Abstract # 185:

Scheduled for Friday, August 18, 2006 07:00 PM-09:00 PM: Session 17 (Regency West 1/3 ) Poster Presentation

Localizing Handedness in the Chimpanzee Brain: A Combined MRI and PET Study

W. Hopkins1,2, J. Taglialatela1,2 and J. L. Russell1,2
1Div. of Psychobiology, Yerkes Reg. Prim. Res. Ctr., Emory Univ., Atlanta, GA 30322, USA, 2Department of Psychology, Berry College, Mount Berry, Georgia 30149
     Most humans are right-handed and historically many have considered population-level handedness to be unique to human evolution. Recent evidence in captive and wild chimpanzees has demonstrated evidence of population-level handedness but still very little in known regarding the underlying neurobiological correlates of hand use in nonhuman primates. In this study, we assessed the association between handedness and neuroanatomical asymmetries in the Chimpanzee brain measured from magnetic resonance imaging (MRI) in a sample of 67 apes. We found that handedness for bimanual actions are associated with variation in a cortical morphological landmark referred to as the KNOB, a region of the precentral gyrus where the hand is presumably represented in the motor cortex. Right-handed chimpanzees had a significantly left KNOB while left-handed subjects had a larger right KNOB F(1,66)=5.67, p < .01. To assess whether the KNOB represents the cortical region of the hand, positron emission tomography (PET) was conducted in two chimpanzees while engaged in a manual grasping task. PET activation during grasping revealed significant activation of the motor cortex in the hemisphere opposite the hand used by the Chimpanzee. The combined MRI and PET studies suggest that the neurobiological basis for handedness in coordinated bimanual actions of chimpanzees is most strongly linked to individual differences in asymmetries of the precental gyrus.