Gating of segmental and transcortical reflexes to human hand muscles depends on the mode of innervation.
We investigated the influence of the innervation pattern on the transmission of reflexes to a hand muscle. Reflexes were elicited by repetitive median nerve stimulation and recorded from the abductor pollicis brevis muscle. Both H and long loop reflexes were exclusively attenuated by irregular isotonic thumb abduction. In 10 of 15 experiments the long loop reflex was blocked completely. Inhibition intercalated between the H and long loop reflexes also decreased considerably. The observed attenuation of both spinal and supraspinal reflexes is suspected to take place mainly at the spinal level. Among the possible mechanisms, reciprocal inhibition is the most likely.
Wagner
S
S
Department of Neurology, University of Heidelberg, INF 400, 69120, Heidelberg, Germany. simone_wagner@med.uni-heidelberg.de
von Waldenfels
A
A
Meinck
H M
HM
D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006181:H-Reflex / Q000502:physiology; D006225:Hand / Q000294:innervation* / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology; D011930:Reaction Time; D012018:Reflex / Q000502:physiology*; D013933:Thumb / Q000294:innervation / Q000502:physiology