RESPONSES TO MOVING TEXTURE PATTERNS OF CELLS IN THE STRIATE-RECIPIENT ZONE OF THE CATS LATERAL POSTERIOR-PULVINAR COMPLEX

We have studied the response properties of cells in the lateral part o f the lateral posterior nucleus or striate-recipient zone (LP1) of the lateral posterior nucleus-pulvinar complex to the motion of textured patterns [visual noise]. Our purpose was to determine basic noise resp onse characteristics and to compare these properties to that of cells in area 17 known to project to the LP1. Practically all LP1 cells (87% ) responded to the motion of visual noise. The evoked discharges were either sustained or characterized by several bursts. On average, as fo und in cortex, LP1 neurons were more broadly tuned for the direction o f noise than that of gratings (bandwidths of 49 and 36 degrees, respec tively; t-test, P < 0.005). Noise tuning function in LP1 was comparabl e to that found in cortex (mean of 48 degrees). One third of the LP1 u nits did not exhibit any preferences for drift direction of noise. Suc h cells were virtually not encountered in the striate cortex. This gro up of LP1 cells was generally not tuned for grating direction. For pra ctically all LP1 cells, responses to noise varied as a function of dri ft velocity. The mean optimal velocity was 27.5 degrees/s with mean ba ndwidth of 2.5 octaves. LP1 cells were sensitive to a broader range of velocities than complex cells in area 17. The results of the present study showed that visual noise is an appropriate stimulus for studying motion sensitivity of cells in the LP1. It also revealed that the noi se response properties, such as direction and velocity tuning function s, are very similar to those reported in the striate cortex. The exact contribution of area 17 in the visual noise responsiveness of LP1 cel ls remains to be determined. This study provides additional evidence t hat the lateral posterior nucleus-pulvinar complex may be involved in many aspects of visual processing.