Combined effects of alcohol and sleep deprivation in normal young adults

The effect of sleep deprivation and restriction on mood, emotion, and emotion regulation: three meta-analyses in one

STUDY OBJECTIVES

New theory and measurement approaches have facilitated nuanced investigation of how sleep loss impacts dimensions of affective functioning. To provide a quantitative summary of this literature, three conceptually related meta-analyses examined the effect of sleep restriction and sleep deprivation on mood, emotion, and emotion regulation across the lifespan (i.e. from early childhood to late adulthood).

METHODS

A total of 241 effect sizes from 64 studies were selected for inclusion, and multilevel meta-analytic techniques were used when applicable.

RESULTS

There was a moderate, positive effect of sleep loss on negative mood (g = 0.45), which was stronger for studies with younger samples, as well as a large, negative effect of sleep loss on positive mood (g = -0.94). For negative mood only, studies that used total sleep deprivation had larger effect sizes than studies that restricted sleep. After correcting for publication bias, a modest but significant negative effect for sleep loss on emotion (g = -0.11) was found; the valence of emotional stimuli did not change the direction of this effect, and type of sleep manipulation was also not a significant moderator. Finally, sleep restriction had a small, negative effect on adaptive emotion regulation (g = -0.32), but no significant impact on maladaptive emotion regulation (g = 0.14); all studies on adaptive emotion regulation were conducted with youth samples.

CONCLUSIONS

Sleep loss compromises optimal affective functioning, though the magnitude of effects varies across components. Findings underscore the importance of sleep for healthy affective outcomes.

Association between work productivity and sleep health: A cross-sectional study in Japan

OBJECTIVES

To examine the impact of sleep health on work in Japan and to investigate the relationship between presenteeism and sleep health.

DESIGN

Cross sectional analysis of a questionnaire survey.

SETTING

Seventeen offices in Tokyo, Japan.

PARTICIPANTS

The study included 2897 participants, of which 1835 were men and 1062 women, aged between 18 and 76 years.

MEASUREMENTS

Productivity loss was measured using the Short Form of the Work Limitations Questionnaire (WLQ-SF).

RESULTS

The decline in productivity due to presenteeism of people with short sleep duration, between 5 and 6 h (β = 0.068, p = 0.004) and less than 5 h (β = 0.105, p < 0.001), was significantly greater compared with those with long sleep duration (7-8 h). Subjective sleep quality (β = 0.124, p < 0.001), sleep latency (β = 0.073, p < 0.001), sleep disturbance (β = 0.123, p < 0.001), use of sleep medication (β = 0.044, p = 0.007), and daytime dysfunction (β = 0.359, p = 0.001) significantly affected presenteeism. When adjusting for confounding factors, sleep duration on workdays, sleep duration on free days, mid-sleep on free days corrected for sleep debt on workdays (MSFsc), and social jet lag were not associated with presenteeism in the multiple regression analysis.

CONCLUSIONS

Sleep health is associated with presenteeism in Japan. Subjective sleep quality, daytime dysfunction, sleep disturbance, and use of sleep medicine are associated with presenteeism. Good sleep hygiene may be important for workers' productivity.

Alcohol use in shiftworkers

It has been suggested that shiftworkers may consume alcohol to help them sleep, resulting in greater consumption. A large study in Australian workers suggested that those on non-standard schedules (outside 8am-6pm, Monday-Friday) do not drink more, but are at increased odds of binge drinking (heavy periods of drinking followed by abstinence) than workers on standard schedules. However, differences in types of non-standard schedules were not examined in the study. The current study examined the alcohol intake of Australian shiftworkers on fixed and rotating shifts. Shiftworkers (n=118, age=43.4±9.9y, 68% male) on 12h-rotating (n=29), 8h-rotating (n=29), morning (n=33) and night (n=27) schedules from printing, postal, nursing and oil industries participated. They completed a Cancer Council Dietary Questionnaire, recording frequency and amount of alcohol consumed on average per day over the preceding year. They also completed a shortened Standard Shiftwork Index, including questions on shift schedule, sleep duration, tiredness, gender and age. Average alcohol consumption was 9.6±13.1 standard drinks/week. One in six reported using alcohol as a sleep aid between shifts at least sometimes and nearly one third reported consuming 12 or more drinks in 24h. Alcohol consumption was higher for males and decreased with age. Controlling for gender and age, there were no significant differences between shift types in standard drinks/week (p=0.50). However, those on 12-h rotating shifts consumed more drinks per 24h (p=0.04) and had less sleep (p<0.001). Results support the suggestion that shiftworkers are likely to binge drink, particularly younger, male workers and those on long, rotating shifts. Alcohol use in shiftworkers may put increased pressure on already vulnerable physiological systems.

