Tadao Hori

Publications (65)91.7 Total impact

• Article: Phasic brain activity related to the onset of rapid eye movements during rapid eye movement sleep: study of event-related potentials and standardized low-resolution brain electromagnetic tomography.

  Keiko Ogawa, Takashi Abe, Hiroshi Nittono, Katuo Yamazaki, Tadao Hori
  [show abstract] [hide abstract]
  ABSTRACT: The function of rapid eye movements (REMs) during REM sleep is still a matter that is open to debate. In a previous study, we found positive brain potential (P200r) time-locked to the onset of REMs. This potential was not observed during saccades of wakefulness. In this study, we estimated the electrical generation of this potential to investigate the phasic brain activity related to REMs. Data were collected in a sleep laboratory from nine healthy university students. REMs during REM sleep were recorded during natural nocturnal sleep. Event-related potential time-locked to the onset of REMs were averaged. Standardized low-resolution brain electromagnetic tomography (sLORETA) was used to identify the current sources of P200r. The results showed that P200r have neuronal generators in the left premotor area, left primary motor and sensory cortices, left inferior parietal lobule and bilateral occipital areas (precuneus, cuneus and lingual gyrus). All these areas are known to contribute to visuomotor processing. These phasic brain activities might play a key role in explaining the function of REMs during REM sleep.
  Journal of Sleep Research 03/2010; 19(3):407-14. · 3.16 Impact Factor
• Article: Activation of fast sleep spindles at the premotor cortex and parietal areas contributes to motor learning: a study using sLORETA.

  Masako Tamaki, Tatsuya Matsuoka, Hiroshi Nittono, Tadao Hori
  [show abstract] [hide abstract]
  ABSTRACT: The present study examined whether slow and/or fast sleep spindles are related to visuomotor learning, by examining the densities of current sleep spindle activities. Participants completed a visuomotor task before and after sleep on the learning night. This task was not performed on the non-learning night. Standard polysomnographic recordings were made. After the amplitudes of slow and fast spindles were calculated, sLORETA was used to localize the source of slow and fast spindles and to investigate the relationship between spindle activity and motor learning. Fast spindle amplitude was significantly larger on the learning than on the non-learning nights, particularly at the left frontal area. sLORETA revealed that fast spindle activities in the left frontal and left parietal areas were enhanced when a new visuomotor skill was learned. There were no significant learning-dependent changes in slow spindle activity. Fast spindle activity increases in cortical areas that are involved in learning a new visuomotor skill. The thalamocortical network that underlies the generation of fast spindles may contribute to the synaptic plasticity that occurs during sleep. Activity of fast sleep spindles is a possible biomarker of memory deficits.
  Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 05/2009; 120(5):878-86. · 3.12 Impact Factor
• Article: Temporal coupling of rapid eye movements and cerebral activities during REM sleep.

  Keiko Ogawa, Takashi Abe, Hiroshi Nittono, Katuo Yamazaki, Tadao Hori
  [show abstract] [hide abstract]
  ABSTRACT: We investigated event-related potentials time locked to the onset and offset of rapid eye movements during rapid eye movement (REM) sleep. Nine healthy university students participated in this study. Data were collected in a sleep laboratory. Rapid eye movements during REM sleep were recorded during natural nocturnal sleep. Saccades during wakefulness were recorded during a visually triggered task. Event-related potentials were averaged, time-locked to the onset and offset of eye movements. During REM sleep, a lambda-like response occurred over the occipital region, time-locked to the offset of rapid eye movements (similar to what occurs during wakefulness). Moreover, we found that a positive potential (P200r) occurred at about 200ms, with the maximal amplitude over the central region and time-locked to the onset of rapid eye movements during REM sleep; this potential was not observed during wakefulness. During REM sleep, the P200r occurs with the start of rapid eye movements, and then the lambda-like response occurs after termination of the movements. We demonstrated temporal coupling of rapid eye movements and cerebral activities during REM sleep. These activities might provide a useful basis for future investigations of brain functions during REM sleep.
  Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 01/2009; 120(1):18-23. · 3.12 Impact Factor
• Article: Neural generators of brain potentials before rapid eye movements during human REM sleep: a study using sLORETA.

