The velocity function of ipsilateral visual units in the frog optic tectum: comparison with retinal ganglion cells.

Ipsilateral retino-tecto-isthmo-tectal units in frogs were commonly classified in two groups (I1 and I2) according to their functional properties. Quantitative measurements of their discharge in response to automatically moved targets are described below for the first time. Results show that the velocity function of these units can be expressed by a power function respectively similar to that described earlier (see ref. 6) for R2 and R3 retinal ganglion cells. The existence of mixed 'sustained' units is also discussed.