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FC4.3 Increased probability of repetitive spinal motoneurone activation after muscle fatigue in healthy subjects
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Oral Communications / Clinical Neurophysiology 117 (2006) S49–S111
FC4.2 Conduction velocity changes during stimulated single muscle fibre fatigue P. Blijham, D. Stegeman, M. Zwarts Radboud University, Nijmegen Medical Centre, Department of Clinical Neurophysiology, Netherlands Background: The purpose of this study was to develop a test that measures the changes in propagation of the sarcolemma during fatigue at the level of single muscle fibres. Methods: We have measured muscle fibre conduction velocity (MFCV) of single fibres using an invasive technique described earlier, at 20 Hz stimulus rate to induce muscle fatigue. The following consecutive measurements were made in the biceps brachii of 13 healthy controls: measurements with 1 Hz stimulation (baseline), after a short stimuli train of 20 Hz, after 60 s of 20 Hz stimulation (fatigue), and after 30 s of rest (recvovery). The MFCV of both fast and slow fibres were analysed. Results: Results of the short 20 Hz stimuli showed supernormality: a significant mean increase of 17% of baseline MFCV of the fast fibres, while a non-significant mean increase was found in the slow fibres. During the fatigue test, the amplitude of most fibres decreased to below 25% of baseline values, but some of the faster fibres, usually 1 or 2 per subject, showed a much smaller decline. The initial supernormality of MFCV disappeared during the fatigue test, and the MFCV of some of the slower fibres decreased to below baseline level. All controls showed full recovery of MFCV after 30 s of rest. Discussion: Our results are in concordance with those from in vitro experiments, although the difference in supernormality of fast and slow fibres has not been reported. Further studies on patients with neuromuscular disorders or complaints of fatigue are needed to test the diagnostic value of this procedure. doi:10.1016/j.clinph.2006.06.014
exercise even if some MNs failed to discharge on arrival of the first volley set up by the brain stimulus. Aim: To quantify repetitive spinal MN discharges in response to TMS after muscle fatigue. Methods: We combined the TST with an additional peripheral nerve stimulus (Z’Graggen et al. Clin Neurophysiol 2005) and applied this quadruple stimulation (QS) after exercise in 12 subjects. The QS permits quantification of the amount of MNs discharging twice, since it eliminates the first action potential descending on each axon after TMS. In some subjects, a quintuple stimulation was used to estimate the number of MNs discharging three times. Results: Following a sustained abductor digiti minimi contraction at 50% maximal force there was a markedly increase in size of the QS response amounting to 50–140% in eight subjects while in one subject double-discharging MNs could be recorded only after exercise. This demonstrated that a greater amount of MNs were fired twice after the contraction. In three subjects the number of MNs firing three times increased by 50%. Conclusions: The study confirmed that a greater fraction of spinal MNs fire not just once, but repetitively after muscle fatigue pointing to complex interactions between failure of activation and increased excitability of the corticospinal path. The results add further evidence to the view that repetitive MN firing may provide a compensatory mechanism to maintain motor unit activation during sustained voluntary activity. doi:10.1016/j.clinph.2006.06.015
FC5.1 Noninvasive evaluation of language dominance and localization using synthetic aperture magnetometry: Comparison with Wada test and stimulation mapping M. Hirata 1, A. Kato 1, Y. Saitoh 1, N. Hashimoto 1, H. Kishima 1, H. Ninomiya 2, S. Oshino 1, S. Yorifuji 3, T. Yoshimine 1 1
FC4.3 Increased probability of repetitive spinal motoneurone activation after muscle fatigue in healthy subjects B. Andersen, U.A. Felding, C. Krarup Rigshospitalet, Copenhagen University Hospital, Department of Clinical Neurophysiology, Denmark Background: Previously we used the triple stimulation technique (TST) to study corticospinal conduction after exercise in healthy subjects and showed that transcranial magnetic stimulation (TMS) fails to activate a proportion of spinal motoneurones (MNs) following a fatiguing contraction (Andersen et al. J Physiol 2003). The findings of a TST response depression but no attenuation in size of the conventional motor evoked potential pointed to increased probability of repetitive MN activation during
Osaka University Medical School, Neurosurgery, Japan Sakai Municipal Hospital, Neurosurgery, Japan 3 Osaka University Graduate School of Medicine, Functional Diagnostic Science, Japan 2
Background: Noninvasive methods to determine language dominance and localization have not been established. Using spatially filtered magnetoencephalography (MEG), we previously proposed a noninvasive method to determine language dominance based on the local oscillatory changes induced by silent reading (Hirata et al. NeuroImage, 2004). Objective: The present study investigated language dominance with larger population and also language localization. The results were compared with Wada test and stimulation mapping.