  Takashi Abe, Keiko Ogawa, Hiroshi Nittono, Tadao Hori
  [show abstract] [hide abstract]
  ABSTRACT: Brain activity preceding rapid eye movements (REM) during human REM sleep has remained poorly understood. Slow negative brain potential (pre-REM negativity) appears before REMs. Current sources of this potential were investigated to identify brain activity immediately preceding REMs. In this study, 22 young healthy volunteers (20-25 years old) participated. Polysomnograms were recorded during normal nocturnal sleep. Brain potentials between 200ms before and 50ms after the onset of REMs and pseudo-triggers (3000ms before the onset of REMs) were averaged. Standardized low-resolution brain electromagnetic tomography (sLORETA) was used to estimate current sources of pre-REM negativity. Pre-REM negativity appeared with the maximal amplitude at right prefrontal sites immediately before REMs. However, this negativity did not appear before pseudo-triggers. Current sources of the pre-REM negativity were estimated in the ventromedial prefrontal cortex, uncus, insula, anterior cingulated cortex, basal forebrain, parahippocampal gyrus, premotor cortex and frontal eye field. The pre-REM negativity reflects brain activity coupled with the occurrence of REMs. Results of this study suggest that emotion, memory, and motor-related brain activity might occur before REMs. Pre-REM negativity is expected to be a psychophysiological index for elucidating functions of REM sleep.
  Clinical Neurophysiology 08/2008; 119(9):2044-53. · 3.41 Impact Factor
• Article: Brain potentials related to rapid eye movements and dreaming during REM sleep: A short review of psychophysiological correlates

  Tadao HORI, Keiko OGAWA, Takashi ABE, Hiroshi NITTONO
  [show abstract] [hide abstract]
  ABSTRACT: Many sleep researchers have examined dream image-generation, which occurs during rapid eye movement (REM) sleep. Furthermore, activation of brain regions related to rapid eye movements during human REM sleep has been reported. Although recent brain imaging techniques have high spatial resolution, their temporal resolution is limited. Consequently, the spatio-temporal structures of brain activities related to rapid eye movement remain largely unknown. This article presents a short review of findings of recent studies that have used brain potentials related to rapid eye movement to examine dream image-generation processes. Brain potentials related to rapid eye movement are obtained using averaged electroencephalography (EEG) that is time-locked to the onset or offset of rapid eye movement. First, based on findings related to presaccadic and pre-REM brain potentials, we discuss why eyes move during REM sleep. Second, the relationship of lambda-like potentials, which occur immediately after the cessation of rapid eye movement, to generation of visual dream images, is discussed. Third, enhancement of gamma-band EEG activity occurring immediately after the offset of rapid eye movement is discussed in terms of information-binding of dream images. Finally in this review, preparatory activation of emotion and memory circuits before the onset of rapid eye movement is discussed in terms of contextual setting of the dream story.
  Sleep and Biological Rhythms 07/2008; 6(3):128 - 138. · 0.48 Impact Factor
• Article: Gamma band EEG activity is enhanced after the occurrence of rapid eye movement during human REM sleep

  Takashi ABE, Tatsuya MATSUOKA, Keiko OGAWA, Hiroshi NITTONO, Tadao HORI
  [show abstract] [hide abstract]
  ABSTRACT: This study investigated changes in gamma band (35–44 Hz) EEG activity associated with rapid eye movement (REM) during human REM sleep. Polysomnograms of eight healthy young volunteers were recorded during their normal nocturnal sleep using 26 scalp electrode sites. The recordings were analyzed for changes in gamma band EEG activity as a function of four sleep states (slow wave sleep, stage 2, tonic and phasic periods of the REM stage), electrode sites (six midline sites) and the time of occurrence (before and after rapid eye movement). The findings revealed that gamma band EEG activity is enhanced during REM sleep, particularly in the prefrontal regions during phasic periods of the REM stage, even after excluding the possible effects of peri-orbital activity. This result suggests that the prefrontal brain area is activated during the phasic periods of the REM stage. Moreover, results of this study show that the gamma band EEG activity is enhanced following the onset of REM. Taken together, these results suggest that enhancement of gamma band EEG activity is caused by processes such as ponto-geniculo-occipital activity, a lambda-like response and corollary discharge associated with REM.
  Sleep and Biological Rhythms 02/2008; 6(1):26 - 33. · 0.48 Impact Factor
• Source

  Available from: Masako Tamaki

  Article: Fast sleep spindle (13-15 hz) activity correlates with sleep-dependent improvement in visuomotor performance.