Chronic escitalopram treatment attenuated the accelerated rapid eye movement sleep transitions after selective rapid eye movement sleep deprivation: a model-based analysis using Markov chains

Background

Shortened rapid eye movement (REM) sleep latency and increased REM sleep amount are presumed biological markers of depression. These sleep alterations are also observable in several animal models of depression as well as during the rebound sleep after selective REM sleep deprivation (RD). Furthermore, REM sleep fragmentation is typically associated with stress procedures and anxiety. The selective serotonin reuptake inhibitor (SSRI) antidepressants reduce REM sleep time and increase REM latency after acute dosing in normal condition and even during REM rebound following RD. However, their therapeutic outcome evolves only after weeks of treatment, and the effects of chronic treatment in REM-deprived animals have not been studied yet.

Results

Chronic escitalopram- (10 mg/kg/day, osmotic minipump for 24 days) or vehicle-treated rats were subjected to a 3-day-long RD on day 21 using the flower pot procedure or kept in home cage. On day 24, fronto-parietal electroencephalogram, electromyogram and motility were recorded in the first 2 h of the passive phase. The observed sleep patterns were characterized applying standard sleep metrics, by modelling the transitions between sleep phases using Markov chains and by spectral analysis.

Based on Markov chain analysis, chronic escitalopram treatment attenuated the REM sleep fragmentation [accelerated transition rates between REM and non-REM (NREM) stages, decreased REM sleep residence time between two transitions] during the rebound sleep. Additionally, the antidepressant avoided the frequent awakenings during the first 30 min of recovery period. The spectral analysis showed that the SSRI prevented the RD-caused elevation in theta (5–9 Hz) power during slow-wave sleep. Conversely, based on the aggregate sleep metrics, escitalopram had only moderate effects and it did not significantly attenuate the REM rebound after RD.

Conclusion

In conclusion, chronic SSRI treatment is capable of reducing several effects on sleep which might be the consequence of the sub-chronic stress caused by the flower pot method. These data might support the antidepressant activity of SSRIs, and may allude that investigating the rebound period following the flower pot protocol could be useful to detect antidepressant drug response. Markov analysis is a suitable method to study the sleep pattern.

Variations in sleep characteristics and sleep-related impairment in at-risk college drinkers: a latent profile analysis

OBJECTIVE

Sleep disturbance and heavy drinking increase risk of negative consequences in college students. Limited research exists on how they act synergistically, and the overall nature of sleep and sleep-related impairment in college student drinkers is poorly understood. A latent profile analysis was conducted on the sleep characteristics and daytime sleep-related consequences of college student drinkers who were at-risk based on Alcohol Use Disorders Identification Test-Consumption scores.

METHODS

Participants (N = 312, mean age = 18.90 (0.97) years) consumed a mean (SD) of 20.93 (13.04) drinks per week. Scores on the 10 items of the Sleep/Wake Behavior Problems Scale (SWPS) were the class indicators.

RESULTS

Four classes best described the sleep and sleep-related consequences of at-risk college drinkers. Classes represented different gradients and types of sleep patterns and sleep-related impairment; nearly half the sample reported late bedtimes and daytime consequences of insufficient sleep. Subsequent validation analyses indicated that these classes were directly correspondent with severity of alcohol consumption, alcohol-related consequences illicit substance use, and perceived health.

