Responses of neurons in the cat posteromedial lateral suprasylvian cortex to moving texture patterns

The posteromedial lateral suprasylvian cortex represents a point of converg ence between the geniculostriate and extrageniculostriate visual pathways. Given its purported role in motion analysis and the conflicting reports reg arding the texture sensitivity of this area, we have investigated the respo nse properties of cells in PMLS to moving texture patterns ("visual noise") . In contrast to previous reports, we have found that a large majority of c ells (80.1%) responds to the motion of a texture pattern with sustained dis charges. In general, responses to noise were more broadly tuned for directi on compared to gratings; however, direction selectivity appeared more prono unced in response to noise. The majority of cells was selective for drift v elocity of the noise pattern (mean optimal velocity: 26.7 degrees/s). Veloc ity tuning was comparable to that of its principal thalamic input, the late ral posterior pulvinar nucleus. In general, responsiveness of cells in the posteromedial lateral suprasylvian cortex increased with increasing texture element size, although some units were tuned to smaller element sizes than the largest presented. Finally, the magnitude of these noise responses was dependent on the area of the visual field stimulated. In general, a stimul us corresponding to roughly twice the size of the receptive field was requi red to elicit an equivalent half-maximal response to that for gratings. The results of this study indicate that the majority of cells in the poster omedial lateral suprasylvian cortex can be driven by the motion of a fine t exture field, and highlight the importance of this area in motion analysis. (C) 2000 IBRO. Published by Elsevier Science Ltd.