Associations of screen time and physical activity with TMS-based measures of motor cortical excitability in...

Adolescence represents a crucial and sensitive period for brain neurobiological development. Screen time and physical activity may impact brain development, but evidence on their associations with cortical inhibition and excitability remains limited. We investigated cross-sectional associations of self-reported screen time and physical activity with cortical inhibition and excitability in adolescents. Altogether, 45 Finnish adolescents (20 males) aged 16-19 years underwentnavigated transcranial magnetic stimulation examination. Corticospinal excitability and corticospinal and intracortical inhibition were measured using resting motor thresholds, long-interval intracortical inhibition, silent period duration, and silent period thresholds. Questionnaires were used to assess screen time (smart device time, computer time, time spent watching television and videos) and physical activity (organized sports in sports clubs, supervised exercise other than sports, unsupervised physical activity). Longer total screen time was associated with weaker corticospinal inhibition. Longer computer use was associated with stronger motor cortex excitability and stronger intracortical inhibition, whereas longer television and video viewing times were associated with weaker intracortical and corticospinal inhibition. Higher levels of organized sports were associated with stronger motor cortex excitability, whereas higher levels of unsupervised physical activity were associated with weaker corticospinal excitability and higher inhibitory thresholds. In conclusion, passive screen time was linked to weaker intracortical and corticospinal inhibition, whereas organized physical activity was associated with stronger motor cortex excitability. These findings highlight the differential associations of active and passive screen time as well as structured and unstructured physical activity with cortical excitability and inhibition, suggesting their distinct roles in neurodevelopment during adolescence.