Preferred spike intervals in the vibration reflex

Abstract

Tonic activation of the soleus motoneuron during vibration was investigated in the decerebrate cat either peripherally in the muscle or centrally at the ventral root level. 1) It was shown that both peripheral EMG spikes and ventral root unit discharges are initiated at intervals corresponding to some multiple of the cyclic time of vibration. Therefore, motoneuronal spike frequency, MNf becomes the inverse multiple of vibration frequency, Vf, and MNf=1/nVf where 1/n is the ratio of vibratory input frequency to output frequency of ventral root spikes, 1/n being defined as the decoding ratio. 2) Interval histograms of the soleus EMG and motoneuron spikes during stretch differ considerably only from those obtained during added vibration. The histograms obtained during stretch showed almost normal distribution but some of them seemed to be composed of several peakings at intervals which corresponded to multiples of the interval of Ia discharge of steady rate elicited by a sustained stretch. 3) Proprioceptive, supraspinal, and contralateral reciprocal facilitation shorten the intervals between the motoneuronal discharge during vibration in accordance with decrease in the decoding ratio. © 1972, PHYSIOLOGICAL SOCIETY OF JAPAN. All rights reserved.