CONDITIONED RESPONSES IN THE GAMMA EFFERENT SYSTEM

Abstract

The role of the gamma efferent system in learned behavior was studied in acute experiments on cats immobilized by Flaxedil. Recordings of gamma efferent activity in L6 or L7 ventral roots were made during conditioning trials in which tone (CS) was paired with shock to the hind paw (US). Tone stimuli alone frequently caused acceleration or slowing of gamma efferent discharge. This gamma response could be habituated with repeated presentations of the tone. Gamma fibers unresponsive or habituated to the tone developed a conditioned response of accelerated discharge after five to 10 presentations of the paired CS-US. The conditioned response evoked by the CS did not occur when a tone of different frequency was presented, nor did the response occur when CS and US were presented alternately in unpaired sequence. The significance of gamma efferent conditioned responses as a substrate of behavioral conditioning is discussed.