Visual receptive field types in the nucleus dorsolateralis anterior of the pigeon's thalamus.

Extracellular recordings were made from cells in the dorsolateral thalamus (DLLv, DLLd, DLAmc) of the pigeon, and their receptive field properties analyzed with stationary and moving visual stimuli. One hundred and ten cells were classified as follows on the basis of their responses. I. On-center and off-center cells (56%). Most of the units in this class had a powerful inhibitory surround which decreased the activity generated at the field center and in some cases gave rise to firing when stimulated alone. II. On-off center cells (16%). These gave on-off responses to static stimulation. More than half of them had an inhibitory surround which suppressed both on and off discharge, or in other cases either the on or the off burst of the center response. This group of cells also responded strongly to motion independently of direction. III. Cells sensitive only to motion (28%). The discharges to movements of units in this class were not affected by the direction of motion. The visual properties of the thalamic units are discussed in conjunction with previous results in the optic tectum of the pigeon.