CONCLUSIONS

These findings indicate the presence of significant heterogeneity in college drinkers' sleep patterns and experiences of sleep-related impairment. Class differences significantly impact the level of alcohol and drug use and the consequences members experience. Greater alcohol use and sleep/wake problems are associated with increased risk for negative consequences for certain classes. These results suggest that college drinking interventions could benefit from the incorporation of sleep-related content and the value in adding brief alcohol assessments and interventions to other college health treatments.

Neurobiological consequences of sleep deprivation

Although the physiological function of sleep is not completely understood, it is well documented that it contributes significantly to the process of learning and memory. Ample evidence suggests that adequate sleep is essential for fostering connections among neuronal networks for memory consolidation in the hippocampus. Sleep deprivation studies are extremely valuable in understanding why we sleep and what are the consequences of sleep loss. Experimental sleep deprivation in animals allows us to gain insight into the mechanism of sleep at levels not possible to study in human subjects. Many useful approaches have been utilized to evaluate the effect of sleep loss on cognitive function, each with relative advantages and disadvantages. In this review we discuss sleep and the detrimental effects of sleep deprivation mostly in experimental animals. The negative effects of sleep deprivation on various aspects of brain function including learning and memory, synaptic plasticity and the state of cognition-related signaling molecules are discussed.

Involvement of the α1-adrenoceptor in sleep-waking and sleep loss-induced anxiety behavior in zebrafish

Sleep is a universal phenomenon in vertebrates, and its loss affects various behaviors. Independent studies have reported that sleep loss increases anxiety; however, the detailed mechanism is unknown. Because sleep deprivation increases noradrenalin (NA), which modulates many behaviors and induces patho-physiological changes, this study utilized zebrafish as a model to investigate whether sleep loss-induced increased anxiety is modulated by NA. Continuous behavioral quiescence for at least 6s was considered to represent sleep in zebrafish; although some authors termed it as a sleep-like state, in this study we have termed it as sleep. The activity of fish that signified sleep-waking was recorded in light-dark, during continuous dark and light; the latter induced sleep loss in fish. The latency, number of entries, time spent and distance travelled in the light chamber were assessed in a light-dark box test to estimate the anxiety behavior of normal, sleep-deprived and prazosin (PRZ)-treated fish. Zebrafish showed increased waking during light and complete loss of sleep upon continuous exposure to light for 24h. PRZ significantly increased sleep in normal fish. Sleep-deprived fish showed an increased preference for dark (expression of increased anxiety), and this effect was prevented by PRZ, which increased sleep as well. Our findings suggest that sleep loss-induced anxiety-like behavior in zebrafish is likely to be mediated by NA's action on the α1-adrenoceptor.

Influence of a conservative sleep management strategy during a solo Pacific Ocean crossing on anxiety and perceived fatigue: a case study

The aim of this case study was to determine whether a sailor's deliberate choice of a conservative strategy to manage sleep deprivation would allow him to cross the Pacific Ocean and to minimize his state of anxiety and perceived fatigue. The participant, who had more than 10 years' sailing experience in severe conditions, was tested on a small catamaran without any living quarters during a solo Pacific Ocean crossing. Estimations of sleep hours, state anxiety, and perceived fatigue were self-reported by the sailor on a daily basis using a specific questionnaire. The most important finding is that the sailor's deliberate sleep strategy, 5.4 h sleep per day (24% less than on-shore), was enough to keep his anxiety and perceived fatigue within acceptable limits and enabled him to achieve his goal, which was the first crossing of the Pacific Ocean on a catamaran of less than 6 m. In conclusion, our results suggest that the sailor observed in the present case study was able to minimize anxiety and perceived fatigue with adequate sleep to optimize his performance, security, and to achieve his goal.