  Masako Tamaki, Tatsuya Matsuoka, Hiroshi Nittono, Tadao Hori
  [show abstract] [hide abstract]
  ABSTRACT: The relationship between memory enhancement and fast (13-16 Hz) versus slow (10-13 Hz) spindle activity during sleep was investigated. Standard polysomnographic recordings were conducted during an adaptation, control nonlearning, and learning night. Automatic spindle detection and measurement was utilized with visual confirmation. Participants slept in individual, temperature-controlled bedrooms in a sleep laboratory. Twelve healthy student volunteers (9 women and 3 men, mean age: 22.3 years) participated. On the learning night, participants completed a presleep learning session on a modified version of mirror-tracing task followed by a postsleep test session. No learning or test sessions were performed on the adaptation and nonlearning nights. Tracing time was reduced by 6.4 seconds (20.6% +/- 2.07%) from the presleep to the postsleep session. Mean amplitude and duration of fast spindles was greater on the learning night than on the nonlearning night (both P values < 0.05). Skill improvement and fast-spindle activity were positively correlated (density [r = 0.76, P < 0.01], amplitude [r = 0.69, P < 0.05], and duration [r = 0.67, P <0.05]). Significant correlations between fast-spindle activity and mirror-tracing performance were also evident for the nonlearning night. There was no significant relationship between mirror-tracing performance and slow-spindle activity on any night. The thalamocortical network underlying fast-spindle generation may contribute to or reflect plasticity during sleep.
  Sleep 02/2008; 31(2):204-11. · 5.05 Impact Factor
• Article: Visual emotional context modulates brain potentials elicited by unattended tones.

  Sayaka Sugimoto, Hiroshi Nittono, Tadao Hori
  [show abstract] [hide abstract]
  ABSTRACT: To examine whether brain electrical responses to environmental stimuli were influenced by emotional contexts, event-related potentials (ERPs) elicited by nonstartle probe tones were recorded from 13 student volunteers while they were viewing emotionally positive, neutral, and negative slides of the International Affective Picture System. The auditory stimuli consisted of high-deviant (2000 Hz, p=.08), low-deviant (1050 Hz, p=.08), and standard (1000 Hz, p=.84) tones with a mean onset-to-onset interval of 600 ms. Participants were told to ignore the tones. High-deviant tones elicited a larger N1 (peaking around 100 ms) when participants were viewing negative slides than when viewing positive slides. The amplitude of the P2 elicited by standard tones (peaking around 170 ms) was smaller when participants were viewing positive slides than when viewing negative and neutral slides. The amplitude of the mismatch negativity (150-200 ms) tended to reduce during positive slide presentation, but this difference appeared to be due to reduction of the P2 elicited by standard tones. These findings suggest that visually induced emotional states have a sequential effect on auditory information processing, in that the influence of negative emotion appears at an earlier stage than that of positive emotion.
  International Journal of Psychophysiology 11/2007; 66(1):1-9. · 2.14 Impact Factor
• Article: Anterior N2 predicts subsequent viewing time and interest rating for novel drawings.

