Oscillatory cortical activity related to voluntary muscle relaxation: Influence of normal aging

Objective In this study we aimed to investigate if there are age-related differences in cortical oscillatory activity induced by self-paced muscular pure relaxation in comparison with muscle contraction as reference movement. Methods Event-related (de)synchronization (ERD/ERS) have been recorded related to voluntary muscle contraction and relaxation in 10 young and 10 elderly right-handed healthy subjects. The muscle relaxation task consisted in a voluntary relaxation of maintained wrist extension without any overt, associated muscle contraction. The muscle contraction task corresponded to a self-initiated brief wrist extension. Results In elderly subjects compared to young ones, mu and beta ERD preceding muscular relaxation was more widespread, beginning significantly earlier over contralateral frontocentral and parietocentral regions (p < 0.05) as well as over ipsilateral regions (p < 0.05). The beta synchronization was significantly attenuated (p < 0.05). Conclusions These results suggest an alteration of inhibitory motor systems and an altered post-movement somesthetic inputs processing with normal aging. These alterations were accompanied by compensatory mechanisms. Significance These age-related alterations during different phases of muscle relaxation could participate to explain global sensorimotor slowing observed with normal aging.