Clayton E Curtis

CUNY Graduate Center, New York, New York, United States

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Publications (13)106.57 Total impact

  • Masih Rahmati · Golbarg Saber · Clayton Curtis
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    ABSTRACT: The read-out of prioritized maps of space in frontal cortex is believed to provide the spatial feedback signals needed to bias activity in early visual cortex. These feedback signals can be spatially directed via a saccade plan. Maintaining a saccade plan in working memory, therefore, may evoke a pattern of activity in topographically organized population of neurons with a peak centered in the neurons with receptive fields that match the saccade goal. Here, we test for such population dynamics using a forward encoding model of the distributed patterns of fMRI activity in human visual cortex. First, using fMRI we measured neural activity in human visual areas V1, V2, V3, V3A/B, hV4 and IPS-0/1 while subjects maintained a planned saccade directed to or away from the location of a brief visual cue. Second, we mapped the retinotopic locations of memory-guided saccade cues within each visual area. Third, we developed a forward encoding model to reconstruct the neural population dynamics in early visual areas. In the forward model, we used a linear combination of outputs from a number of information channels (i.e., basis functions) to estimate each voxel's response to visual cues at a variety of retinal locations. We validated the model by successfully reconstructing both the locations of both remembered visual cues and prospective saccade goals based on fMRI responses during working memory delay periods. Our ability to build a forward model that reconstructs the locations of maintained representations allows us to make strong inferences about the population dynamics of topographic visual areas and how these dynamics are related to working memory storage. Moreover, these results show that the population activity in early topographic areas is sculpted by top-down feedback signals representing spatial priority. Meeting abstract presented at VSS 2015.
    No preview · Article · Sep 2015 · Journal of Vision
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    David A Markowitz · Clayton E Curtis · Bijan Pesaran
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    ABSTRACT: Lateral prefrontal cortex (PFC) is regarded as the hub of the brain's working memory (WM) system, but it remains unclear whether WM is supported by a single distributed network or multiple specialized network components in this region. To investigate this problem, we recorded from neurons in PFC while monkeys made delayed eye movements guided by memory or vision. We show that neuronal responses during these tasks map to three anatomically specific modes of persistent activity. The first two modes encode early and late forms of information storage, whereas the third mode encodes response preparation. Neurons that reflect these modes are concentrated at different anatomical locations in PFC and exhibit distinct patterns of coordinated firing rates and spike timing during WM, consistent with distinct networks. These findings support multiple component models of WM and consequently predict distinct failures that could contribute to neurologic dysfunction.
    Full-text · Article · Aug 2015 · Proceedings of the National Academy of Sciences
  • Golbarg T Saber · Franco Pestilli · Clayton E Curtis
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    ABSTRACT: Saccade planning may invoke spatially-specific feedback signals that bias early visual activity in favor of top-down goals. We tested this hypothesis by measuring cortical activity at the early stages of the dorsal and ventral visual processing streams. Human subjects maintained saccade plans to (prosaccade) or away (antisaccade) from a spatial location over long memory-delays. Results show that cortical activity persists in early visual cortex at the retinotopic location of upcoming saccade goals. Topographically specific activity persists as early as V1, and activity increases along both dorsal (V3A/B, IPS0) and ventral (hV4, VO1) visual areas. Importantly, activity persists when saccade goals are available only via working memory and when visual targets and saccade goals are spatially disassociated. We conclude that top-down signals elicit retinotopically specific activity in visual cortex both in the dorsal and ventral streams. Such activity may underlie mechanisms that prioritize locations of task-relevant objects. Copyright © 2015 the authors 0270-6474/15/350245-08$15.00/0.
    No preview · Article · Jan 2015 · The Journal of Neuroscience : The Official Journal of the Society for Neuroscience
  • Zuzanna Klyszejko · Masih Rahmati · Clayton E Curtis
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    ABSTRACT: Visual working memory is a system used to hold information actively in mind for a limited time. The number of items and the precision with which we can store information has limits that define its capacity. How much control do we have over the precision with which we store information when faced with these severe capacity limitations? Here, we tested the hypothesis that rank-ordered attentional priority determines the precision of multiple working memory representations. We conducted two psychophysical experiments that manipulated the priority of multiple items in a two-alternative forced choice task (2AFC) with distance discrimination. In Experiment 1, we varied the probabilities with which memorized items were likely to be tested. To generalize the effects of priority beyond simple cueing, in Experiment 2, we manipulated priority by varying monetary incentives contingent upon successful memory for items tested. Moreover, we illustrate our hypothesis using a simple model that distributed attentional resources across items with rank-ordered priorities. Indeed, we found evidence in both experiments that priority affects the precision of working memory in a monotonic fashion. Our results demonstrate that representations of priority may provide a mechanism by which resources can be allocated to increase the precision with which we encode and briefly store information.
    No preview · Article · Sep 2014 · Journal of Vision
  • Kartik K Sreenivasan · Clayton E Curtis · Mark D'Esposito