  Hiroshi Nittono, Yoshie Shibuya, Tadao Hori
  [show abstract] [hide abstract]
  ABSTRACT: Event-related brain potentials (ERPs) in response to novel pictures and subsequent visual exploration were examined. Eighteen undergraduates viewed 120 novel drawings as long as they wished. ERPs were calculated separately for drawings that were viewed longer or shorter than the median viewing time of each participant. The drawings viewed longer elicited a larger anterior negativity (N2) peaking at 245 ms than the shorter viewed drawings. This effect disappeared and the overall amplitude of the N2 decreased when the same set of drawings was presented again in a subsequent interest-rating session. Drawings rated as more interesting elicited a larger N2 than did drawings rated as less interesting. This study demonstrates a type of anterior N2 that is sensitive to stimulus unfamiliarity or difficulty in encoding, which reflects a conflict between stimulus input and existing knowledge and prompts further recognition processes and visual exploration.
  Psychophysiology 10/2007; 44(5):687-96. · 3.29 Impact Factor
• Source

  Available from: Masako Tamaki

  Article: Efficacy of overnight sleep for a newly acquired visuomotor skill

  Masako TAMAKI, Hiroshi NITTONO, Tadao HORI
  [show abstract] [hide abstract]
  ABSTRACT: The present study examined the efficacy of overnight sleep for a newly acquired visuomotor skill. Twenty healthy student volunteers were randomly assigned to either the Wake or the Sleep group. Figures rotated visually to the right (rotated image) and non-rotated figures (non-rotated image) were presented alternately on a display. Participants traced the figures without looking at their hand. Prior to the experimental day, they were trained to trace the non-rotated image. On the experimental day, the Sleep group performed the learning session before retiring and the test session on the next morning. The Wake group performed the learning session in the morning and after a waking interval they performed the test session in the early evening. Tracing time for the rotated image was shortened between the learning and the test session only in the Sleep group. There was no remarkable change in performance for the non-rotated image in both groups. The present study demonstrates that one night of sleep after training is efficacious for learning a newly acquired visuomotor skill. The consolidation process supported by neural plasticity is likely to continue during subsequent night sleep.
  Sleep and Biological Rhythms 03/2007; 5(2):111 - 116. · 0.48 Impact Factor
• Source

  Available from: Madoka Takahara

  Article: Effect of voluntary attention on auditory processing during REM sleep.

  Madoka Takahara, Hiroshi Nittono, Tadao Hori
  [show abstract] [hide abstract]
  ABSTRACT: The study investigates whether there is an effect of voluntary attention to external auditory stimuli during rapid eye movement (REM) sleep in humans by measuring event-related potentials (ERPs). Using a 2-tone auditory-discrimination task, a standard 1000-Hz tone and a deviant 2000-Hz tone were presented to participants when awake and during sleep. In the ATTENTIVE condition, participants were requested to detect the deviant stimuli during their sleep whenever possible. In the PASSIVE sleep condition, participants were only exposed to the tones. ERPs were measured during REM sleep and compared between the 2 conditions. All experiments were conducted at the sleep laboratory of Hiroshima University. Twenty healthy university student volunteers. N/A. Measurements and Results: In the tonic period of REM sleep (the period without REM), P200 and P400 were elicited by deviant stimuli, with scalp distributions maximal at central and occipital sites, respectively. The P400 in REM sleep showed larger amplitudes in the ATTENTIVE condition, whereas the P200 amplitude did not differ between the 2 conditions. No effects on ERPs due to attention were observed during stage 2 sleep. The instruction to pay attention to external stimuli during REM sleep influenced the late positive potentials. Thus electrophysiologic evidence of voluntary attention during REM sleep has been demonstrated.
  Sleep 08/2006; 29(7):975-82. · 5.05 Impact Factor
• Article: REM sleep EEG pattern: Examination by a new EEG scoring system for REM sleep period

