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Gating of the afferent volley of the monosynaptic stretch reflex during movement in man.
Author(s) -
Meunier S,
PierrotDeseilligny E
Publication year - 1989
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1989.sp017896
Subject(s) - reflex , facilitation , soleus muscle , h reflex , contraction (grammar) , neuroscience , chemistry , stimulation , afferent , presynaptic inhibition , anatomy , muscle contraction , excitatory postsynaptic potential , psychology , medicine , skeletal muscle , inhibitory postsynaptic potential
1. The time course of the changes in presynaptic inhibition of Ia fibres to soleus motoneurones has been investigated during a voluntary ramp‐and‐hold plantar flexion. 2. Monosynaptic Ia facilitation of the soleus H reflex was evoked by stimulation of the inferior soleus (homonymous) and femoral (heteronymous) nerves. Changes in presynaptic inhibition of the Ia fibres mediating the conditioning volleys were inferred from changes in the amount of reflex facilitation evoked by such constant conditioning stimulations. 3. At the beginning of the voluntary contraction, both homonymous and heteronymous Ia facilitations were markedly increased with respect to their rest values. Then, they dropped abruptly in the middle of the ramp, whatever the ramp duration. 4. The stronger the contraction at the end of the ramp, the larger the initial increase in reflex facilitation. 5. These results indicate that presynaptic inhibition of Ia terminals on motoneurones of the contracting muscle is decreased during the first half of the ramp and then returns to its rest level. It is argued that these changes in presynaptic inhibition are centrally programmed, and it is suggested that, under certain conditions, presynaptic inhibition can be modulated according to both the strength and timing of the contraction. 6. The functional role of the resulting changes in the gain of the stretch reflex is discussed.