Neurophysiological correlates of aging-related muscle weakness
| Autor: | Bernadett Mamone, Nicole Varnerin, Mehmed Bugrahan Bayram, David A. Cunningham, Corin Bonnett, Dina Gohar, Guang H. Yue, Andre G. Machado, Juliet Hou, Ela B. Plow, Alexandria Wyant, Vlodek Siemionow |
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| Rok vydání: | 2013 |
| Předmět: |
Adult
Male Aging Physiology medicine.medical_treatment Pyramidal Tracts Neural Inhibition Neural degeneration Sex Factors medicine Humans Muscle Strength Muscle Skeletal Aged Pyramidal tracts General Neuroscience Motor Cortex Muscle weakness Articles Transcranial Magnetic Stimulation Transcranial magnetic stimulation medicine.anatomical_structure Female medicine.symptom Primary motor cortex Psychology Neuroscience Motor cortex Muscle contraction Muscle Contraction |
| Zdroj: | Journal of neurophysiology. 110(11) |
| ISSN: | 1522-1598 |
| Popis: | Muscle weakness associated with aging implicates central neural degeneration. However, role of the primary motor cortex (M1) is poorly understood, despite evidence that gains in strength in younger adults are associated with its adaptations. We investigated whether weakness of biceps brachii in aging analogously relates to processes in M1. We enrolled 20 young (22.6 ± 0.87 yr) and 28 old (74.79 ± 1.37 yr) right-handed participants. Using transcranial magnetic stimulation, representation of biceps in M1 was identified. We examined the effect of age and sex on strength of left elbow flexion, voluntary activation of biceps, corticospinal excitability and output, and short-interval intracortical and interhemispheric inhibition. Interhemispheric inhibition was significantly exaggerated in the old ( P = 0.047), while strength tended to be lower ( P = 0.075). Overall, women were weaker ( P < 0.001). Processes of M1 related to strength or voluntary activation of biceps, but only in older adults. Corticospinal excitability was lower in weaker individuals ( r = 0.38), and corticospinal output, intracortical inhibition and interhemispheric inhibition were reduced too in individuals who poorly activated biceps ( r = 0.43, 0.54 and 0.38). Lower intracortical inhibition may reflect compensation for reduced corticospinal excitability, allowing weaker older adults to spread activity in M1 to recruit synergists and attempt to sustain motor output. Exaggerated interhemispheric inhibition, however, conflicts with previous evidence, potentially related to greater callosal damage in our older sample, our choice of proximal vs. distal muscle and differing influence of measurement of inhibition in rest vs. active states of muscle. Overall, age-specific relation of M1 to strength and muscle activation emphasizes that its adaptations only emerge when necessitated, as in a weakening neuromuscular system in aging. |
| Databáze: | OpenAIRE |
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