To the Editor.—
In their study of normal hand tremor (Archives 1982;39:358-362), Wade et al describe an 8- to 12-Hz "shoulder" in their hand tremor spectra and suggest that this component is neurogenic, citing my work with Randall.1 In citing that work, they comment that the 8- to 12-Hz component is somehow related to the recruitment rates of individual motor units. However, Randall and I specifically demonstrated that much more is involved. In particular, motor units firing at mean frequencies of 10 to 22 spikes/s are involved, and, regardless of the mean firing frequency, the firing pattern of each motor unit is modulated at 8 to 12 Hz.1 The synchronous 8- to 12-Hz modulation of neighboring motor units is then responsible for the 8- to 12-Hz component of hand tremor2 and finger tremor.1 As Wade et al have noted, the amplitude of the 8- to 12-Hz component
Elble RJ. Physiologic Hand Tremor. Arch Neurol. 1982;39(11):737–738. doi:10.1001/archneur.1982.00510230063023
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