
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http://dx.doi.org/10.1016/j.pneurobio.2020.101889DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7736487PMC
December 2020

Microstructural organization of human insula is linked to its macrofunctional circuitry and predicts cognitive control.

Elife 2020 06 4;9. Epub 2020 Jun 4.

Parietal, Inria Saclay Île-de-France, CEA Université Paris Sud, Palaiseau, France.

The human insular cortex is a heterogeneous brain structure which plays an integrative role in guiding behavior. The cytoarchitectonic organization of the human insula has been investigated over the last century using postmortem brains but there has been little progress in noninvasive in vivo mapping of its microstructure and large-scale functional circuitry. Quantitative modeling of multi-shell diffusion MRI data from 413 participants revealed that human insula microstructure differs significantly across subdivisions that serve distinct cognitive and affective functions. Insular microstructural organization was mirrored in its functionally interconnected circuits with the anterior cingulate cortex that anchors the salience network, a system important for adaptive switching of cognitive control systems. Furthermore, insular microstructural features, confirmed in Macaca mulatta, were linked to behavior and predicted individual differences in cognitive control ability. Our findings open new possibilities for probing psychiatric and neurological disorders impacted by insular cortex dysfunction, including autism, schizophrenia, and fronto-temporal dementia.
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http://dx.doi.org/10.7554/eLife.53470DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7308087PMC
June 2020

Author Correction: Organizing principles of pulvino-cortical functional coupling in humans.

Nat Commun 2019 03 26;10(1):1443. Epub 2019 Mar 26.

Princeton Neuroscience Institute, Princeton University, Princeton, NJ, 08540, USA.

The original version of this Article contained an error in the author affiliations. Affiliation 3 incorrectly read 'Department of Biological and Brain Sciences, Johns Hopkins University, Baltimore, MD 21218, USA'.
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http://dx.doi.org/10.1038/s41467-019-09368-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6435744PMC
March 2019

The mediodorsal pulvinar coordinates the macaque fronto-parietal network during rhythmic spatial attention.

Nat Commun 2019 01 15;10(1):215. Epub 2019 Jan 15.

Princeton Neuroscience Institute, Princeton University, Princeton, NJ, 08544, USA.

Spatial attention is discontinuous, sampling behaviorally relevant locations in theta-rhythmic cycles (3-6 Hz). Underlying this rhythmic sampling are intrinsic theta oscillations in frontal and parietal cortices that provide a clocking mechanism for two alternating attentional states that are associated with either engagement at the presently attended location (and enhanced perceptual sensitivity) or disengagement (and diminished perceptual sensitivity). It has remained unclear, however, how these theta-dependent states are coordinated across the large-scale network that directs spatial attention. The pulvinar is a candidate for such coordination, having been previously shown to regulate cortical activity. Here, we examined pulvino-cortical interactions during theta-rhythmic sampling by simultaneously recording from macaque frontal eye fields (FEF), lateral intraparietal area (LIP), and pulvinar. Neural activity propagated from pulvinar to cortex during periods of engagement, and from cortex to pulvinar during periods of disengagement. A rhythmic reweighting of pulvino-cortical interactions thus defines functional dissociations in the attention network.
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http://dx.doi.org/10.1038/s41467-018-08151-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6333835PMC
January 2019

Organizing principles of pulvino-cortical functional coupling in humans.

Nat Commun 2018 12 19;9(1):5382. Epub 2018 Dec 19.

Princeton Neuroscience Institute, Princeton University, Princeton, NJ, 08540, USA.

