THE IMPORTANCE OF EQUATING FLEXION FORCE WHEN STUDYING "INSTRUMENTAL LEARNING" IN SPINALIZED SUBJECTS. D.G. Barstow, J.W. Grau, & M.W. Meagher. Dept. of Psychology, Texas A&M Univ., College Station, TX 77843.

Evidence suggests spinal mechanisms are capable of supporting instrumental conditioning. In these experiments, one group of spinalized subjects (Exp) can terminate shock to its hind leg by flexing that leg. A "Yoked" group experiences the same shock irrespective of leg position. Although we were previously able to obtain an Exp/Yoked difference (Parker et al., Neurosci. Abs., 18, 1026) we failed to replicate important details of past studies. These include: 1) an increase in response duration in Exp Ss; and 2) poor learning after noncontingent shock (a "learned helplessness" effect). In the present study we show that these effects are observed if one matches response force.

A day after subjects (N=24) received a spinal transection at T2, they were placed in restraining tubes. For half the subjects, shock intensity was then adjusted so that it elicited a flexion with a force of 0.4 N; the other half experienced an intensity capable of eliciting a flexion of 0.6 N. Subjects then received 30 m of contingent shock (Exp), noncontingent shock (Yoked), or no shock (Unshk). Subjects in the Exp group, but not the yoked group, exhibited leg flexions that steadily increased in duration across training. At the end of training, response force was again equated across subjects. All subjects then received 30 m of contingent shock. Both the Exp and the Unshk groups acquired the flexion response whereas subjects in the Yok group did not. Supported by MH48994 to J.W.G.

Published in Society for Neuroscience Abstracts, 19, 1993, 1001.

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