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Key Words
Capgras delusion * Right hemisphere * White-matter pathology * Face processing
Abstract
Previous neuropsychological studies have demonstrated an association between person misidentification and right-hemisphere dysfunction. In the study reported here, we explore the contribution of facial and visual recognition impairments in a patient with right-hemisphere subcortical white-matter pathology in the frontal and parietal lobes and a diagnosis of vascular cognitive impairment. The patient displayed false recognition of unfamiliar faces and deficient retrieval of key biographic detail for famous faces. These results are discussed in the context of the contribution of deficiencies in the visual system and subcortical white-matter lesions to the development of Capgras delusion.
Introduction
Disorders of face memory and face perception have been the focus of much neuropsychological investigation over the past 50 years. The most extensively studied of these is prosopagnosia - a condition characterised by the inability to identify all familiar faces, including famous persons, friends, family and even the prosopagnosic's own face [1]. The critical lesion sites in prosopagnosia involve right ventromedial occipitotemporal regions which include the inferior temporal cortex and medial temporal lobe limbic areas [2].
Although less well documented, areas of the prefrontal cortex are also involved in facial processing: projections from the face-processing areas in the right ventromedial occipitotemporal regions to the ventromedial prefrontal cortex via the uncinate fasciculus as well as limbothalamic pathways are well established [3]; single cell recordings have identified face-sensitive neurons in the inferior frontal convexity region of non-human primates [41, and neuropsychological studies have documented an association between false facial recognition and right frontal lobe dysfunction [5]. These frontal patients, in striking contrast to the lack of conscious facial recognition described in prosopagnosics, mistakenly believe that unfamiliar faces are familiar [6, 71.
In a small subset of psychotic patients, false recognition can lead to frank misidentification which can reach delusional proportions [5, 8-10] - as in the case of Fregoli delusion (FD) [ 11]. The hallmark of FD is the recognition of a familiar other in a stranger. The patient believes that the familiar other is able to take on different physical forms and adopt another's appearance. It has been suggested that FD develops when spurious feelings of familiarity evoked by novel faces are combined with the...