The pulvinar influences communication between cortical areas. We use fMRI to characterize the functional organization of the human pulvinar and its coupling with cortex. The ventral pulvinar is sensitive to spatial position and moment-to-moment transitions in visual statistics, but also differentiates visual categories such as faces and scenes. The dorsal pulvinar is modulated by spatial attention and is sensitive to the temporal structure of visual input. Cortical areas are functionally coupled with discrete pulvinar regions. The spatial organization of this coupling reflects the functional specializations and anatomical distances between cortical areas. The ventral pulvinar is functionally coupled with occipital-temporal cortices. The dorsal pulvinar is functionally coupled with frontal, parietal, and cingulate cortices, including the attention, default mode, and human-specific tool networks. These differences mirror the principles governing cortical organization of dorsal and ventral cortical visual streams. These results provide a functional framework for how the pulvinar facilitates and regulates cortical processing.
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http://dx.doi.org/10.1038/s41467-018-07725-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6300667PMC
December 2018

A Dynamic Interplay within the Frontoparietal Network Underlies Rhythmic Spatial Attention.

Neuron 2018 08;99(4):842-853.e8

Princeton Neuroscience Institute, Princeton University, Princeton, NJ 08544, USA; Department of Psychology, Princeton University, Princeton, NJ 08544, USA.

Classic studies of spatial attention assumed that its neural and behavioral effects were continuous over time. Recent behavioral studies have instead revealed that spatial attention leads to alternating periods of heightened or diminished perceptual sensitivity. Yet, the neural basis of these rhythmic fluctuations has remained largely unknown. We show that a dynamic interplay within the macaque frontoparietal network accounts for the rhythmic properties of spatial attention. Neural oscillations characterize functional interactions between the frontal eye fields (FEF) and the lateral intraparietal area (LIP), with theta phase (3-8 Hz) coordinating two rhythmically alternating states. The first is defined by FEF-dominated beta-band activity, associated with suppressed attentional shifts, and LIP-dominated gamma-band activity, associated with enhanced visual processing and better behavioral performance. The second is defined by LIP-specific alpha-band activity, associated with attenuated visual processing and worse behavioral performance. Our findings reveal how network-level interactions organize environmental sampling into rhythmic cycles.
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http://dx.doi.org/10.1016/j.neuron.2018.07.038DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6474777PMC
August 2018

The Anatomical and Functional Organization of the Human Visual Pulvinar.

J Neurosci 2015 Jul;35(27):9848-71

Princeton Neuroscience Institute and Department of Psychology, Princeton University, Princeton, New Jersey 08544.

Unlabelled: The pulvinar is the largest nucleus in the primate thalamus and contains extensive, reciprocal connections with visual cortex. Although the anatomical and functional organization of the pulvinar has been extensively studied in old and new world monkeys, little is known about the organization of the human pulvinar. Using high-resolution functional magnetic resonance imaging at 3 T, we identified two visual field maps within the ventral pulvinar, referred to as vPul1 and vPul2. Both maps contain an inversion of contralateral visual space with the upper visual field represented ventrally and the lower visual field represented dorsally. vPul1 and vPul2 border each other at the vertical meridian and share a representation of foveal space with iso-eccentricity lines extending across areal borders. Additional, coarse representations of contralateral visual space were identified within ventral medial and dorsal lateral portions of the pulvinar. Connectivity analyses on functional and diffusion imaging data revealed a strong distinction in thalamocortical connectivity between the dorsal and ventral pulvinar. The two maps in the ventral pulvinar were most strongly connected with early and extrastriate visual areas. Given the shared eccentricity representation and similarity in cortical connectivity, we propose that these two maps form a distinct visual field map cluster and perform related functions. The dorsal pulvinar was most strongly connected with parietal and frontal areas. The functional and anatomical organization observed within the human pulvinar was similar to the organization of the pulvinar in other primate species.

Significance Statement: The anatomical organization and basic response properties of the visual pulvinar have been extensively studied in nonhuman primates. Yet, relatively little is known about the functional and anatomical organization of the human pulvinar. Using neuroimaging, we found multiple representations of visual space within the ventral human pulvinar and extensive topographically organized connectivity with visual cortex. This organization is similar to other nonhuman primates and provides additional support that the general organization of the pulvinar is consistent across the primate phylogenetic tree. These results suggest that the human pulvinar, like other primates, is well positioned to regulate corticocortical communication.
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http://dx.doi.org/10.1523/JNEUROSCI.1575-14.2015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4495241PMC
July 2015

Functional and structural architecture of the human dorsal frontoparietal attention network.

