Facilitation of supplementary motor area excitability improves dual-task walking in young adults

Transcranial direct current stimulation facilitates backward walking training

Backward walking training presents a great challenge to the physical and neural systems, which may result in an improvement in gait performance. Transcranial direct current electrical stimulation (tDCS), which can non-invasively enhance cortical activity, has been reported to strengthen corticomotor plasticity. We investigated whether excitatory tDCS over the primary motor cortex (M1) or the dorsolateral prefrontal cortex (DLPFC) enhances the effects of backward walking training in healthy participants. Thirty-six healthy participants (16 men and 20 women, mean age 21.3 ± 1.4 years) participated in this study. The participants were randomly assigned to one of the three tDCS groups (M1, DLPFC, and sham). They performed 5 min of backward walking training during 15 min of tDCS. We evaluated dual-task forward and backward walking performance before and after training. Both tDCS groups increased walking speed in the backward condition, but the DLPFC group increased the dual-task backward walking speed more than the M1 group. The M1 group showed decreased gait variability in dual-task backward walking, whereas the DLPFC group showed increased gait variability. Backward walking training combined with M1 stimulation may increase the backward walking speed by reducing gait variability. Backward walking training combined with DLPFC stimulation may prioritize walking speed over gait stability. Our results indicate that backward walking training combined with tDCS may be extended to other rehabilitation methods to improve gait performance.

Effects of noninvasive brain stimulation on dual-task performance in different populations: A systematic review

Background

Increasing research has investigated the use of noninvasive brain stimulation (NIBS) on augmenting dual-task (DT) performance.

Objective

To investigate the effects of NIBS on DT performance in different populations.

Methods

Extensive electronic database search (from inception to November 20, 2022) was conducted in PubMed, Medline, Cochrane Library, Web of Science and CINAHL to identify randomized controlled trials (RCTs) that investigated the effects of NIBS on DT performance. Main outcomes were balance/mobility and cognitive function under both single-task (ST) and DT conditions.

Results

Fifteen RCTs were included, involving two types of intervention techniques: transcranial direct current stimulation (tDCS) (twelve RCTs) and repetitive transcranial magnetic stimulation (rTMS) (three RCTs); and four different population groups: healthy young adults, older adults, Parkinson's disease (PD), and stroke. For tDCS, under DT condition, significant improvement in speed was only observed in one PD and one stroke RCT, and stride time variability in one older adults RCT. Reduction in DTC in some gait parameters was demonstrated in one RCT. Only one RCT showed significant reduction in postural sway speed and area during standing under DT condition in young adults. For rTMS, significant improvements in fastest walking speed and time taken to Timed-up-and-go test under both ST and DT conditions were observed at follow-up in one PD RCT only. No significant effect on cognitive function in any RCT was observed.

Conclusion

Both tDCS and rTMS showed promising effects in improving DT walking and balance performance in different populations, however, due to the large heterogeneity of included studies and insufficient data, any firm conclusion cannot be drawn at present.

Optimal timing and neural loci: a scoping review on the effect of non-invasive brain stimulation on post-stroke gait and balance recovery

BACKGROUND

Little is known about the optimal timing and neural loci for applying noninvasive brain stimulation (NIBS) to promote gait and balance recovery after stroke.

OBJECTIVE

To identify the optimal timing and neural loci of NIBS for gait and balance recovery after stroke.

METHODS

We performed a PubMed search using keywords of stroke, transcranial magnetic stimulation, transcranial direct current stimulation, NIBS, balance, and gait. Interventional trials with various designs published in English were selected. Both flowcharts and tables were used for the result presentation.

RESULTS

The majority of selected 31 studies included individuals with chronic stroke and primary motor cortex (M1) stimulation. Studies' quality ranged from 4 to 10 (max = 10) on the Pedro scale. NIBS led to improvements in gait and balance in individuals with chronic and subacute stroke, yet the evidence for the acute phase of stroke is limited. Further, stimulation over the ipsilesional M1 resulted in improvement in gait and balanced performance. Stimulation over non-motor regions such as the cerebellum has been limitedly explored.

CONCLUSION

Current evidence supports the use of NIBS to the M1 in conjunction with behavioral training to improve gait and balance performance in individuals with subacute and chronic stroke. Future research is recommended to evaluate the effect of NIBS during acute stroke and over neural loci other than M1, and to implement a more rigorous method.

The Effect of a Single Session of Non-Invasive Brain Stimulation on Balance in Healthy Individuals: A Systematic Review and Best Evidence Synthesis

Aim: To evaluate the effects of a single session of non-invasive brain stimulation (NIBS) on postural balance. Introduction: The NIBS has been used widely in improving balance. However, the effect of a single session of NIBS on balance in healthy individuals has not been systemically reviewed. Methods: A systematic literature review and best evidence synthesis were conducted, according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines, to determine the effects of different NIBS techniques on balance function in healthy individuals. The methodological quality of included articles was assessed by the risk of bias, and the Downs and Black tool. Data were analyzed by using the best evidence synthesis. Thirty-five articles were included that used the following NIBS techniques: anodal transcranial direct current stimulation (a-tDCS), cathodal transcranial direct current stimulation (c-tDCS), continuous theta burst stimulation (cTBS), and repetitive transcranial magnetic stimulation (rTMS) on primary motor cortex (M1), supplementary motor area (SMA), dorsolateral prefrontal cortex (DLPFC), and cerebellum on balance. Results: Strong evidence showed that a-tDCS of M1, SMA improve balance in healthy participants, and the a-tDCS of DLPFC induces improvement only in dual task balance indices. Also, the findings indicate that cerebellar a-tDCS might significantly improve balance, if at least 10 min cerebellar a-tDCS with an intensity of ≥1 mA, over or maximum 1.5 cm below the inion, is used. Strong evidence showed that c-tDCS, cTBS, and rTMS are not effective on the balance. Conclusion: According to the results, the a-tDCS may be a useful technique to improve balance in healthy adults.

Single session of repetitive transcranial magnetic stimulation to left dorsolateral prefrontal cortex increased dual-task gait speed in chronic stroke: A pilot study

BACKGROUND

Individuals with stroke often experience difficulty in dual-task walking and are prone to falling when walking and talking. Previous studies in other populations have suggested that non-invasive brain stimulation could enhance dual-task gait performance by stimulating dorsolateral prefrontal cortex (DLPFC) or supplementary motor area (SMA). It was unclear if the benefits of brain stimulation would be observed in individuals with stroke.

RESEARCH QUESTION

Would single-session 5 Hz rTMS applied to DLPFC or SMA improve dual-task gait performance in individuals with stroke?

METHODS

This single group repeated measure study included fifteen individuals with left chronic stroke (mean age = 58 years). Participants received 5 Hz rTMS to either DLPFC, SMA, or M1 of the left lesioned hemisphere across three different sessions. Single- and dual-task gait speed was assessed before and after rTMS with the dualtask gait being walking and counting backward by 3 s.

RESULTS

We observed that rTMS to left DLPFC resulted in a greater increase in dual-task gait speed, but not single-task gait speed, compared to the other two stimulation sites (M1 and SMA) but the difference was not statistically significant (p = 0.06). Five out of fifteen participants demonstrated a clinically significant improvement in dual-task gait speed (> 0.1 m/s) after rTMS to DLPFC.

SIGNIFICANCES

The results suggest that DLPFC could be a potential treatment target to improve dual-task gait performance in persons with chronic stroke.