Interactions between age and moderate alcohol effects on simulated driving performance

Rationale

There is a substantial body of literature documenting the deleterious effects of both alcohol consumption and age on driving performance. There is, however, limited work examining the interaction of age and acute alcohol consumption.

Objectives

The current study was conducted to determine if moderate alcohol doses differentially affect the driving performance of older and younger adults.

Methods

Healthy older (55–70) and younger (25–35) adults were tested during a baseline session and again following consumption of one of three beverages [0.0 % (placebo), 0.04 % or 0.065 % target breath alcohol concentration]. Measures of driving precision and average speed were recorded.

Results

Older adults performed more poorly on precision driving measures and drove more slowly than younger adults at baseline. After controlling for baseline performance, interactions between alcohol and age were observed following beverage consumption on two measures of driving precision with older adults exhibiting greater impairment as a result of alcohol consumption.

Conclusions

These data provide evidence that older adults may be more susceptible to the effects of alcohol on certain measures of driving performance. An investigation of mechanisms accounting for alcohol’s effects on driving in older and younger adults is required. Further evaluation using more complex driving environments is needed to assess the real-world implication of this interaction.     

MDMA (ecstasy) effects on actual driving performance before and after sleep deprivation, as function of dose and concentration in blood and oral fluid

Rationale

Experimental research has shown that 3,4-methylenedioxymethamphetamine (MDMA) can improve some psychomotor driving skills when administered during the day. In real life, however, MDMA is taken during the night, and driving may likely occur early in the morning after a night of ??raving?? and sleep loss.

Objectives

The present study assessed the effects of MDMA on road-tracking and car-following performance in on-the-road driving tests in normal traffic.

Methods

Sixteen recreational MDMA users participated in a randomized double-blind placebo-controlled four-way cross-over design. They received single, evening doses of 0, 25, 50, and 100?mg MDMA on separate occasions. Actual driving tests were conducted in the evening when MDMA serum concentrations were maximal and in the morning after a night of sleep loss.

Results

The primary measure of driving, i.e., standard deviation of lateral position (SDLP, a measure of weaving) was significantly increased during driving tests in the morning in all treatment conditions, irrespective of MDMA dose and concentration. The increments in SDLP were of high clinical relevance and comparable to those observed for alcohol at blood alcohol concentrations >0.8?mg/mL. These impairments were primarily caused by sleep loss.

Conclusions

In general, MDMA did not affect driving performance nor did it change the impairing effects of sleep loss. It is concluded that MDMA cannot compensate for the impairing effects of sleep loss and that drivers who are under the influence of MDMA and sleep deprived are unfit to drive.     

Residual effects of zopiclone 7.5 mg on highway driving performance in insomnia patients and healthy controls: a placebo controlled crossover study

Rationale

Residual effects of hypnotics on driving performance have been mainly determined in studies using a standardized driving test with healthy good sleepers. Responses to effects may differ, however, between insomniacs and healthy volunteers due to the underlying sleep disorder. In addition, a majority of insomniacs uses hypnotics chronically resulting in the development of tolerance to impairing effects. Impaired driving performance in healthy volunteers may then be an overestimation of the actual effects in insomniacs.

Objectives

The present study aims to compare the residual effects of zopiclone 7.5 mg on on-the-road driving performance of 16 middle-aged insomniacs chronically using hypnotics (chronic users), 16 middle-aged insomniacs not or infrequently using hypnotics (infrequent users), and 16 healthy, age matched, good sleepers (controls).

Methods

The study was conducted according to a 3?×?2 double-blind, placebo controlled crossover design, with three groups and two treatment conditions. Treatments were single oral doses of zopiclone 7.5 mg and placebo administered at bedtime (2330 hours). Between 10 and 11 h after administration subjects performed a standardized highway driving test.

Results

Zopiclone 7.5 mg significantly impaired on-the-road driving performance in both insomnia groups and healthy controls. The magnitude of impairment was significantly less in the chronic users group as compared with the controls.

Conclusions

The smaller magnitude of effects suggests that investigating residual effects of hypnotics in healthy volunteers may yield a minor overestimation of the actual effects in insomnia patients.     

