Spatial structure of neuronal receptive field in awake monkey secondary visual cortex (V2)
Significance Using a computational method to analyze neuronal responses evoked by natural scene stimuli, we performed a comprehensive identification of secondary visual cortex (V2) neuronal receptive fields (RFs) and found several novel spatial structures of RFs. This approach imposes no assumption about the selectivity of the neurons, thus allowing a more objective search of RFs. Furthermore, by combining single unit recording with optical imaging of intrinsic signals, we examined the spatial distribution of V2 neurons exhibiting different RFs, with respect to the V2 stripes defined previously by cytochrome oxidase staining. The identified V2 RFs could be explained by convergence of V1 neurons with well known primary visual cortex RFs. This study illustrates that computational approach is useful for comprehensive RF identification in higher visual cortices. Visual processing depends critically on the receptive field (RF) properties of visual neurons. However, comprehensive characterization of RFs beyond the primary visual cortex (V1) remains a challenge. Here we report fine RF structures in secondary visual cortex (V2) of awake macaque monkeys, identified through a projection pursuit regression analysis of neuronal responses to natural images. We found that V2 RFs could be broadly classified as V1 like (typical Gabor shaped subunits) ultralong (subunits with high aspect ratios) or complex shaped (subunits with multiple oriented components) Furthermore, single unit recordings from functional domains identified by intrinsic optical imaging showed that neurons with ultralong RFs were primarily localized within pale stripes, whereas neurons with complex shaped RFs were more concentrated in thin stripes. Thus, by combining single unit recording with optical imaging and a computational approach, we identified RF subunits underlying spatial feature selectivity of V2 neurons and demonstrated the functional organization of these RF properties.
Proceedings of the National Academy of Sciences