Effects of cerebellar electrical stimulation on electromyography of triceps surae in tree shrews (Tupaia glis)

Abstract

The effects of cerebellar stimulation on electromyography (EMG) of triceps surae in tree shrews with substantia rigra (SN) lesioned were investigated in this study. The stimulus parameters (i.e., frequencies, durations and current intensities) and areas of anterior cerebellar cortex which inhibited the EMG of triceps surae were identified. Six frequencies (1, 5, 10, 50, 100 and 200 Hz) and four pulses widlth (0.02, 0.05, 0.1 and 0.2 ms) of the electrical stimulation were used on nine areas of anterior cerebellar cortex. The stimulation periods was 40 sec. The EMG studies of both triceps surae were recorded in control group (before SN – lesioned) and in experimental group (after unilateral SN-lesioned) at rest. In control group, the EMG pattern of both triceps surae at rest showed silent. However, the continuous motor units activities were found in ipsilateral triceps surae of unilateral SN-lesioned of tree shrews. These EMG patterns were disappeared by using stimulus frequencies of 50 Hz and 100 Hz with pulse midth of 0.2 ms on vermis and both intermediate parts of anterior cerebellar cortex. But the current intensity of stimulus frequency at 100 Hz, which was used to suppress abnormal EMG pattern was less than that of 50 Hz. Furthermore, the latencies of these effects were 18.7 ± 11.05 sec to 28.1 ± 3.34 sec. And the prolong effects persisted for seconds to minute after cessation of stimulation. The results of this study may be assumed that electrical stimulation of vermis and both intermediate parts of anterior cerebellar cortex by stimulus fraquencies of 100 Hz and 50 Hz with 0.2 mS could produce the suppression of continuous motor units activities at rest in SN-lesioned tree shrews.