A placebo-controlled study to assess Standardized Field Sobriety Tests performance during alcohol and cannabis intoxication in heavy cannabis users and accuracy of point of collection testing devices for detecting THC in oral fluid

Rationale

Standardized Field Sobriety Tests (SFST) and oral fluid devices are used to screen for driving impairment and roadside drug detection, respectively. SFST have been validated for alcohol, but their sensitivity to impairment induced by other drugs is relatively unknown. The sensitivity and specificity for Δ⁹-tetrahydrocannabinol (THC) of most oral fluid devices have been low.

Objective

This study assessed the effects of smoking cannabis with and without alcohol on SFST performance. Presence of THC in oral fluid was examined with two devices (Dr?ger Drug Test? 5000 and Securetec Drugwipe? 5).

Methods

Twenty heavy cannabis users (15 males and 5 females; mean age, 24.3?years) participated in a double-blind, placebo-controlled study assessing percentage of impaired individuals on the SFST and the sensitivity of two oral fluid devices. Participants received alcohol doses or alcohol placebo in combination with 400?μg/kg body weight THC. We aimed to reach peak blood alcohol concentration values of 0.5 and 0.7?mg/mL.

Results

Cannabis was significantly related to performance on the one-leg stand (p?=?0.037). Alcohol in combination with cannabis was significantly related to impairment on horizontal gaze nystagmus (p?=?0.029). The Dr?ger Drug Test? 5000 demonstrated a high sensitivity for THC, whereas the sensitivity of the Securetec Drugwipe? 5 was low.

Conclusions

SFST were mildly sensitive to impairment from cannabis in heavy users. Lack of sensitivity might be attributed to tolerance and time of testing. SFST were sensitive to both doses of alcohol. The Dr?ger Drug Test? 5000 appears to be a promising tool for detecting THC in oral fluid as far as correct THC detection is concerned.     

Effects of dexamphetamine with and without alcohol on simulated driving

Rationale

In party circuits dexamphetamine is frequently used in combination with alcohol. It is hypothesized that co-administration of dexamphetamine to alcohol might reduce the sedative effects of alcohol, but may potentiate risk-taking behaviour.

Objectives

The study was aimed at assessing the effects of alcohol, dexamphetamine and the combination of both on simulated driving and cognitive performance.

Method

Eighteen subjects participated in a randomized, crossover, placebo-controlled study employing four conditions: 10?mg dexamphetamine, 0.8?g/kg alcohol, 10?mg dexamphetamine + 0.8?g/kg alcohol, and placebo. Fundamental driving skills and risk-taking behaviour were assessed in a driving simulator. Subjects also completed vigilance and divided attention tasks, and subjective ratings.

Results

Mean BAC levels during simulated driving were between 0.91?? and 0.64??. Subjects using alcohol showed a significantly larger mean standard deviation of lateral position and shorter accepted gap time and distance. Use of alcohol or dexamphetamine + alcohol was associated with a higher frequency of red light running and collisions than the dexamphetamine or placebo conditions. Performance of vigilance and divided attention tasks was significantly impaired in the alcohol condition and, to a lesser degree, in the dexamphetamine + alcohol condition.

Conclusion

Single doses of 0.8?g/kg alcohol increased risk-taking behaviours and impaired tracking, attention and reaction time during a 3-h period after drinking when BACs declined from 0.9 to 0.2?mg/ml. The stimulatory effects of co-administration of dexamphetamine 10?mg were not sufficient to overcome the impairing effects of alcohol on skills related to driving.     

Effects of alcohol (BAC 0.5‰) and ecstasy (MDMA 100?mg) on simulated driving performance and traffic safety

Rational

An increasing number of fatal road-accidents have been reported in which ecstasy was found in the blood of drivers. Although, ecstasy is frequently found to have been used in combination with alcohol, studies on the acute effects of ecstasy co-administered with alcohol on driving performance are relatively rare.

