Age-related weakness of proximal muscle studied with motor cortical mapping: a TMS study

Aging-related weakness is due in part to degeneration within the central nervous system. However, it is unknown how changes to the representation of corticospinal output in the primary motor cortex (M1) relate to such weakness. Transcranial magnetic stimulation (TMS) is a noninvasive method of corti...

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Bibliographic Details
Published in:PloS one 2014-02, Vol.9 (2), p.e89371-e89371
Main Authors: Plow, Ela B, Varnerin, Nicole, Cunningham, David A, Janini, Daniel, Bonnett, Corin, Wyant, Alexandria, Hou, Juliet, Siemionow, Vlodek, Wang, Xiao-Feng, Machado, Andre G, Yue, Guang H
Format: Article
Language:English
Subjects:
Activation
Adults
Age
Aged
Aging
Aging - physiology
Biology
Biomedical engineering
Brain Mapping
Brain research
Center of gravity
Central nervous system
Contraction
Cortex (motor)
Degeneration
Elbow
Elbow (anatomy)
Electromyography
Engineering
Evoked Potentials, Motor - physiology
Excitation
Female
Geriatrics
Handedness
Humans
Magnetic fields
Male
Mapping
Medicine
Motor Cortex - physiology
Motor Cortex - physiopathology
Muscle contraction
Muscle Contraction - physiology
Muscle Weakness - physiopathology
Muscle, Skeletal - physiopathology
Muscles
Neurosurgery
Older people
Physiology
Pyramidal tracts
Representations
Spinal cord injuries
Strength
Stroke
Transcranial Magnetic Stimulation
Women
Young Adult
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Summary:Aging-related weakness is due in part to degeneration within the central nervous system. However, it is unknown how changes to the representation of corticospinal output in the primary motor cortex (M1) relate to such weakness. Transcranial magnetic stimulation (TMS) is a noninvasive method of cortical stimulation that can map representation of corticospinal output devoted to a muscle. Using TMS, we examined age-related alterations in maps devoted to biceps brachii muscle to determine whether they predicted its age-induced weakness. Forty-seven right-handed subjects participated: 20 young (22.6 ± 0.90 years) and 27 old (74.96 ± 1.35 years). We measured strength as force of elbow flexion and electromyographic activation of biceps brachii during maximum voluntary contraction. Mapping variables included: 1) center of gravity or weighted mean location of corticospinal output, 2) size of map, 3) volume or excitation of corticospinal output, and 4) response density or corticospinal excitation per unit area. Center of gravity was more anterior in old than in young (p
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0089371