Tran T D, Hoshiyama M, Inui K, Kakigi R
Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki 444-8585, Japan.
Clin Neurophysiol. 2003 Sep;114(9):1704-14. doi: 10.1016/s1388-2457(03)00151-2.
To investigate the effect of conditioning painful stimulation on the early somatosensory magnetic fields (SEF) of test stimulation, in order to clarify the location of the gating effect of pain on tactile response.
We used a conditioning stimulus (CS) and test stimulus (TS) paradigm. The CS was applied at the left index finger followed by the TS at the left median nerve. The interstimulus interval between the CS and TS was varied from 100 to 1000 ms. There were two sessions corresponding to two intensities of the CS, painful CS (PCS) and non-painful CS (NPCS). Early components of SEF recorded 20 (1M) and 30 ms (2M) following the TS and the components obtained 20 (1m) and 30 ms (2m) following the CS were analyzed. Each value was compared between the two sessions.
PCS and NPCS attenuated the response of the 2M but not the 1M. The effect of PCS was significantly stronger and lasted longer than that of NPCS. The 1m and 2m components did not differ between PCS and NPCS in terms of amplitude and latency.
Our data indicated that the early components of the median nerve SEF were affected by a preceding painful stimulation much more than a non-painful stimulus given on the median nerve, and that the sensory gating effect of a painful stimulation on tactile sensation lasted longer than that of a non-painful stimulation. Furthermore, our findings suggested the existence of a 'touch gate' (effect of pain on tactile sensation) at the level of the thalamus or primary somatosensory cortex (SI).
The finding suggested that the touch gate might lie in the thalamus or SI.
研究条件性痛刺激对测试刺激早期体感磁场（SEF）的影响，以阐明疼痛对触觉反应的闸门效应的位置。
我们采用了条件刺激（CS）和测试刺激（TS）范式。CS施加于左手食指，随后TS施加于左正中神经。CS与TS之间的刺激间隔从100毫秒到1000毫秒不等。有两个阶段分别对应两种强度的CS，即痛性CS（PCS）和非痛性CS（NPCS）。分析了TS后20毫秒（1M）和30毫秒（2M）记录的SEF早期成分，以及CS后20毫秒（1m）和30毫秒（2m）获得的成分。比较了两个阶段的每个值。
PCS和NPCS均减弱了2M成分的反应，但未减弱1M成分的反应。PCS的效应比NPCS显著更强且持续时间更长。在幅度和潜伏期方面，PCS和NPCS的1m和2m成分没有差异。
我们的数据表明，正中神经SEF的早期成分受先前痛刺激的影响远大于正中神经上施加的非痛刺激，并且痛刺激对触觉的感觉闸门效应持续时间比非痛刺激更长。此外，我们的研究结果提示在丘脑或初级体感皮层（SI）水平存在“触觉闸门”（疼痛对触觉的效应）。
该发现提示触觉闸门可能位于丘脑或SI。
