Food memory: neuronal involvement in food recognition

Previous studies indicate that ablation of the temporal cortex including the amygdala (AM) and hippocampal formation (HF) induce the Kluver-Bucy syndrome in which animals cannot discriminate food from nonfood. Of 710 AM neurons tested, 129 (18.2%) responded to single sensory stimulation (48 to vision, 32 to audition, 49 to ingestion), 142 (20.0%) to multimodal stimulation and 20 to only one item with affective significance. Eight food related AM neurons were tested in reversal by salting food or introducing saline, and all responses were modulated by reversal. In HF and parahippocampal cortices (PH), 864 neurons were recorded, and 160 (18.5%) responded lo the sight of certain objects. Of these, 23 responded predominantly to food related rewarding objects, 13 to several aversive objects such as a spider model, syringe, objects associated with weak electric shock, ten to one object or one kind of object, seven to unfamiliar objects. Of 14 rewarding or aversive object-related neurons tested, responses of seven to the same test object did not change in extinction or reversal tests. Although responses of the other seven decreased in extinction or reversal tests, the magnitude of response remaining in five of those seven still exceeded that of responses to other categories. Results suggest complementary AM and HF-PH functions. The AM may be important in ongoing recognition of the affective significance of complex stimuli (food-nonfood discrimination) and the HF-PH in sustaining past affective significance.