Research reportPlanum temporale surface area and grey matter asymmetries in chimpanzees (Pan troglodytes): The effect of handedness and comparison with findings in humans
Section snippets
Subjects
Magnetic resonance images were obtained from a sample of 103 chimpanzees including 41 males and 62 females. The subjects ranged in age from 6 to 51 years (mean = 24.736, s.d. = 11.91). All the chimpanzees were members of a captive colony housed at Yerkes National Primate Research Center (YNPRC) in Atlanta, Georgia. All procedures used with the chimpanzees were approved by the Institutional Animal Care and Use Committee of Emory University. Shown in Table 1 are the handedness distributions and the
Descriptive statistics
The left and right PT surface areas and grey matter volumes for each scanner type are shown in Table 2. In the initial analyses, we compared the left and right PT areas and GM volumes between sexes (male, female) and the scanner type (1.5, 3.0 and cadaver) using a mixed model ANOVA. Hemisphere was the repeated measure while sex and scanner types were the between group factors. For the PT surface area, a significant main effect for hemisphere was found F(1, 99) = 28.36, p < .001 with the left PT
Discussion
Two main results emerged from this study. First, chimpanzees show significant population-level leftward asymmetries in the planum temporale when measuring both the surface area and the grey matter volumes. Second, chimpanzees that prefer to gesture with the right hand show significantly greater leftward asymmetries in the grey matter volume of the PT compared to left-handed individuals. Hand preferences for non-communicative functions were not associated with asymmetries in either the surface
Acknowledgments
This research was supported in part by NIH grants NS-36605, NS-42867, HD-38051, and HD-56232. The Yerkes Center is fully accredited by the American Association for Accreditation of Laboratory Animal Care. American Psychological Association guidelines for the ethical treatment of animals were adhered to during all aspects of this study. We are grateful to the helpful assistance of the entire veterinary staff at the Yerkes Center for their assistance in collection of the MRI scans.
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