Studies of physiologic tremor in the dog

Abstract

Tremor was studied in dogs under conditions of wakefulness and sleep and after making lesions in various parts of the central and peripheral nervous systems. The mean frequency of tremor in the normal waking animal is 8.5 cycles per second in the resting forelimb and 11.9 cycles per second in the resting hind limb. Tremor in the fore limb of the normal dog when awake differs from that of the hind limb by showing lower frequency, greater waveform regularity, and higher amplitude. Sleeping normal animals exhibit decreased frequency, increased regularity, but no amplitude change of tremor in the fore limb as compared to the same limb in the waking state. However, during sleep as during wakefulness, the fore limb shows lower frequency, greater waveform regularity, and higher amplitude of tremor than the hind limb. There is no significant or consistent change in the tremor pattern of any animal following surgically produced lesions of the forebrain, brain stem, cerebellum, spinal cord or root structures, as performed in this study. Sleeping postsurgical animals reveal the same changes as do the sleeping normal dogs with 1 alteration; there was a significant decrease in tremor of the hind limbs in sleep as compared to wakefulness. No significant difference is found in the tremor recordings of dogs made decerebrate by Sherrington''s intercollicular transection method as compared to the animals which were made decerebrate following prior cerebellar lesions. The failure of lesions of the nervous system, and especially lesions of the dorsal and ventral roots, to abolish significantly or alter normal tremor in a resting extremity causes one to seriously question the primary role of neuromuscular mechanisms in the production of physiologic tremor.