Mrachacz-Kersting Natalie, Gervasio Sabata, Marchand-Pauvert Veronique
Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
INSERM, CNRS, Laboratoire d'Imagerie Biomédicale (LIB), Sorbonne Universités, Paris, France.
Front Hum Neurosci. 2018 Jun 29;12:260. doi: 10.3389/fnhum.2018.00260. eCollection 2018.
In humans, an ipsilateral tibial nerve (iTN) stimulation elicits short-latency-crossed-responses (SLCR) comprised of two bursts in the contralateral gastrocnemius lateralis (cGL) muscle. The average onset latency has been reported to be 57-69 ms with a duration of 30.4 ± 6.6 ms. The aim of this study was to elucidate if a transcortical pathway contributes to the SLCR. In Experiment 1 ( = 9), single pulse supra-threshold transcranial magnetic stimulation (supraTMS) was applied alone or in combination with iTN stimulation (85% of the maximum M-wave) while participants walked on a treadmill (delay between the SLCR and the motor evoked potentials (MEP) varied between -30 and 200 ms). In Experiment 2 ( = 6), single pulse sub-threshold TMS (subTMS) was performed and the interstimulus interval (ISI) varied between 0-30 ms. In Experiment 3, somatosensory evoked potentials (SEPs) were recorded during the iTN stimulation to quantify the latency of the resulting afferent volley at the cortical level. SLCRs and MEPs in cGL occurred at 63 ± 6 ms and 29 ± 2 ms, respectively. The mean SEP latency was 30 ± 3 ms. Thus, a transcortical pathway could contribute no earlier than 62-69 ms (SEP+MEP+central-processing-delay) after iTN stimulation. Combined iTN stimulation and supraTMS resulted in a significant MEP extra-facilitation when supraTMS was timed so that the MEP would coincide with the late component of the SLCR, while subTMS significantly depressed this component. This is the first study that demonstrates the existence of a strong cortical control on spinal pathways mediating the SLCR. This likely serves to enhance flexibility, ensuring that the appropriate output is produced in accord with the functional demand.
在人类中，同侧胫神经（iTN）刺激会引发短潜伏期交叉反应（SLCR），该反应由对侧腓肠肌外侧头（cGL）肌肉中的两个爆发组成。据报道，平均起始潜伏期为57 - 69毫秒，持续时间为30.4±6.6毫秒。本研究的目的是阐明经皮质通路是否对SLCR有贡献。在实验1（n = 9）中，当参与者在跑步机上行走时（SLCR与运动诱发电位（MEP）之间的延迟在 - 30至200毫秒之间变化），单独应用单脉冲阈上经颅磁刺激（supraTMS）或与iTN刺激（最大M波的85%）联合应用。在实验2（n = 6）中，进行单脉冲阈下TMS（subTMS），刺激间隔（ISI）在0 - 30毫秒之间变化。在实验3中，在iTN刺激期间记录体感诱发电位（SEP），以量化在皮质水平产生的传入冲动的潜伏期。cGL中的SLCR和MEP分别在63±6毫秒和29±2毫秒出现。平均SEP潜伏期为30±3毫秒。因此，经皮质通路在iTN刺激后最早不早于62 - 69毫秒（SEP + MEP + 中枢处理延迟）起作用。当supraTMS定时使MEP与SLCR的晚期成分重合时，联合iTN刺激和supraTMS会导致显著的MEP额外易化，而subTMS则显著抑制该成分。这是第一项证明对介导SLCR的脊髓通路存在强大皮质控制的研究。这可能有助于增强灵活性，确保根据功能需求产生适当的输出。
