Investigation of mechanisms for human pain perception and its clinical application, mainly on function of signals ascending through C fibers.

目的：利用脑电图（EEG）、脑磁图（MEG）、重复经颅磁刺激（rTMS）和功能磁共振成像（fMRI）对人体疼痛感知的电生理研究。方法：为了记录与首次疼痛相关的δ纤维刺激后的活动，现在广泛使用了几种激光器，如CO2， Tm: YAG和氩气激光器。这种活动通常被称为激光诱发电位（LEP）。我们还开发了一种新的方法，表皮刺激（ES），它可以通过A δ纤维上升的信号来记录大脑活动。为了记录与第二次疼痛相关的C纤维刺激后的活动，已经使用了几种方法，但最近使用的是应用于皮肤微小区域的微弱CO2激光刺激。结果：C纤维刺激后的脑电图和脑磁图与A纤维刺激后的脑电图和脑磁图相似，只是潜伏期更长。我们还研究了rTMS对急性疼痛感知的影响。rTMS减轻了皮内注射辣椒素引起的急性疼痛，激活了C纤维，但增强了激光刺激引起的急性疼痛，激活了A δ纤维。在fMRI研究中，双侧半球的丘脑、次级体感皮层（SII）、岛皮层和扣带皮层在A δ和C纤维刺激后都被激活。然而，只有一小部分区域，区域6/8/32和补充前运动区（SMA）在C纤维刺激后被选择性激活。讨论：除了上述方法外，在不久的将来，一种很有前途的方法是分析频段的变化。该方法可能用于评价诸如癌性疼痛等诱发反应研究无法评价的持续性强直性疼痛。

OBJECTIVE : We studied electrophysiological studies using electroencephalography (EEG), magnetoencephalography (MEG) and repetitive transcranial magnetic stimulation (rTMS) as well as functional magnetic resonance imaging (fMRI) on human pain perception.METHODS : For recording activities following A delta fiber stimulation relating to first pain, several kinds of lasers such as CO2, Tm : YAG and argon lasers are now widely used. The activity is frequently termed laser evoked potential (LEP). We also developed new method, epidermal stimulation (ES), which is useful for recording brain activities by the signals ascending through A delta fibers. For recording activities following C fiber stimulation relating to second pain, several methods have been used but weak CO2 laser stimuli applied to tiny areas of the skin were recently used.RESULTS : EEG and MEG findings following C fiber stimulation were similar to those following A delta fiber stimulation except for a longer latency. We also studied the effect of rTMS on acute pain perception. rTMS alleviated acute pain induced by intracutaneous injection of capsaicin, which activated C fibers, but it enhanced acute pain induced by laser stimulation, which activated A delta fibers. As for fMRI studies, thalamus, secondary somatosensory cortex (SII), insula and cingulate cortex in the bilateral hemispheres were activated following both A delta and C fiber stimulation. However, only a small region, area 6/8/32 and pre supplementally motor area (SMA) were selectively activated following C fiber stimulation.DISCUSSION : In addition to the above methods, one promising approach in the near future is to analyze the change of a frequency band. This method will probably be used for evaluation of continuous tonic pain such as cancer pain, which evoked response studies cannot evaluate.