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

目的：应用脑电(EEG)、脑磁图(MEG)、重复经颅磁刺激(RTMS)和功能磁共振成像(FMRI)等方法研究人类痛觉的电生理研究。方法：目前广泛使用的激光有CO2、Tm：YAG和Ar激光等。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，即表皮刺激(ES)，它有助于通过A三角纤维上行的信号来记录大脑活动。为了记录刺激C纤维后与第二次疼痛有关的活动，已经使用了几种方法，但最近使用的是对皮肤微小区域施加微弱的CO2激光刺激。结果：C纤维刺激后的EEG和MEG结果与刺激A Delta纤维后的相似，只是潜伏期更长。我们还研究了rTMS对急性痛觉的影响。RTMS可减轻皮内注射辣椒素引起的急性疼痛，激活C纤维，但增强激光刺激引起的急性疼痛，激活A三角纤维。在fMRI研究中，双侧丘脑、次级躯体感觉皮质(SII)、岛叶和扣带回皮质在刺激A-Delta和C纤维后均被激活。然而，在刺激C纤维后，只有一小部分区域、6/8/32区和前补充运动区(SMA)被选择性地激活。讨论：除了上述方法外，一种有希望的方法是分析一个频段的变化。这种方法可能会被用于评估持续性紧张性疼痛，如癌症疼痛，而诱发反应研究无法对其进行评估。

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.