Effect of geniohyoid, cricothyroid and sternothyroid muscle stimulation on voice fundamental frequency of electrically elicited phonation in rhesus macaque.

Vocalizations were elicited in three anesthetized rhesus macaques by electrical stimulation of a site in the brain stem. At the same, the laryngeal muscles--cricothyroid (CT), geniohyoid (GH) and sternothyroid (ST)--were electrically stimulated to assess their effect on the elicited phonation. Analysis of the recorded vocalizations indicated that stimulation of each of the muscles produced a substantial increase in the voice fundamental frequency (Fo), with the CT muscle causing the greatest Fo increase. Maximum elevation in Fo was obtained when the CT muscle was stimulated simultaneously with the GH or ST muscles. Changes in Fo were typically accompanied by changes in voice quality.