The perspective during gestural executions alters hemispherical specialization

The left hemisphere may be particularly specialized for gestures from an egocentric movement perspective, i.e., when executing tool-use pantomime (TUP) gestures. Because nonverbal hand movements from an allocentric perspective such as motion quality presentation (MQP) gestures (i.e., when gesturing actions such as when a girl slides down a slideway) may rely on right hemispheric correlates, we contrasted such gestures with the hypothesis that TUP and MQP rely on different hemispherically lateralized functions.

24 right-handed healthy individuals were investigated by applying functional Near-Infrared Spectroscopy (fNIRS) above pre- and postcentral gyri of either hemisphere during three types of gesture production: (I) TUP, (II) MQP, and (III) meaningless gestures.

Increased changes of oxygenated hemoglobin (∆HbO₂) were found for TUP gestures within the left hemispheric supramarginal gyrus (SMG) as well as the right hemispheric precentral gyrus and when contrasted to meaningless gestures. The contrast of MQP versus meaningless gestures resulted in increased ∆HbO₂ of the precentral gyrus within the right hemisphere. No difference (∆HbO₂) was found when contrasting TUP versus MQP gestures directly.

The present results demonstrate that tool-use pantomimes and motion quality presentations share motor-cognitive functions of gesture production. However, action depicting gestures may depend on the perspective during their execution. In fact, the egocentric perspective of tool-use pantomime gestures relies on left and right hemispheric functions whereas allocentric gestures may be rather grounded in functions of the right hemisphere alone.