Oral Communications / Clinical Neurophysiology 117 (2006) S49–S111
FC4.2 Conduction velocity changes during stimulated single muscle fibre fatigue P. Blijham, D. Stegeman, M. Zwarts Radboud University, Nijmegen Medical Centre, Department of Clinical Neurophysiology, Netherlands Background: The purpose of this study was to develop a test that measures the changes in propagation of the sarcolemma during fatigue at the level of single muscle fibres. Methods: We have measured muscle fibre conduction velocity (MFCV) of single fibres using an invasive technique described earlier, at 20 Hz stimulus rate to induce muscle fatigue. The following consecutive measurements were made in the biceps brachii of 13 healthy controls: measurements with 1 Hz stimulation (baseline), after a short stimuli train of 20 Hz, after 60 s of 20 Hz stimulation (fatigue), and after 30 s of rest (recvovery). The MFCV of both fast and slow fibres were analysed. Results: Results of the short 20 Hz stimuli showed supernormality: a significant mean increase of 17% of baseline MFCV of the fast fibres, while a non-significant mean increase was found in the slow fibres. During the fatigue test, the amplitude of most fibres decreased to below 25% of baseline values, but some of the faster fibres, usually 1 or 2 per subject, showed a much smaller decline. The initial supernormality of MFCV disappeared during the fatigue test, and the MFCV of some of the slower fibres decreased to below baseline level. All controls showed full recovery of MFCV after 30 s of rest. Discussion: Our results are in concordance with those from in vitro experiments, although the difference in supernormality of fast and slow fibres has not been reported. Further studies on patients with neuromuscular disorders or complaints of fatigue are needed to test the diagnostic value of this procedure. doi:10.1016/j.clinph.2006.06.014
exercise even if some MNs failed to discharge on arrival of the first volley set up by the brain stimulus. Aim: To quantify repetitive spinal MN discharges in response to TMS after muscle fatigue. Methods: We combined the TST with an additional peripheral nerve stimulus (Z’Graggen et al. Clin Neurophysiol 2005) and applied this quadruple stimulation (QS) after exercise in 12 subjects. The QS permits quantification of the amount of MNs discharging twice, since it eliminates the first action potential descending on each axon after TMS. In some subjects, a quintuple stimulation was used to estimate the number of MNs discharging three times. Results: Following a sustained abductor digiti minimi contraction at 50% maximal force there was a markedly increase in size of the QS response amounting to 50–140% in eight subjects while in one subject double-discharging MNs could be recorded only after exercise. This demonstrated that a greater amount of MNs were fired twice after the contraction. In three subjects the number of MNs firing three times increased by 50%. Conclusions: The study confirmed that a greater fraction of spinal MNs fire not just once, but repetitively after muscle fatigue pointing to complex interactions between failure of activation and increased excitability of the corticospinal path. The results add further evidence to the view that repetitive MN firing may provide a compensatory mechanism to maintain motor unit activation during sustained voluntary activity. doi:10.1016/j.clinph.2006.06.015
FC5.1 Noninvasive evaluation of language dominance and localization using synthetic aperture magnetometry: Comparison with Wada test and stimulation mapping M. Hirata 1, A. Kato 1, Y. Saitoh 1, N. Hashimoto 1, H. Kishima 1, H. Ninomiya 2, S. Oshino 1, S. Yorifuji 3, T. Yoshimine 1 1
FC4.3 Increased probability of repetitive spinal motoneurone activation after muscle fatigue in healthy subjects B. Andersen, U.A. Felding, C. Krarup Rigshospitalet, Copenhagen University Hospital, Department of Clinical Neurophysiology, Denmark Background: Previously we used the triple stimulation technique (TST) to study corticospinal conduction after exercise in healthy subjects and showed that transcranial magnetic stimulation (TMS) fails to activate a proportion of spinal motoneurones (MNs) following a fatiguing contraction (Andersen et al. J Physiol 2003). The findings of a TST response depression but no attenuation in size of the conventional motor evoked potential pointed to increased probability of repetitive MN activation during
Osaka University Medical School, Neurosurgery, Japan Sakai Municipal Hospital, Neurosurgery, Japan 3 Osaka University Graduate School of Medicine, Functional Diagnostic Science, Japan 2
Background: Noninvasive methods to determine language dominance and localization have not been established. Using spatially filtered magnetoencephalography (MEG), we previously proposed a noninvasive method to determine language dominance based on the local oscillatory changes induced by silent reading (Hirata et al. NeuroImage, 2004). Objective: The present study investigated language dominance with larger population and also language localization. The results were compared with Wada test and stimulation mapping.