Electrophysiology of ventromedial striatal neurons during movement.

The firing rate of ventromedial striatal cells was studied in rats trained to run in place on a rotating turntable treadmill. Animals were trained to run clockwise and counter-clockwise as they propelled a turntable for a water reward. After a period of training, Parylene C coated stainless steel wire electrodes were chronically implanted for single unit recording. Nearly all ventromedial striatal cells increased their firing rate concomitant with locomotion in the treadmill (32 of 36 cells). The magnitude of this response was influenced by the order of testing and by the direction of circling relative to the side of brain being recorded. The increase in firing rate was greater during the first test of the day and was greater when animals circled contralateral to the side of the recording electrode than when they circled ipsilateral to the recorded side.