Natural Images, Natural Percepts and Primary Visual Cortex

March 7, 2006
  • Visualization algorithms
  • 76M27
The traditional model of primary visual cortex (V1) is in terms of a retinotopically organized set of spatio-temporal filters. This model has been extraordinarily fruitful, providing explanations of a considerable body of psychophysical and neurophysiological results. It has also produced compelling linkages between natural image statistics, efficient coding theory, and neural responses. However,there is increasing evidence that V1 is doing a whole lot more. We can get insight into early cortical processing by studying not only the relationship between image input and neural activity, but also between human visual percepts and early cortical activity. Natural percepts (in the sense of tapping into natural modes of processing) are as important as understanding natural images when trying to find out what primary visual cortex is doing. I will describe several results from functional magnetic resonance imaging (fMRI) studies which show that human V1 blood oxygenation level dependent (BOLD) response to patterns perceived as well-organized is less than to patterns perceived as less organized, V1 response to natural image contrast is correlated with perceived contrast, and apparent size modulates the spatial extent of V1 activity.