Modulation of cortex-muscle oscillatory interaction by ischaemia-induced deafferentation.

We studied the effect of sensory feedback on the oscillatory interaction between activity of the motor cortex and the spinal motoneuron pool during isometric contraction. After inducing ischaemic sensory deafferentation in the upper limb in six subjects, we calculated coherences between simultaneously recorded whole-scalp magnetoencephalographic (MEG) signals and electromyographic (EMG) signals from the first dorsal interosseus muscles. We expected that the dominant frequency of coherence would change if there were interaction through a sensory feedback loop. However, the MEG-EMG coherence frequency did not change significantly during ischaemia. The strength of the coherence was reduced during ischaemia, but returned to the pre-ischaemic level after ischaemia had ended. Reduction of sensory feedback may thus indirectly reduce the amount of corticomuscular coherence, but the lack of change in the dominant coherent frequency suggests that a sensory feedback loop is not essential for the generation of this coherence.