A Cervical Propriospinal System in Man
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Peripheral stimuli facilitate, at a pre-motoneuronal level, the responses elicited in human upper limb motoneurons (MNs) by transcranial magnetic stimulation over the motor cortex (TMS). Several features indicate that the ‘relevant premotoneurones are distinct from segmental interneurones and located rostra] to MNs. Thus, corticospinal volleys would have an indirect (propriospinal) pathway to upper limb MNs, in addition to the direct cortico-motoneuronal pathway. Slightly increasing the corticospinal input causes the facilitation to be reversed to inhibition. This is consistent with a well-developed system of inhibitory intemeurones activated by corticospinal and afferent inputs inhibiting propriospinal neurones (PNs). Corticospinal activation of these inhibitory intemeurones would explain why propriospinally-mediated corticospinal EPSPs are weak in primate MNs after artificial (electrical or magnetic) activation of the corticospinal system by itself. However, indirect evidence for descending facilitation of PNs can be provided during normal voluntary contractions, while using the modulation of the ongoing EMG or of the H reflex.
KeywordsTranscranial Magnetic Stimulation Flexor Digitorum Superficialis Transcranial Magnetic Stimulation Intensity Combine Stimulation Separate Stimulus
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- Pierrot-Deseilligny, E., Morin, C., Bergego, C., and Tankov, N., 1981, Pattern of group I fibre projections from ankle flexor and extensor muscles in manExperimental Brain Research42, 337–350.Google Scholar