Exercise prevents sleep deprivation-associated anxiety-like behavior in rats: potential role of oxidative stress mechanisms

Our previous work suggests that pharmacological induction of oxidative stress causes anxiety-like behavior in rats. Interestingly, sleep deprivation is reported to cause oxidative damage in the brain and is also reported to be anxiogenic. Minimal mechanistic insights are available. In this study, using a behavioral and biochemical approach, we investigated involvement of oxidative stress mechanisms in sleep deprivation-induced anxiety-like behavior of rats and the protective role of treadmill exercise in this process. We report that acute sleep deprivation (SD) increases oxidative stress in the cortex, hippocampus and amygdala while prior treadmill exercise prevents this increase. Serum corticosterones also increase with SD but its levels are normalized in exercised sleep-deprived rats. Also, anxiety-like behavior of rats significantly increases with SD while prior treadmill exercise prevents this increase. Protein expression of two enzymes involved in antioxidant defense, glyoxalase (GLO)-1 and glutathione reductase (GSR)-1 increased after 24h SD in the hippocampus, cortex and amygdala while their levels were normalized in exercised sleep-deprived rats. It is plausible that oxidative stress via regulation of GLO1 and GSR1 is involved in sleep deprivation-induced anxiety-like behavior of rats.

Surgical dexterity after a 'night out on the town'

BACKGROUND

This study examines the effect of alcohol intake on surgical dexterity immediately after and the morning after alcohol intake and minimal sleep deprivation by simulating a typical night out on the town.

METHODS

Five surgeons (all men, aged 31-40 years) were trained on a laparoscopic surgical simulator (minimally invasive surgical trainer-virtual reality) to reach a desired standard of performance. Three experimental settings were used: (i) a control night with no alcohol and full night's sleep; (ii) a sham night out (sleep deprived) without alcohol; and (iii) a night out with alcohol ad libitum. The parameters recorded were the average time taken to carry out a task, error rate, average diathermy time and diathermy (damage) time to main object. Comparisons between baseline readings, those in the middle of the night and those of the following morning were made by applying ANOVA methods after logarithmic transformation of the data.

RESULTS

The candidates consumed, on average, 10.33 units (range, 6-15 units) of alcohol and had 0.86% (range, 0.71-1.1%) of breath alcohol levels and an average of 3.75 h (range, 3-5 h) of sleep after a typical night out. The morning-after breath alcohol levels were 0%. There was significant deterioration in performance, as measured by all indicators, immediately after alcohol consumption. The adverse effects on time taken to complete the task and total diathermy time were still apparent the morning after. The sham night out appeared to affect only 'time parameters'. No significant changes in performance were seen in the control setting.

CONCLUSION

Both alcohol consumption and sleep deprivation adversely affect the ability to carry out surgical procedures. Our simulation study suggests that the adverse effects of alcohol intake persist the following morning.

Anxiogenic effect of sleep deprivation in the elevated plus-maze test in mice

RATIONALE

Several clinical studies demonstrate that the absence of periods of sleep is closely related to occurrence of anxiety symptoms. However, the basis of these interactions is poorly understood. Studies performed with animal models of sleep deprivation and anxiety would be helpful in the understanding of the mechanisms underlying this relationship, but some animal studies have not corroborated clinical data, reporting anxiolytic effects of sleep deprivation.

OBJECTIVES

The aim of the present study was to verify the effects of different protocols of sleep deprivation in mice tested in the elevated plus-maze and to assess the effect of chlordiazepoxide and clonidine.

METHODS

Three-month-old male mice were sleep-deprived for 24 or 72 h using the methods of single or multiple platforms in water tanks. Mice kept in their home cages were used as controls. Plus-maze behavior was observed immediately after the deprivation period.

RESULTS

Mice that were sleep-deprived for 72 h spent a lower percent time in the open arms of the apparatus than control animals. This sleep deprivation-induced anxiety-like behavior was unaffected by treatment with chlordiazepoxide (5.0 and 7.5 mg/kg IP), but reversed by an administration of 5 or 10 microg/kg IP clonidine.

CONCLUSION

The results indicate that under specific methodological conditions sleep deprivation causes an increase in anxiety-like behavior in mice exposed to the elevated plus-maze.

