Indelibility of subcortical emotional memories

Acquisition and extinction of fear responses conditioned to a visual stimulus were examined in rats with ablations of visual cortex. Visual cortex lesions did not interfere with acquisition, indicating that visual fear conditioning, like auditory fear conditioning, is mediated by subcortical, probably thalamo-amygdala, sensory pathways. In contrast to acquisition, extinction was greatly prolonged, if not prevented, by cortical ablation. This resistance to extinction of subcortical emotional memories may explain certain aspects of emotional memory in man.