Reflex Factors in Clonus and Tremor

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Abstract
Inkwriter and oscillographic records of responses to single and double stimuli, or to a repetitive series, applied to various sensory nerves of the hind leg, were obtained from several muscles of the same leg. Each stimulus was followed by 15 msec. facilitation of a 2d stimulus, followed in turn by a period of inhibition complete for 60-100 msec. and recovering over several tenths of a sec. Muscles opposed in normal use responded similarly and equally in what resembled a startle reaction instead of a purposive reflex. Under lighter anesthesia, when a spontaneous tonic background of contraction appeared, this was inhibited in a similar pattern. A 2d stimulus late in the inhibitory period of the 1st might then produce a short burst of activity of a duration comparable to the period of facilitation, instead of the single twitches occurring in a quiescent prepn. This was followed by a 2d period of inhibition. Trains of shocks in quiescent prepns. or in those with a tonic background gave patterns of response depending on strength and frequency of stimulation. In relating these results to clinical tremor, the tonic activity of rigidity seems comparable to the tonic contraction of lightly anesthetized animals, and the successive facilitations and inhibitions following repetitive shocks against a tonic background might correspond to the alternate bursts and quiescent periods of tremor.

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