Behavioral and subjective effects of marijuana following partial sleep deprivation

This study tested whether performance would be more impaired when marijuana use followed partial sleep deprivation (PSD) than when marijuana use followed a typical night of sleep. Seven recreational marijuana users (mean 15 of last 30 days) completed six test sessions in a double-blind randomized within-subject design. Each session began with an overnight stay in a sleep laboratory. Bed and wake times were calculated from mean data on individual sleep diaries. Time-in-bed was either regular (mean=8.2 h) or shortened (first 65% of regular time-in-bed deprived). At 3 and 5 h after waking, daytime sleepiness was measured with self-report questionnaires and a sleep latency test. Approximately 6.5 h after waking, subjects smoked a marijuana cigarette (0.003, 2, or 3.5% delta-9 tetrahydrocannabinol [THC]). Test batteries were completed 2, 62, and 122 min after smoking ended. Sleepiness was significantly greater following PSD than after regular sleep. Following regular sleep, heart rate increases with active THC doses were comparable, but heart rate with 2% THC was significantly less elevated following PSD. Ratings of "impaired" and "stoned" increased with both THC doses after regular sleep and were further increased with 3.5% THC after PSD. High-potency marijuana increased body sway similarly across sleep conditions. There were no significant effects of marijuana or PSD, alone or in combination, on brake latency. Thus, while PSD increased the dose-dependence of THC effects on heart rate and subjective impairment, it did not enhance the effects of marijuana on standing balance and brake latency.

[Interindividual variability of contingent negative variation]

The use of CNV in clinical practice requires the choice of a standardised protocol, the constitution of reference normative data and the consideration of intra- and interindividual variability. For this purpose, we recorded CNV in 86 control subjects (44 men and 42 women, 18 to 62 years old (mean age = 34 +/- 13 years) during a reaction time paradigm with a warning signal and a 1-second S1-S2 interval. Moreover, the role of inter-stimulation interval was analysed in a group of 12 subjects through the comparison of recordings made with 1- and 3-second intervals. The CNV amplitude, its morphology and topographic distribution as well as its resolution mode and evolution through the recording were studied. The subjects' performances and their interactions with electroencephalographic data were also included in the analyses. Our results underscore the contribution of age and gender and psychological factors to CNV variability. CNV amplitude (both M1 and M2) increased and changed topographic distribution toward more central sites in older. Men had faster reaction times than women and lower post-S1 P300. Moreover, the life events-related stress and the subject's current anxiety level were accompanied by a decreased CNV amplitude.

Simulated driving performance following prolonged wakefulness and alcohol consumption: separate and combined contributions to impairment

The separate and combined effects of prolonged wakefulness and alcohol were compared on measures of subjective sleepiness, simulated driving performance and drivers' ability to judge impairment. Twenty-two males aged between 19 and 35 years were tested on four occasions. Subjects drove for 30 min on a simulated driving task under conditions determined by the factorial combination of 16 and 20 h of wakefulness and blood alcohol concentrations of 0.00 and 0.08%. The simulated driving session took place 30 min postingestion; subjects in the two alcohol conditions participated in a second 30-min driving session 90-min postingestion. Subjects made simultaneous ratings of their impairment while driving and retrospective ratings at the end of each test session. Subjective sleepiness measures were completed before and after each driving session. The combination of 20 h of prolonged wakefulness and alcohol produced significantly lower ratings of subjective sleepiness and driving performance that was worse, but not significantly so, than would be expected from the additive effects of each condition alone. Driving performance was always worse in the second driving session, during the elimination phase of alcohol metabolism, despite blood alcohol concentrations being lower than during the first driving session. There was a modest association between perceived and actual impairments in driving performance following prolonged wakefulness and alcohol. The findings suggest that the combination of prolonged wakefulness and alcohol consumption produced greater decrements in simulated driving performance than each condition alone and that drivers have only a modest ability to appreciate the magnitude of their impairment.

