scholarly journals Compound stimuli reveal velocity separability of spatiotemporal receptive fields in macaque area MT

2015 ◽  
Vol 15 (12) ◽  
pp. 485
Author(s):  
Andrew Zaharia ◽  
Robbe Goris ◽  
J. Movshon ◽  
Eero Simoncelli
Keyword(s):  
Receptive Fields ◽  
Area Mt ◽  
Compound Stimuli ◽  
Spatiotemporal Receptive Fields

Area MT Neurons Respond to Visual Motion Distant From Their Receptive Fields

2005 ◽  
Vol 94 (6) ◽  
pp. 4156-4167 ◽  
Author(s):  
Daniel Zaksas ◽  
Tatiana Pasternak
Keyword(s):  
Time Course ◽  
Visual Motion ◽  
Cognitive Task ◽  
Receptive Fields ◽  
Direction Selectivity ◽  
Task Demands ◽  
Visual Signals ◽  
Area Mt ◽  
Mt Neurons ◽  
Stimulus Offset

Neurons in cortical area MT have localized receptive fields (RF) representing the contralateral hemifield and play an important role in processing visual motion. We recorded the activity of these neurons during a behavioral task in which two monkeys were required to discriminate and remember visual motion presented in the ipsilateral hemifield. During the task, the monkeys viewed two stimuli, sample and test, separated by a brief delay and reported whether they contained motion in the same or in opposite directions. Fifty to 70% of MT neurons were activated by the motion stimuli presented in the ipsilateral hemifield at locations far removed from their classical receptive fields. These responses were in the form of excitation or suppression and were delayed relative to conventional MT responses. Both excitatory and suppressive responses were direction selective, but the nature and the time course of their directionality differed from the conventional excitatory responses recorded with stimuli in the RF. Direction selectivity of the excitatory remote response was transient and early, whereas the suppressive response developed later and persisted after stimulus offset. The presence or absence of these unusual responses on error trials, as well as their magnitude, was affected by the behavioral significance of stimuli used in the task. We hypothesize that these responses represent top-down signals from brain region(s) accessing information about stimuli in the entire visual field and about the behavioral state of the animal. The recruitment of neurons in the opposite hemisphere during processing of behaviorally relevant visual signals reveals a mechanism by which sensory processing can be affected by cognitive task demands.

Area 17 lesions deactivate area MT in owl monkeys

1992 ◽  
Vol 9 (3-4) ◽  
pp. 399-407 ◽  
Author(s):  
Jon H. Kaas ◽  
Leah A. Krubitzer
Keyword(s):  
Visual Stimuli ◽  
Receptive Fields ◽  
Area 17 ◽  
Area Mt ◽  
Mt Neurons ◽  
Visual Hemifield ◽  
Cortex Area ◽  
Owl Monkeys ◽  
Evoked Activity ◽  
Visual Area Mt

AbstractThe middle temporal visual area, MT, is one of three major targets of the primary visual cortex, area 17, in primates. We assessed the contribution of area 17 connections to the responsiveness of area MT neurons to visual stimuli by first mapping the representation of the visual hemifield in MT of anesthetized owl monkeys with microelectrodes, ablating an electrophysiologically mapped part of area 17, and then immediately remapping MT. Before the lesions, neurons at recording sites throughout MT responded vigorously to moving slits of light and other visual stimuli. In addition, the relationship of receptive fields to recording sites revealed a systematic representation of the contralateral visual hemifield in MT, as reported previously for owl monkeys and other primates. The immediate effect of removing part of the retinotopic map in area 17 by gentle aspiration was to selectively deactivate the corresponding part of the visuotopic map in MT. Lesions of dorsomedial area 17 representing central and paracentral vision of the lower visual quadrant deactivated neurons in caudomedial MT formerly having receptive fields in the central and paracentral lower visual quadrant. Most neurons at recording sites throughout other parts of MT had normal levels of responsiveness to visual stimuli, and receptive-field locations that closely matched those before the lesion. However, neurons at a few sites along the margin of the deactivated zone of cortex had receptive fields that were slightly displaced from the region of vision affected by the lesion into other parts of the visual field, suggesting some degree of plasticity in the visual hemifield representation in MT. Subsequent histological examination of cortex confirmed that the lesions were confined to area 17 and the recordings were in MT. The results indicate that the visually evoked activity of neurons in MT of owl monkeys is highly dependent on inputs relayed directly or indirectly from area 17.

scholarly journals Spatial precision of population activity in primate area MT

2015 ◽  
Vol 114 (2) ◽  
pp. 869-878 ◽  
Author(s):  
Spencer C. Chen ◽  
John W. Morley ◽  
Samuel G. Solomon
Keyword(s):  
Neural Activity ◽  
Visual Processing ◽  
Receptive Fields ◽  
Object Motion ◽  
Spatial Position ◽  
Multielectrode Arrays ◽  
Visual World ◽  
Population Activity ◽  
Area Mt ◽  
Mt Neurons

The middle temporal (MT) area is a cortical area integral to the “where” pathway of primate visual processing, signaling the movement and position of objects in the visual world. The receptive field of a single MT neuron is sensitive to the direction of object motion but is too large to signal precise spatial position. Here, we asked if the activity of MT neurons could be combined to support the high spatial precision required in the where pathway. With the use of multielectrode arrays, we recorded simultaneously neural activity at 24–65 sites in area MT of anesthetized marmoset monkeys. We found that although individual receptive fields span more than 5° of the visual field, the combined population response can support fine spatial discriminations (<0.2°). This is because receptive fields at neighboring sites overlapped substantially, and changes in spatial position are therefore projected onto neural activity in a large ensemble of neurons. This fine spatial discrimination is supported primarily by neurons with receptive fields flanking the target locations. Population performance is degraded (by 13–22%) when correlations in neural activity are ignored, further reflecting the contribution of population neural interactions. Our results show that population signals can provide high spatial precision despite large receptive fields, allowing area MT to represent both the motion and the position of objects in the visual world.

