Evidence that a transcortical pathway contributes to stretch reflexes in the tibialis anterior muscle in man

摘要: 1In human subjects, stretch applied to ankle dorsiflexors elicited three bursts of reflex activity in the tibialis anterior (TA) muscle (labelled M1, M2 and M3) at mean onset latencies 44, 69 95 ms, respectively. The possibility that later these is mediated by a transcortical pathway was investigated. 2The evoked cerebral potential recorded from somatosensory cortex latency 47 ms nine subjects. In same subjects compound motor-evoked (MEP) TA muscle, magnetic stimulation motor cortex, had 32 ms. M1 reflexes thus too short be caused (minimum latency, 79 (47 + 32)), whereas part all M3 sufficiently long latency. 3When transcranial timed so MEP arrived time as or reflexes, no extra increase observed. However, when significant (P < 0.01) extra-facilitation observed twelve investigated. 4Peaks post-stimulus histogram discharge probability single units (n= 28) were strongly facilitated they occurred response. This not case for first peaks electrical any investigated. 5We suggest findings are explained an increased cortical excitability following this supports hypothesis response - least partly reflex.