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内容記述 |
Cerebral activities in humans, particularly responses to various kinds of sensory stimuli, should be much changed during sleep. We used magnetoencephalography (MEG) to study the effect of sleep on cerebral activities following painful stimulation.<br /> In the first study, while the subjects were awake, non-painful and painful electrical stimulations were applied, and while asleep, painful stimulation was applied to the left index finger. During awake, five components (1M-5M) were identified following both non-painful and painful stimulation, but the 4M and 5M at around 70-100 ms and 140-180 ms, respectively, were significantly enhanced following painful stimulation. During sleep, magnetic fields recorded in stage 1 sleep and stage 2 sleep were analyzed. 1M and 2M generated in the primary somatosensory cortex (SI) did not show a significant change, 3M in SI showed a slight but significant amplitude reduction, and 4M and 5M generated in both SI and the secondary somatosensory cortex (SII) were significantly decreased in amplitude or disappeared during sleep. The 4M and 5M are complicated components generated in SI and SII ascending through both A-beta fibers and A-delta fibers. They are specifically enhanced by painful stimulation due to an increase of signals ascending through A-delta fibers, and are markedly decreased during sleep, because they much involve cognitive function.<br /> In the second study, painful intra-epidermal electrical stimulation (ES), which selectively activates A-delta fibers, was applied to the dorsum of the left hand. While awake, subjects were asked to count the number of stimuli silently (Attention) or ignore the stimuli (Control). During sleep, magnetic fields recorded in stage 1 sleep and stage 2 sleep were analyzed. The contralateral SI, bilateral SII, insular cortex, medial temporal area (MT) and cingulate cortex were activated by ES. Cortical responses in the contralateral SI, ipsilateral SII and MT, bilateral insula and cingulated cortex were significantly enhanced in Attention as compared with Control. All of these activities were significantly reduced during sleep. The present results suggested that SI, SII, insula, cingulated cortex and MT are involved in pain cognition. |
要旨・審査要旨 / Abstract, Screening Result (177.7 kB)
