RESPONSES OF COMPLEX CELLS IN CAT AREA-17 TO APPARENT MOTION OF RANDOM PIXEL ARRAYS

The characteristics of directionally selective cells in area 17 of the cat are studied using moving random pixel arrays (RPAs) with 50% whit e and 50% black pixels. The apparent motion stimulus is similar to tha t used in human psychophysics Fredericksen et al. (1993). Vision Resea rch, 33, pp. 1193-1205]. We compare motion sensitivity measured with s ingle-step pixel lifetimes and unlimited pixel lifetimes. A motion sti mulus with a single-step pixel lifetime contains directional motion en ergy primarily at one combination of spatial displacement and temporal delay. We recorded the responses of complex cells to different combin ations of displacement and delay to describe their spatio-temporal cor relation characteristics. The response to motion of RPAs with unlimite d lifetime is strongest along the preferred speed line in a delay vs d isplacement size diagram. When using an RPA with a single-step pixel l ifetime, the cells are responsive to a much smaller range of spatial d isplacements and temporal delays of the stimulus. The maximum displace ment that still gives a directionally selective response is larger whe n the preferred speed of the cell is higher. It is on average about th ree times smaller than the receptive held size. (C) 1997 Elsevier Scie nce Ltd. All rights reserved.