Showing papers on "Delta wave published in 1994"

Effect of unilateral somatosensory stimulation prior to sleep on the sleep EEG in humans.

Abstract: SUMMARY The hypothesis that local activation of brain regions during wakefulness affects the EEG recorded from these regions during sleep was tested by applying vibratory stimuli to one hand prior to sleep. Eight subjects slept in the laboratory for five consecutive nights. During a 6-h period prior to night 3, either the left or the right hand was vibrated intermittently (20 min on-8 min off), while prior to night 5 the same treatment was applied to the contralateral hand. The sleep EEG was recorded from frontal, central, parietal and occipital derivations and subjected to spectral analysis. The interhemispheric asymmetry index (IAI) was calculated for spectral power in nonREM sleep in the frequency range 0.25-25.0 Hz for 0.5-Hz or 1-Hz bins. In the first hour of sleep following right-hand stimulation, the IAI of the central derivation was increased relative to baseline, which corresponds to a shift of power towards the left hemisphere. This effect was most prominent in the delta range, was limited to the first hour of sleep and was restricted to the central derivation situated over the somatosensory cortex. No significant changes were observed following left-hand stimulation. Although the effect was small, it is consistent with the hypothesis that the activation of specific neuronal populations during wakefulness may have repercussions on their electrical activity pattern during subsequent sleep.

Changes in Sleep and Sleep Electroencephalogram During Pregnancy

Abstract: The impairment of sleep quality is a common complaint during pregnancy. To investigate the changes in sleep in the course of pregnancy, the sleep electroencephalogram (EEG) was recorded and analyzed in nine healthy women on 2 consecutive nights during each trimester of pregnancy. Waking after sleep onset increased from the second (TR2) to the third (TR3) trimester, whereas rapid eye movement (REM) sleep decreased from the first trimester (TR1) to TR2. Spectral analysis of the EEG in nonrapid eye movement (NREM) sleep revealed a progressive reduction of power density in the course of pregnancy. In comparison to TR1, the values in TR2 were significantly lower in the 10.25-11.0-Hz and 14.25-17.0-Hz bands. In TR3, the significant reduction extended over the ranges of 1.25-12.0 Hz and 13.25-16.0 Hz. The largest decrease (30%) occurred in the 14.25-15.0-Hz band. In REM sleep, the spindle frequency range was not affected, and a minor reduction of power density in some frequency bins below 12 Hz was present only in TR3. The study documents major alterations of the sleep EEG that are not evident from the sleep scores and that may be associated with the characteristic hormonal changes occurring during pregnancy.

Short-term homeostasis of active sleep and the architecture of sleep in the rat.

Abstract: 1. Sixteen rats were recorded continuously for 3 days using an automated system that detected, quantified, and stored the incidence of cortical delta waves, cortical sigma spindles, hippocampal theta rhythm, and electromyographic activity. A time series then was constructed wherein 15-s epochs were ascribed to one behavioral state: wakefulness (W), quiet sleep (QS), or active sleep (AS, a state also referred to as REM sleep). From those series, AS episodes and non-AS intervals could be determined. Episodes and intervals were defined as lasting at least two epochs and the one-epoch episodes and intervals were incorporated to the ongoing state. 2. Having established the length of each AS episode and non-AS interval, pairings were made, on the one hand between episodes and their preceding intervals, and on the other, between episodes and the intervals that followed. 3. Highly significant correlations were found between the length of AS episodes and the length of the non-AS intervals that followed. Correlations were also significant when calculated separately versus the amount of QS and of W within the following interval. Correlations improved when they were performed against the log of the interval and when only intervals with a predominance of QS were selected. 4. No significant correlation was found between the length of AS episodes and the length of the preceding non-AS intervals, except for a negative one that was present only when the statistical analysis was performed in the unsmoothed array where the one-epoch episodes and intervals were preserved. 5. These results suggest that there is a short-term homeostasis operating within the spontaneous architecture of sleep in rats. This homeostatic mechanism is not manifested by the regulation of the length of AS episodes. Instead, there is a forward regulatory mechanism that, given the duration of an AS episode, permissively controls the interval that the animal may abstain from AS, and hence the timing of the triggering of a new AS episode.

Sleep restriction and SWS-suppression: effects on daytime alertness and night-time recovery.

