Studies examining the central control of the laryngeal musculature using magnetic stimulation both transcranially and peripherally in normal speakers are ongoing. The purpose is to estimate central conduction time from the cortico-bulbar pathways to the laryngeal musculature. By stimulating the figure 8 coil over the mastoid area, the expected conduction times to the laryngeal muscles have been obtained. By subtracting the peripheral latencies from the transcranial latencies obtained in each of the laryngeal muscles on its two sides, an estimate of the central conduction time can be obtained. These times range from 4 to 7 ms and vary between muscles. The shorter central conduction times are obtained for the left thyroarytenoid muscles rather than the right thyroarytenoid muscles and for the thyroarytenoid muscles in comparison with the cricothyroid muscles. The results suggest that the conduction times for various laryngeal muscles differ and may balance peripheral differences in nerve lengths. A detailed study of cluttering has been completed in an extended family. Additional families are being recruited to examine for similar patterns of vertical transmission and behavioral abnormalities in cluttering. Linkage studies are being planned once a large enough sample size is obtained. A study of the long-term effects of clomipramine over one year was completed in chronically affected stuttering adults. Although the effects of clomipramine were maintained these were similar to placebo effects during the same period. A double blind study comparison of paroxetine (a SSRI) and pimozide (a D2 antagonist) was initiated. Unexpected side effects occurred in several subjects, necessitating that the study be closed. No significant speech benefits were seen although the sample size was small.
