[An increase in the excitability of the cortical neurons during reinforcing stimulation of the lateral hypothalamus].

Pyramidal tract response (PTR) was recorded from unanaesthetized rabbits. The following three experimental paradigms were used which imitated behavioural conditioning procedures: pairing of direct stimulation of two cortical points; similar pairing conjoint with stimulation of additional reinforcing the lateral hypothalamus (LH); LH stimulation in response to increased PTR in a manner similar to instrumental conditioning procedure. An increase in the monosynaptic wave was the most common result for all three paradigms. The direct wave increase was significantly larger for the second and third experimental paradigms in comparison with the first one. In general the data obtained suggest that an increase in the synaptic efficacy is the major mechanism of behavioural conditioning, while changes in the membrane excitability reflect a participation of motivational components of reinforcement resulted from the LH activation.