Effects of lower limb segmental muscle vibration on primary motor cortex short-latency intracortical inhibition and spinal excitability in healthy humans

Preclinical studies have demonstrated that Brain-Derived Neurotrophic Factor (BDNF) plays a crucial role in the homeostatic regulation of cortical excitability and excitation/inhibition balance. Using transcranial magnetic stimulation (TMS) techniques we investigated whether BDNF polymorphism could influence cortical excitability of the left and right primary motor cortex in healthy humans. Twenty-nine participants were recruited and genotyped for the presence of the BDNF Val66Met polymorphism, namely homozygous for the valine allele (Val/Val), heterozygotes (Val/Met), and homozygous for the methionine allele (Met/Met). Blinded to the latter, we evaluated inhibitory and facilitatory circuits of the left (LH) and right motor cortex (RH) by measuring resting (RMT) and active motor threshold (AMT), short interval intracortical inhibition (SICI) and intracortical facilitation (ICF). For each neurophysiological metric we also considered the inter-hemispheric balance expressed by the Laterality Index (LI). Val/Val participants (n= 21) exhibited an overall higher excitability of the LH compared to the RH, as probed by lower motor thresholds, lower SICI and higher ICF. Val/Val participants displayed positive LI, especially for AMT and ICF (all p< 0.05), indicating higher LH excitability and more pronounced inter-hemispheric excitability imbalance as compared to Met carriers. Our preliminary results suggest that BDNF Val66Met polymorphism might influence interhemispheric balance of motor cortex excitability.

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O34: Short latency inputs from ventral premotor cortex to the primary motor cortex in healthy humans

Clinical Neurophysiology ◽

10.1016/s1388-2457(14)50139-3 ◽

2014 ◽

Vol 125 ◽

pp. S39

Author(s):

R. Hanajima ◽

H. Matsumoto ◽

S. Nakatani-Enomoto ◽

Y. Shirota ◽

R. Tsutsumi ◽

...

Keyword(s):

Motor Cortex ◽

Primary Motor Cortex ◽

Premotor Cortex ◽

Short Latency ◽

Ventral Premotor Cortex ◽

Healthy Humans

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Reorganization of the primary motor cortex following lower-limb amputation for vascular disease: a pre-post-amputation comparison

Disability and Rehabilitation ◽

10.1080/09638288.2016.1207110 ◽

2016 ◽

Vol 39 (17) ◽

pp. 1722-1728 ◽

Cited By ~ 1

Author(s):

Brenton Hordacre ◽

Lynley V. Bradnam ◽

Maria Crotty

Keyword(s):

Motor Cortex ◽

Vascular Disease ◽

Lower Limb ◽

Primary Motor Cortex ◽

Lower Limb Amputation ◽

Limb Amputation

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The Influence of Primary Motor Cortex Inhibition on Upper Limb Impairment and Function in Chronic Stroke: A Multimodal Study

Neurorehabilitation and Neural Repair ◽

10.1177/1545968319826052 ◽

2019 ◽

Vol 33 (2) ◽

pp. 130-140 ◽

Cited By ~ 4

Author(s):

Ronan A. Mooney ◽

Suzanne J. Ackerley ◽

Deshan K. Rajeswaran ◽

John Cirillo ◽

P. Alan Barber ◽

...

Keyword(s):

Motor Cortex ◽

Upper Limb ◽

Primary Motor Cortex ◽

Motor Impairment ◽

Intracortical Inhibition ◽

Chronic Stroke ◽

Stroke Patients ◽

Gaba Concentration ◽

Chronic Stage ◽

And Function

Background. Stroke is a leading cause of adult disability owing largely to motor impairment and loss of function. After stroke, there may be abnormalities in γ-aminobutyric acid (GABA)-mediated inhibitory function within primary motor cortex (M1), which may have implications for residual motor impairment and the potential for functional improvements at the chronic stage. Objective. To quantify GABA neurotransmission and concentration within ipsilesional and contralesional M1 and determine if they relate to upper limb impairment and function at the chronic stage of stroke. Methods. Twelve chronic stroke patients and 16 age-similar controls were recruited for the study. Upper limb impairment and function were assessed with the Fugl-Meyer Upper Extremity Scale and Action Research Arm Test. Threshold tracking paired-pulse transcranial magnetic stimulation protocols were used to examine short- and long-interval intracortical inhibition and late cortical disinhibition. Magnetic resonance spectroscopy was used to evaluate GABA concentration. Results. Short-interval intracortical inhibition was similar between patients and controls ( P = .10). Long-interval intracortical inhibition was greater in ipsilesional M1 compared with controls ( P < .001). Patients who did not exhibit late cortical disinhibition in ipsilesional M1 were those with greater upper limb impairment and worse function ( P = .002 and P = .017). GABA concentration was lower within ipsilesional ( P = .009) and contralesional ( P = .021) M1 compared with controls, resulting in an elevated excitation-inhibition ratio for patients. Conclusion. These findings indicate that ipsilesional and contralesional M1 GABAergic inhibition are altered in this small cohort of chronic stroke patients. Further study is warranted to determine how M1 inhibitory networks might be targeted to improve motor function.

