Cellular Basis of Operant-Conditioning of Leg Position

Summary

Leg position learning is accomplished rapidly and successfully by insect thoracic ganglia in operant-conditioning paradigms using either negative or positive reinforcements. This opens up the possibility of analysis of the cellular mechanisms underlying learning and retention because the neurons are relatively few in number, identifiable and repeatedly addressable. Starting with positions controlled by single identified motorneurons we find that these are changed in relation to reinforcement either by very long-lasting frequency shifts or by adjustment of the strength and repetition interval of spontaneously-occurring plateau movements, depending on the paradigm. Postural change is accomplished by altered resistance of a motorneuron, specifically associated with potassium conductance. The resistance range is from 3–10 M Ω , with associated mean frequency range of 5–30 Hz. Only goal-related inputs lead to postural shifts, by way of association of reinforcement with efference or afference memory.