OPERANT LEARNING AT THE LEVEL OF THE SPINAL CORD: INDUCTION AND RETENTION. R. L. Joynes*, S. McLemore & J. W. Grau. Department of Psychology, Texas A&M University, College Station, TX 77843.

Prior work suggests that spinal neurons can support a simple form of operant learning. In a typical experiment, spinal rats (Exp. Group) are given shock to one hind leg whenever the leg is extended. Yoked subjects experience the same amount of shock irrespective of leg position. Rats in the Exp., but not the Yoked, group learn to maintain a flexion response. In a subsequent test phase, all subjects receive controllable shock. Rats in the Exp. group show faciliated learning (positive transfer), while subjects that previously experienced inescapable shock fail to learn (a learned helplessness-like effect).

The present experiment explores the conditions needed to induce this learning effect. Spinal rats received 30 min of controllable shock with a minimum shock duration of 40, 80 or 160 msec (training phase). Immediately after training, all rats received controllable shock for 30 min with a min shock duration of 80 msec (testing phase). Eighty msec minimum shock duration in training resulted in robust learning and positive transfer during testing. Decreasing the minimum shock duration undermined acquisition of the flexion response. While exposure to longer shocks rapidly induced a flexion response, they did not induce positive transfer. Instead, training with a minimum shock duration of 160 msec appeared to have the opposite effect (negative transfer). A similar effect was observed when response-reinforcer contiguity was disrupted by delaying shock offset. Studies examing the retention of these learning effects will also be reported. Supported by MH48994 to J.W.G.

Published in Society for Neuroscience Abstracts, 23, 1997, 1041.

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