Physiological plasticity of single neurons in auditory cortex of the cat during acquisition of the pupillary conditioned response: I. Primary field (AI).

The effects of conditioning on the discharges of single neurons in primary auditory cortex (AI) were determined during acquisition of the pupillary conditioned response in chronically prepared cats. Acoustic stimuli (1-s white noise or tone) were presented with electrodermal stimulation unpaired during a sensitization control phase followed by pairing during a subsequent conditioning phase. Stimulus constancy at the periphery was ensured by the use of neuromuscular blockade. Discharge plasticity developed rapidly for both evoked and background activity, the former attaining criterion faster than the latter. The pupillary dilation conditioned response was acquired at the same rate as were changes in evoked activity (i.e., 10-15 trials) and faster than background activity (i.e., 20-25 trials). Increases in background activity were correlated with increasing level of tonic arousal, as indexed by pretrial size of the pupil.