Dendritic and sustained shifts in potential to electrical stimulation of the anuran tectal surface.

1. Recordings of dendritic potentials and sustained potential shifts (SPS) were made from the brain of immobilised frogs during surface tectal electrical stimulation. 2. Single pulses evoked dendritic responses; trains caused decay of dendritic responses on the background of the evoked SPS. 3. The tectal surface SPS declined with distance from the stimulating electrode. 4. The negative surface SPS declined with tectal depth to ca 300 microns, then reversed polarity and increased in amplitude with depth up to 700 microns.