Objective

The present study was designed to establish the extent of driver impairment as a consequence of ecstasy or combined ecstasy and alcohol use as compared to driving under the influence of 0.3??, 0.5?? and 0.8?? alcohol. Furthermore, subjective performance was also assessed.

Results

Alcohol and ecstasy mainly influenced automated driving performance such as lateral and speed control. However, small to no effects of the substances were found on more complex driving behaviour. Overall, variance within the different driving measures was high especially when participants were treated with 3.4-methylenedioxy-methamphetamine (MDMA) and alcohol. Furthermore, equivalence testing showed that combined use may lead to impaired driving for some, but not all, drivers. Participants rated their own performance to be slightly worse than normal in both studies. Since driving was actually seriously deteriorated, this was a falsely positive assessment of their condition.

Conclusions

The dissociation between subjective perceptions and objective performance decrements are important notions for traffic safety since this may affect a driver??s judgement of whether or not it is safe to drive. For example, an intoxicated individual might decide to drive because the feelings of alertness caused by MDMA cloud the impairing effects of other drugs such as alcohol, thereby creating a potentially serious risk for traffic safety.     

Effects of chronic fluoxetine treatment on serotonin 1B receptor-induced deficits in delayed alternation

Rationale

Obsessive-compulsive disorder (OCD) patients show overactivation of the orbitofrontal cortex and deficits in cognitive tasks that require proper orbitofrontal functioning including delayed alternation tests of spatial working memory. We recently showed that OCD-like behavior is induced in mice by activating orbitofrontal serotonin 1B receptors (5-HT1Bs). However, the role of 5-HT1Bs in delayed alternation remains unclear.

Objectives

We examined the effects of 5-HT1B receptor activation on delayed alternation task (DAT) performance. We also assessed the ability of an effective OCD treatment, fluoxetine, to prevent 5-HT1B-induced deficits in DAT performance.

Methods

Mice were tested on the DAT after acute treatment with saline, 3 or 6 mg/kg RU24969 (5-HT1B/1A agonist), 0.3 or 3 mg/kg 8-OH-DPAT (5-HT1A agonist), or co-injection with 3 mg/kg RU24969 and 5 mg/kg GR127935 (5-HT1B/1D antagonist). Separate mice were pretreated chronically (28 days) with 10 mg/kg fluoxetine and then tested on the DAT after acute treatment with 3 mg/kg RU24969, 0.3 mg/kg 8-OH-DPAT, or saline.

Results

Both doses of RU24969 decreased accuracy and increased latency on the DAT, and GR127935 blocked RU24969-induced effects on accuracy. The 0.3 mg/kg 8-OH-DPAT did not affect the DAT performance, whereas 3 mg/kg increased omissions on the DAT. Finally, RU24969-induced DAT deficits were absent in fluoxetine-pretreated mice.

Conclusions

We show that 5-HT1B receptor activation disrupts DAT performance in mice, and chronic fluoxetine pretreatment blocks these 5-HT1B-induced deficits. Our findings suggest that 5-HT1B receptors play an important role in modulating orbitofrontal-dependent delayed alternation. Moreover, 5-HT1B-induced DAT deficits may provide a mouse model for DAT deficits in OCD.     

Reduced Acute Recovery from Alcohol Impairment in Adults with ADHD

Rationale

Prior research has found that adults with attention-deficit/hyperactivity disorder (ADHD) show increased sensitivity to the impairing effects of alcohol (Weafer et al., Exp Clin Psychopharmacol 17: 113–121, 2009). However, these studies have focused exclusively on the ascending limb of the blood alcohol concentration (BAC) curve, and it is unclear whether these adults continue to show increased sensitivity during the later phase of the dose as BAC is declining.

Objective

This study tested the hypothesis that those with ADHD would display increased response to alcohol during the ascending limb of the BAC curve and less recovery from the impairing effects during the descending limb.

Methods

Adult social drinkers with ADHD and control adults completed measures of motor coordination, reaction time (RT), and subjective intoxication twice following 0.64 g/kg alcohol and placebo. The measures were administered during the ascending limb of the BAC curve and again during the descending limb.

