Transcranial direct stimulation: what are the effects on cognitive and motor functions in older adults?

This study investigated the effects of transcranial direct stimulation (tDCS) on cognitive and motor performance in healthy older adults. This study concluded that tDCS significantly improved performance across a variety of tasks.

Normal aging is associated with gradual decline in cognitive function, particularly in memory, and motor function. For older adults, this can negatively impact quality of life, and the ability to live independently. Research suggests that impaired brain plasticity (the brain’s ability to adapt to change) is linked to this decline in a variety of disorders, such as Parkinson’s disease (PD).

Transcranial direct stimulation (tDCS) is a type of non-invasive brain stimulation technique that modifies the brain’s plasticity. This technique applies a weak electrical current from two small electrodes on the scalp for 10 – 20 minutes. Anodal tDCS makes brain regions more active, while cathodal tDCS makes brain regions less active. Whether tDCS can enhance the cognitive and motor abilities of healthy older adults remains under investigation.

This study analyzed the results of 25 studies. These studies involved 610 healthy older adults. Participants received tDCS on one or both sides of the brain. tDCS was compared to sham (inactive treatment), cognitive training, or motor practice. 

Overall, tDCS had a medium positive effect. Cognitive and motor functions were significantly improved. 

tDCS improved cognitive function before and during a cognitive task. Only memory and language production tasks were significantly improved with tDCS. The effect of tDCS on problem-solving or decision-making tasks was not significant.

Motor performance before and during a motor task was also significantly improved. 

This study concluded that tDCS significantly improved performance across a variety of tasks. However, the authors suggest that a complete understanding of how tDCS works in the brain is needed before it can be recommended for the elderly.

The studies analyzed here had varying sample sizes (8 – 72 participants). Also, the studies applied brain stimulation with different intensity, duration, and electrode size. These may influence the effectiveness of tDCS. Thus, these factors may limit the conclusions that may be drawn from these results.