Elsevier

NeuroImage

Volume 78, September 2013, Pages 152-158
NeuroImage

Consequences of polar form coherence for fMRI responses in human visual cortex

https://doi.org/10.1016/j.neuroimage.2013.04.036Get rights and content
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Highlights

  • We used fMRI to investigate cortical processing of polar spatial form.

  • We collected coherence response functions from visual cortex to polar Glass patterns.

  • Low-level areas V1 and V2 were not significantly modulated by coherence.

  • Low-level area V3 showed positive linear coherence response.

  • Dorsal, ventral, and hMT + mid-level areas showed positive linear coherence response.

Abstract

Relevant features in the visual image are often spatially extensive and have complex orientation structure. Our perceptual sensitivity to such spatial form is demonstrated by polar Glass patterns, in which an array of randomly-positioned dot pairs that are each aligned with a particular polar displacement (rotation, for example) yield a salient impression of spatial structure. Such patterns are typically considered to be processed in two main stages: local spatial filtering in low-level visual cortex followed by spatial pooling and complex form selectivity in mid-level visual cortex. However, it remains unclear both whether reciprocal interactions within the cortical hierarchy are involved in polar Glass pattern processing and which mid-level areas identify and communicate polar Glass pattern structure. Here, we used functional magnetic resonance imaging (fMRI) at 7T to infer the magnitude of neural response within human low-level and mid-level visual cortex to polar Glass patterns of varying coherence (proportion of signal elements). The activity within low-level visual areas V1 and V2 was not significantly modulated by polar Glass pattern coherence, while the low-level area V3, dorsal and ventral mid-level areas, and the human MT complex each showed a positive linear coherence response functions. The cortical processing of polar Glass patterns thus appears to involve primarily feedforward communication of local signals from V1 and V2, with initial polar form selectivity reached in V3 and distributed to multiple pathways in mid-level visual cortex.

Keywords

fMRI
Visual cortex
Orientation
Spatial vision

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