Abstract # 13:

Scheduled for Thursday, June 19, 2008 10:00 AM-10:10 AM: Session 2 (Meeting Room 1GHI) Oral Presentation

Sylvian Fissure Asymmetries in Capuchin Monkeys (Cebus apella)

K. A. Phillips and S. T. Liu
Hiram College, Departments of Psychology and Biology, 11715 Garfield Rd., Hiram, OH 44234-0067, USA
     Asymmetries of the Sylvian fissure (SF) are believed to reflect an enlargement of the posterior temporal lobe, particularly a region that corresponds to part of Wernicke’s area in humans. In nonhuman primates the homolog to the region may be involved in the discrimination and processing of species-specific vocalizations. Behavioral studies have shown a leftward head orientation bias in response to species-specific vocalizations in macaques. As capuchin monkeys are large brained, socially complex primates with a rich vocal repertoire, it was hypothesized that they would display leftward asymmetry of the SF. We used high-resolution T3 MRI scans to investigate this asymmetry in 17 monkeys (9 males; 8 females). The SF fissure was traced from the anterior to the posterior temporal region on three sagittal sections of each hemisphere, corresponding to lateral, medial and insular regions. Results indicated a trend toward population-level leftward asymmetry in the lateral region of the SF [t(16)=-1.70, p<0.10]; the medial and insular regions did not show significant asymmetry. Post hoc analyses revealed significant sex differences in SF asymmetry, with females displaying a population-level leftward asymmetry of the lateral region of the SF [t(7)=-2.65, p=0.03]. These results provide further evidence that New World primates may display population-level asymmetry of the SF and may reflect the involvement of this region in the processing of species-specific vocalizations.