The localization of instrumental learning within the spinal cord

Abstract

Spinal neurons of surgically transected rats can support a simple form of instrumental learning. Rats learn to maintain leg flexion as a response to shock. The present experiments localized the region of the spinal cord that mediates this learning. Experiment 1 used histological procedures to trace the fiber pathways that innervate the region of stimulation. The retrograde fluorescent tracer Fluoro-Gold was used to mark the neurons innervating the tibialis anterior muscle. Cell bodies were shown primarily in lamina IX of the lower lumbar segments. Experiment 2 used surgical transections at different spinal column levels to establish the segments involved in the learning. The surgical cuts established the boundary of tissue necessary for the learning. The lowest cut that supported learning was in L5 (lumbar segment 5).