Results

During the ascending limb, alcohol reduced motor coordination, slowed RT, and increased self-reports of subjective intoxication. Those with ADHD displayed greater impairment of motor coordination compared with controls. During the descending limb, controls reported diminished subjective intoxication and showed recovery from the impairing effects of alcohol on both their motor coordination and their RT. Those with ADHD showed reduced subjective intoxication and faster RT during this time, but they did not recover motor control.

Conclusions

The protracted time course of motor impairment in adults with ADHD despite reductions in subjective intoxication may contribute to poor decision making and diminished behavioral control in this group.     

Effects of three therapeutic doses of codeine/paracetamol on driving performance, a psychomotor vigilance test, and subjective feelings

Rationale

Some recent pharmacoepidemiological studies revealed an elevated risk of driving accidents after opioid analgesics uses. Among analgesics, codeine is often associated with paracetamol in numerous pharmaceutical specialties.

Objectives

The objective of this study was to evaluate the dose–effect relationship of three usual therapeutic doses of codeine/paracetamol on driving ability, psychomotor performance, subjective alertness, in link with blood concentrations in healthy young volunteers.

Methods

Driving performance, responses to psychomotor vigilance tests, and scales reflecting alertness were evaluated during the morning after drug intake in a double-blind, randomized, placebo-controlled study. Sixteen healthy volunteers (23.4?±?2.7 years old, 8 men and 8 women) participated in this balanced, cross-over study. Three doses of codeine/paracetamol (20/400, 40/800, 60/1200 mg) were evaluated against placebo. Two blood samples were collected, 1 and 4 h after drug intake. In serum, codeine and morphine concentrations were determined in serum using high-performance liquid chromatography electrospray ionization-tandem mass spectrometry, and paracetamol concentrations using fluorescence polarization immunoassay.

Results

Driving and psychomotor performance were not affected by any of the three codeine/paracetamol doses. However, significant, though modest, correlations were observed between the driving parameters and both morphine and codeine blood concentrations.

Conclusions

This study did not reveal any significant impairment in performance due to the three therapeutic doses used in healthy young volunteers. However, the relationships between drug blood concentration and behavioral measures suggest that an inter-subject variability in blood concentration may influence the power of the observed drug effect.     

Tolerance and cross-tolerance to neurocognitive effects of THC and alcohol in heavy cannabis users

Introduction

Previous research has shown that heavy cannabis users develop tolerance to the impairing effects of ??9-tetrahydrocannabinol (THC) on neurocognitive functions. Animal studies suggest that chronic cannabis consumption may also produce cross-tolerance for the impairing effects of alcohol, but supportive data in humans is scarce.

Purpose

The present study was designed to assess tolerance and cross-tolerance to the neurocognitive effects of THC and alcohol in heavy cannabis users.

Methods

Twenty-one heavy cannabis users participated in a double-blind, placebo-controlled, three-way study. Subjects underwent three alcohol-dosing conditions that were designed to achieve a steady blood alcohol concentration of about 0, 0.5, and 0.7?mg/ml during a 5-h time window. In addition, subjects smoked a THC cigarette (400???g/kg) at 3?h post-onset of alcohol dosing during every alcohol condition. Performance tests were conducted repeatedly between 0 and 7?h after onset of drinking and included measures of perceptual motor control (critical tracking task), dual task processing (divided-attention task), motor inhibition (stop-signal task), and cognition (Tower of London).

Results

Alcohol significantly impaired critical tracking, divided attention, and stop-signal performance. THC generally did not affect task performance. However, combined effects of THC and alcohol on divided attention were bigger than those by alcohol alone.

Conclusion

In conclusion, the present study generally confirms that heavy cannabis users develop tolerance to the impairing effects of THC on neurocognitive task performance. Yet, heavy cannabis users did not develop cross-tolerance to the impairing effects of alcohol, and the presence of the latter even selectively potentiated THC effects on measures of divided attention.     

