Lateral interactions in the primary visual cortex and their role in perception
Abstract
An important task of visual processing is to recognize objects that are embedded in complicated visual scenes. To accomplish this task, the visual cortex must integrate local information from the retina into global percepts such as contours, surfaces and three-dimensional shapes. The process of visuospatial integration was thought to take place in high-order areas of visual processing, but here we present evidence that the integration process begins as early as the primary visual cortex. We performed parallel experiments using psychophysical techniques in human observers and neural recordings in the primary visual cortex of alert primates. We find that neurons in the primary visual cortex have response properties that are considerably more complicated than expected from previous studies. A simple visual stimulus elicits action potentials over a very limited region of visual space, however there is a much larger region of visual space that contributes subthreshold inputs to the neuron. Stimuli in this part of the visual field can not activate the cell directly, but can substantially modulate a neuron's response to another stimulus centered in the neuron's receptive field (RF). We find that the properties of these long-range inputs are consistent with a role in visuospatial integration. Excitatory and inhibitory inputs to V1 neurons are spatially segregated and may allow individual neurons to participate in different perceptual tasks. Excitatory inputs are consistent with a role in contour integration and inhibitory inputs may play a role in surface segmentation. Psychophysical experiments using similar stimuli indicate that the long-range inputs play an important role in visual perception. The perceived orientation, brightness and spatial position of an object can be modified by contextual stimuli that invoke long-range interactions in the physiological experiments. Taken as a group, these findings indicate that, even this early stage of cortical processing, neurons can play a role in rather sophisticated perceptual computations. ^
Subject Area
Biology, Neuroscience
Recommended Citation
Mitesh K Kapadia,
"Lateral interactions in the primary visual cortex and their role in perception"
(January 1, 1999).
Dissertations available from ProQuest.
Paper AAI9953552.
http://repository.upenn.edu/dissertations/AAI9953552
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