Recruitment gain of spinal motor neuron pools in cat and human
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Recruitment gain of spinal motor neuron pools in cat and human. / Nielsen, J. B.; Morita, H.; Wenzelburger, R.; Deuschl, G.; Gossard, J-P; Hultborn, H.
In: Experimental Brain Research, Vol. 237, No. 11, 2019, p. 2897-2909.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Recruitment gain of spinal motor neuron pools in cat and human
AU - Nielsen, J. B.
AU - Morita, H.
AU - Wenzelburger, R.
AU - Deuschl, G.
AU - Gossard, J-P
AU - Hultborn, H.
PY - 2019
Y1 - 2019
N2 - The output from a motor nucleus is determined by the synaptic input to the motor neurons and their intrinsic properties. Here, we explore whether the source of synaptic inputs to the motor neurons (cats) and the age or post-stroke conditions (humans) may change the recruitment gain of the motor neuron pool. In cats, the size of Ia EPSPs in triceps surae motor neurons (input) and monosynaptic reflexes (MSRs; output) was recorded in the soleus and medial gastrocnemius motor nerves following graded stimulation of dorsal roots. The MSR was plotted against the EPSP thereby obtaining a measure of the recruitment gain. Conditioning stimulation of sural and peroneal cutaneous afferents caused significant increase in the recruitment gain of the medial gastrocnemius, but not the soleus motor neuron pool. In humans, the discharge probability of individual soleus motor units (input) and soleus H-reflexes (output) was performed. With graded stimulation of the tibial nerve, the gain of the motor neuron pool was assessed as the slope of the relation between probability of firing and the reflex size. The gain in young subjects was higher than in elderly subjects. The gain in post-stroke survivors was higher than in age-matched neurologically intact subjects. These findings provide experimental evidence that recruitment gain of a motor neuron pool contributes to the regulation of movement at the final output stage from the spinal cord and should be considered when interpreting changes in reflex excitability in relation to movement or injuries of the nervous system.
AB - The output from a motor nucleus is determined by the synaptic input to the motor neurons and their intrinsic properties. Here, we explore whether the source of synaptic inputs to the motor neurons (cats) and the age or post-stroke conditions (humans) may change the recruitment gain of the motor neuron pool. In cats, the size of Ia EPSPs in triceps surae motor neurons (input) and monosynaptic reflexes (MSRs; output) was recorded in the soleus and medial gastrocnemius motor nerves following graded stimulation of dorsal roots. The MSR was plotted against the EPSP thereby obtaining a measure of the recruitment gain. Conditioning stimulation of sural and peroneal cutaneous afferents caused significant increase in the recruitment gain of the medial gastrocnemius, but not the soleus motor neuron pool. In humans, the discharge probability of individual soleus motor units (input) and soleus H-reflexes (output) was performed. With graded stimulation of the tibial nerve, the gain of the motor neuron pool was assessed as the slope of the relation between probability of firing and the reflex size. The gain in young subjects was higher than in elderly subjects. The gain in post-stroke survivors was higher than in age-matched neurologically intact subjects. These findings provide experimental evidence that recruitment gain of a motor neuron pool contributes to the regulation of movement at the final output stage from the spinal cord and should be considered when interpreting changes in reflex excitability in relation to movement or injuries of the nervous system.
KW - Motor neurons
KW - Recruitment
KW - Cutaneous afferents
KW - Ageing
KW - Stroke
U2 - 10.1007/s00221-019-05628-6
DO - 10.1007/s00221-019-05628-6
M3 - Journal article
C2 - 31492990
VL - 237
SP - 2897
EP - 2909
JO - Experimental Brain Research
JF - Experimental Brain Research
SN - 0014-4819
IS - 11
ER -
ID: 229141615