Enhanced tiredness among young impaired male nighttime drivers

This study focuses on the incidence and amount of tiredness among young impaired male nighttime drivers during the hours between midnight and 6 a.m. One hundred and twenty impaired drivers, aged 18-30 years, with an average blood alcohol concentration of 1.54 g/l (range 0.81-2.99 g/l) are compared to 240 sober drivers of similar age stopped by the police in roadside surveys. A questionnaire shows that the increase in median awake period during the six observation hours is gradual and directly proportional to the time of the night for both groups, while the average awake period is significantly longer and that the average previous sleep period is significantly shorter for the impaired drivers. Self-assessment of tiredness shows 30 "rested," 68 "tired," and 22 "very tired" impaired drivers and 123 "rested," 105 "tired," and 12 "very tired" sober control drivers. This difference in level of "tiredness" is also significant. The questionnaire and the results of a simple visual reaction time test show individual differences for the drivers in both groups, but the difference in mean reaction time between the impaired drivers and the sober drivers is significant. Sub-division of the impaired drivers according to their self-assessed level of "tiredness" also shows significant differences in mean reaction time. The findings of the present study support the hypothesis that tiredness is an inherent and common accident risk factor among young male impaired drivers in nighttime traffic.

Sleepiness and ethanol effects on simulated driving

Twelve healthy young men were assessed in each of four experimental conditions presented in a Latin Square design: 8-hr time in bed (TIB) and placebo, 4-hr TIB and placebo, 8-hr TIB and ethanol, and 4-hr TIB and ethanol. After consuming ethanol (0.6 g/kg) or placebo (0900-0930 hr) with 20% supplements at 1030 and 1100 hr, subjects were tested for sleepiness (Multiple Sleep Latency Test at 1000, 1200, 1400, and 1600 hr) and divided attention (1030 hr) performance on day 1, and for simulated driving and divided attention (1000-1200 and 1400-1600 hr) performance on day 2. In the morning testing, with breath ethanol concentrations (BECs) averaging 0.049%, sleepiness was increased, divided attention reaction times increased (on both days), and simulated driving performance was disturbed in the ethanol and 4-hr TIB relative to placebo. Similarly in the afternoon, with BECs averaging 0.013%, the ethanol and 4-hr TIB condition increased sleepiness and disrupted divided attention and simulated driving performance. The results show that sleepiness and low-dose ethanol combine to impair simulated automobile driving, an impairment that extends beyond the point at which BEC reaches zero. They provide a possible explanation for the incidence of alcohol-related automobile accidents at low BECs.

The use of psychophysiology to assess driver status

Twenty subjects completed an on-the-road driving experiment, consisting of two different tests conducted on two separate days. A two-part test was administered while subjects were under the influence of alcohol (BAC < = 0.05%); a four-part test was administered without alcohol consisting of a 2.5 h driving test under vigilance conditions on a quiet highway. The order of the tests was balanced across subjects. Changes in relevant physiological parameters, such as ECG and EEG, reflected changes in driver status and predicted driving impairment. Impairment of driving performance was measured in a standard driving test (SD lateral position and SD steering wheel movements) and in a recently developed car-following test (reaction to speed changes of a leading car).

Simple reaction time event-related potentials: effects of alcohol and sleep deprivation

The effects of two levels of alcohol intoxication and 30 hr of sleep deprivation on visual event-related potential (ERP) waveforms concomitant to simple reaction time (RT) were examined in 54 normal male subjects. In a previous study, we reported that alcohol and sleep deprivation each increased RT. At a 0.05 breath alcohol concentration (BAC), the combined treatments produced an additive increase in RT, whereas at a 0.08 BAC the combined treatments produced no increase beyond that seen with each alone. In this study we present the ERP findings. Sleep deprivation alone increased the latency of a 150 msec negative component (N1) of the ERP. Alcohol increased the latency of a 250 msec negative component (N2), but only in the absence of sleep deprivation. Furthermore, this increased latency of N2 was correlated with RT measures. These results suggested that sleep deprivation slowed initial stimulus detection, whereas alcohol slowed later processing and response activation.

The influence of alcohol and sleep deprivation on stimulus evaluation

The effects of alcohol and sleep deprivation on choice reaction time (RT) as a function of stimulus intensity, stimulus quality, and response compatibility were investigated. Fifty-four male subjects were assigned to one of three levels of alcohol (0.00, 0.07, or 0.10 BAC), and one of two levels of sleep deprivation (0 or 24 h). Stimulus intensity, stimulus quality, and response compatibility were varied (high or low), with RTs identified according to time on task. Significant main effects of each of the stimulus variables were present in baseline analysis, with low-level conditions producing longer RTs. Alcohol produced an overall slowing of RT. The combination of both treatments led to larger increases in RT for low stimulus quality. Sleep deprivation increased RT for high stimulus intensity. Alcohol increased RT for low stimulus intensity, but only when subjects were not sleep deprived. These results imply higher risk with degraded stimulus conditions, e.g., driving in settings of low visibility or at night.

