Physiological Plasticity of Single Neurons in Auditory Cortex of the Cat during Acquisition of the Pupillary Dilation Conditioned Response: II. Secondary Field (AII)

Recorded the discharges of 22 single neurons in the secondary auditory cortical field (AII) during acquisition of the pupillary dilation conditioned defensive response in 12 chronically prepared cats. All 22 neurons developed discharge plasticity in background activity, and 21 of 22 cells developed plasticity in their responses to the acoustic CS. Decreases in background activity developed at the time that Ss began to display CRs. Increases in background activity developed in Ss that became more tonically aroused during conditioning. However, both increases and decreases in evoked activity developed independently of the rate of pupillary learning, tonic arousal level, or changes in background activity. Findings indicate that changes in background activity are closely related to behavioral processes of learning and arousal, whereas stimulus-evoked discharge plasticity develops solely as a consequence of stimulus pairing. Comparison with data obtained by the 2nd author and colleagues (see record 1985-03305-001) for the primary auditory cortical field (AI) indicates that both regions developed neuronal discharge plasticity early in the conditioning phase and that increases in background activity in primary auditory cortex were also associated with elevated levels of tonic arousal. The incidence of single neurons developing learning-related discharge plasticity was significantly greater in AII than in AI. Findings are discussed in terms of parallel processing in sensory systems and multiple sensory cortical fields