DEPRESSION OF AN INHIBITORY REFLEX, THE MASSETERIC SILENT PERIOD, IN RECOVERING ALCOHOLICS

Because inhibitory deficits may contribute to motor incoordination of alcoholics, we proposed that the duration of the masseteric silent per iod (SP), an inhibitory reflex, might be shorter in alcoholics (ALs) t han in nonalcoholics (NAs). To test this hypothesis, we measured the S P in a racially mixed group of 12 ALs and 12 NAs matched for age (31-4 9 years) and sex. All subjects were normotensive, had full dentition, and reported no major medical problems. Sensory and motor conduction v elocities of the anterior tibialis, ulnar, and medial nerves were meas ured for each subject, and were not different in ALs and NAs. Jaw jerk and SP were evoked by tapping the chin manually with a rubber hammer containing a circuit to trigger the oscilloscope display of the masset er EMGs. Averaged mean latencies and durations of the SPs were not sig nificantly different between the right and left masseters, SP latencie s were significantly (0.7 msec) shorter in ALs than NAs (p < 0.01). Th e mean SP duration for ALs (13.9 +/- 1.6 msec) was also significantly shorter than that of the NAs (24.4 +/- 2.4 msec; p < 0.001). Results s upport the hypothesis that chronic alcoholism may interfere with inhib itory mechanisms in the CNS.