  Madoka TAKAHARA, Sakon KANAYAMA, Hiroshi NITTONO, Tadao HORI
  [show abstract] [hide abstract]
  ABSTRACT: The pattern of rapid eye movement (REM) sleep was examined using a new scoring system for electroencephalogram (EEG) stages. An all-night polysomnogram (PSG) was recorded from 12 young healthy volunteers. First, all the data were scored according to the standard criteria of Rechtschaffen and Kales’A Manual of Standardized Terminology, Techniques and Scoring System for Sleep Stages of Human Subjects (1968), and epochs of typical REM sleep were collected. The extracted data were then re-scored for each 5 s using the criteria of seven EEG stages of REM sleep: (1) alpha wave, train; (2) alpha wave, intermittent A; (3) alpha wave, intermittent B; (4) EEG flattening; (5) theta wave; (6) sawtooth wave; and (7) movement time. The results showed that the EEG flattening (4) and theta wave stages (5) occupied 92.7% of the epochs of REM sleep. The most frequent transition pattern was also between these two stages (71.1%), and these stages rarely transitioned to other stages. The number of stage continuations within 2 epochs (10 s) was largest in EEG stage 4, and those in stage 5 followed it (64.5% and 54.2%, respectively). EEG stages 4 and 5 sometimes lasted for more than 13 epochs (over 1 min). The number of stages containing sawtooth waves was less than expected, and was more frequent at the beginning than at the end of REM sleep. The distinguishing feature of the REM sleep EEG pattern was the stability of the stages of EEG flattening and theta wave, compared with the sleep onset period EEG pattern.
  Sleep and Biological Rhythms 06/2006; 4(2):105 - 110. · 0.48 Impact Factor
• Article: Self-awakening, sleep inertia, and P3 amplitude in elderly people.

  Kosuke Kaida, Keiko Ogawa, Hiroshi Nittono, Mitsuo Hayashi, Masaya Takahashi, Tadao Hori
  [show abstract] [hide abstract]
  ABSTRACT: It is well known that sleepiness is sometimes experienced in the afternoon. A short afternoon nap is thought to be effective in reducing sleepiness. However, sleep inertia occurs even after a short nap, and this could be a major risk factor for injuries from falling by the elderly. In the present study, the effect of self-awakening on sleep inertia after a 20-min. nap was examined. Nine participants (M=74.1 yr., SD=5.0 yr.) took part in the three experimental conditions: the self-awakened nap, the forced-awakened nap, and the control (no-nap) conditon. Analysis showed sleepiness and performance after the nap significantly improved compared with the control condition. P3 amplitude tended to be larger after self-awakening than after forced-awakening. The present study indicates a 20-min. nap reduces afternoon sleepiness, and the application of self-awakening may contribute to higher arousal after a nap taken by this elderly group.
  Perceptual and Motor Skills 05/2006; 102(2):339-51. · 0.49 Impact Factor
• Article: Cortical regions activated after rapid eye movements during REM sleep

  Keiko OGAWA, Hiroshi NITTONO, Tadao HORI
  [show abstract] [hide abstract]
  ABSTRACT: The present study investigated the cortical regions activated during rapid eye movement (REM) sleep by identifying the sources of electric currents of brain potentials related to rapid eye movements using low-resolution brain electromagnetic tomography (LORETA). The brain potentials measured were the lambda response (P1 and P2) during wakefulness and the lambda-like response (P1r and P2r) during REM sleep. Fifteen healthy university students participated in this study. During wakefulness, the sources of the electric current of the lambda response (P1 and P2) were estimated to be in the primary and secondary visual cortices (BA 17, 18). During REM sleep, the P1r has a source in a higher order visual area (precuneus; BA 7, 31) and P2r comes from the primary and secondary visual cortices (BA 17, 18). In addition, the density of electric current in the premotor and fronto-central regions including anterior cingulate gyrus was higher after rapid eye movements, which was a discriminative feature of REM sleep. The results of this study suggest that these activities that occur after rapid eye movements might underlie the generation of vivid visual images of dreaming.
  Sleep and Biological Rhythms 02/2006; 4(1):63 - 71. · 0.48 Impact Factor
• Article: Brain potentials before and after rapid eye movements: an electrophysiological approach to dreaming in REM sleep.

