Fig. 4.

Elimination by ketamine of the evoked firing of a striatal neuron in response to light cutaneous stimulation in chronically implanted animal. The upper lip was near the center of the receptive field, which included the perioral area and snout. Each offour panels shows the raster, PSTH, and representative waveform of the neuron at different stages ofthe experiment. Top panel(Pre), Control response during the alert state before injection. Second panel, Ten minutes after injection of a subanesthetic dose of ketamine (40 mg/kg, i.p.). Third panel, After two additional injections of ketamine, 40 mg/kg each. Bottom panel, Partial recovery of evoked firing 5 hr after the initial injection. The number of sweeps in each condition was 100. The average stimulus duration (determined from videotape) was 100 msec. The evoked response epoch was time 0 to 0.35 sec; the baseline epoch was −0.3 to −0.05 sec. Each tick on thex-axis = 50 msec; each bin = 6 msec.Arrows at time 0 indicate the approximate stimulus onset. Waveform calibration (bottom right):vertical bar, 0.2 mV; duration of eachtrace, 2.0 msec.