Correlates of motor unit size, recruitment threshold, and H-reflex jitter.
The aim of this research was to study the neurophysiology of the anterior horn cell (AHC) using single-fiber EMG (SFEMG) study of the flexor carpi radialis (FCR) H-reflex. Twelve men and 7 women, ages 20-80 years, were studied. The mean H-jitter was 138 +/- 59 microseconds. H-jitter increased with age (while the M-jitter did not) and was greater in men than in women. There was a direct correlation between the H-jitter and H-latency which was used as an indirect measure of the AHC's size. Given that small AHCs have a higher input resistance than large ones, the H-jitter can be used as an indirect indicator of the AHC's input resistance and therefore its size. When subjects fell asleep, the H-jitter increased over tenfold the baseline value, raising the possibility of an alternative, oligosynaptic pathway. H-reflex jitter studies provide a useful clinical neurophysiological tool for the study of AHC physiology.
Jabre
J F
JF
Boston University Department of Neurology, Massachusetts, USA.
Rainville
J
J
Salzsieder
B
B
Smuts
J
J
Limke
J
J
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004056:Differential Threshold; D004576:Electromyography; D005260:Female; D006181:H-Reflex; D006801:Humans; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000166:cytology*; D009132:Muscles / Q000294:innervation; D011999:Recruitment, Neurophysiological; D014953:Wrist / Q000294:innervation