SPATIAL RELATIONSHIPS AMONG 3 COLUMNAR SYSTEMS IN CAT AREA-17

In the primary visual cortex, neurons with similar response properties are arranged in columns. As more and more columnar systems are discov ered it becomes increasingly important to establish the rules that gov ern the geometric relationships between different columns. As a first step to examine this issue we investigated the spatial relationships b etween the orientation, ocular dominance, and spatial frequency domain s in cat area 17. Using optical imaging of intrinsic signals we obtain ed high resolution maps for each of these stimulus features from the s ame cortical regions. We found clear relationships between orientation and ocular dominance columns: many iso-orientation lines intersected the borders between ocular dominance borders at right angles, and orie ntation singularities were concentrated in the center regions of the o cular dominance columns. Similar, albeit weaker geometric relationship s were observed between the orientation and spatial frequency domains. The ocular dominance and spatial frequency maps were also found to be spatially related: there was a tendency for the low spatial frequency domains to avoid the border regions of the ocular dominance columns. This specific arrangement of the different columnar systems might ensu re that all possible combinations of stimulus features are represented at least once in any given region of the visual cortex, thus avoiding the occurrence of functional blind spots for a particular stimulus at tribute in the visual field.