Abstract # 28:

Scheduled for Saturday, September 19, 2009 11:30 AM-11:40 AM: Session 3 (Del Mar Room) Oral Presentation


A PROBABILISTIC MAP OF THE BROCA'S AREA HOMOLOG IN CHIMPANZEES (PAN TROGLODYTES): GREY MATTER ASYMMETRY CORRELATES WITH ORO-FACIAL MOTOR CONTROL

W. Hopkins1,2, J. Taglailatela1,3 and T. Nir1
1Yerkes National Primate Res. Ctr., Division of Psychobiology, Atlanta, GA 30329, USA, 2Agnes Scott College, 3Clayton State University
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Broca’s area in the left hemisphere of the human brain is fundamentally involved in language and speech. There are reports of leftward asymmetries in the inferior frontal gyrus (IFG) in the chimpanzee brain, which some consider the homolog to Broca’s area. The validity of these findings has been questioned due to inter-individual variability in the sulci comprising this brain region. Here, we computed three probabilistic maps of the IFG from magnetic resonance images in a sample of 48 chimpanzees. The three probabilistic maps included those regions of the IFG that overlapped in 30 %, 50 %, and 70 % of our sample. We subsequently applied these maps to individual segmented grey matter volumes to determine if the chimpanzees exhibit population-level asymmetries. With respect to grey matter, the chimpanzees showed a population-level leftward asymmetry, but only at the highest threshold level (i. e. 70 %) [F(2, 88)=3.11, p<0.05]. We further found that variation in grey matter asymmetries were associated oro-facial motor control. Chimpanzees that reliably produce attention-getting sounds show a leftward asymmetry in the IFG compared to those that do not [F(2, 88)=4.71, p<0.02]. These results suggest that the presence of neuroanatomical asymmetries in the Broca’s area homolog was present prior to the split between chimpanzees and humans and that this brain region may play a key role in oro-facial motor control.