STIMULUS-GENERALIZATION OF FEAR RESPONSES - EFFECTS OF AUDITORY-CORTEX LESIONS IN A COMPUTATIONAL MODEL AND IN RATS

The conditioning of fear responses ta a simple acoustic stimulus (pure tone) paired with footshock can be mediated by the transmission of au ditory information to the lateral nucleus of the amygdala from either the auditory thalamus or the auditory cortex. We examined the processi ng capacity of the thalamo-amygdala pathway by making lesions of the a uditory cortex and testing the extent to which conditioned fear respon ses generalized to tones other than the one paired with footshock. Two studies were performed, one in an anatomically constrained computatio nal model of the fear conditioning network and the other in rats. Stim ulus generalization was unaffected in both. These findings support the validity of the model as an approach to studying the neural basis of conditioned fear learning, and in addition suggest that tbe thalamo-am ygdala pathway, possibly by the use of population coding, is capable o f performing at least crude stimulus discriminations.