Response properties of neurons in area 17 projecting to the striate-recipient zone of the cat's lateralis posterior-pulvinar complex: comparison with cortico-tectal cells.

The main input of the lateral part of the cat's lateralis posterior-pulvinar complex (LP-P) comes from the primary visual cortex. We investigated the response properties of cells in area 17 projecting to the striate-recipient zone (LP1) of the cat's LP-P complex. The cells' receptive fields were stimulated with drifting sine-wave gratings. Cells whose fibres terminate in the superior colliculus were also recorded, to determine how their properties compare with those of cortico-LP1 cells and to investigate the possibility that LP1 is innervated by collaterals of cortico-tectal units. A total of 26 cells in the striate cortex were identified by antidromic activation from the LP1 (mean latency 2.2 ms) and 22 from the colliculus (mean latency 2.5 ms). Only six cortical cells could be activated from the LP1 and the colliculus. All cortico-LP1 cells except for two responded to drifting sinusoidal gratings with unmodulated discharges (AC/DC ratios < 1). On the basis of their modulation index, these units were classified as complex cells. All cortico-LP1 cells were selective for the orientation of gratings (mean bandwidth of 28 degrees). There was a tendency for cortico-LP1 cells to prefer vertical and horizontal orientations. More than half of these cells (57%) were direction selective. Strong orientation anisotropies were also found in the receptive fields of cortico-tectal cells, since almost all units responded preferentially to horizontally oriented gratings.(ABSTRACT TRUNCATED AT 250 WORDS)