Suppression of Single Spinal Motoneurones by Transcranial Magnetic Stimulation: Studies in Healthy Subjects, Multiple Sclerosis and Stroke
Transcranial magnetic stimulation produces at least two peaks in firing probability in single human spinal motoneurones (Boniface, Mills & Schubert, 1991, Mills, Boniface & Schubert, 1992). These have latencies varying from 20 – 31 ms and 64 – 100 ms in the first dorsal interosseus muscle and have been termed the primary and secondary peaks, respectively. These events are also detectable in patients with motoneurone disease, multiple sclerosis and stroke (Mills, Boniface & Schubert, 1991, Schubert, Mills, Boniface, Konstanzer & Dengler, 1991), but often requiring higher stimulus intensities. The aim of this study was to determine whether or not periods of reduced firing probability of motor units were produced at stimulus intensities sub-threshold for an early excitatory response (primary peak) in health and disease. Findings have also been reported in full elsewhere (Boniface, Mills & Schubert, 1994).
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