DOUBLE DISSOCIATION BETWEEN OVERT AND COVERT FACE RECOGNITION

Some patients with face agnosia (prosopagnosia) caused by occipitotemp oral damage produce discriminatory covert responses to the familiar fa ces that they fail to identify overtly. For example, their average ski n conductance responses (SCRs) to familiar faces are significantly lar ger than average SCRs to unfamiliar faces. In this study we describe t he 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 fa miliar faces. Taken together, the two sets of results constitute a dou ble dissociation: bilateral occipitotemporal damage impairs recognitio n but allows SCR discrimination, whereas bilateral ventromedial damage causes the opposite. The findings suggest that the neural systems tha t process the somatic-based valence of stimuli are separate from and p arallel to the neural systems that process the factual, nonsomatic inf ormation associated with the same stimuli.