Unitary and field potential responses in the pigeon optic tectum evoked by luminous stimuli.

Receptive fields of retinotectal axons and of tectal cells were plotted, and the magnification factor at the tectal surface was measured. In the SGFS, receptive fields were often below 6 degrees in size and are probably derived from radially disposed pyriform cells. In the SGC, receptive fields were up to 40 degrees in size and are probably derived from the multipolar cells. Spike discharge in the retino-recipient layers was accompanied by a phasic negative-going slow potential, occurring at on and off to flashed spot stimuli.