- 著者
-
大住 倫弘
草場 正彦
中野 英樹
森岡 周
- 出版者
- 日本疼痛学会
- 雑誌
- PAIN RESEARCH (ISSN:09158588)
- 巻号頁・発行日
- vol.27, no.3, pp.165-174, 2012-08-10 (Released:2013-02-19)
- 参考文献数
- 29
Habituation to pain has been addressed in many recent studies. It is clear that patients with chronic pain do not become habituated to the pain; however, little is known about habituation to the inner experience of pain. We investigated the brain mechanisms underlying habituation to the inner experience of pain by using event-related potentials (ERPs), which provide superior temporal resolution, and low-resolution brain electromagnetic tomography (LORETA), which enables identification of regions of nervous activity. Fifteen healthy subjects participated in this study. The subjects were shown 4 sets of photographic images, with each set shown 30 times. The images included 15 images of a hand subjected to pain (painful condition). The subjects were instructed to imagine themselves in that condition and to imagine the pain they may experience in such a situation (inner experience of pain). Electroencephalography was continuously performed via 128 scalp electrodes mounted on an electrode cap. ERPs were recorded during the inner experience of pain; we also recorded N110 responses for emotional components and P3 responses for cognitive evaluation. To investigate habituation to the inner experience of pain, the mean amplitudes of P3 and N110 recordings were calculated for the first 2 (early sets) and last 2 (late sets) sets of trials for each painful condition; next, early sets were compared with late sets. We also analyzed the change in nervous activity after habituation to the inner experience of pain by LORETA analysis. The amplitude of central P3 responses was significantly lower for the late image sets than the early image sets of the painful condition. However, the mean amplitude of N110 responses did not significantly change. LORETA analysis of P3 responses showed reduced activity in the left secondary somatosensory area and left posterior insular cortex, indicating that the sensory component of the inner experience of pain was lower in the late sets than in the early sets. During habituation to the inner experience of pain, the P3 response, which is related to cognitive evaluation of this experience, changed, and brain activity, which reveals the sensory component of the inner experience of pain, reduced. Our study suggests that habituation to the inner experience of pain occurs at the point of recognition of the sensory component of pain. We hypothesize that pain recognition necessary for habituation to the inner experience of pain.