Motor learning induces time‐dependent plasticity that is observable at the spinal cord level

Giboin, Louis Solal; Tokuno, Craig D.; Krämer, Andreas; Henry, Maureen; Grüber, Markus

doi:10.1113/jp278890

Cited by 29 publications

(37 citation statements)

References 65 publications

(155 reference statements)

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“…We detail the effects of healthy ageing on MVT and MU firing characteristics using linear mixed effects models. More specifically, we took into consideration all of our data points rather than averaging across them and based our analysis on the mean within an individual trial or subject (Giboin et al 2020). All of these analysis were performed in R (R Core Team 2020, R Foundation for Statistical Computing, Vienna, Austria) using the lme4 package (Bates et al, 2015) and significance was calculated using the lmerTest package (Kuznetsova et al 2017), which applies Satterthwaite's method to estimate degrees of freedom and generate P-values for mixed effects models by comparing the full model including the effect of interest against a null model excluding the effect of interest.…”

Section: Discussionmentioning

confidence: 99%

Estimates of persistent inward currents are reduced in upper limb motor units of older adults

Hassan

Fajardo

Cummings

et al. 2021

The Journal of Physiology

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support-information-section).Altamash Hassan is a biomedical engineer who earned his PhD from Northwestern University. During his time at Northwestern, he was mentored by Dr Julius P. A. Dewald, and his research investigates the neural control of movement through analyses of motor unit firing patterns in both healthy and pathological states. Investigating the effects of ageing on motor unit behaviour stemmed from an informal discussion with Dr Gregory Pearcey and provides the foundation for future investigations of interventions aimed at ameliorating motor deficits associated with ageing, and providing appropriate age-matched controls for those deficits seen in individuals post-stroke.

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Section: Discussionmentioning

confidence: 99%

Estimates of persistent inward currents are reduced in upper limb motor units of older adults

Hassan

Fajardo

Cummings

et al. 2021

The Journal of Physiology

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“…We detail the effects of healthy aging on MU firing characteristics using linear mixed effects models. More specifically, we take into consideration all of our data points rather than averaging across them and basing our analysis on the mean within an individual trial or subject (Giboin et al, 2020). All of these analysis were performed in R (R Core Team 2020, R Foundation for Statistical Computing, Vienna, AUT) using the lme4 package (Bates & Maechler, 2015) and significance was calculated using the lmerTest package (Kuznetsova et al, 2017), which applies Satterthwaite's method to estimate degrees of freedom and generate p-values for mixed effects models by comparing the full model including the effect of interest against a null model excluding the effect of interest.…”

Section: Discussionmentioning

confidence: 99%

Estimates of persistent inward currents are reduced in upper limb motor units of older adults

Hassan

Fajardo

Cummings

et al. 2021

Preprint

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Aging is a natural process that causes alterations in the neuromuscular system, which contribute to weakness and reduced quality of life. Reduced firing rates of individual motor units (MUs) likely contribute to weakness, but the mechanisms underlying reduced firing rates are not clear. Persistent inward currents (PICs) are crucial for the initiation, gain control, and maintenance of motoneuron firing, and are directly proportional to the level of monoaminergic input. Since the concentration of monoamines (i.e. serotonin and norepinephrine) are reduced with age, we sought to determine if estimates of PICs are reduced in older (>60 years old) compared to young adults (<35 years old). We decomposed MU spike trains from high-density surface electromyography over the biceps brachii and triceps brachii during isometric ramp contractions to 20% of maximum. Estimates of PICs (i.e. ΔF) were computed using the paired MU analysis technique. Regardless of the muscle, peak firing rates of older adults were reduced by ~1.6 pulses per second (pps) (P = 0.0292), and ΔF was reduced by ~1.9 pps (P < 0.0001), compared to young adults. We further found that age predicted ΔF in older adults (P = 0.0261), resulting in a reduction of ~1pps per decade, but there was no relationship in young adults (P = 0.9637). These findings suggest that PICs are reduced in older adults, and, further, age is a significant predictor of estimates of PICs in older adults. Reduced PIC magnitude represents one plausible mechanism for reduced firing rates and weakness in older individuals.

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“…One possible explanation for this is that the acute increase in LEP was a result of 'reactive plasticity' , in which general, possibly compensatory, changes at the spinal cord occur due to a change in the activity of surrounding networks directly implicated in the task, i.e. those involved in 'primary plasticity' (Giboin, Tokuno, Kramer, Henry, & Gruber, 2020;Wolpaw, 2010). In turn, this could induce secondary changes in spinal pathways not directly implicated in the task, in our case leading to an increase in LEP amplitude during both the IS and KE.…”

Section: Further Considerationsmentioning

confidence: 99%

“…In turn, this could induce secondary changes in spinal pathways not directly implicated in the task, in our case leading to an increase in LEP amplitude during both the IS and KE. Subsequently, time-dependent, task-specific neural reorganisation might have occurred throughout the training period, meaning that spinal alterations could only be observed during the task itself (Giboin et al, 2020). Despite the more task-specific nature of the IS, the differences in characteristics of the dynamic squats involved in the task (see 'limitations' section)…”

Section: Further Considerationsmentioning

confidence: 99%

Task‐specific strength increases after lower‐limb compound resistance training occurred in the absence of corticospinal changes in vastus lateralis

Ansdell

Brownstein

Škarabot

et al. 2020

Experimental Physiology

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Neural adaptations subserving strength increases have been shown to be task-specific, but responses and adaptation to lower-limb compound exercises such as the squat are commonly assessed in a single-limb isometric task. This two-part study assessed neuromuscular responses to an acute bout (Study A) and 4 weeks (Study B) of squat resistance training at 80% of one-repetition-maximum, with measures taken during a task-specific isometric squat (IS) and non-specific isometric knee extension (KE). Eighteen healthy volunteers (25 ± 5 years) were randomised into either a training (n = 10) or a control (n = 8) group. Neural responses were evoked at the intracortical, corticospinal and spinal levels, and muscle thickness was assessed using ultrasound. The results of Study A showed that the acute bout of squat resistance training decreased maximum voluntary contraction (MVC) for up to 45 min post-exercise (−23%, P < 0.001). From 15-45 min post-exercise, spinally evoked responses were increased in both tasks (P = 0.008); however, no other evoked responses were affected (P ≥ 0.240). Study B demonstrated that following short-term resistance training, participants improved their one repetition maximum squat (+35%, P < 0.001), which was reflected by a task-specific increase in IS MVC (+49%, P = 0.001), but not KE (+1%, P = 0.882). However, no training-induced changes were observed in muscle thickness (P = 0.468) or any evoked responses (P = 0.141). Adjustments in spinal motoneuronal excitability are evident after acute resistance training. After a period of short-term training, there were no changes in the responses to central nervous system stimulation, which suggests that alterations in corticospinal properties of the vastus lateralis might not contribute to increases in strength.

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Motor learning induces time‐dependent plasticity that is observable at the spinal cord level

Cited by 29 publications

References 65 publications

Estimates of persistent inward currents are reduced in upper limb motor units of older adults

Estimates of persistent inward currents are reduced in upper limb motor units of older adults

Estimates of persistent inward currents are reduced in upper limb motor units of older adults

Task‐specific strength increases after lower‐limb compound resistance training occurred in the absence of corticospinal changes in vastus lateralis

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