Lack of tolerance to the disinhibiting effects of alcohol in heavy drinkers

Rationale

Alcohol tolerance is observed as a diminished response to a given dose as a function of repeated administrations of the drug. Research has consistently shown that heavier drinkers display reduced reactions to alcohol (i.e., tolerance) compared with lighter drinkers. However, the majority of this work has focused primarily on measures of motor performance, whereas the development of tolerance to alcohol's impairing effects on cognitive processes, such as inhibitory mechanisms of behavioral control, remains relatively unexplored.

Objective

The purpose of the present study was to examine the relationship between drinking habits and the degree to which alcohol affects drinkers' inhibitory control and motor coordination.

Methods

Fifty-two non-dependent drinkers reported their recent drinking patterns. Their inhibitory control and motor coordination were measured in response to placebo and 0.65?g/kg alcohol.

Results

Alcohol significantly impaired inhibitory control and motor coordination compared with placebo. Moreover, greater quantity and frequency of recent consumption predicted less alcohol impairment of motor coordination. However, there was no relationship between recent drinking habits and the degree of impairment of inhibitory control.

Conclusions

These findings suggest that tolerance to the disinhibiting effects of alcohol might not readily develop as a result of recent, heavy drinking.     

The effects of energy drink in combination with alcohol on performance and subjective awareness

Rationale

This study investigated the coadministration of an energy drink with alcohol to study the effects on subjective intoxication and objective performance.

Objectives

This study aims to evaluate the objective and subjective effects of alcohol versus placebo at two alcohol doses, alone and in combination with an energy drink, in a balanced order, placebo-controlled, double-blind design.

Methods

Two groups of ten healthy volunteers, mean (SD) age of 24 (6.5), participated in the study. One group consumed energy drink containing 80?mg of caffeine and the other consumed a placebo drink, with both receiving two alcohol doses (0.046 and 0.087% breathalyser alcohol concentration). Tests included breath alcohol assessment, objective measures of performance (reaction time, word memory and Stroop task) and subjective visual analogue mood scales.

Results

Participants showed significantly impaired reaction time and memory after alcohol compared to the no alcohol condition and had poorer memory after the higher alcohol dose. Stroop performance was improved with the energy drink plus alcohol combination compared to the placebo drink plus alcohol combination. Participants felt significant subjective dose-related impairment after alcohol compared to no alcohol. Neither breath alcohol concentration nor the subjective measures showed a significant difference between the energy drink and the placebo energy drink when combined with alcohol.

Conclusions

Subjective effects reflected awareness of alcohol intoxication and sensitivity to increasing alcohol dose. There were no overall significant group differences for subjective measures between energy drink and placebo groups in the presence of alcohol and no evidence that the energy drink masked the subjective effects of alcohol at either dose.     

Effects of caffeine and alcohol on mood and performance changes following consumption of lager

Rationale

The present study examined whether caffeine would modify the behavioural effects of alcohol.

Objectives

The aim of the study was to determine whether caffeine modifies the effects of alcohol on mood and psychomotor performance and to identify possible dose–response and temporal relationships.

Methods

A double-blind study examined the effects of three successive lager drinks (330 ml each) in the early afternoon on mood and psychomotor performance assessed at 30-min intervals over a 2-h period. Participants carried out a baseline session and were then randomly assigned to one of six conditions formed by combining three different doses of caffeine (0, 62.5 and 125 mg per drink) with either no alcohol or 4.3 % alcohol. One hundred and forty-six young adults (65 male, 81 female; age range 18–30 years) participated in the study. Mood (alertness, hedonic tone and anxiety) was assessed before and after performing simple reaction time and choice reaction time tasks.

Results

Alcohol was associated with higher hedonic tone (p?<?0.005), reduced anxiety (p?<?0.05) and reduced alertness (p?<?0.005). Caffeine had no modifying effect on hedonic tone or anxiety. However, the highest dose of caffeine did remove the effect of alcohol on alertness (p?<?0.05). Effects of alcohol and caffeine were found on the performance tasks (all p values?<?0.05) but these were independent effects.

Conclusions

The results from the present study confirm that caffeine does not remove the negative effects of alcohol on performance although high doses counteract the drop in subjective alertness produced by alcohol.     

