Individual hemispheric asymmetry in vocal fold control of the squirrel monkey

In ten squirrel monkeys (Saimiri sciureus), electrodes were implanted into the left and right facial motor cortex at sites producing bilateral vocal f old adduction when electrically stimulated. All animals, in addition, had e lectrodes in the periaqueductal grey of the midbrain (PAC) at sites produci ng vocalization when electrically stimulated. In eight out of ten animals, motorcortical stimulation during periaqueductally elicited vocalization cau sed a change in vocal output. This change, in four cases, was more severe w ith left-sided ipsilateral motor cortex/PAG stimulation than with right-sid ed ipsilateral stimulation. In the other four cases, right-sided stimulatio n was more effective than left-sided stimulation It is concluded that the m ajority of squirrel monkeys show a hemispheric asymmetry in vocal fold cont rol with left- and right-sided dominance distributed about equally in the p opulation. (C) 2000 Elsevier Science B.V. All rights reserved.