SHORT-LATENCY, NONRECIPROCAL GROUP-I INHIBITION IS REDUCED DURING THESTANCE PHASE OF WALKING IN HUMANS

Citation
Mj. Stephens et Jf. Yang, SHORT-LATENCY, NONRECIPROCAL GROUP-I INHIBITION IS REDUCED DURING THESTANCE PHASE OF WALKING IN HUMANS, Brain research, 743(1-2), 1996, pp. 24-31
Citations number
30
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Neurosciences
Journal title
ISSN journal
0006-8993
Volume
743
Issue
1-2
Year of publication
1996
Pages
24 - 31
Database
ISI
SICI code
0006-8993(1996)743:1-2<24:SNGIIR>2.0.ZU;2-E
Abstract
Activation of group Ib afferents from extensor muscles produces an inh ibition in the parent muscle and its synergists in a resting cat. This reflex switches to excitation of the parent muscle and its synergists when the cat walks. This study determined if a similar reflex undergo es the same type of reversal in the intact human. A putative Ib reflex was elicited by conditioning the Hoffmann (H) reflex in the soleus mu scle with stimuli to the nerve innervating the medial gastrocnemius mu scle. The reflex was observed while subjects: (1) sat quietly; (2) sat and activated the triceps surae muscle isometrically at a low level; (3) stood and activated the triceps surae to the same level as (2); an d (4) walked on a treadmill. Condition-test intervals of 1 to 16 ms we re used. Ten out of the 15 subjects studied in quiet sitting showed an early, presumably disynaptic inhibition. Walking resulted in a signif icant reduction in the size of this inhibition at condition-test inter vals of 4, 5, 6, and 8 ms for these subjects. No significant differenc es were observed at longer condition-test intervals. As a group, the i nhibition of the conditioned H-reflex was diminished during walking, b ut not significantly excited. Four out of the 10 subjects, however, sh owed a significant excitation of the conditioned H-reflex during walki ng. The inhibition was significantly reduced at a condition-test inter val of 7 ms when the triceps surae group was activated isometrically. No differences were seen in the reflex between matched levels of contr action in sitting and standing. It is concluded that the short latency group I inhibition seen at rest is reduced during walking, in a manne r similar to that seen in spinal and decerebrate cats. The reduction m ay be accounted for, at least partially, by activation of the triceps surae.