Scalp Eeg and Tms Based Electrophysiological Study of Brain Function of Motor Control in Aging

Voluntary movements of human body are controlled by the brain through corticomuscular pathways. Although neuromuscular control mechanisms of voluntary movements have been studied extensively, many remain to be learned, especially neuromuscular adaptations related to clinical conditions such as neurological disorders and aging. This research aims at a better understanding of functional connection between the brain and muscle during voluntary motor activities in aging and the extent to which this connection can be changed by training the neuromuscular system. Three research projects were conducted to achieve this aim. The analyses in the first two projects are based on comparisons of non-invasive electroencephalographic (EEG) and electromyographic (EMG) signals recorded in young and elderly individuals performing voluntary muscle contractions whereas the third project is based on transcranial magnetic stimulation (TMS). The first project examines the relationship between EEG frequency power and muscle force to identify an EEG or brain signal parameter directly related to voluntary motor action. The second project investigates further the strength of functional brain-muscle connectivity by quantifying EEG-EMG coherence and effects of aging on the connectivity. The third project identifies the representation of the biceps brachii muscle in primary motor cortex with TMS examine its excitability of corticospinal tracts, intra-cortical excitability reflecting activity of both inhibitory and facilitatory inter-neurons and inter-hemispheric inhibition. This research reveals that aging brain has impaired coupling between the central and peripheral neuromuscular systems and also significantly different intra-cortical excitability both may have an influence for weakened muscle output in the elderly. This research will contribute to a better understanding of neural mechanisms underlying voluntary movement deficit in aging and its recovery following training the neuromuscular syste