Caloric restriction increases the sensitivity to the hyperphagic effect of nociceptin/orphanin FQ limiting its ability to reduce binge eating in female rats

Rationale

Several studies have documented impairments in memory processes as a result of ketamine administration; however, few studies have compared the profile of cognitive effects of ketamine to other drugs.

Objectives

The aim of this study was to compare the cognitive effects of ketamine with those of triazolam in healthy volunteers.

Methods

Doses of ketamine (0.2, 0.4 mg/kg intramuscular (i.m.)), triazolam (0.2, 0.4 mg/70 kg p.o.), and double-dummy placebos were administered to 20 volunteers under repeated measures, counterbalanced, double-blind conditions. Peak physiological, psychomotor, subjective, and cognitive effects were examined.

Results

Ketamine impaired balance when balance was assessed early in the task order, whereas triazolam impaired psychomotor coordination and divided attention irrespective of task order. Triazolam also tended to produce greater effects on working memory and episodic memory tasks than ketamine at doses that produced lower subjective effects and higher estimates of performance.

Conclusions

Ketamine produces less cognitive impairment than triazolam at doses that produced greater subjective effects. Thus ketamine does not produce the underestimation of cognitive impairment typically seen with triazolam.     

Hydrocortisone impairs working memory in healthy humans, but not in patients with major depressive disorder

Objective

Several studies have shown that stress or the administration of glucocorticoids can impair hippocampus-based declarative memory retrieval and prefrontal dependent working memory performance in healthy subjects. Major Depressive Disorder (MDD) is often characterized by memory impairment and increased cortisol secretion. Studies indicate that the impairing effects of glucocorticoids on declarative memory performance are missing in patients with MDD. The purpose of our study was to investigate whether the finding of missing effects of acute cortisol administration on memory performance in MDD is also seen when examining prefrontal-based working memory.

Methods

In a placebo-controlled study, 57 patients with MDD and 56 sex- and age-matched healthy control subjects received either placebo or 10?mg of hydrocortisone orally before memory testing. To test the verbal modality of working memory, the Word Suppression Test was applied with one negative and one neutral test part.

Results

After hydrocortisone intake, healthy subjects showed a significantly poorer working memory performance compared to placebo treatment when negative interference words were administered. In contrast, memory performance of MDD patients was not affected by hydrocortisone treatment.

Conclusions

The missing effects of glucocorticoid administration on working memory in MDD might be interpreted in the context of reduced central glucocorticoid receptor function.     

Effects of acute alcohol tolerance on perceptions of danger and willingness to drive after drinking

Rationale

Drinking and driving is associated with elevated rates of motor vehicle accidents and fatalities. Previous research suggests that alcohol impairs judgments about the dangers of risky behaviors; however, how alcohol affects driving-related judgments is less clear. Impairments have also been shown to differ across limbs of the blood alcohol concentration (BAC) curve, which is known as acute tolerance.

Objectives

The objectives of this study were to examine whether perceptions about the dangerousness of driving after drinking and willingness to drive differed across the ascending and descending limbs of the BAC curve and to test whether reductions in perceived danger were associated with willingness to drive on the descending limb.

Methods

Fifty-six participants were randomly assigned to receive either a moderate dose of alcohol (peak BAC?=?0.10 g%) or placebo. We assessed perceived dangerousness and willingness to drive at matched BACs (~0.067–0.068 g%) on the ascending and descending limbs.

Results

Both perceived danger and willingness to drive showed acute tolerance in the alcohol group. Participants judged driving to be significantly less dangerous and were more willing to drive on the descending limb compared to the ascending limb. The magnitude of change in perceived danger significantly predicted willingness to drive on the descending limb.

Conclusions

Decreased impairment associated with acute tolerance may lead individuals to underestimate the dangerousness of driving after drinking and in turn make poor decisions regarding driving. This study further emphasizes the descending limb as a period of increased risk and offers support for enhancing prevention efforts by targeting drivers at declining BAC levels.     

Decreases in recollective experience following acute alcohol: a dose–response study

Rationale

Acute alcohol intoxication induces a selective impairment of recognition memory associated with conscious recollection whilst recognition based on familiarity is left intact.

