Effect of amygdalectomy on habituation and CER in rats.

Amygdalectomized, Sham operates and unoperated rats received 20 habituation trials followed by CER training during which the habituation stimulus was made a CS for 10 CS-UCS pairings. Although no reliable differences in rate of magnitude of habituation as measured by suppression ratio magnitudes and ITI durations were apparent between any groups, these same measures indicated that substantial deficits in conditioned suppression were produced by bilateral amygdalectomy. In addition the lesion produced a reliable deficit in unconditioned suppression and a slight but reliable reduction in the number of ccs of water consumed in a 24 hour period. These results are more consistent with the hypothesis that amygdalectomy interferes with the arousal of fear than with the proposals that this lesion produces deficits in habituation or in response inhibition.