Corticomuscular coherence during upright standing in unilateral transfemoral amputees.

Patients with a lower limb amputation suffer from an impaired balance control and thereby are at a higher risk to fall. To cope with this deficit, they adapt their neuromuscular system by modifying biomechanical and neuromuscular structures. In this study, we investigated changes in corticomuscular coherence between the motor cortex and muscles of the trunk and the intact lower leg. We recorded electroencephalogram (EEG) and electromyogram (EMG) data from 10 unilateral transfemoral amputees and 10 age-matched able-bodied controls during quiet upright stance with eyes open, eyes closed and during dual tasking. To analyse afferent and efferent corticomuscular coherence, directional wavelet coherence between EEG and EMG signals was computed. The corticomuscular coherence analysis showed significant differences between amputees and controls in the afferent and efferent direction and across visual conditions, suggesting differences in the processing of sensory feedback. A power spectral density analysis of the motor cortex contralateral to the amputated leg of amputees showed increased power, as well as a pronounced decrease in alpha frequencies indicating an increased cognitive load. This exploratory study stimulates further hypotheses on how coordination of brain and muscle activity is modulated after a lower limb amputation.