Mirror Symmetric Bimanual Movement Priming Can Increase Corticomotor Excitability and Enhance Motor Learning

What will it take for our researchers to move from wishy-washy terms like 'can increase' to will do this? I don't see that occurring until we get survivors in charge who won't fund research that doesn't directly lead to 100% recovery.  You'll have to ask your doctor to demonstrate repetitive active-passive bimanual wrist flexion and extension

Mirror Symmetric Bimanual Movement Priming Can Increase Corticomotor Excitability and Enhance Motor Learning

• Winston D. Byblow ,
• Cathy M. Stinear,
• Marie-Claire Smith,
• Lotte Bjerre,
• Brian K. Flaskager,
• Alana B. McCambridge

• Published: March 22, 2012
• https://doi.org/10.1371/journal.pone.0033882
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Abstract

Repetitive mirror symmetric bilateral upper limb may be a suitable priming technique for upper limb rehabilitation after stroke. Here we demonstrate neurophysiological and behavioural after-effects in healthy participants after priming with 20 minutes of repetitive active-passive bimanual wrist flexion and extension in a mirror symmetric pattern with respect to the body midline (MIR) compared to an control priming condition with alternating flexion-extension (ALT). Transcranial magnetic stimulation (TMS) indicated that corticomotor excitability (CME) of the passive hemisphere remained elevated compared to baseline for at least 30 minutes after MIR but not ALT, evidenced by an increase in the size of motor evoked potentials in ECR and FCR. Short and long-latency intracortical inhibition (SICI, LICI), short afferent inhibition (SAI) and interhemispheric inhibition (IHI) were also examined using pairs of stimuli. LICI differed between patterns, with less LICI after MIR compared with ALT, and an effect of pattern on IHI, with reduced IHI in passive FCR 15 minutes after MIR compared with ALT and baseline. There was no effect of pattern on SAI or FCR H-reflex. Similarly, SICI remained unchanged after 20 minutes of MIR. We then had participants complete a timed manual dexterity motor learning task with the passive hand during, immediately after, and 24 hours after MIR or control priming. The rate of task completion was faster with MIR priming compared to control conditions. Finally, ECR and FCR MEPs were examined within a pre-movement facilitation paradigm of wrist extension before and after MIR. ECR, but not FCR, MEPs were consistently facilitated before and after MIR, demonstrating no degradation of selective muscle activation. In summary, mirror symmetric active-passive bimanual movement increases CME and can enhance motor learning without degradation of muscle selectivity. These findings rationalise the use of mirror symmetric bimanual movement as a priming modality in post-stroke upper limb rehabilitation.

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Citation: Byblow WD, Stinear CM, Smith M-C, Bjerre L, Flaskager BK, McCambridge AB (2012) Mirror Symmetric Bimanual Movement Priming Can Increase Corticomotor Excitability and Enhance Motor Learning. PLoS ONE 7(3): e33882. https://doi.org/10.1371/journal.pone.0033882

Editor: Alessio Avenanti, University of Bologna, Italy

Received: June 6, 2011; Accepted: February 23, 2012; Published: March 22, 2012

Copyright: © 2012 Byblow et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: The authors have no support or funding to report.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Repetitive transcranial magnetic stimulation (rTMS) offers promise for increasing or decreasing M1 excitability to promote recovery of motor function after stroke [1]–[9], but a practical limitation is that it requires expensive equipment, a medical environment and is contraindicated for people with a history of seizure, metal implants, cardiac pacemaker, or who are taking certain common medications [10], [11]. Compared with rTMS, transcranial direct current stimulation (tDCS) has fewer contraindications but still requires the use of medically certified electrical equipment and application by a skilled operator [12]. Motor point stimulation [13], [14] and combined peripheral nerve and TMS can enhance or suppress M1 excitability through presumed spike-timing dependent mechanisms [15]–[17] but also require expensive equipment, skilled operators, or lengthy treatment periods and also has potential contraindications. The present study explores an alternative method for increasing M1 excitability by using patterned repetitive movement, without brain or nerve stimulation per se [18], [19].

It is well known that mirror symmetric bimanual movements, with homologous muscles activated simultaneously, are more stable than any other pattern [20]–[22]. Enhanced M1 excitability and presumed GABAergic M1 disinhibition have been noted during production of mirror symmetric active-passive bimanual movement [23], [24] and may facilitate upper limb recovery after stroke by acting as a neurophysiological priming mechanism [18], [19]. Until now, there has been no direct examination of M1 excitability and inhibition immediately after repetitive active-passive bimanual movement and no examination of the immediate behavioural consequences of active-passive movement priming.

To address these issues we first examined corticomotor excitability (CME), M1 intracortical and interhemispheric inhibition and H-reflex excitability, in healthy participants before and after 20 minutes (1200 cycles) of active-passive movement made in either a mirror symmetric (MIR) pattern, or an alternating (ALT) pattern. We hypothesised that MIR but not ALT movements would facilitate corticomotor excitability within forearm flexor and extensor representations of the passive left M1. We also predicted that any difference in CME noted between patterns would be accompanied by differences in intracortical inhibition. To examine this we obtained measures of short afferent inhibition (SAI), long-latency intracortical inhibition (LICI), interhemispheric inhibition (IHI) across two experiments, and examined H-reflex excitability in a third experiment. In a separate study we examined the behavioural consequences of active-passive movement priming and hypothesised that MIR priming would facilitate motor learning. Finally we examined whether increases in CME obtained after MIR would be associated with persistent reductions in short-latency intracortical inhibition that could potentially interfere with selective voluntary muscle activation.

 

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