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The human dorsal premotor cortex facilitates the excitability of ipsilateral primary motor cortex via a short latency cortico-cortical route

Human Brain Mapping ◽

10.1002/hbm.21221 ◽

2011 ◽

Vol 33 (2) ◽

pp. 419-430 ◽

Cited By ~ 50

Author(s):

Sergiu Groppa ◽

Boris H. Schlaak ◽

Alexander Münchau ◽

Nicole Werner-Petroll ◽

Janin Dünnweber ◽

...

Keyword(s):

Motor Cortex ◽

Primary Motor Cortex ◽

Premotor Cortex ◽

Short Latency ◽

Dorsal Premotor Cortex

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Effects of short interval intracortical inhibition and intracortical facilitation on short interval intracortical facilitation in human primary motor cortex

The Journal of Physiology ◽

10.1113/jphysiol.2009.181446 ◽

2009 ◽

Vol 587 (23) ◽

pp. 5665-5678 ◽

Cited By ~ 53

Author(s):

Aparna Wagle-Shukla ◽

Zhen Ni ◽

Carolyn A. Gunraj ◽

Nina Bahl ◽

Robert Chen

Keyword(s):

Motor Cortex ◽

Primary Motor Cortex ◽

Short Interval ◽

Intracortical Inhibition ◽

Intracortical Facilitation

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Task-related changes in intracortical inhibition assessed with paired- and triple-pulse transcranial magnetic stimulation

Journal of Neurophysiology ◽

10.1152/jn.00651.2014 ◽

2015 ◽

Vol 113 (5) ◽

pp. 1470-1479 ◽

Cited By ~ 12

Author(s):

George M. Opie ◽

Michael C. Ridding ◽

John G. Semmler

Keyword(s):

Transcranial Magnetic Stimulation ◽

Motor Cortex ◽

Magnetic Stimulation ◽

Muscle Activation ◽

Primary Motor Cortex ◽

Index Finger ◽

Precision Grip ◽

Intracortical Inhibition ◽

Presynaptic Mechanisms ◽

First Dorsal Interosseous Muscle

Recent research has demonstrated a task-related modulation of postsynaptic intracortical inhibition within primary motor cortex for tasks requiring isolated (abduction) or synergistic (precision grip) muscle activation. The current study sought to investigate task-related changes in pre- and postsynaptic intracortical inhibition in motor cortex. In 13 young adults (22.5 ± 3.5 yr), paired-pulse transcranial magnetic stimulation (TMS) was used to measure short (SICI)- and long-interval intracortical inhibition (LICI) (i.e., postsynaptic motor cortex inhibition) in first dorsal interosseous muscle, and triple-pulse TMS was used to investigate changes in SICI-LICI interactions (i.e., presynaptic motor cortex inhibition). These measurements were obtained at rest and during muscle activation involving isolated abduction of the index finger and during a precision grip using the index finger and thumb. SICI was reduced during abduction and precision grip compared with rest, with greater reductions during precision grip. The modulation of LICI during muscle activation depended on the interstimulus interval (ISI; 100 and 150 ms) but was not different between abduction and precision grip. For triple-pulse TMS, SICI was reduced in the presence of LICI at both ISIs in resting muscle (reflecting presynaptic motor cortex inhibition) but was only modulated at the 150-ms ISI during index finger abduction. Results suggest that synergistic contractions are accompanied by greater reductions in postsynaptic motor cortex inhibition than isolated contractions, but the contribution of presynaptic mechanisms to this disinhibition is limited. Furthermore, timing-dependent variations in LICI provide additional evidence that measurements using different ISIs may not represent activation of the same cortical process.

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