Proc Natl Acad Sci U S A 2013 Sep 9;110(39):15806-11. Epub 2013 Sep 9.

Departments of Psychology and Electrical Engineering and Princeton Neuroscience Institute, Princeton University, Princeton, NJ 08540.

The dorsal frontoparietal attention network has been subdivided into at least eight areas in humans. However, the circuitry linking these areas and the functions of different circuit paths remain unclear. Using a combination of neuroimaging techniques to map spatial representations in frontoparietal areas, their functional interactions, and structural connections, we demonstrate different pathways across human dorsal frontoparietal cortex for the control of spatial attention. Our results are consistent with these pathways computing object-centered and/or viewer-centered representations of attentional priorities depending on task requirements. Our findings provide an organizing principle for the frontoparietal attention network, where distinct pathways between frontal and parietal regions contribute to multiple spatial representations, enabling flexible selection of behaviorally relevant information.
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http://dx.doi.org/10.1073/pnas.1313903110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3785784PMC
September 2013

Electrophysiological low-frequency coherence and cross-frequency coupling contribute to BOLD connectivity.

Neuron 2012 Dec;76(5):1010-20

Princeton Neuroscience Institute, Princeton University, Princeton, NJ 08544, USA.

Brain networks are commonly defined using correlations between blood oxygen level-dependent (BOLD) signals in different brain areas. Although evidence suggests that gamma-band (30-100 Hz) neural activity contributes to local BOLD signals, the neural basis of interareal BOLD correlations is unclear. We first defined a visual network in monkeys based on converging evidence from interareal BOLD correlations during a fixation task, task-free state, and anesthesia, and then simultaneously recorded local field potentials (LFPs) from the same four network areas in the task-free state. Low-frequency oscillations (<20 Hz), and not gamma activity, predominantly contributed to interareal BOLD correlations. The low-frequency oscillations also influenced local processing by modulating gamma activity within individual areas. We suggest that such cross-frequency coupling links local BOLD signals to BOLD correlations across distributed networks.
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http://dx.doi.org/10.1016/j.neuron.2012.09.033DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3531830PMC
December 2012

The pulvinar regulates information transmission between cortical areas based on attention demands.

Science 2012 Aug;337(6095):753-6

Princeton Neuroscience Institute, Princeton University, Princeton, NJ 08544, USA.

Selective attention mechanisms route behaviorally relevant information through large-scale cortical networks. Although evidence suggests that populations of cortical neurons synchronize their activity to preferentially transmit information about attentional priorities, it is unclear how cortical synchrony across a network is accomplished. Based on its anatomical connectivity with the cortex, we hypothesized that the pulvinar, a thalamic nucleus, regulates cortical synchrony. We mapped pulvino-cortical networks within the visual system, using diffusion tensor imaging, and simultaneously recorded spikes and field potentials from these interconnected network sites in monkeys performing a visuospatial attention task. The pulvinar synchronized activity between interconnected cortical areas according to attentional allocation, suggesting a critical role for the thalamus not only in attentional selection but more generally in regulating information transmission across the visual cortex.
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http://dx.doi.org/10.1126/science.1223082DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3714098PMC
August 2012

Visuotopic organization of macaque posterior parietal cortex: a functional magnetic resonance imaging study.

J Neurosci 2011 Feb;31(6):2064-78

Department of Psychology and Princeton Neuroscience Institute, Princeton University, Princeton, New Jersey 08540, USA.