Effects of alcohol and white noise on recall of relevant and irrelevant task components

This study examined the effects of arousal, induced by alcohol and white noise, on the free recall of intentionally learned words and incidentally learned word-locations, in the presence or absence of word-order cues. The Activation-Deactivation Adjective Check List, a self-report measure of arousal showed that noise affected the tension dimension of arousal, whereas the moderate alcohol dose primarily affected the energy dimension of arousal. That the low dose exerted an arousing effect was evidenced by an increase in tension but only when combined with noise. When word-order was randomized over trials, noise improved word-recall and counteracted the deleterious effect of the moderate alcohol dose. When order remained fixed, however, the moderate dose impaired recall, and at that dose recall was worse under noise. Location-recall was impaired by the moderate dose, and it was superior when word-order remained fixed. It was concluded that recall was influenced by arousal mechanisms and that perceived task demand and consequent effort were possible factors contributing to the obtained effects.

Ethanol-induced alterations in EEG alpha activity and apparent source of the auditory P300 evoked response potential

The relationship among topographic brain electrical activity mapping, auditory-evoked response potentials (ERPs), plasma ethanol levels and subjective reports of intoxication was examined in 4 male volunteers. The source of the auditory P300 ERP (a measure of selective attention and memory encoding) was estimated using a recently developed computer program. The effect of ethanol on the P300 wave was studied using a standard oddball paradigm both with and without a concomitant divided attention task. Ethanol (0.7 g/kg) administration produced marked increases in EEG alpha activity during the ascending limb of the blood ethanol curve. Acute ethanol administration caused a delay in the latency and a reduction in the amplitude of the auditory P300 ERP. A similar effect on P300 topography was noted in waves that were affected by the tones while the subjects also listened to a story (divided attention). After ethanol, the source of the P300 wave appeared to have shifted to a position posterior and inferior to its original location. P300 ERP's generated during the divided attention task were also disrupted and shifted to positions inferior to their original. However, the variability of the dipole vector was much greater during the divided attention task than after ethanol administration. These data demonstrate that ethanol's effects on cognitive processing skills may be similar to those produced when individuals experience distractions while concentrating on a task.

Complex event-related potentials (P300 and CNV) and MSLT in the assessment of excessive daytime sleepiness in narcolepsy-cataplexy

The P300 and contingent negative variation (CNV) evoked potential (EP) paradigms were performed by 12 untreated narcoleptics and controls immediately prior to each nap of the Multiple Sleep Latency Test (MSLT) in order to assess whether they might hold promise as rapid quantitative techniques to assess excessive daytime sleepiness. The Stanford Sleepiness Scale (SSS) was also completed across test days and immediately before and after both the evoked potential recordings and MSLT naps. MSLT findings confirmed shorter sleep latencies and frequent SOREMPs in narcoleptics and a strong mid-afternoon increase in sleepiness based upon pressure for NREM sleep in both groups. On SSS narcoleptics were sleepier and they showed greater increase in sleepiness induced by the EP tests and greater sleepiness reduction by the MSLT naps. In the P300 paradigm, narcoleptics showed smaller component P3 amplitudes and larger P1 amplitudes. In the CNV paradigm, N1 latencies were greater in narcoleptics to both S1 and S2 and the post-CNV negative component was larger: but no significant differences were seen for the main CNV measures of negativity amplitude in the first or second halves of the response. The P300 paradigm but not the CNV, therefore, appeared to be a sensitive EP measure of sleepiness. Finally, EP components in both the P300 and CNV paradigms showed time-of-day (circadian) differences between narcoleptics and controls.