Objectives

We aimed to further elucidate the acute effects of alcohol on recognition memory by assessing three different doses of alcohol and examining the way in which this affected the recollection and familiarity components of recognition memory in comparison to a placebo group.

Methods

A double-blind independent design was used, and participants received either alcohol (0.4, 0.6 or 0.8 g/kg) or a placebo drink. Participants encoded word pairs with depth of processing manipulated under generate and read conditions. Recognition memory was assessed and recollective awareness was examined through use of the remember–know procedure.

Results

Alcohol produced a dose-dependent reduction in recognition memory associated with recollection, evidenced by decreases in the number of correctly recognised items with ‘remember’ responses compared to placebo. Recognition based on a familiarity, evidenced by ‘know’ responses, showed no differences between groups or pattern of reduction compared to the placebo group. However, a negative correlation was found between recognition based on familiarity and levels of intoxication.

Conclusions

Alcohol-induced impairments in recognition memory occur in a dose-dependent manner, specifically driven by reductions in recognition associated with conscious awareness.     

The acute effects of MDMA and ethanol administration on electrophysiological correlates of performance monitoring in healthy volunteers

Rationale

Knowing how commonly used drugs affect performance monitoring is of great importance, because drug use is often associated with compromised behavioral control. Two of the most commonly used recreational drugs in the western world, 3,4-methylenedioxymethamphetamine (MDMA or “ecstasy”) and ethanol (alcohol), are also often used in combination. The error-related negativity (ERN), correct-related negativity (CRN), and N2 are electrophysiological indices of performance monitoring.

Objectives

The present study aimed to investigate how ethanol, MDMA, and their co-administration affect performance monitoring as indexed by the electrophysiological correlates.

Methods

Behavioral and EEG data were obtained from 14 healthy volunteers during execution of a speeded choice-reaction-time task after administration of ethanol, MDMA, and combined ethanol and MDMA, in a double-blind, placebo-controlled, randomized crossover design.

Results

Ethanol significantly reduced ERN amplitudes, while administration of MDMA did not affect the ERN. Co-administration of MDMA and ethanol did not further impair nor ameliorate the effect of ethanol alone. No drug effects on CRN nor N2 were observed.

Discussion

A decreased ERN following ethanol administration is in line with previous work and offers further support for the impairing effects of alcohol intoxication on performance monitoring. This impairment may underlie maladaptive behavior in people who are under influence. Moreover, these data demonstrate for the first time that MDMA does not affect performance monitoring nor does it interact with ethanol in this process. These findings corroborate the notion that MDMA leaves central executive functions relatively unaffected.     

Effects of d-amphetamine on simulated driving performance before and after sleep deprivation

Rationale

Stimulant drugs are commonly abused and also used to promote wakefulness, yet their effects on driving performance during sleep deprivation have not been thoroughly researched in experimental studies.

Objectives

The aims were to assess the effects on fundamental driving parameters during simulated driving of two doses of d-amphetamine and further to assess the interaction between d-amphetamine and sleep deprivation.

Methods

A double-blind, placebo-controlled experiment including 18 healthy male volunteers was conducted.

Results

The participants felt more alert when taking a dose of d-amphetamine than when taking placebo, and the effect was stronger for the higher dose. However, the data did not show any evidence that taking d-amphetamine prevented the subjects from becoming successively sleepier during the night. A significant main effect of the dose was found for three out of the five primary indicators where the lower dose led to improved driving. These indicators were crossing-car reaction time, and coherence and delay from a car-following event. Regarding sleep deprivation, a main effect was found for four of the primary indicators and three of the secondary indicators. The results showed overall impaired driving with respect to standard deviation of lateral position and delay in reaction time when the sleep-deprived conditions were compared to the alert condition. We found no interactions between dose and sleep deprivation for any of the performance indicators.

Conclusions

Our results suggest that administration of d-amphetamine does not compensate for impairment of driving due to fatigue. The positive effects of 10?mg were not further improved or even sustained when increasing the dose to 40?mg.