SCIATIC TRANSECTION ELIMINATES CONTRALATERAL TRANSFER OF THE LEARNING DEFICIT FOLLOWING NONCONTINGENT SHOCK IN SPINAL RATS. A. Ferguson*, E. Crown, and J. Grau. Dept. of Psychology, Texas A&M Univ., College Station TX, 77843.

Previous studies suggest that the spinal cord can support a simple form of instrumental learning (Grau et al., 1998, Behav. Neuro. ****). In a typical experiment, spinal rats are given contingent shock to one hindleg whenever the leg is extended (cont.). Noncontingently shocked subjects (noncont.) receive shock irrespective of leg position. In a subsequent test phase all subjects receive contingent shock to the contralateral leg. Rats in the cont. group learn whereas rats in the noncont. group display a learned helplessness-like learning deficit. Although previous studies indicate that these phenomena are centrally mediated, little is known about the peripheral projections necessary for both learning and the learning deficit.

The sciatic nerve is one of the major sources of innervation for the hindlegs. Thus, the present study examined the effect of sciatic transection on the ability to learn the shock-leg position contingency (Experiment 1) and the induction of the learning deficit (Experiment 2). In Experiment 1 spinal rats were either given a sciatic transection or sham surgery and then contingently shocked on the leg that underwent surgery. Rats with an intact sciatic nerve, acquired the shock-leg position contingency but rats with sciatic transections did not. In Experiment 2 rats were given sciatic transection or sham surgery, and either contingently or noncontingently shocked on the leg that underwent surgery. Sham operated rats that received noncontingent shock during training failed to learn when contingent shock was applied to the contralateral leg. Cutting the sciatic nerve blocked this effect. The findings suggest that the sciatic nerve is necessary for both acquisition of the instrumental response and the induction of the learning deficit.