Grasp-Dependent Modulations in EEG-EMG Coherence Are Observed in Young but Not Older Adults

EEG-EMG coherence (Corticomuscular coherence - CMC) reveals the functional connection between the cortical activity and muscle activity during voluntary movements. During voluntary movements the cortical and muscle activity are synchronized in the beta band range. Age-related deteriorations in the central and peripheral system can impair communication between the brain's cortical regions and the muscle activity. This study aim to examine the beta band EEG - EMG coherence in older individuals and compare the results with young adults. Twenty-two-channel EEG and two-channel EMG data were collected from twenty healthy young adults aged 20-30 ( $26.96\pm 2.68$ ) and fourteen older adults aged 58-72 ( $62.57\pm 3.58$ ). Participants were instructed to hold a handle gently for five seconds, then lift and hold it for an additional five seconds under fixed and free conditions (with the thumb platform either fixed or sliding). EEG - EMG coherence magnitude was lower in the older group compare to the young group. Furthermore, the magnitude of EEG-EMG coherence of the young group was greater in the fixed condition than the free condition. In contrast, no difference in EEG-EMG coherence magnitude was observed in the older group between the task conditions. In summary, older adults exhibit reduced and consistent EEG - EMG coherence across different motor tasks compared to younger adults, reflecting age-related declines in neural synchrony and motor control efficiency. In contrast, younger individuals exhibit task related modulation in EEG-EMG coherence magnitude. This suggests a fundamental difference in motor control mechanisms between younger and older populations during task performance.