Evidence for the sequential participation of inferior temporal cortex and amygdala in the acquisition of stimulus-reward associations.

On a test of one-trial learning of object-reward associations, monkeys showed marked impairment after lesions of either the anterior part of inferior temporal cortex (area TE) or the amygdala (A). By contrast, little or no loss followed lesions of either the posterior part of inferior temporal cortex (area TEO) or the fusiform-hippocampal gyrus and hippocampus (FHH). The finding of impairment after either the area TE or A lesions fits the view [11] that stimulus-reward learning in vision is mediated by a functional chain connecting the visual system to the limbic system through relays in the inferior temporal cortex and the amygdala. Area TE is considered to be the last purely visual link in this pathway. A previous study [19] showed that damage to area TE, but not to other temporal lobe structures (TEO, A or FHH), severely impairs performance on a one-trial-learning test of object recognition as distinguished from object-reward association. Presumably, the impairment after TE lesions in the present study was due to this same basic recognition disorder. The impairment after amygdalectomy, however, not being attributable to a recognition disorder, appears to reflect instead a disorder in object-reward association learning. Together, these results provide evidence that the formation of object-reward associations in vision involves the sequential participation of a recognition mechanism dependent on the inferior temporal cortex and an associative process dependent on the amygdala.