Macaque anatomy and physiology studies have revealed multiple visual areas in posterior parietal cortex (PPC). While many response properties of PPC neurons have been probed, little is known about PPC's large-scale functional topography-specifically related to visuotopic organization. Using high-resolution functional magnetic resonance imaging at 3 T with a phase-encoded retinotopic mapping paradigm in the awake macaque, a large-scale visuotopic organization along lateral portions of PPC anterior to area V3a and extending into the lateral intraparietal sulcus (LIP) was found. We identify two new visual field maps anterior to V3a within caudal PPC, referred to as caudal intraparietal-1 (CIP-1) and CIP-2. The polar angle representation in CIP-1 extends from regions near the upper vertical meridian (that is the shared border with V3a and dorsal prelunate) to those within the lower visual field (that is the shared border with CIP-2). The polar angle representation in CIP-2 is a mirror reversal of the CIP-1 representation. CIP-1 and CIP-2 share a representation of central space on the lateral border. Anterior to CIP-2, a third polar angle representation was found within LIP, referred to as visuotopic LIP. The polar angle representation in LIP extends from regions near the upper vertical meridian (that is the shared border with CIP-2) to those near the lower vertical meridian. Representations of central visual space were identified within dorsal portions of LIP with peripheral representations in ventral portions. We also consider the topographic large-scale organization found within macaque PPC relative to that observed in human PPC.
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http://dx.doi.org/10.1523/JNEUROSCI.3334-10.2011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3074253PMC
February 2011

Neural representations of faces and body parts in macaque and human cortex: a comparative FMRI study.

J Neurophysiol 2009 May 18;101(5):2581-600. Epub 2009 Feb 18.

Department of Psychology, Princeton University, Princeton, NJ 08544, USA.

Single-cell studies in the macaque have reported selective neural responses evoked by visual presentations of faces and bodies. Consistent with these findings, functional magnetic resonance imaging studies in humans and monkeys indicate that regions in temporal cortex respond preferentially to faces and bodies. However, it is not clear how these areas correspond across the two species. Here, we directly compared category-selective areas in macaques and humans using virtually identical techniques. In the macaque, several face- and body part-selective areas were found located along the superior temporal sulcus (STS) and middle temporal gyrus (MTG). In the human, similar to previous studies, face-selective areas were found in ventral occipital and temporal cortex and an additional face-selective area was found in the anterior temporal cortex. Face-selective areas were also found in lateral temporal cortex, including the previously reported posterior STS area. Body part-selective areas were identified in the human fusiform gyrus and lateral occipitotemporal cortex. In a first experiment, both monkey and human subjects were presented with pictures of faces, body parts, foods, scenes, and man-made objects, to examine the response profiles of each category-selective area to the five stimulus types. In a second experiment, face processing was examined by presenting upright and inverted faces. By comparing the responses and spatial relationships of the areas, we propose potential correspondences across species. Adjacent and overlapping areas in the macaque anterior STS/MTG responded strongly to both faces and body parts, similar to areas in the human fusiform gyrus and posterior STS. Furthermore, face-selective areas on the ventral bank of the STS/MTG discriminated both upright and inverted faces from objects, similar to areas in the human ventral temporal cortex. Overall, our findings demonstrate commonalities and differences in the wide-scale brain organization between the two species and provide an initial step toward establishing functionally homologous category-selective areas.
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http://dx.doi.org/10.1152/jn.91198.2008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2681436PMC
May 2009

Speech perception: linking comprehension across a cortical network.

Curr Biol 2007 Jun;17(11):R420-2

Program in Neuroscience, Department of Psychology, Green Hall, Princeton University, Princeton, New Jersey 08540, USA.

Listening to speech amidst noise is facilitated by a variety of cues, including the predictable use of certain words in certain contexts. A recent fMRI study of the interaction between noise and semantic predictability has identified a cortical network involved in speech comprehension.
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http://dx.doi.org/10.1016/j.cub.2007.03.047DOI Listing
June 2007

Neuroscience: unconscious networking.

Nature 2007 May;447(7140):46-7

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http://dx.doi.org/10.1038/447046aDOI Listing
May 2007

Quantitative investigation of connections of the prefrontal cortex in the human and macaque using probabilistic diffusion tractography.

J Neurosci 2005 Sep;25(39):8854-66

Centre for Functional Magnetic Resonance Imaging of the Brain, Department of Clinical, University of Oxford, John Radcliffe Hospital, Headington, Oxford OX3 9DU, United Kingdom.

