Abstract # 90:

Scheduled for Thursday, August 17, 2006 07:00 PM-09:00 PM: Session 8 (Regency West 1/3 ) Poster Presentation

Gesture handedness predicts asymmetry in the chimpanzee inferior frontal gyrus

J. P. Taglialatela1, C. Cantalupo2 and W. D. Hopkins1,3
1Yerkes National Primate Research Center, Division of Psychobiology, Emory University, 954 Gatewood Road, Atlanta, Georgia 30329, USA, 2Department of Psychology, Clemson University, 3Department of Psychology, Berry College
     Neuroanatomical asymmetries have been identified in chimpanzee frontal and temporal lobes including regions believed to be homologous to human Broca's and Wernicke's areas, respectively. Previous work has demonstrated that handedness for non-communicative manual actions in chimpanzees are associated with asymmetries of the primary motor cortex, but not with the homologous language regions. The purpose of this study was to assess whether or not morphological differences between hemispheres in the chimpanzee inferior frontal gyrus were evident in captive chimpanzees based on the hand they most frequently used for manual communicative gestures. To accomplish this aim, magnetic resonance images and behavioral data were collected in 56 chimpanzees, Pan troglodytes. Anatomical asymmetries were compared between chimpanzees classified as right- and non-right handed for manual gestures. For comparison, the same subjects were then re-classified for hand use during a non-communicative motor action. The hypothesis was that hand use associated with communicative behavior would be associated with asymmetries in the inferior frontal gyrus whereas hand use for non-communicative actions would not. Analyses revealed that those chimpanzees that reliably employ their right hand for manual gestures have larger inferior frontal gyri in the left hemisphere compared to subjects that did not show consistent hand use for gestures (F(1,46)=7.59, p<0.01). In contrast, there is no difference in the size of the inferior frontal gyri between those same subjects when classified as right- and non-right handed for a non-communicative motor action (F(1,46)=2.06, p=0.16). These findings are the first to provide a direct link between neuroanatomical asymmetries and lateralized communicative behavior in chimpanzees.