Research press release


Nature Neuroscience

A specific brain activity pattern for dreaming



今回、Giulio Tononiたちの研究チームは、32人が参加する実験を行い、睡眠時の脳波検査記録をとり、睡眠中の被験者を起こして夢を見ていたかどうかを尋ね、夢を見ていた被験者に夢の内容と長さを尋ねて、レム睡眠時とノンレム睡眠時に夢を見ていることに対応する脳活動パターンの共通の変化を明らかにすることを試みた。その結果分かったのは、レム睡眠時とノンレム睡眠時のいずれの夢も脳の後部領域(Tononiたちが「後部皮質ホットゾーン」と呼ぶ領域)での低周波脳活動の強度の低下に関連していたことだった。この結果は、被験者が夢の内容または長さを思い出したかどうかと無関係だった。また、夢を見ることは、高周波脳活動の強度上昇にも関連しており、それがノンレム睡眠時に同じ後部皮質ホットゾーンから始まり、前頭部と側頭部に向けて広がっていた。レム睡眠時に夢を見た場合も前頭部と側頭部での高周波脳活動が増加していた。


A specific pattern of activity changes within a particular brain region can indicate when a person experiences a dream during both rapid eye movement (REM) sleep and non-REM (NREM) sleep, reports a paper published online this week in Nature Neuroscience. The study challenges the current understanding of the pattern of brain activity that corresponds with dreaming.

Dreaming is often associated with increased high-frequency brain activity - measured with electroencephalography (EEG) - during REM sleep, whereas the absence of dreaming is typically linked with increased low-frequency brain activity during NREM sleep. However, there are studies that describe people waking from NREM sleep and reporting dreams and, conversely, people who deny dreaming when awakened from REM sleep.

Giulio Tononi and colleagues took EEG recordings from 32 sleeping people who were awakened and then asked to report the presence or absence of a dream, as well as the dream’s content and duration, to try to identify a shared pattern of brain activity changes that corresponds to dreaming in both REM and NREM sleep. They found that, during both forms of sleep, dreaming was associated with decreased strength of low-frequency brain activity within a region at the back of the brain (which the authors dub the posterior cortical hot zone), regardless of whether the participants could recall the dreams’ content or duration. Dreaming was also associated with increased strength of high-frequency activity, starting in the same posterior cortical hot zone and spreading towards frontal and temporal regions during NREM sleep. Frontal and temporal regions also showed more high-frequency activity during dreaming in REM sleep.

In a different group of seven participants, who were experienced in providing detailed reports on dream content, the authors found increased high-frequency activity during REM sleep in brain regions that are normally recruited to process real sensory stimuli like faces or speech, but specifically when a dream contained these elements. Finally, the authors show that this combination of decreased low-frequency and increased high-frequency activity strength in the posterior hot zone can be used to predict, in real time, when a person is dreaming during NREM sleep with about 90% accuracy.

doi: 10.1038/nn.4545

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