Optical Imaging of Contextual Interactions in V1 of the Behaving Monkey

AUTOR(ES)

Kinoshita, Masaharu

FONTE

American Physiological Society

RESUMO

Interactions in primary visual cortex (V1) between simple visual elements such as short bar segments are believed to underlie our ability to easily integrate contours and segment surfaces. We used intrinsic signal optical imaging in alert fixating macaques to measure the strength and cortical distribution of V1 interactions among collinear bars. A single short bar stimulus produced a broad-peaked hill of activation (the optical point spread) covering multiple orientation hypercolumns in V1. Flanking the bar stimulus with a pair of identical collinear bars led to a strong nonlinear suppression in the optical signal. This nonlinearity was strongest over the center bar region, with a spatial distribution that cannot be explained by a simple gain control. It was a function of the relative orientation and separation of the bar stimuli in a manner tuned sharply for collinearity, being strongest for immediately adjacent bars lying on a smooth contour. These results suggest intracortical interactions playing a major role in determining V1 activation by smooth extended contours. Our finding that the interaction is primarily suppressive when imaged optically, which presumably reflects the combined inhibitory and excitatory inputs, suggests a complex interplay between these cortical inputs leading to the collinear facilitation seen in the spiking response of V1 neurons. This disjuncture between the facilitation seen in spiking and the suppression in imaging also suggests that cortical representations of complex stimuli involve interactions that need to be studied over extended networks and may be hard to deduce from the responses of individual neurons.

Documentos Relacionados

• Optical imaging of functional domains in the cortex of the awake and behaving monkey
• Spatial and temporal frequency selectivity of neurones in visual cortical areas V1 and V2 of the macaque monkey.
• Contextual influences in V1 as a basis for pop out and asymmetry in visual search
• High-resolution optical imaging of functional brain architecture in the awake monkey.
• Cells and circuits contributing to functional properties in area V1 of macaque monkey cerebral cortex: bases for neuroanatomically realistic models.