Novel human models for elucidating mechanisms of rate-sensitive H-reflex depression

Ya-Ju Chang; Yu-Ching Liu; Miao-Ju Hsu; Chia-Ying Fang; Alice M. Wong; Stacey L. DeJong; Richard K. Shields

doi:10.1016/j.bj.2019.07.007

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Novel human models for elucidating mechanisms of rate-sensitive H-reflex depression

Journal article

Open access

Peer reviewed

Novel human models for elucidating mechanisms of rate-sensitive H-reflex depression

Ya-Ju Chang, Yu-Ching Liu, Miao-Ju Hsu, Chia-Ying Fang, Alice M. Wong, Stacey L. DeJong and Richard K. Shields

Biomedical Journal, Vol.43(1), pp.44-52

02/2020

DOI: 10.1016/j.bj.2019.07.007

PMCID: PMC7090317

PMID: 32200955

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Abstract

This study used novel human neurophysiologic models to investigate whether the mechanism of rate-sensitive H-reflex depression lies in the pre-synaptic or post-synaptic locus in humans. We hypothesized that pre-synaptic inhibition would suppress Ia afferents and H-reflexes without suppressing alpha motor neurons or motor evoked potentials (MEPs). In contrast, post-synaptic inhibition would suppress alpha motor neurons, thereby reducing H-reflexes and MEPs. We recruited 23 healthy adults with typical rate-sensitive H-reflex depression, 2 participants with acute sensory-impaired spinal cord injury (SCI) (to rule out influence of sensory stimulation on supra-spinal excitability), and an atypical cohort of 5 healthy adults without rate-sensitive depression. After a single electrical stimulation to the tibial nerve, we administered either a testing H-reflex or a testing MEP at 50–5000 ms intervals. Testing MEPs were not diminished in healthy subjects with or without typical rate-sensitive H-reflex depression, or in subjects with sensory-impaired SCI. MEP responses were similar in healthy subjects with versus without rate-sensitive H-reflex depression. Results from these novel in vivo human models support a pre-synaptic locus of rate-sensitive H-reflex depression for the first time in humans. Spinal reflex excitability can be modulated separately from descending corticospinal influence. Each represents a potential target for neuromodulatory intervention.

H-reflex

Motor evoked potential

Pre-synaptic

Soleus

Spinal cord

Spinal cord injury

Details

Title: Subtitle: Novel human models for elucidating mechanisms of rate-sensitive H-reflex depression
Creators: Ya-Ju Chang - Chang Gung University
Yu-Ching Liu - Chang Gung University
Miao-Ju Hsu - Kaohsiung Medical University
Chia-Ying Fang - Chang Gung University
Alice M. Wong - Chang Gung University
Stacey L. DeJong - University of Iowa
Richard K. Shields - Roy J. and Lucille A. Carver College of Medicine
Resource Type: Journal article
Publication Details: Biomedical Journal, Vol.43(1), pp.44-52
DOI: 10.1016/j.bj.2019.07.007
PMID: 32200955
PMCID: PMC7090317
NLM abbreviation: Biomed J
ISSN: 2319-4170
eISSN: 2320-2890
Publisher: Elsevier B.V
Grant note: DOI: 10.13039/501100004663, name: Ministry of Science and Technology, Taiwan, award: 105-2918-I-182-002, 107-2221-E-182-009-MY3; DOI: 10.13039/501100002836, name: Chang Gung University, award: EMRPD1I0501; DOI: 10.13039/501100004606, name: Chang Gung Medical Foundation, award: CMRPD3E0112; DOI: 10.13039/100008245, name: Neuroscience Research Center; DOI: 10.13039/100012553, name: Chang Gung Memorial Hospital; name: Linkou Medical Center; DOI: 10.13039/100000002, name: United States National Institutes of Health, award: R01-HD084645, R01-HD082109, K12-HD055931
Language: English
Date published: 02/2020
Academic Unit: Orthopedics and Rehabilitation; Physical Therapy and Rehabilitation Science
Record Identifier: 9984295053502771

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