Complex motion sensitivity of neurons, in the visual part of the anterior ectosylvian cortex in cats

In cats, it is generally believed that the visual part of the anterior ectosylvian cortex (AEV) is involved in motion integration. It receives a substantial proportion of its afferents from cortical (e.g. lateral suprasylvian cortex) and subcortical (e.g. lateral posterior-pulvinar complex) areas known to participate in complex motion analysis. It has been established that a subset of AEV neurons can code the vericlical motion of a moving plaid pattern (pattern-motion selectivity). In our study, we have further investigated the possibility that AEV neurons may play a role in higher-order motion processing by studying their responses to complex stimuli which necessitate higher order spatial and temporal integration. Experiments were performed in anesthetized adult cats. Classical receptive fields were stimulated with (1) complex random-dot kinematograms (RDKs), where the individual elements of the pattern do not provide coherent motion cues; (2) optic flow fields which require global spatial integration. We report that a large proportion of AEV neurons were selective to the direction and speed of RDKs. Close to two-thirds of the cells were selective to the direction of optic flow fields with about equal proportions being selective to contraction and expansion. The complex RDK and optic flow responsive units could not be systematically characterized based on their responses to plaid patterns; they were either pattern- or com_ ponent-motion selective. These findings support the proposal that AEV is involved in higher-order motion processing. Our data suggest that the AEV may be more involved in the analysis of motion of visual patterns in relation to the animal's behavior rather than the analysis of the constituents of the patterns. (c) 2008 IBRO. Published by Elsevier Ltd. All rights reserved.