The functions of prefrontal cortex (PFC) areas are constrained by their anatomical connections. There is little quantitative information about human PFC connections, and, instead, our knowledge of primate PFC connections is derived from tracing studies in macaques. The connections of subcortical areas, in which white matter penetration and hence diffusion anisotropy are greatest, can be studied with diffusion-weighted imaging (DWI) tractography. We therefore used DWI tractography in four macaque and 10 human hemispheres to compare the connections of PFC regions with nine subcortical regions, including several fascicles and several subcortical nuclei. A distinct connection pattern was identified for each PFC and each subcortical region. Because some of the fascicles contained connections with posterior cortical areas, it was also possible to draw inferences about PFC connection patterns with posterior cortical areas. Notably, it was possible to identify similar circuits centered on comparable PFC regions in both species; PFC regions probably engage in similar patterns of regionally specific functional interaction with other brain areas in both species. In the case of one area traditionally assigned to the human PFC, the pars opercularis, the distribution of connections was not reminiscent of any macaque PFC region but, instead, resembled the pattern for macaque ventral premotor area. Some limitations to the DWI approach were apparent; the high diffusion anisotropy in the corpus callosum made it difficult to compare connection probability values in the adjacent cingulate region.
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http://dx.doi.org/10.1523/JNEUROSCI.1311-05.2005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6725599PMC
September 2005

The evolution of prefrontal inputs to the cortico-pontine system: diffusion imaging evidence from Macaque monkeys and humans.

Cereb Cortex 2006 Jun 24;16(6):811-8. Epub 2005 Aug 24.

Cognitive Neuroscience Laboratory, Department of Psychology, Royal Holloway University of London, UK.

The cortico-ponto-cerebellar system is one of the largest projection systems in the primate brain, but in the human brain the nature of the information processing in this system remains elusive. Determining the areas of the cerebral cortex which contribute projections to this system will allow us to better understand information processing within it. Information from the cerebral cortex is conveyed to the cerebellum by topographically arranged fibres in the cerebral peduncle - an important fibre system in which all cortical outputs spatially converge on their way to the cerebellum via the pontine nuclei. Little is known of their anatomical organization in the human brain. New in vivo diffusion imaging and probabilistic tractography methods now offer a way in which input tracts in the cerebral peduncle can be characterized in detail. Here we use these methods to contrast their organization in humans and macaque monkeys. We confirm the dominant contribution of the cortical motor areas to the macaque monkey cerebral peduncle. However, we also present novel anatomical evidence for a relatively large prefrontal contribution to the human cortico-ponto-cerebellar system in the cerebral peduncle. These findings suggest the selective evolution of prefrontal inputs to the human cortico-ponto-cerebellar system.
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http://dx.doi.org/10.1093/cercor/bhj024DOI Listing
June 2006

Symmetry perception in humans and macaques.

Trends Cogn Sci 2005 Sep;9(9):405-6

Department of Psychology, Center for the Study of Brain, Mind, and Behavior, Princeton University, Green Hall, Princeton, NJ 08544, USA.

The human ability to detect symmetry has been a topic of interest to psychologists and philosophers since the 19th century, yet surprisingly little is known about the neural basis of symmetry perception. In a recent fMRI study, Sasaki and colleagues begin to remedy this situation. By identifying the neural structures that respond to symmetry in both humans and macaques, the authors lay the groundwork for understanding the neural mechanisms underlying symmetry perception.
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http://dx.doi.org/10.1016/j.tics.2005.07.002DOI Listing
September 2005

Representations of faces and body parts in macaque temporal cortex: a functional MRI study.

Proc Natl Acad Sci U S A 2005 May 28;102(19):6996-7001. Epub 2005 Apr 28.

Department of Psychology and Center for the Study of Brain, Mind, and Behavior, Princeton University, Green Hall, Princeton, NJ 08544, USA.

