[Circadian, infradian and seasonal changes in neural conduction velocity with reference to effects of temperature; I.: Circadian rhythm]

Using results of two collectives (one cross-section study covering 212 individuals and a longitudinal study of 10 individuals over a period of 4 days with 4 examinations/individual/day) circadian, infradian and seasonal influences on the changes observed are considered. The skin temperatures displayed significant circadian variations subsequent to electrical stimulation in 4 of 5 topographic regions from which the measurements were performed. Before stimulation in only one of five regions significant circadian changes were observed. Thus stimulation caused an increase in amplitude but no changes in phase. Pre- and post-stimulation rhythms were in phase. There was found a two-peaked circadian rhythm with maxima at late noon and at midnight. Probably there were systematic differences in skin temperature in the upper extremities compared to the lower ones. The latter showed a minimum in the early morning hours. The circadian effects are presented almost completely free of temperature influences for the sensory NCV of the n. medianus on the hand. As opposed to the simultaneously acquired 2-peaked circadian rhythm of the skin temperature an almost continuous decrease in the NCV can be observed from the early morning until midnight. After midnight there was an abrupt increase of the NCV by about 5%. The significant influences of the time-of-day on the NCV of the upper- and lower-arm could not be attained independent of temperature influences. It was nonetheless apparent that the motor and sensory NCV of the lower arm increased throughout the day in contrast to the NCV of the hand. Possibly, local' influences interfered thereby with the autonomic rhythm of the nerve.