Changes in Physiological Tremor during Repeated Performance of a Motor Task in Normal Subjects and Anxious Patients

¹ Lecturer, Institute of Psychiatry, Maudsley Hospital, Denmark Hill, London, S.E.5.

The tremor occurring at the metacarpophalangeal joint of the index finger during a motor task involving a controlled muscle effort was detected and measured. The subjects were required to maintain the finger as accurately as possible in a constant alignment against a 50-gm. load with the aid of an amplified visual display of the position of the finger.

The tremor displayed by 18 morbidly anxious male patients was compared with that occurring in a matched group of 18 male control subjects.

The tremor of the anxious patients differed from that of the controls in that (1) it was of greater average amplitude, and (2) the 7-10 c/sec. components were relatively more prominent than other components in the 4-12 c/sec. range. Both of these differences were found to be statistically significant.

The proportional reduction in tremor amplitude observed in the 4-12 c/sec. range during repeated performance of the task did not differ significantly in the anxious patients as compared with the controls.

The relevance of these findings to other investigations of habituation of physiological variables in psychiatric patients is considered.