Persistent inward currents in spinal motoneurones: how can we study them in human participants?

Thorstensen, Jacob R

doi:10.1113/jp283249

Cited by 4 publications

(3 citation statements)

References 5 publications

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“…The subsequent release of noradrenaline from the locus coeruleus and serotonin from raphe neurons enhances the plasticity of sensory networks [240]. This release of noradrenaline and serotonin increases the gain for synaptic inputs, thus, likely facilitating the activity of persistent inward currents and subsequent motor unit activity [597,598]. Together, these processes may support a cortical reorganization in people with restored sensory feedback.…”

Section: Vagus Nervementioning

confidence: 98%

Vascular and Neural Response to Focal Vibration, Sensory Feedback, and Piezo Ion Channel Signaling

Penasso

Petersen²,

Peternell

2023

JVD

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Focal vibration therapy seeks to restore the physiological function of tissues and the nervous system. Recommendations for vibration settings, e.g., that could improve residual limb health and prosthesis acceptance in people with amputation, are pending. To establish a physiological connection between focal vibration settings, clinical outcomes, and molecular and neuronal mechanisms, we combined the literature on focal vibration therapy, vibrotactile feedback, mechanosensitive Piezo ion channels, touch, proprioception, neuromodulation, and the recovery of blood vessels and nerves. In summary, intermittent focal vibration increases endothelial shear stress when applied superficially to blood vessels and tissues and triggers Piezo1 signaling, supporting the repair and formation of blood vessels and nerves. Conversely, stimulating Piezo1 in peripheral axon growth cones could reduce the growth of painful neuromas. Vibrotactile feedback also creates sensory inputs to the motor cortex, predominantly through Piezo2-related channels, and modulates sensory signals in the dorsal horn and ascending arousal system. Thus, sensory feedback supports physiological recovery from maladaptations and can alleviate phantom pain and promote body awareness and physical activity. We recommend focal vibration of phantom limb maps with frequencies from ~60–120 Hz and amplitudes up to 1 mm to positively affect motor control, locomotion, pain, nerves, and blood vessels while avoiding adverse effects.

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Section: Vagus Nervementioning

confidence: 98%

Vascular and Neural Response to Focal Vibration, Sensory Feedback, and Piezo Ion Channel Signaling

Penasso

Petersen²,

Peternell

2023

JVD

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“…There remains a scarcity of research in humans, however, that establishes a relationship between reciprocal inhibition and PIC magnitude (Thorstensen, 2022). Mesquita et.…”

Section: Introductionmentioning

confidence: 99%

“…The majority of evidence on the inhibitory control of PICs arises from animal studies and computer models (Hultborn et al ., 2003; Kuo et al ., 2003; Hyngstrom et al ., 2007; Bui et al ., 2008) but the magnitude of PICs in human motoneurons can be estimated quite easily due to recent advances in technology and analysis techniques (Klotz et al ., 2023; Möck & Del Vecchio, 2023). There remains a scarcity of research in humans, however, that establishes a relationship between reciprocal inhibition and PIC magnitude (Thorstensen, 2022). Mesquita et.…”

Section: Introductionmentioning

confidence: 99%

Voluntary co-contraction of ankle muscles alters motor unit discharge characteristics and reduces estimates of persistent inward currents

Gomes,

Jenz,

Beauchamp

et al. 2024

Preprint

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Motoneuronal persistent inward currents (PICs) are both facilitated by neuromodulatory inputs and highly sensitive to local inhibitory circuits (e.g., Ia reciprocal inhibition). Methods aimed to increase group Ia reciprocal inhibition from the antagonistic muscle have been successful in decreasing PICs, and the diffuse actions of neuromodulators released during activation of remote muscles have increased PICs. However, it remains unknown how motoneurons function in the presence of simultaneous excitatory and inhibitory commands. To probe this topic, we investigated motor unit (MU) discharge patterns and estimated PICs during voluntary co-contraction of ankle muscles, which simultaneously demands the contraction of agonist-antagonist pairs. Twenty young adults randomly performed triangular ramps (10s up and down) of both co-contraction (simultaneous dorsiflexion and plantarflexion) and isometric dorsiflexion to a peak of 30% of their maximum muscle activity from a maximal voluntary contraction. Motor unit spike trains were decomposed from high-density surface electromyography recorded over the tibialis anterior (TA) using blind source separation algorithms. Voluntary co-contraction altered motor unit discharge rate characteristics, decreasing estimates of PICs by 20% (4.47 pulses per second (pps) vs 5.57 pps during isometric dorsiflexion). These findings suggest that, during voluntary co-contraction, the inhibitory input from the antagonist muscle overcomes the additional excitatory and neuromodulatory drive that may occur due to the co-contraction of the antagonist muscle, which constrains PIC behavior.

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Voluntary co‐contraction of ankle muscles alters motor unit discharge characteristics and reduces estimates of persistent inward currents

Gomes,

Jenz,

Beauchamp

et al. 2024

The Journal of Physiology

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Motoneuronal persistent inward currents (PICs) are facilitated by neuromodulatory inputs but are highly sensitive to local inhibitory circuits. Estimates of PICs are reduced by group Ia reciprocal inhibition, and increased with the diffuse actions of neuromodulators released during remote muscle contraction. However, it remains unknown how motoneurons function in the presence of simultaneous excitatory and inhibitory commands. To probe this topic, we investigated motor unit discharge patterns and estimated PICs during voluntary co‐contraction of ankle muscles, which simultaneously demands the contraction of agonist–antagonist pairs. Twenty participants performed triangular ramps of both co‐contraction (simultaneous dorsiflexion and plantar flexion) and isometric dorsiflexion to a peak of 30% of their maximum muscle activity from a maximal voluntary contraction. Motor unit spike trains were decomposed from high‐density surface EMG activity recorded from tibialis anterior using blind source separation algorithms. Voluntary co‐contraction altered motor unit discharge rate characteristics. Discharge rate at recruitment and peak discharge rate were modestly reduced (∼6% change; P < 0.001; d = 0.22) and increased (∼2% change; P = 0.001, d = −0.19), respectively, in the entire dataset but no changes were observed when motor units were tracked across conditions. The largest effects during co‐contraction were that estimates of PICs (ΔF) were reduced by ∼20% (4.47 vs. 5.57 pulses per second during isometric dorsiflexion; P < 0.001, d = 0.641). These findings suggest that, during voluntary co‐contraction, the inhibitory input from the antagonist muscle overcomes the additional excitatory and neuromodulatory drive that may occur due to the co‐contraction of the antagonist muscle, which constrains PIC behaviour. imageKey points Voluntary co‐contraction is a unique motor behaviour that concurrently provides excitatory and inhibitory synaptic input to motoneurons. Co‐contraction of agonist–antagonist pairs alters agonist motor unit discharge characteristics, consistent with reductions in persistent inward current magnitude.

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Persistent inward currents in spinal motoneurones: how can we study them in human participants?

Abstract: support-information-section). Persistent inward currents, neuromodulators and inhibitionAcquired Brain Injury in Children (ABiC) group,

Cited by 4 publications

References 5 publications

Vascular and Neural Response to Focal Vibration, Sensory Feedback, and Piezo Ion Channel Signaling

Vascular and Neural Response to Focal Vibration, Sensory Feedback, and Piezo Ion Channel Signaling

Voluntary co-contraction of ankle muscles alters motor unit discharge characteristics and reduces estimates of persistent inward currents

Voluntary co‐contraction of ankle muscles alters motor unit discharge characteristics and reduces estimates of persistent inward currents

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