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    ABSTRACT: What are the neural mechanisms underlying working memory (WM)? One influential theory posits that neurons in the lateral prefrontal cortex (lPFC) store WM information via persistent activity. In this review, we critically evaluate recent findings that together indicate that this model of WM needs revision. We argue that sensory cortex, not the lPFC, maintains high-fidelity representations of WM content. By contrast, the lPFC simultaneously maintains representations of multiple goal-related variables that serve to bias stimulus-specific activity in sensory regions. This work highlights multiple neural mechanisms supporting WM, including temporally dynamic population coding in addition to persistent activity. These new insights focus the question on understanding how the mechanisms that underlie WM are related, interact, and are coordinated in the lPFC and sensory cortex.
    No preview · Article · Jan 2014 · Trends in Cognitive Sciences
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    Zuzanna Klyszejko · Masih Rahmati · Clayton Curtis
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    ABSTRACT: Background / Purpose: The amount of noise or details in the visual field requires ordering available items according to their priority, which relates to our current goals or selection history. The question we asked in this experiment is whether we have a control over the precision with which we store the information when we are faced with capacity limitations. Main conclusion: We found that priority affected the precision with which we store locations in visual working memory by measuring the slope of the psychometric functions related to items in the visual field.
    Preview · Conference Paper · Sep 2013
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    Akiko Ikkai · Sangita Dandekar · Clayton E Curtis
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    ABSTRACT: Background / Purpose: Here, we tested the hypothesis that attention modulates neural oscillation in a spatially selective manner.Using magnetoencephalography (MEG), we measured the alpha power (5-15Hz) while subjects’ attention was endogenously oriented to the peripheral visual field. Main conclusion: We found posterior alpha desynchronization in sensors contralateral to the attended visual field. This desynchronization and spatial selectivity persisted throughout the delay period.These findings suggest that spatial attention modulates neural synchrony in a spatially biased manner. The decrease in alpha synchronization may cause the excitation of the task-related cortical regions for enhanced visual information processing.
    Preview · Conference Paper · Jun 2011
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    Clayton E Curtis
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    ABSTRACT: We know more about the primate oculomotor system than any other motor system. From numerous studies that have measured electrical activity in single neurons, applied electrical microstimulation, characterized the behavioural sequelae of lesions, and mapped the afferent and efferent connections in oculomotor areas, exquisite animal models of human oculomotor control have evolved. In this chapter, I review studies that have begun to test these animal models in humans using neuroimaging techniques. I hope to highlight the importance of this form of translational research by describing several successes involving our understanding of the roles of the frontal and parietal cortex in saccade control. Moreover, I will discuss several problematic methodological issues that have proven challenging to our efforts of translation.
    Preview · Article · Jan 2011
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    Katherine Duncan · Clayton Curtis · Lila Davachi
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    ABSTRACT: Incoming events that match or mismatch stored representations are thought to influence the ability of the hippocampus to switch between memory encoding and retrieval modes. Electrophysiological work has dissociated match and mismatch signals in the monkey perirhinal cortex, where match signals were selective for matches to goal states, whereas mismatch signals were not modulated by intention (Miller and Desimone, 1994). To investigate whether the theoretically important relational match and mismatch signals in the hippocampus are modulated by goal states, we fully crossed whether a probe stimulus relationally matched or mismatched a previously perceived image or goal state. Subjects performed two working memory tasks in which they either responded "yes" to probes that were identical to the previous sample scene or, after performing a relational manipulation of the scene, responded "yes" only to a probe that was identical to this perceptually novel image. Using functional magnetic resonance imaging, we found evidence for relational match enhancements bilaterally in the hippocampus that were selective for matches between the probe stimulus and goal state, but were not modulated by whether that goal was perceptually novel. Moreover, we found evidence for a complementary hippocampal mismatch enhancement that was triggered by stimuli containing salient perceptual manipulations. Our results provided evidence for parallel memory signatures in the hippocampus: a controlled match signal that can detect matches to internally generated goal states and an automatic mismatch signal that can identify unpredicted perceptual novelty.
    Full-text · Article · Feb 2009 · The Journal of Neuroscience : The Official Journal of the Society for Neuroscience
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    Clayton Curtis · Lila Davachi

    Preview · Article · Aug 2008 · Nature Neuroscience
  • Clayton Curtis · Lila Davachi

    No preview · Article · Jul 2008 · Nature Neuroscience
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    Clayton E. Curtis · Mark D'Esposito
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    ABSTRACT: The dorsolateral prefrontal cortex (DLPFC) plays a crucial role in working memory. Notably, persistent activity in the DLPFC is often observed during the retention interval of delayed response tasks. The code carried by the persistent activity remains unclear, however. We critically evaluate how well recent findings from functional magnetic resonance imaging studies are compatible with current models of the role of the DLFPC in working memory. These new findings suggest that the DLPFC aids in the maintenance of information by directing attention to internal representations of sensory stimuli and motor plans that are stored in more posterior regions.
    Full-text · Article · Oct 2003 · Trends in Cognitive Sciences
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    Clayton E Curtis · Mark D ' Esposito

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