Anodal Transcranial Direct Current Stimulation Does Not Facilitate Dynamic Balance Task Learning in Healthy Old Adults.

Elisabeth Kaminski,Christopher J Steele,Maike Hoff,Christopher Gundlach,Patrick Ragert,Viola Rjosk,Arno Villringer,Bernhard Sehm

doi:10.3389/fnhum.2017.00016

Abstract

Older adults frequently experience a decrease in balance control that leads to increased numbers of falls, injuries and hospitalization. Therefore, evaluating older adults’ ability to maintain balance and examining new approaches to counteract age-related decline in balance control is of great importance for fall prevention and healthy aging. Non-invasive brain stimulation techniques such as transcranial direct current stimulation (tDCS) have been shown to beneficially influence motor behavior and motor learning. In the present study, we investigated the influence of tDCS applied over the leg area of the primary motor cortex (M1) on balance task learning of healthy elderly in a dynamic balance task (DBT). In total, 30 older adults were enrolled in a cross-sectional, randomized design including two consecutive DBT training sessions. Only during the first DBT session, either 20 min of anodal tDCS (a-tDCS) or sham tDCS (s-tDCS) were applied and learning improvement was compared between the two groups. Our data showed that both groups successfully learned to perform the DBT on both training sessions. Interestingly, between-group analyses revealed no difference between the a-tDCS and the s-tDCS group regarding their level of task learning. These results indicate that the concurrent application of tDCS over M1 leg area did not elicit DBT learning enhancement in our study cohort. However, a regression analysis revealed that DBT performance can be predicted by the kinematic profile of the movement, a finding that may provide new insights for individualized approaches of treating balance and gait disorders.

Highlights

Due to the demographic change, the older population is constantly increasing
Groups did not differ in their level of attention (RM-ANOVA Time × Group interaction, Training Day 1 (TD1): F(1,28) = 2.87, p = 0.1, Training Day 2 (TD2): F(1,28) = 1.26, p = 0.27), fatigue anodal Transcranial direct current stimulation (tDCS) (a-tDCS), n = 15 66.8 ± 5.63 29.33 ± 0.72 6855.6 ± 5682 36.67 ± 2.72 sham transcranial direct current stimulation (s-tDCS), n = 15 68.6 ± 6.00 29.13 ± 0.99 5383.8 ± 3590 36.53 ± 3.02
Consolidation and Training Day 2 (TD2) When comparing the retention scores of the two groups, we found no significant difference (MWU: U = 76, p = 0.13), which indicates that a-tDCS did not affect skill retention from TD1 to TD2 (Figure 1C)

Summary

Introduction

Due to the demographic change, the older population is constantly increasing. understanding the mechanisms of aging processes and examining strategies to decelerate age-related decline is of great importance. Older adults, compared with younger adults, show a reduced amount of structural and functional brain plasticity (Burke and Barnes, 2006) and learning-dependent plasticity decreases with age (Sawaki et al, 2003) All these factors contribute to an age-related decrease of postural stability, which is an important risk factor for falls (Granacher et al, 2008; Panel on Prevention of Falls in Older Persons, American Geriatrics Society and British Geriatrics Society, 2011). Our results showed that performance improvements were mediated by tDCS-induced changes in movement velocity According to this previous study, we hypothesized that (A) a-tDCS over M1 leg area during DBT learning facilitates learning performance compared with a group receiving s-tDCS in an older age cohort. We expected that (B) the kinematic profile assessed during DBT learning predicts the DBT performance level of elderly with a special impact of velocity on performance improvement

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