  Keiko Ogawa, Hiroshi Nittono, Tadao Hori
  [show abstract] [hide abstract]
  ABSTRACT: This study examined hypotheses regarding dreaming in rapid eye movement (REM) sleep by comparing brain potentials related to rapid eye movements in REM sleep with those in wakefulness. Within participants. Data were collected in a sleep laboratory. Fifteen healthy university students who reported having dreams frequently. Rapid eye movements in REM sleep were recorded during natural nocturnal sleep. Saccades in wakefulness were recorded during a self-paced visual search task. The presaccadic negativity before and the lambda response after eye movements were examined. It was assumed that the presaccadic negativity reflects voluntary readiness activity before eye movements, and the lambda response reflects visual information processing after saccades in wakefulness. Brain potentials were averaged, time-locked to the onset and offset of eye movements for the presaccadic negativity and the lambda response, respectively. In wakefulness, the presaccadic negativity occurred at the centroparietal site. However, no presaccadic negativity was found during REM sleep. Lambda-like responses (P1r, P2r) were observed in REM sleep over the parietooccipital site, as were the lambda responses (P1, P2) in wakefulness. The finding that rapid eye movements are initiated without preparation but elicit some neural activity in the cortical visual area suggests that rapid eye movements may trigger dream images.
  Sleep 10/2005; 28(9):1077-82. · 5.05 Impact Factor
• Source

  Available from: Masako Tamaki

  Article: Spectral analysis of the first‐night effect on the sleep‐onset period

  Masako TAMAKI, Hiroshi NITTONO, Mitsuo HAYASHI, Tadao HORI
  [show abstract] [hide abstract]
  ABSTRACT: The first-night effect (FNE) refers to the disruption of the sleep structure, which is recognized particularly on the first night of sleep in the laboratory. Difficulty in falling asleep is the most frequently reported characteristic of the FNE. We examined the FNE on the sleep-onset period (SOP) quantitatively to investigate how the wake- and the sleep-promoting systems were related to the occurrence of the FNE. Eight healthy student volunteers participated in the study. Polysomnogram recording was made for three consecutive nights. Power spectra of electroencephalogram (EEG) activities were computed by using a Fast Fourier Transform during waking and the SOP. The data obtained was divided into seven bands and the mean amplitudes in each band were calculated. On the first night, EEG amplitudes in the alpha and gamma bands were higher during waking and the SOP compared with the second and the third nights. In contrast, theta and sigma amplitudes were lower on the first night. It was suggested that the wake-promoting system was excited and the smooth activation of the sleep-promoting system was inhibited during the SOP on the first night. This phenomenon might contribute to the cause of the sleep onset difficulty, which occurs as the FNE.
  Sleep and Biological Rhythms 09/2005; 3(3):122 - 129. · 0.48 Impact Factor
• Source

  Available from: journalsleep.org

  Article: Effects of hypnagogic imagery on the event-related potential to external tone stimuli.

  Nanae Michida, Mitsuo Hayashi, Tadao Hori
  [show abstract] [hide abstract]
  ABSTRACT: The purpose of this study was to examine the influence of hypnagogic imagery on the information processes of external tone stimuli during the sleep onset period with the use of event-related potentials. Event-related potentials to tone stimuli were compared between conditions with and without the experience of hypnagogic imagery. To control the arousal level when the tone was presented, a certain criterion named the electroencephalogram stage was used. Stimuli were presented at electroencephalogram stage 4, which was characterized by the appearance of a vertex sharp wave. Data were collected in the sleep laboratory at Hiroshima University. Eleven healthy university and graduate school students participated in the study. N/A. Experiments were performed at night. Reaction times to tone stimuli were measured, and only trials with shorter reaction times than 5000 milliseconds were analyzed. Electroencephalograms were recorded from Fz, Cz, Pz, Oz, T5 and T6. There were no differences in reaction times and electroencephalogram spectra between the conditions of with and without hypnagogic imagery. These results indicated that the arousal levels were not different between the 2 conditions. On the other hand, the N550 amplitude of the event-related potentials in the imagery condition was lower than in the no-imagery condition. The decrease in the N550 amplitude in the imagery condition showed that experiences of hypnagogic imagery exert some influence on the information processes of external tone stimuli. It is possible that the processing of hypnagogic imagery interferes with the processing of external stimuli, lowering the sensitivity to external stimuli.
  Sleep 08/2005; 28(7):813-8. · 5.05 Impact Factor
• Source

  Available from: journalsleep.org

  Article: Recuperative power of a short daytime nap with or without stage 2 sleep.

