METHODS

Cats were employed and the recruiting response, elicited by thalamic stimulation was recorded with a Grass model-3 amplifier and inkwriter, The animals were under nembutal, Dial or chloralosane anesthesia or, after preparation under ether and local procaine, were immobilized with beta-erythroidine or by transection of the cord at Cl and maintained with artificial respiration, The thalamus was stimulated with stereotaxically oriented bipolar concentric electrodes. A Goodwin stimulator was employed, the condenser discharges of which had voltages between 1. and 7, a falling phase of 1 msec. and a usual frequency of 7.5/sec. Grounding both temporal muscles effectively reduced shock artifacts. Regional cortical pickups were between screw electrodes, I cm. apart, inserted into the calvarium until their tips rested on the underlying dura. More detailed pickups were obtained with silver ball tips, applied to the exposed cortex with the aid of a Grass multiple electrode holder. The most precise cortical and subcortical records were gained with bipolar concentric electrodes oriented stereotaxically. The recently prepared atlas of the cat’s