Oscillatory interaction between human motor cortex and trunk muscles during isometric contraction

We investigated oscillatory interaction between magnetoencephalographic sig nals of the human motor cortex and surface electromyogram from the paraspin al (PS) and abdominal (ABD) muscles. The results were compared with data ob tained during contraction of the first dorsal interosseus (FDI) and tibiali s anterior (TA) muscles. Significant coherence at 15-35 Hz was observed for both PS and ABD muscles in all subjects but the coherence was weak compare d with that for FDI and TA. The cortical sources for both the PS and the AB D coherences were located in the motor cortex between the source areas for the FDI and TA coherences, thereby agreeing with the classical trunk area o f the motor homunculus previously determined by invasive studies. The sourc es were strictly contralateral for PS but bilateral for ABD contractions. O ur results indicate that during isometric contractions descending motor com mands are modulated by cortical oscillations for both limb and trunk muscle s, although the modulation is weaker and may be bilateral for trunk muscles . (C) 2001 Academic Press.