Exteroceptive Reflex with Seven Peaks Elicited by Mental Nerve Stimulation in the Unrectified EMG Recordings

Kenji Nakashima, Yuping Wang, Manabu Shimoda, Kenji Sakuma, John C. Rothwell* and Kazuro Takahashi

Division of Neurology, Institute of Neurological Sciences, Faculty of Medicine, Tottori University, Yonago 683, Japan and *MRC Human Movement & Balance Unit, University Department of Clinical Neurology, Institute of Neurology, London, United Kingdom

In the present study, we found a reflex produced by 3 Hz repetitive mental nerve stimulation which consisted of four negative peaks (NI N2 N3 and N4) and three positive peaks (P1, P2 and P3) in unrectified electromyographic (EMG) recordings. The seven peaks response has not yet been reported on. Exteroceptive suppression (ES) in the masseter muscles was also examined. According to the latencies, N1 and N2 peaks seem to be the onset and end of ES1; N3 and N4 peaks the onset and end of ES2, respectively. The exteroceptive reflex in the masseter muscles could be observed both in rectified and unrectified EMG recordings. In rectified EMG recordings, two suppressions are seen, seven peaks are observed in unrectified EMG recordings.

Key words: brain stem, exteroceptive suppression, masseter muscle, motor control, reticular formation

RETURN