2001 Fiscal Year Final Research Report Summary
Occurrence of Sleepiness and Mechanism of Attention during Sleep
| Project/Area Number |
11301003
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
実験系心理学
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
HORI Tadao Hiroshima University, Faculty of Integrated Arts and Sciences, Professor, 総合科学部, 教授 (10020132)
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| Co-Investigator(Kenkyū-buntansha) |
NITTONO Hiroshi Hiroshima University, Faculty of Integrated Arts and Sciences, Research Associate, 総合科学部, 助手 (20304371)
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| Project Period (FY) |
1999 – 2001
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| Keywords | sleep / sleep onset period / REM sleep / attention / neural mechanism / electroencephalogram / event-related potential / autonomic nervous system |
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| Research Abstract |
Attention mechanism (or environment monitoring system) during sleep was investigated in normal young adults using non-invasive psychophysiological measures. First, sleep onset period was classified into five stages according to characteristic patterns of electroencephalogram (EEG). Event-related potentials (ERPs) were recorded to examine the responsiveness to auditory stimuli at each EEG stage. When alpha waves characteristics of wakefulness flattened and theta waves characteristics of sleep emerged, wake-specific ERPs (e.g., mismatch negativity and P300) disappeared and sleep-specific ERPs (e.g., P200 and P400) appeared. Unlike the wake-specific ERPs, the sleep-specific ERPs were evoked independently of voluntary attention to the stimuli, indicating that they were exogenous components. Similar sleep-specific ERPs were observed also in stage 2 sleep and REM sleep. In subsequent studies, the relationship between the change of central nervous system and that of autonomic nervous system w
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as examined. Heart rate and blood pressure were recorded continuously during a daytime nap. Heart rate increased a few minute before awakening, suggesting that preparation for awakening progressed internally during sleep. This heart rate change was accompanied with a sustaining light sleep characterized by early EEG stages, whereas blood pressure did not show any corresponding change. On the basis of these findings, we proposed the following model of attention during sleep :
(1) In the wake-sleep transition period, directing attention voluntarily to environmental events becomes difficult. Neural mechanism of attention during wakefulness is replaced by a sleep-specific mechanism that detects infrequent events automatically.
(2) This sleep-specific neural mechanism works all night (in both non-REM and REM sleep) for monitoring whether an unusual event occurs in the environment, although the sensitivity of this system is lower than that in wakefulness.
(3) The switching of neural mechanisms from wakefulness to sleep is partly associated with the change of autonomic nervous activities. Less
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