The Journal of Neuroscience, December 15, 1999, 19(24):10966-10976
Proprioceptive Control of Extensor Activity during Fictive
Scratching and Weight Support Compared to Fictive Locomotion
Marie-Claude
Perreault,
Manuel
Enriquez-Denton, and
Hans
Hultborn
Department of Medical Physiology, The Panum Institute, University
of Copenhagen, DK-2200 Copenhagen, Denmark
At rest, extensor group I afferents produce oligosynaptic
inhibition of extensor motoneurons. During locomotor activity, however, such inhibition is replaced by oligosynaptic excitation. Oligosynaptic excitation from extensor group I afferents plays a crucial role in the
regulation of extensor activity during walking. In this study we
investigate the possibility that this mechanism also regulates extensor
muscle activity during other motor tasks.
We show that the reflex pathways responsible for extensor group I
oligosynaptic excitation during fictive locomotion can be activated
during both fictive scratching and fictive weight support (tonic motor
activity induced by contralateral scratching). These observations
suggest that the excitatory group I oligosynaptic reflex pathways are
open for transmission during several forms of motor activities. We also
show that extensor group I input during fictive scratching can affect
the amplitude and the timing of extensor activity in a pattern similar
to that observed during locomotion. Most likely these effects involve
the activation of the excitatory group I oligosynaptic reflex pathways.
Accordingly, it is suggested that extensor group I oligosynaptic
excitation during motor activities other than locomotion is also used
to regulate extensor muscle activity. Furthermore, the similarity of
effects from extensor group I input on the rhythmicity during scratching and locomotion supports the hypothesis that both rhythms are
generated by a common network.
Key words:
primary muscle spindles; Golgi tendon organs; spinal
cord; sensory feedback; rhythm generating networks; motoneuron; motor
control
Copyright © 1999 Society for Neuroscience 0270-6474/99/192410966-11$05.00/0
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