The aging brain as a model to understand motor skill acquisition in humans and its restoration using non-invasive brain stimulation

Motor skill acquisition is essential to our survival, as it enables an efficient interaction with the changing world around us. The acquisition of novel sequential tasks, of particular relevance due to their pervasiveness in everyday life activities, can become more challenging at an advanced age, with structural and functional changes in the brain often resulting in diminished learning abilities. During the pursuit of my doctoral degree, I studied some of the processes leading to the acquisition of a novel sequential motor task, and how some of the mechanisms underlying these processes differ between healthy young and older adults. Young adults acquired the sequential task effectively by prioritizing its accurate execution early in training and focusing on increasing their speed thereafter, resulting in the generation of mechanically efficient execution patterns in the replication of the sequence. In contrast, older adults improved both the accuracy and the speed simultaneously and gradually after more extensive practice, which resulted in an overall decreased performance of the task. However, anodal direct current stimulation applied over the motor cortex partially restored skill acquisition in older adults by facilitating the early improvement of the accuracy, enabling an accelerated generation of efficient execution patterns in the sequence, similar to those seen in young adults. Further investigations into the effects of stimulation to improve skill acquisition in healthy older adults showed age not to be a determinant factor for an individual's proneness to benefit from stimulation; rather, it is the state of the neural system of each individual what likely determines the potential benefits to be had from stimulation. Therefore, a better understanding of the mechanisms targeted by stimulation and the identification of parameters signaling an individual's likelihood to benefit from it are needed to use these techniques to their full potential. Leveraging this knowledge and taking advantage of the portability, robustness and accessibility of this technique could represent an attractive option for applications involving extensive motor training, such as rehabilitative training provided after stroke.