CONDITIONED CHANGES IN THE BASAL FOREBRAIN - RELATIONS WITH LEARNING-INDUCED CORTICAL PLASTICITY

Simultaneous recordings were performed in the auditory cortex and in the basal forebrain (BF) of rats subjected to habituation, conditioning (tone followed by a footshock), extinction, and reconditioning. Quantification of myographic activity from the neck muscles revealed behavioral conditioning in 10-20 trials. Short-latency, increased discharges of the BF neurons were observed within the first 5 conditioning trials, whereas tone-evoked responses above the level of the first habituation trials only started to occur between the 5th and the 10th trial in the auditory cortex. Increased discharges persisted in the BF during extinction; the cortical responses returned to their habituation level. Relative to conditioning, pseudoconditioning induced much smaller increased discharges in both structures. The role of the BF neurons in promoting learning-induced cortical plasticity is discussed in light of these results.