The long-term objectives of the proposed studies are to understand the role that early environment plays in the development of asymmetries in manual gestures and facial expressions and their relationship to different structures of the brain. In the proposed research, behavioral studies on functional asymmetries in hand use for gestural communication and facial expressions used with referential vocalizations will be correlated with neuroanatomical asymmetries as assessed by magnetic resonance imaging (MRI). Specifically, whether hand use for gestures represents a unique functional asymmetry or whether it reflects a general asymmetry for all motor functions will be assessed by comparing handedness indices for gestures compared to motor tasks with similar situational demands. In another series of experiments, the influence on vocal communication on the expression of hand use for referential gestures will be assessed to determine whether the vocal signals enhances or inhibits the magnitude of asymmetries in communicative behavior. In a third set of experiments, asymmetries in facial expressions that made by chimpanzees that have a referential function will be compared to asymmetries in facial expressions that are not accompanied by the use of a referential vocalization. Finally, asymmetries in gestural communication and facial expressions will be correlated with asymmetries in the brain from specific regions of interest including the planum temporale, Brodmann's area 44, the motor/hand area of the precentral gyrus, cingulate gyrus and basal ganglia. Of specific interest in all analyses will be, the comparison of chimpanzee subjects that have been reared by human compared to those reared by chimpanzees. This comparison will allow for determination of how human environments and communication systems alter the development of communicative behavior and the cerebral organization of chimpanzees. Overall, the proposed research will lead to a better understanding of factors which influence the development of laterality in the central nervous systems and behavioral and communicative correlates of these asymmetries.
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