Differences between REM and NREM sleepiness measured by event-related potentials (P300, CNV), MSLT and subjective estimate in narcolepsy-cataplexy

Differences between 'REM sleepiness' and 'NREM sleepiness' states in wakefulness studied respectively prior to REM-containing and NREM-only multiple sleep latency test (MSLT) naps were compared by complex evoked potentials (P300, CNV), subjective estimate (Stanford Sleepiness Scale, SSS) and MSLT measures in 12 untreated patients with narcolepsy-cataplexy. The EP paradigms lasted about 7 min each and were done during the 10 min immediately before MSLT naps at 10.00, 12.00, 14.00, 16.00 and 18.00 h. SSS forms were completed immediately before and after the EP studies and MSLT naps. Patients were studied on 2 days and performed either the P300 or CNV paradigm on each day. 'REM sleepiness' was found to be subjectively and objectively (shorter mean sleep latency on MSLT) greater. Although subjects were sleepier in REM sleepiness, the subsequent REM nap was relatively more refreshing and reduced SSS estimates to levels equivalent to those after NREM-only naps. EP measures also showed differences between the 2 sleepiness states. REM sleepiness was associated with a significantly larger P2 component (in both the P300 paradigm and the CNV paradigm), a strong but not significant trend towards reduced amplitude of the P3 component, and almost total suppression of the slow negative components of the CNV. REM sleepiness and NREM sleepiness therefore appear to be district and differentiable cerebral states.

The effect of attentional effort on visual evoked potential N1 latency

The latency of the visual evoked potential N1 component evoked by nontarget stimuli increases with an increased attention to nontarget stimuli. The latency increase seems related to a general effort at processing, rather than any early filtering. This phenomenon is illustrated in one study of hyperactive children and another of normal young adults. The literature of this phenomenon is reviewed, and various explanations are considered. It does not appear to be a result of a slow negative wave, but rather a genuine effect of one aspect of attention on N1.

Self-selected exercise intensity is unchanged by sleep loss

Sleep loss alters the perceptual response to exercise: subjects describe constant external work loads as more severe after sleep deprivation. However, since subjects cannot be "blind" to their sleep status and have knowledge of previous exertional ratings, it remains unknown if this increase in perceived exertion merely represents expectations of increased difficulty of exercise after sleep loss. As one approach to this problem, we asked 24 subjects to produce equivalent "very hard" efforts, once after normal sleep, and once after 30 h without sleep. This was done by allowing the subject, while walking at constant speed, to adjust treadmill grade, without knowledge of the actual elevation. We found that exercise at equal perceived exertion was associated with the choice of a nearly equal absolute work load after sleep deprivation as after normal sleep (17.1 vs. 17.5% grade; p = n.s.). In addition, after 10 min of exercise at the self-selected intensity, subjects displayed identical ventilation, oxygen uptake, and CO2 production. However, heart rate was significantly lower during exercise after sleep loss (170 +/- 3 vs. 178 +/- 3 b X min-1; p less than 0.001). These results suggest that previously measured increases in perceived exertion during constant-load exercise after sleep loss may be spurious.

The interaction of alcohol and stress. A review

The literature on the interaction of ethanol and stress is reviewed. Stress has amethystic properties in both experimental animals and human subjects when analgesia or various behavioral parameters were evaluated. In addition studies have shown that ethanol counteracts some effects of stress in non-alcoholic subjects. Improvement in performance and in the effective state of humans and reversal of some behavioral and pathological concomitants of stress in experimental animals have been reported. Although there is indication that ethanol improves the affective state in humans, reduction of anxiety has not been a universal finding. Recent studies have pointed out a number of variables (the drinking environment, cognitive set, mood and personality of subjects, prior experience with ethanol, sex, dose and type of beverage) which can significantly alter the effects of alcohol in human subjects. These may account for the variability in results in the literature. Although some studies have shown that alcohol ingestion increases under stressful conditions, others have failed to do so in both experimental animals and in humans. In alcoholics ethanol ingestion, in general, does not appear to relieve anxiety. In fact anxiety usually increases with time during a drinking binge. Therefore more research needs to be done to assess the validity of the anxiety-reducing theory for alcohol abuse. Possible mechanisms for the interaction of stress and alcohol are discussed.