Integrative Neuroscience, Center for Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
J Neurophysiol. 2021 Aug 1;126(2):373-382. doi: 10.1152/jn.00155.2021. Epub 2021 Jun 30.
Spatial information of nociceptive stimuli applied in the skin of healthy humans is integrated in the spinal cord to determine the appropriate withdrawal reflex response. Double-simultaneous stimulus applied in different skin sites are integrated, eliciting a larger reflex response. The temporal characteristics of the stimuli also modulate the reflex, e.g., by temporal summation. The primary aim of this study was to investigate how the combined tempo-spatial aspects of two stimuli are integrated in the nociceptive system. This was investigated by delivering single- and double-simultaneous stimulation and sequential stimulation with different interstimulus intervals (ISIs ranging 30-500 ms) to the sole of the foot of 15 healthy subjects. The primary outcome measure was the size of the nociceptive withdrawal reflex (NWR) recorded from the tibialis anterior (TA) and biceps femoris (BF) muscles. Pain intensity was measured using a numerical rating scale (NRS) scale. Results showed spatial summation in both TA and BF when delivering simultaneous stimulation. Simultaneous stimulation provoked larger reflexes than sequential stimulation in TA, but not in BF. Larger ISIs elicited significantly larger reflexes in TA, whereas the opposite pattern occurred in BF. This differential modulation between proximal and distal muscles suggests the presence of spinal circuits eliciting a functional reflex response based on the specific tempo-spatial characteristics of a noxious stimulus. No modulation was observed in pain intensity ratings across ISIs. Absence of modulation in the pain intensity ratings argues for an integrative mechanism located within the spinal cord governed by a need for efficient withdrawal from a potentially harmful stimulus. Tempo-spatial integration of electrical noxious stimuli was studied using the nociceptive withdrawal reflex and a perceived intensity. Tibialis anterior and biceps femoris muscles were differentially modulated by the temporal characteristics of the stimuli and stimulated sites. These findings suggest that spinal neurons are playing an important role in the tempo-spatial integration of nociceptive information, leading to a reflex response that is distributed across multiple spinal cord segments and governed by an efficient defensive withdrawal strategy.
应用于健康人体皮肤的伤害性刺激的空间信息在脊髓中被整合,以确定适当的退缩反射反应。应用于不同皮肤部位的双同时刺激被整合,引起更大的反射反应。刺激的时间特征也调节反射,例如通过时间总和。本研究的主要目的是研究两个刺激的联合时空方面如何在伤害性系统中被整合。这是通过向 15 名健康受试者的足底同时给予单刺激和双同时刺激以及不同的刺激间隔(ISI 范围为 30-500ms)来进行的。主要的结果测量是从前肌(TA)和股二头肌(BF)肌肉记录的伤害性退缩反射(NWR)的大小。使用数字评定量表(NRS)来测量疼痛强度。结果表明,在同时给予刺激时,TA 和 BF 均表现出空间总和。同时刺激在 TA 中引起的反射比顺序刺激大,但在 BF 中则不然。较大的 ISI 在 TA 中引起明显较大的反射,而 BF 则相反。这种近端和远端肌肉之间的差异调制表明存在脊髓回路,根据有害刺激的特定时空特征引发功能性反射反应。在 ISI 范围内,疼痛强度评分没有观察到调制。ISIs 范围内疼痛强度评分的无调制表明,位于脊髓内的整合机制受需要从潜在有害刺激中有效撤退的支配。使用伤害性退缩反射和感知强度研究了电伤害性刺激的时空整合。TA 和 BF 肌肉受到刺激的时间特征和部位的不同调制。这些发现表明,脊髓神经元在伤害性信息的时空整合中起着重要作用,导致反射反应分布在多个脊髓节段,并由有效的防御撤退策略控制。