Middle ear muscle activity during vocalization in normal speakers and stutterers.

Although it has been established that the middle ear muscles contract prior to vocalization, it is not known which muscle is mainly responsible for this activity. Also, there have been contradictory reports about whether this activity in stutterers differs from that of normal speakers. To tackle these questions, extratympanic pressure measurements prior to vocalization are reported for normal speakers and stutterers. This measure allows activity deriving from the two middle ear muscles to be differentiated and for the temporal course to be followed more accurately than by impedance measurement. To establish which muscle is primarily responsible for the pre-vocalization activity, the measured pressure changes prior to vocalization are compared with activity measured in tasks known to involve the stapedius or tensor tympani alone. These data show that in normal speakers and stutterers, the activity that is measured prior to vocalization resembles that of the tensor tympani. Contrary to other reports, there is no difference between normal speakers and stutterers in the time course of this activity.