Rhythmical corticomotor communication.

Recent non-invasive human studies show that rhythmic oscillatory activity of the motor cortex and the firing of motor units of the muscle are coherent during isometric contraction, with peak frequencies around 20 Hz or 40 Hz, depending on the contraction strength. The cortical signals precede the motor unit firing and appear to reflect modulation of the common central drive to the spinal motoneuron pool. The rhythmic modulation may form a tool for efficient driving of motor units but we express some reservations about the assumed binding and attention-related roles of the rolandic brain rhythms. The cortex-muscle coherence is of interest for understanding of cortical control of voluntary movements and the pathophysiology of various motor disorders, as well as for unravelling the functional significance of cortical rhythms.