Cognitive task influence on relative hemispheric motor control: mouth asymmetry and lateral eye movements.

While strictly verbal cognitive tasks showed a strong left-hemisphere dominance, the presence of visualization and emotion in cognitive tasks resulted in increased involvement of the right hemisphere in motor control of speech as measured by mouth asymmetry. Spontaneous smiles showed right-hemisphere dominance. Lateral eye movements showed an unexpected shift to left gaze during speech which may suggest a dual task interference between speech and gaze motor control.