Rapidly induced changes in neuromagnetic fields following repetitive hand movements.

Sensory feedback plays a major role in movement execution and motor learning, particularly in motor rehabilitation. Whilst elaborating therapeutic strategies, it is of interest to visualize the effect of a therapeutic intervention at the moment of its application. We analyzed the effect of repeated execution of a simple extension and flexion movement of the wrist on the sensorimotor cortex of seven healthy subjects using magnetoencephalography. Spatial filtering based on current dipoles was used to quantify the strength of cortical activation. Our results showed an increase of cortical activation reflecting activity of efferent neurons, whereas the activity of proprioceptive afferent neurons was not affected. Since only efferent activity increased, it is suggested that this reflects phenomena of long-term potentiation.