Limbic lesions and the problem of stimulus—Reinforcement associations

Abstract

Previous anatomical work has shown that the inferotemporal visual cortex projects to three regions within or closely related to the limbic system—the orbitofrontal cortex (OF), the temporal pole and amygdala (TPA), and the fusiform-hippocampal gyrus and hippocampus (FHH). To determine which of these limbic projections might be the most important for the formation of stimulus-reinforcement associations in vision and in other modalities, groups of monkeys with lesions in these three regions (and controls) were compared on both object and place discrimination reversal learning. While each of the three different limbic removals produced an impairment, the effect of the FHH lesion was limited to the place reversal task, and the deficit after the OF ablation, although supramodal, was characterized by a difficulty in the suppression of stimulus-reinforcement associations. Only the impairment produced by the TPA lesion, also supramodal, was consistent with a difficulty in the formation of such associations, an interpretation which is strengthened by a consideration of the gross behavioral abnormalities that have been described repeatedly following this same lesion.