  Mitsuo Hayashi, Naoko Motoyoshi, Tadao Hori
  [show abstract] [hide abstract]
  ABSTRACT: The recuperative effect of a nap of less than 30 minutes has been confirmed. Such naps consist mainly of stages 1 and 2 sleep. The present study examined whether sleep stage 1 or 2 contributed to the recuperative effect of a short nap. Repeated-measurement within-subject design. After sleep was restricted to 1.5 hours less than their usual nocturnal sleep, participants took a rest (No-nap condition) or a nap at 2:00 PM. In the nap condition, they were awakened after 5 minutes of stage 1 sleep (S1-nap condition) or 3 minutes after stage 2 sleep appeared (S2-nap condition). University sleep laboratory. Ten healthy university students (aged 19 to 24 years). Subjective mood, performance on visual detection and symbol-digit substitution tasks, and the number of slow eye movements during a performance task were measured before and after the nap or rest. In the No-nap condition, subjective mood and performance deteriorated, and Slow eye movements increased during mid-afternoon, suggesting that the post-lunch dip occurred. In contrast, subjective alertness and performance improved and slow eye movements rarely occurred in the S2-nap condition. Although subjective sleepiness and fatigue improved, performance deteriorated and slow eye movements increased in the S1-nap condition. A daytime short nap containing 3 minutes of stage 2 sleep has recuperative effects, whereas these effects are limited following only stage 1 sleep.
  Sleep 08/2005; 28(7):829-36. · 5.05 Impact Factor
• Source

  Available from: Masako Tamaki

  Article: The first‐night effect occurs at the sleep‐onset period regardless of the temporal anxiety level in healthy students

  Masako TAMAKI, Hiroshi NITTONO, Tadao HORI
  [show abstract] [hide abstract]
  ABSTRACT: The present study analyzed if the temporal change in anxiety level under the critical range of the State Trait Anxiety Inventory determines the occurrence of the first-night effect (FNE) during the sleep-onset period (SOP) in healthy adults. Polysomnogram recordings were made for three consecutive nights. Electroencephalograms (EEG) were scored for every 5 s into nine EEG stages. Regardless of the anxiety level, the smooth process of the SOP was inhibited on the first night, which was expressed as delayed attenuation of alpha waves. The FNE during the SOP occurs especially as enhanced alpha activity even when the level of anxiety is not heightened on the first-night sleep taken in unfamiliar situation.
  Sleep and Biological Rhythms 05/2005; 3(2):92 - 94. · 0.48 Impact Factor
• Source

  Available from: Masako Tamaki

  Article: Examination of the first-night effect during the sleep-onset period.

  Masako Tamaki, Hiroshi Nittono, Mitsuo Hayashi, Tadao Hori
  [show abstract] [hide abstract]
  ABSTRACT: The present study examined the first-night effect during the sleep-onset period using the 9 electroencephalogram stage scoring system. After a week of monitoring sleep-wake habits with sleep diaries and wrist actigraphy, polysomnography recording was made for 3 consecutive nights. Participants slept in their own private, individual, temperature-controlled bedroom in a sleep laboratory at the university. Eleven healthy student volunteers (5 women and 6 men, 21 to 25 years old, mean 22.7 years) who had no experience sleeping in a laboratory participated in the study. N/A. The electroencephalogram during the sleep-onset period was scored manually for every 5-second epoch into 9 electroencephalogram stages. Latencies of the electroencephalogram stages were delayed on the first night, especially during the alpha-wave intermittent stages. The average time of the alpha-wave train, intermittent (> 50%) and the electroencephalogram flattening stage increased on Night 1. Stage changes among these stages also increased on Night 1. In contrast, stage changes between the alpha-wave intermittent stage (< 50%) and the theta-wave stage increased on Night 3. Alpha-wave activity increased on Night 1, demonstrating that the activity of the wake-promoting system during the sleep-onset period was enhanced on the first night. From the second to the third night, the alpha-wave intermittent stage jumped to the theta-wave stage, omitting electroencephalogram flattening, suggesting that the electroencephalogram flattening stage is unlikely to appear during stable sleep-onset period. This is the first study to demonstrate the detail of the first-night effect during the sleep-onset period.
  Sleep 03/2005; 28(2):195-202. · 5.05 Impact Factor