Defective corticomuscular connectivity during walking in Parkinson's disease patients.

Gait disturbances are common in individuals with Parkinson's disease (PD). Although the basic patterns of walking are thought to be controlled by the brainstem and spinal networks, recent studies have found significant corticomuscular coherence in healthy individuals during walking. However, it still remains unknown how PD affect the cortical control of muscles during walking. Since PD typically develops in older adults, it is important to investigate the effects of both ageing and PD when examining disorders in PD patients. Here, we assessed the effects of PD and ageing on corticomuscular communication during walking by investigating corticomuscular coherence. We recorded electroencephalographic and electromyographic signals in 10 individuals with PD, 9 healthy older and 15 healthy young individuals. We assessed the corticomuscular coherence between the motor cortex and two lower leg muscles, tibialis anterior (TA) and medial gastrocnemius, during walking. Older and young groups showed sharp peaks in muscle activation patterns at specific gait phases, whereas the PD group showed prolonged patterns. Smaller corticomuscular coherence was found in the PD group compared to the healthy older group in the α band (8-12 Hz) for both muscles, and in the β band (16-32 Hz) for TA. Older and young groups did not differ in the magnitude of corticomuscular coherence. Our results indicated that PD decreased the corticomuscular coherence during walking, while it was not affected by ageing. This lower corticomuscular coherence in PD may indicate lower-than-normal corticomuscular communication, though direct or indirect communication is unknown, and may cause impaired muscle control during walking.