THE ROLE OF THE RIGHT-HEMISPHERE IN THE CAPGRAS DELUSION

Following a general review of the literature linking right hemisphere dysfunction to psychoses in general and Capgras delusion (CD) in parti cular, two studies are described that confirm the link. Study 1 reveal ed that, compared with matched psychiatric controls, 3 CD patients wer e particularly poor at matching pairs of faces shown briefly in the le ft visual field which implies dysfunctioning right hemisphere performa nce. However there was no difference in performance when the faces app eared bilaterally, which fails to support the hypothesis that poor int erhemispheric communication may give rise to CD. The second study invo lved tests of face memory and word memory. CD and other delusional mis identification groups scored markedly low on the face test, again impl ying right hemisphere deficit. Finally, a model of what may be the rig ht hemisphere mechanism giving rise to CD was explored. This assumes t wo routes to face recognition, ventral and dorsal. It is argued that e xclusive damage to the former may cause prosopagnosia and problems in the latter may give rise to the symptoms of CD.