Journal of Neurophysiology, Vol 46, Issue 4 788-796, Copyright © 1981 by APS
Component of muscle spindle discharge related to arterial pulse
B. McKeon and D. Burke
1. In human subjects microelectrode recordings were made from 25 muscle
spindle afferents from the pretibial muscles. 2. The spike discharges of
three endings were locked in time to the arterial pulse. With 17 of the
remaining endings, there was a significant pulse-related modulation of
discharge rate. For these 20 endings the latency to the onset of the
pulse-related influence was 200-310 ms. 3. The time course of the
modulation of discharge rate was similar to that of arterial blood flow, as
estimated using a Doppler flowmeter. With four endings occlusion of blood
flow using a sphygmomanometer cuff reduced any modulation. 4. For five
endings the contribution by the arterial modulation to the variance of
discharge of the ending was 3-54%. For the population of endings there was
no significant relationship between the depth of modulation and coefficient
of variation. 5. It is concluded that the arterial pulse can be significant
contributor to the variability of muscle spindle discharge. The pulsatile
effects seen in the responses of single afferents are unlikely to be
eliminated in the summed activity forming the population response. This
could constitute a limitation of the information capacity of the population
of muscle spindle afferents.
