Some patients with face agnosia (prosopagnosia) caused by occipitotemporal damage produce discriminatory covert responses to the familiar faces that they fail to identify overtly. For example, their average skin conductance responses (SCRs) to familiar faces are significantly larger than average SCRs to unfamiliar faces. In this study we describe the opposite dissociation in four patients with bilateral ventromedial frontal damage: The patients recognized the identity of familiar faces normally, yet failed to generate discriminatory SCRs to those same familiar faces. Taken together, the two sets of results constitute a double dissociation: bilateral occipitotemporal damage impairs recognition but allows SCR discrimination, whereas bilateral ventromedial damage causes the opposite. The findings suggest that the neural systems that process the somatic-based valence of stimuli are separate from and parallel to the neural systems that process the factual, nonsomatic information associated with the same stimuli.

Following bilateral damage to the entire medial temporal lobe and interconnected cortices in the anterior temporal and medial frontal regions, patient Boswell developed a severe learning defect for all types and levels of Factual knowledge, including faces. In the experiments described here, however, we demonstrate that Boswell can acquire a non conscious bond between entirely new persons and the affective valence they display. The finding is important on the followng accounts. First, Boswell's lesions guarantee that the entorhinal and perirhinal cortices, hippocampus, amygdala, and higher-order neocortices in the anterior temporal region are not required to support this form of covert learning. Second, this demonstration is possible only in a patient such as Boswell, because in individuals with normal or only partially impaired factual learning, fact memory will contaminate the performance.