Spatiotemporal receptive fields: a dynamical model derived from cortical architectonics

1986 ◽  
Vol 226 (1245) ◽  
pp. 421-444 ◽  
Keyword(s):  
Cortical Neurons ◽  
Receptive Fields ◽  
Pyramidal Cells ◽  
Tuning Curves ◽  
Cell Responses ◽  
Intrinsic Connectivity ◽  
Output System ◽  
Spatiotemporal Receptive Fields ◽  
External Connections ◽  
Insight Into

We assume that the mammalian neocortex is built up out of some six layers which differ in their morphology and their external connections. Intrinsic connectivity is largely excitatory, leading to a considerable amount of positive feedback. The majority of cortical neurons can be divided into two main classes: the pyramidal cells, which are said to be excitatory, and local cells (most notably the non-spiny stellate cells), which are said to be inhibitory. The form of the dendritic and axonal arborizations of both groups is discussed in detail. This results in a simplified model of the cortex as a stack of six layers with mutual connections determined by the principles of fibre anatomy. This stack can be treated as a multi-input-multi-output system by means of the linear systems theory of homogeneous layers. The detailed equations for the simulation are derived in the Appendix. The results of the simulations show that the temporal and spatial behaviour of an excitation distribution cannot be treated separately. Further, they indicate specific processing in the different layers and some independence from details of wiring. Finally, the simulation results are applied to the theory of visual receptive fields. This yields some insight into the mechanisms possibly underlying hypercomplexity, putative nonlinearities, lateral inhibition, oscillating cell responses, and velocity-dependent tuning curves.

scholarly journals Feature attention for binocular disparity in primate area MT depends on tuning strength

2015 ◽  
Vol 113 (5) ◽  
pp. 1545-1555 ◽  
Author(s):  
Douglas A. Ruff ◽  
Richard T. Born
Keyword(s):  
Binocular Disparity ◽  
Receptive Fields ◽  
Sensory Information ◽  
Neuronal Population ◽  
Area Mt ◽  
Temporal Area ◽  
Mt Neurons ◽  
Feature Attention ◽  
The Difference ◽  
The Relationship

Attending to a stimulus modulates the responses of sensory neurons that represent features of that stimulus, a phenomenon named “feature attention.” For example, attending to a stimulus containing upward motion enhances the responses of upward-preferring direction-selective neurons in the middle temporal area (MT) and suppresses the responses of downward-preferring neurons, even when the attended stimulus is outside of the spatial receptive fields of the recorded neurons (Treue S, Martinez-Trujillo JC. Nature 399: 575–579, 1999). This modulation renders the representation of sensory information across a neuronal population more selective for the features present in the attended stimulus (Martinez-Trujillo JC, Treue S. Curr Biol 14: 744–751, 2004). We hypothesized that if feature attention modulates neurons according to their tuning preferences, it should also be sensitive to their tuning strength, which is the magnitude of the difference in responses to preferred and null stimuli. We measured how the effects of feature attention on MT neurons in rhesus monkeys ( Macaca mulatta) depended on the relationship between features—in our case, direction of motion and binocular disparity—of the attended stimulus and a neuron's tuning for those features. We found that, as for direction, attention to stimuli containing binocular disparity cues modulated the responses of MT neurons and that the magnitude of the modulation depended on both a neuron's tuning preferences and its tuning strength. Our results suggest that modulation by feature attention may depend not just on which features a neuron represents but also on how well the neuron represents those features.

scholarly journals Attention directed by expectations enhances receptive fields in cortical area MT

2010 ◽  
Vol 50 (4) ◽  
pp. 441-451 ◽  
Author(s):  
Geoffrey M. Ghose ◽  
David W. Bearl
Keyword(s):  
Cortical Area ◽  
Receptive Fields ◽  
Area Mt

Development of spatiotemporal receptive fields of simple cells: I. Model formulation

1997 ◽  
Vol 77 (6) ◽  
pp. 453-461 ◽  
Author(s):  
S. Wimbauer ◽  
O.G. Wenisch ◽  
K.D. Miller ◽  
J.L. van Hemmen
Keyword(s):  
Receptive Fields ◽  
Model Formulation ◽  
Simple Cells ◽  
Spatiotemporal Receptive Fields

Dynamic shifts of visual receptive fields in cortical area MT by spatial attention

2006 ◽  
Vol 9 (9) ◽  
pp. 1156-1160 ◽  
Author(s):  
Thilo Womelsdorf ◽  
Katharina Anton-Erxleben ◽  
Florian Pieper ◽  
Stefan Treue
Keyword(s):  
Spatial Attention ◽  
Cortical Area ◽  
Receptive Fields ◽  
Area Mt ◽  
Visual Receptive Fields
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