Medium latency excitatory reflex of soleus re-examined

Uysal, Hilmi; Özyurt, Mustafa Görkem; Göztepe, Mehmet Berke; Türker, Kemal S.

doi:10.1007/s00221-019-05544-9

Cited by 5 publications

(16 citation statements)

References 43 publications

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“…Interestingly, the “rebound contraction” persisted after de-afferentation [1]. Later, the same phenomenon of motor unit postinhibitory excitation was reported in several studies [e.g., 2, 3, 4, 5, 6]. The proposed mechanisms include reflex pathways activated by muscle spindles as well as intrinsic neuron characteristics originating from the behavior of specific ion channels, but none of these studies has systematically investigated the origin of the phenomenon.…”

Section: Introductionmentioning

confidence: 81%

Postinhibitory excitation in motoneurons can be facilitated by hyperpolarization-activated inward currents: a simulation study

Schmid,

Klotz,

Röhrle

et al. 2023

Preprint

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Postinhibitory excitation is a transient overshoot of a neuron’s baseline firing rate following an inhibitory stimulus and can be observedin vivoin human motoneurons. However, the biophysical origin of this phenomenon is still unknown and both reflex pathways and intrinsic motoneuron properties have been proposed. We hypothesized that postinhibitory excitation in motoneurons can be facilitated by hyperpolarization-activated inward currents (h-currents). Using an electrical circuit model we investigated how h-currents can modulate the postinhibitory response of motoneurons. Further, we analyzed the spike trains of human motor units from the tibialis anterior muscle during reciprocal inhibition. The simulations revealed that the activation of h-currents by an inhibitory postsynaptic potential can cause a short-term increase in a motoneuron’s firing probability. This result suggests that the neuron can be excited by an inhibitory stimulus. In detail, the modulation of the firing probability depends on the time delay between the inhibitory stimulus and the previous action potential. Further, the strength of the postinhibitory excitation correlates with the amplitude of the inhibitory stimulus and is negatively correlated with the baseline firing rate as well as the level of input noise. Hallmarks of h-current activity, as identified from the modeling study, were found in 50 % of the human motor units that showed postinhibitory excitation. This study suggests that h-currents can facilitate postinhibitory excitation and act as a modulatory system to increase motoneuron excitability after a strong inhibition.Author SummaryHuman movement is determined by the activity of specialized nerve cells, the motoneurons. Each motoneuron activates a specific set of muscle fibers. The functional unit consisting of a neuron and muscle fibers is called a motor unit. The activity of motoneurons can be observed noninvasively in living humans by recording the electrical activity of the motor units using the electromyogram. We studied the behavior of human motor units in an inhibitory reflex pathway and found an unexpected response pattern: a rebound-like excitation following the inhibition. This has occasionally been reported for human motor units, but its origin has never been systematically studied. In non-human cells of the neural system, earlier studies reported that a specific membrane protein, the so-called h-channel, can cause postinhibitory excitation. In our study, we use a computational motoneuron model to investigate whether h-channels can cause postinhibitory excitation as observed in the experimental recordings. Using the model, we developed a method to detect features of h-channel activity in human recordings. Because we found these features in a half of the recorded motor units, we conclude that h-channels can facilitate postinhibitory excitation in human motoneurons.

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Section: Introductionmentioning

confidence: 81%

Postinhibitory excitation in motoneurons can be facilitated by hyperpolarization-activated inward currents: a simulation study

Schmid,

Klotz,

Röhrle

et al. 2023

Preprint

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“…Although these effects could have a central and peripheral origin, the latter would be the main mechanism for MLR, as it can still be obtained in patients with central lesions (Uysal et al, 2011). Moreover, just before obtaining the MLR, TA-induced reciprocal inhibition of soleus motoneurons was observed as the first event in the circuitry possibly also includes recurrent inhibition (Özyurt et al, 2019;Uysal et al, 2019). Following this early inhibition, the activation of the group II fibers along with Ia fibers due to soleus muscle tension can activate the soleus motor pool eliciting the late responses 13 (Figure 4).…”

Section: Discussionmentioning

confidence: 99%

“…The indirect approach allows electrophysiological determination of the stretch reflex and can be easily used towards clinical examination for muscle spindle function in health and disease (Calota and Levin 2009;Matsumoto and Ugawa 2008;Mullick et al, 2013;Yates et al, 2011). However, some deficiencies for using indirect stretch reflex, including the lack of information on prestimulus activation level, should be overcome to make this method as the primary tool to be used to test the functionality of muscle spindles (Uysal et al, 2012;Uysal et al, 2009;Uysal et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

“…Soleus-MLR: To stimulate the common peroneal nerve, we employed the same configuration as we have used earlier in Uysal et al, 2019. The peroneal nerve was stimulated using a bipolar stimulation configuration where the anode and cathode were placed with an elastic bandage just under the head of the fibula.…”

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confidence: 99%

“…The peroneal nerve was stimulated using a bipolar stimulation configuration where the anode and cathode were placed with an elastic bandage just under the head of the fibula. (Uysal et al, 2019). After the motor threshold of TA muscle was determined, stimuli with an intensity of 1.5x motor threshold were delivered to the peroneal nerve while recording from the TA and soleus muscles, simultaneously.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Comparison of the temporal properties of medium latency responses induced by cortical and peripheral stimulation

Göztepe

Özyurt

Türker

et al. 2020

Journal of Electromyography and Kinesiology

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