August 2012
Volume 12, Issue 9
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2012
The role of feedback and long-range horizontal connections in brightness-related responses in visual cortex: a computational model
Author Affiliations
  • Bo Cao
    The Graduate Program in Cognitive & Neural Systems, Boston University
  • Ennio Mingolla
    Center for Computational Neuroscience and Neural Technology, Boston University\nDepartment of Psychology, Boston University
  • Arash Yazdanbakhsh
    Center for Computational Neuroscience and Neural Technology, Boston University
Journal of Vision August 2012, Vol.12, 1220. doi:10.1167/12.9.1220
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      Bo Cao, Ennio Mingolla, Arash Yazdanbakhsh; The role of feedback and long-range horizontal connections in brightness-related responses in visual cortex: a computational model. Journal of Vision 2012;12(9):1220. doi: 10.1167/12.9.1220.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Rossi et al. (1996, Science) reported a drop-off at 4 Hz in the modulation amplitude of neural responses to large (up to 14 degrees) simultaneous contrast stimuli in cat striate cortex, as the temporal frequency of the luminance of flanking patches increases, while the luminance of the central patch covering the neurons’ receptive fields is held constant. Their results indicate that the modulation may involve slow processing of information over a visual area that is sufficiently large to require that cortical magnification be considered in any explanation. To explore the possible roles that cortical feedback and horizontal connections may play in modulating neural responses, we develop a model of visual cortex that incorporates constraints including the lengths and conduction speeds of both inter-area feedback and intra-area horizontal connections, the cortical magnification factor, and the sizes of receptive fields at different eccentricities. Our model shows that it is very unlikely that intra-area horizontal connections alone can account for the Rossi et al. data. (1) We find that the cortical distance of a monosynaptic horizontal connection is smaller than the cortical distance between the neuron whose receptive field is covered by the central patch and the nearest neuron whose receptive field is covered by the flanking patch (Gilbert & Wiesel, 1989, Journal of Neuroscience). (2) Functionally, the response invoked by horizontal connections is limited to a smaller cortical region than is needed to account for the lateral modulation of neural responses to large simultaneous contrast stimuli (Das & Gilbert, 1995, Nature; Nauhaus, et al., 2009, Nature Neuroscience). Given the limited spatial range of feedforward projections from LGN to striate cortex, our results indicate that inter-area feedback is involved in the long-range modulation of contrast responses in striate cortex, as opposed to the view that spreading activity within that cortical area is sufficient.

Meeting abstract presented at VSS 2012

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