Activity of neurons in the pedunculopontine nucleus during a food-related operant conditioned reflex.

The activity of 91 neurons in the compact and diffuse zones of the pedunculopontine nucleus of freely mobile rabbits was studied during performance of a food-related operant conditioned reflex. A total of 37.4% of the neurons recorded showed reactivity to the conditioned stimulus, which is evidence that the pedunculopontine nucleus is involved in operant learning. A significant predominance of excitatory responses to the conditioned stimulus and to food reinforcement was demonstrated. The main patterns of cell responses were identified, these reflecting the nature of the effect of the conditioned stimulus on neuron activity, the structure of the behavioral act, and the properties of the reinforcement, and demonstrating a relationship between the pedunculopontine nucleus and the processes of attention, motor learning, and reinforcement. Differences were seen in the associative reactive properties of the compact and diffuse zones of the pedunculopontine nucleus to the conditioned stimulus and reinforcement, which is evidence for the functional diversity of this formation and suggests a leading role for the cholinergic compact zone in food-related operant learning and reinforcement, the diffuse zone having a leading role in food-related classical conditioned-reflex learning.