[Conditioned reflex analog of sensomotor cortex neurons to acetylcholine microinjection].

Conditioned responses to time were studied in neurones of the sensorimotor cortex in alert rabbits using fixed time interval (2 min) combinations of sound stimuli with microionophoretic injection of acetylcholine in the recorded cell's area. Conditioned responses to time were elaborated in 26 out of 50 recorded cells (52%), both of activation (21 cells) and inhibitory (5 cells) types. They appeared after 10--30 pairings and were reproduced during 10--15 consequent omissions of the signal which points to persistence of the conditioned trace responses. It is assumed that the reinforcing effect of acetylcholine is basically due to the increased excitability of the neurone during application of the drug.