Abstract
Areas V1 and V2 of Macaque monkey visual cortex are characterized by unique cytochrome oxidase staining patterns. Initial electrophysiological studies associated cytochrome oxidase blobs in V1 with processing of surface properties such as color and brightness and the interblobs with contour information processing. Numerous studies followed, some supporting this proposal and others failing to find significant functional differences between blobs and interblobs. In V2, controversy also remains regarding the functional distinctness of the thin, pale, and thick stripes. In this study, to resolve this long-standing issue, we have used optical imaging to map color-selective responses in V1 and V2.
In V1, we find striking ‘blob-like’ patterns of color response. Careful alignment of optical maps and cytochrome oxidase stained tissue revealed that color domains in V1 align well with cytochrome oxidase blobs in V1. Furthermore, consistent with cytochrome oxidase blobs, we find color blobs align along centers of ocular dominance columns and co-align with regions of high monocularity. Finally, we find color blobs in V1 are centers of low orientation selectivity and do not overlap with centers of orientation domains in V1. In V2, color domains overly thin stripes; orientation selective domains overly thick and pale stripes.
We conclude that color and orientation selective responses are preferentially located in distinct cytochrome oxidase compartments in V1 and V2. We propose that the term ‘blob’ encompass both the concept of ‘cytochrome oxidase blob’ and ‘color domain’ in V1.
Supported by EY11744, Vanderbilt Vision Research Center, Center for Integrative & Cognitive Neuroscience.