Human neuroimaging studies suggest that areas in temporal cortex respond preferentially to certain biologically relevant stimulus categories such as faces and bodies. Single-cell studies in monkeys have reported cells in inferior temporal cortex that respond selectively to faces, hands, and bodies but provide little evidence of large clusters of category-specific cells that would form "areas." We probed the category selectivity of macaque temporal cortex for representations of monkey faces and monkey body parts relative to man-made objects using functional MRI in animals trained to fixate. Two face-selective areas were activated bilaterally in the posterior and anterior superior temporal sulcus exhibiting different degrees of category selectivity. The posterior face area was more extensively activated in the right hemisphere than in the left hemisphere. Immediately adjacent to the face areas, regions were activated bilaterally responding preferentially to body parts. Our findings suggest a category-selective organization for faces and body parts in macaque temporal cortex.
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http://dx.doi.org/10.1073/pnas.0502605102DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1100800PMC
May 2005

Visual attention as a multilevel selection process.

Cogn Affect Behav Neurosci 2004 Dec;4(4):483-500

Center for the Study of Brain, Mind, and Behavior, Department of Psychology, Princeton University, Princeton, NJ 08544, USA.

Natural visual scenes are cluttered and contain many different objects that cannot all be processed simultaneously. Therefore, attentional mechanisms are needed to select relevant and to filter out irrelevant information. Evidence from functional brain imaging reveals that attention operates at various processing levels within the visual system and beyond. First, the lateral geniculate nucleus appears to be the first stage in the processing of visual information that is modulated by attention, consistent with the idea that it may play an important role as an early gatekeeper in controlling neural gain. Second, areas at intermediate cortical-processing levels, such as V4 and TEO, appear to be important sites at which attention filters out unwanted information by means of receptive field mechanisms. Third, the attention mechanisms that operate in the visual system appear to be controlled by a distributed network of higher order areas in the frontal and parietal cortex, which generate top-down signals that are transmitted via feedback connections to the visual system. And fourth, the pulvinar of the thalamus may operate by integrating and coordinating attentional functions in concert with the fronto-parietal network, although much needs to be learned about its functional properties. The overall view that emerges from the studies reviewed in this article is that neural mechanisms of selective attention operate at multiple stages in the visual system and beyond and are determined by the visual processing capabilities of each stage. In this respect, attention can be considered in terms of a multilevel selection process.
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http://dx.doi.org/10.3758/cabn.4.4.483DOI Listing
December 2004

Methods for functional magnetic resonance imaging in normal and lesioned behaving monkeys.

J Neurosci Methods 2005 Apr 8;143(2):179-95. Epub 2004 Dec 8.

Department of Psychology, Princeton University, Green Hall, NJ 08544, USA.

Methods for performing functional magnetic resonance imaging (fMRI) studies in behaving and lesioned monkeys using a human MR scanner are reported. Materials for head implant surgery were selected based on tests for magnetic susceptibility. A primate chair with a rigid head fixation system and a mock scanner environment for training were developed. To perform controlled visual studies, monkeys were trained to maintain fixation for several minutes using a novel training technique that utilized continuous juice rewards. A surface coil was used to acquire anatomical and functional images in four monkeys, one with a partial lesion of striate cortex. High-resolution anatomical images were used after non-uniform intensity correction to create cortical surface reconstructions of both lesioned and normal hemispheres. Our methods were confirmed in two visual experiments, in which functional activations were obtained during both free viewing and fixation conditions. In one experiment, face-selective activity was found in the fundus and banks of the superior temporal sulcus and the middle temporal gyrus in monkeys viewing pictures of faces and objects while maintaining fixation. In a second experiment, regions in occipital, parietal, and frontal cortex were activated in lesioned and normal animals viewing a cartoon movie. Importantly, in the animal with the striate lesion, fMRI signals were obtained in the immediate vicinity of the lesion. Our results extend those previously reported by providing a detailed account of the technique and by demonstrating the feasibility of fMRI in monkeys with lesions.
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http://dx.doi.org/10.1016/j.jneumeth.2004.10.003DOI Listing
April 2005

Push-pull mechanism of selective attention in human extrastriate cortex.

J Neurophysiol 2004 Jul 18;92(1):622-9. Epub 2004 Feb 18.

Department of Psychology, Center for the Study of Brain, Mind, and Behavior, Princeton University, Green Hall, Princeton, NJ 08544, USA.