Abstract: This study evaluated tile effects of sleep curtailment and SWS-suppression, respectively, on daytime alertness and subsequent night sleep. Seven subjects participated in four conditions: an undisturbed 8-h sleep (8U; 23.00-07.00 hours), an undisturbed 4-h sleep (4U; 03.00-07.00 hours), a 4-h sleep (4D; 03.00-07.00 hours) that was acoustically disturbed when delta waves appeared, and a condition with no sleep (0). Subjective sleepiness, sleep latency, and simple reaction time (RT) were measured. In addition, sleep quality was rated. 4D contained 50% of the SWS (as well as spectral slow-wave energy; SWE) compared to 8U, whereas the curtailment to 4-h did not significantly decrease SWS. 4D had lower subjective quality than the other two sleeps. The main difference in daytime sleep latency was between the 8U and the 0 conditions. Rated alertness was highest after the 8U sleep. The two 4-h sleeps did not differ significantly with respect to rated sleepiness or sleep latency. However, the effects of the 4U sleep were closer to those of the 8U sleep and the effects of the 4D sleep were closer to those of the no sleep condition. RT performance was significantly better during the 8U condition. Recovery sleep after 4D sleep contained significantly more SWS than recovery after 4U and 8U. The effects on SWE during recovery were less clear. It was concluded that sleep duration might be more important for daytime alertness than SWS content and that loss of SWS during one night is recovered during the following night.

Serial EEG and sleep polygraphic studies on lissencephaly (agyria-pachygyria)

Abstract: We carried out serial EEG studies on 12 cases of lissencephaly (6 of agyria and 6 of pachygyria), polysomnograms being recorded in 8 of the 12 cases. Fourteen Hz sleep spindles appeared from early infancy in all cases. They were poorly observed after the age of 1 year, and 5-11 Hz high-amplitude rhythmic activity (HARA) of more than 300 microV appeared predominantly in place of the 14 Hz spindles. Both the 14 Hz spindles and HARA showed asymmetry, but the dominant cerebral area for both types of waves was much the same. Four of the 6 agyria cases showed hypsarrhythmia within the first 6 months after birth, 3 of the 4 cases showing asymmetric hypsarrhythmia at first. Their hypsarrhythmia consisted of very high-voltage 5-7 Hz slow sharp waves and delta waves. The EEG abnormalities transformed from hypsarrhythmia to focal spikes in the 6 pachygyria cases. The polygraphic study on 8 cases revealed that the proportion of REM sleep decreased in 3 cases and the REMs/min values decreased in 7. Infantile spasms occurred in 4 of the 8 cases. The REM/min values decreased in all of these 4 cases, and, furthermore, the proportion of REM sleep decreased in 3 of the 4 cases. These findings suggest that lissencephaly involves a disorder of the brainstem, and that the combination of brainstem lesions and severe cerebral dysplasia is important for the manifestation of infantile spasms in lissencephaly.

Effects of tetrabamate and of diazepam on sleep polygraphy during subacute withdrawal in alcohol‐dependent patients

Abstract: We have studied the effects of two anxiolytic drugs frequently prescribed in alcohol withdrawal, diazepam and tetrabamate, on sleep polygraphy of alcohol-dependent patients hospitalized for alcohol detoxification. Twenty-three inpatients (16 M and 7F) fulfilling the DSM 3R alcohol-dependence criteria were included. Twelve patients were treated with tetrabamate and the other 11 with diazepam. Sleep polygraphy was carried out on average 15 days after alcohol withdrawal. The sleep of tetrabamate-treated patients differs from that of diazepam-treated patients in having a much longer duration of stage 4, at the expense mainly of stage 2. The two groups of patients had a greater total sleep time and duration of delta sleep than comparable untreated patients. These results suggest that the delta sleep deficit of abstinent alcoholics is paradoxically corrected by anxiolytic treatment. Tetrabamate seems to induce the production of delta waves during the sleep of abstinent alcoholics.

EEGs in cognitive stages of Alzheimer's-type dementia.

Abstract: The purpose of this study was to evaluate electroencephalogram (EEG) changes in various stages of dementia of the Alzheimer's type (DAT) through comparison with normal persons of the same age and gender. The study included 20 patients with DAT in four cognitive stages as defined by the Global Deterioration Scale (GDS) and a control group of 20 age- and gender-matched individuals without DAT. The EEGs were recorded using a Grass Model C7 Polygraph instrument and analyzed for number of alpha, beta, delta and theta waves in four leads. Statistical analysis included two-way analysis of variance (ANOVA), multiple linear regression and profile analysis. Alpha and theta waves were significant when comparing persons with DAT and control participants (p = 0.05). Delta waves were significant for group, gender and lead placement (p = 0.012). Linear regression showed a high significance between cognitive stage of the participant and alpha (p = 0.000), theta (p = 0.000) and delta (p = 0.005) waves.

Source Estimation of Auditory Evoked Responses during Sleep and Waking Using MEG.

Abstract: This study focuses on the sources of electrical activities in the brain during sleep, and in particular on the sources of auditory evoked responses, to clarify the origins of the K-complexes and delta waves. The relationships between the sources of the N100, P200 and N330 components of auditory evoked responses and sleep stages were investigated, using both magnetoencephalographic (MEG) and electroencephalographic (EEG) topographies. The sources of N100 and P200 during waking and during sleep stages 1, 2 and 3 were estimated. The sources of the N100 component for each stage were estimated at slightly different locations in the auditory area. On the basis of the results of the MEG measurements and EEG mappings, the source of the N330 components can be modeled by multiple current dipoles located in diffuse areas of the cortex.