Abstract
We examined the influence of anodal transcranial direct current stimulation (tDCS) over the supplementary motor area (SMA) on anticipatory postural adjustments (APAs) and center of pressure (COP) sway in older adults. The study enrolled 12 healthy older adult volunteers. Subjects received anodal tDCS (2 mA) or sham stimulation over the SMA for 15 min and performed a self-paced rapid upward arm movement task on a force plate before, immediately after, and 15 min after the stimulation condition. APAs were measured as the temporal difference between activation onset in the deltoid anterior (AD) and biceps femoris (BF) muscles. The root mean square (RMS) area of COP sway, sway path length, medio-lateral mean velocity, and antero-posterior mean velocity of standing posture were also measured before and after the stimulation condition during the task. Anodal tDCS of the SMA extended APAs and decreased COP sway path length immediately after and 15 min after stimulation compared to baseline. These findings suggest that anodal tDCS over the SMA enhanced APAs function and improved postural sway during rapid upward arm movement in older adults.
Highlights
Nitsche and Paulus (2000) were the first to report modulation of the primary motor cortex (M1) by anodal transcranial direct current stimulation in human subjects
EMG onset was extended after anodal transcranial direct current stimulation (tDCS) compared to baseline
The present study demonstrated that anodal tDCS over the supplementary motor area (SMA) extended EMG onset time for the AD and biceps femoris (BF) muscles during a rapid upward arm movement task in healthy older adults
Summary
Nitsche and Paulus (2000) were the first to report modulation of the primary motor cortex (M1) by anodal transcranial direct current stimulation (tDCS) in human subjects. Since this discovery, numerous studies have described anodal tDCS as a useful tool for improving motor performance in healthy subjects and patients with neurological disorders such as stroke hemiplegia (see review, Hashemirad et al, 2016; Kang et al, 2016). Anodal tDCS over SMA modulates anticipatory postural adjustments tDCS Improves Anticipatory Postural Adjustments (APAs) in index finger flection tasks (Bolzoni et al, 2015) while cathodal stimulation has an inhibitory effect on APAs in rapid upward arm movements while standing (Kirimoto et al, 2013). Anodal tDCS over the SMA may have important therapeutic utility for older adults with deteriorated balance function
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