VISUAL-MOTION PROCESSING IN THE ANTERIOR ECTOSYLVIAN SULCUS OF THE CAT

1. Neurons that are selectively sensitive to the direction of motion o f elongated contours have been found in several cortical areas in many species. However, in the striate cortex of the cat and monkey, and th e extrastriate posteromedial lateral suprasylvian visual area of the c at, such cells are generally component motion selective, signaling onl y the direction of movement orthogonal to the preferred orientation; a direction that is not necessarily the same as the motion of the entir e pattern or texture of which the cell's preferred contour is part. Th e primate extrastriate middle temporal area is the only cortical regio n currently known to contain a substantial population of pattern-motio n-selective cells that respond to the shared vector of motion of mixtu res of contours. 2. From analyzing published data on the connectivity of the cat's cortex, we predicted that the anterior ectosylvian visual area (AEV), situated within the anterior ectosylvian sulcus, might be a higher-order motion processing area and thus likely to contain patt ern-motion-selective neurons. This paper presents the results of a stu dy on neuronal responses in AEV. 3. Ninety percent of AEV cells that r esponded strongly to drifting grating and/or plaid stimuli were direct ionally selective (directionality index > 0.5).For this group, the mea n directionality index was 0.75. Moreover, 55% of these cells were une vequivocally classified as pattern motion selective and only one neuro n was classified as definitely component motion selective. Thus high-l evel pattern motion coding occurs in the cat extrastriate cortex and i s not Limited to the primate middle temporal area. 4. AEV contains a h eterogeneous population of directionally selective cells. There was no clear relation between the degree of directional selectivity for plai ds or gratings and the degree of selectivity for pattern motion or com ponent motion. Nevertheless, 28% of the highly responsive cells were b oth more strongly modulated by plaids than gratings and more pattern m otion selective than component motion selective. Such cells could corr espond to a population of ''selection units'' signaling the salience o f local motion information. 5. AEV lacks global retinotopic order but the preferred direction of motion of neurons (rather than axis of moti on, as in the middle temporal area and the posteromedial lateral supra sylvian visual area) is mapped systematically across the cortex. Our d ata are compatible with AEV being a nonretinotopic, feature-mapped are a in which cells representing similar parts of ''motion space'' are br ought together on the cortical sheet.