Selective attention operates in visual cortex by facilitating processing of selected stimuli and by filtering out unwanted information from nearby distracters over circumscribed regions of visual space. The neural representation of unattended stimuli outside this focus of attention is less well understood. We studied the neural fate of unattended stimuli using functional magnetic resonance imaging by dissociating the activity evoked by attended (target) stimuli presented to the periphery of a visual hemifield and unattended (distracter) stimuli presented simultaneously to a corresponding location of the contralateral hemifield. Subjects covertly directed attention to a series of target stimuli and performed either a low or a high attentional-load search task on a stream of otherwise identical stimuli. With this task, target-search-related activity increased with increasing attentional load, whereas distracter-related activity decreased with increasing load in areas V4 and TEO but not in early areas V1 and V2. This finding presents evidence for a load-dependent push-pull mechanism of selective attention that operates over large portions of the visual field at intermediate processing stages. This mechanism appeared to be controlled by a distributed frontoparietal network of brain areas that reflected processes related to target selection during spatially directed attention.
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http://dx.doi.org/10.1152/jn.00974.2003DOI Listing
July 2004

Functional imaging of the human lateral geniculate nucleus and pulvinar.

J Neurophysiol 2004 Jan 17;91(1):438-48. Epub 2003 Sep 17.

Department of Psychology, Center for the Study of Brain, Mind, and Behavior, Princeton University, Princeton, New Jersey 08544, USA.

In the human brain, little is known about the functional anatomy and response properties of subcortical nuclei containing visual maps such as the lateral geniculate nucleus (LGN) and the pulvinar. Using functional magnetic resonance imaging (fMRI) at 3 tesla (T), collective responses of neural populations in the LGN were measured as a function of stimulus contrast and flicker reversal rate and compared with those obtained in visual cortex. Flickering checkerboard stimuli presented in alternation to the right and left hemifields reliably activated the LGN. The peak of the LGN activation was found to be on average within +/-2 mm of the anatomical location of the LGN, as identified on high-resolution structural images. In all visual areas except the middle temporal (MT), fMRI responses increased monotonically with stimulus contrast. In the LGN, the dynamic response range of the contrast function was larger and contrast gain was lower than in the cortex. Contrast sensitivity was lowest in the LGN and V1 and increased gradually in extrastriate cortex. In area MT, responses were saturated at 4% contrast. Response modulation by changes in flicker rate was similar in the LGN and V1 and occurred mainly in the frequency range between 0.5 and 7.5 Hz; in contrast, in extrastriate areas V4, V3A, and MT, responses were modulated mainly in the frequency range between 7.5 and 20 Hz. In the human pulvinar, no activations were obtained with the experimental designs used to probe response properties of the LGN. However, regions in the mediodorsal right and left pulvinar were found to be consistently activated by bilaterally presented flickering checkerboard stimuli, when subjects attended to the stimuli. Taken together, our results demonstrate that fMRI at 3 T can be used effectively to study thalamocortical circuits in the human brain.
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http://dx.doi.org/10.1152/jn.00553.2003DOI Listing
January 2004

Attention modulates responses in the human lateral geniculate nucleus.

Nat Neurosci 2002 Nov;5(11):1203-9

Department of Psychology, Center for the Study of Brain, Mind, and Behavior, Princeton University, Green Hall, Princeton, New Jersey 08544, USA.

Attentional mechanisms are important for selecting relevant information and filtering out irrelevant information from cluttered visual scenes. Selective attention has previously been shown to affect neural activity in both extrastriate and striate visual cortex. Here, evidence from functional brain imaging shows that attentional response modulation is not confined to cortical processing, but can occur as early as the thalamic level. We found that attention modulated neural activity in the human lateral geniculate nucleus (LGN) in several ways: it enhanced neural responses to attended stimuli, attenuated responses to ignored stimuli and increased baseline activity in the absence of visual stimulation. The LGN, traditionally viewed as the gateway to visual cortex, may also serve as a 'gatekeeper' in controlling attentional response gain.
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http://dx.doi.org/10.1038/nn957DOI Listing
November 2002