Stationary gaze entropy predicts lane departure events in sleep-deprived drivers.

Performance decrement associated with sleep deprivation is a leading contributor to traffic accidents and fatalities. While current research has focused on eye blink parameters as physiological indicators of driver drowsiness, little is understood of how gaze behaviour alters as a result of sleep deprivation. In particular, the effect of sleep deprivation on gaze entropy has not been previously examined. In this randomised, repeated measures study, 9 (4 male, 5 female) healthy participants completed two driving sessions in a fully instrumented vehicle (1 after a night of sleep deprivation and 1 after normal sleep) on a closed track, during which eye movement activity and lane departure events were recorded. Following sleep deprivation, the rate of fixations reduced while blink rate and duration as well as saccade amplitude increased. In addition, stationary and transition entropy of gaze also increased following sleep deprivation as well as with amount of time driven. An increase in stationary gaze entropy in particular was associated with higher odds of a lane departure event occurrence. These results highlight how fatigue induced by sleep deprivation and time-on-task effects can impair drivers' visual awareness through disruption of gaze distribution and scanning patterns.

The effects of cannabis and alcohol on simulated driving: Influences of dose and experience.

BACKGROUND: Cannabis and alcohol are the most popular drugs amongst recreational users, and most prevalent in injured and deceased drivers. Clarification of the interactive effects of these drugs upon driving behaviour is critical for reducing drug-related road deaths. OBJECTIVES: The current study had two objectives, to examine the effects of cannabis and alcohol on driving performance, and identify if any differences between the effects of cannabis and alcohol on driving performance exist between regular cannabis users and non-regular cannabis users. METHODS: The project involved 80 participants (49 male, 31 female) who were abstinent recreational users of alcohol and marijuana. They participated in six experimental sessions that involved the consumption of cannabis cigarettes containing no THC, 1.8% THC or 3% THC together with the consumption of alcohol to obtain either 0% BAC, 0.03% BAC or 0.05% BAC. The six sessions were double-blind, counter-balanced, placebo-controlled and medically supervised. Forty participants were allocated to the cannabis with low alcohol (0.03% BAC) group, and 40 participants were allocated to the cannabis with high alcohol (0.05% BAC) group. Driving simulator performance was assessed at 20min post-drug administration and blood samples were taken before and after driving. RESULTS: Driving simulator performance was more impaired in the THC and alcohol combined conditions. Consistent with past research, the level of THC detected in blood is higher when THC is consumed with alcohol, than when cannabis is consumed alone, and regular cannabis users returned higher levels of THC in plasma than non-regular users. Generally, regular cannabis users displayed more driving errors than non-regular cannabis users.

Detecting impairment associated with cannabis with and without alcohol on the Standardized Field Sobriety Tests.

RATIONALE: Cannabis and alcohol are the most popular drugs amongst recreational users and most prevalent in injured and deceased drivers. The Standardized Field Sobriety Tests (SFST) are commonly used to establish impairment due to drugs and alcohol, but limited empirical evidence exists concerning the combined effects of these drugs on SFST performance. METHODS: The sample comprised 80 individuals (31 females; 49 males). Age ranged between 21 and 35 years (M = 26.5, SD = 5). Forty participants (15 females; 25 males) took part in the low alcohol condition (BAC, <0.05 %), and 40 participants (16 females; 24 males), took part in the high alcohol condition (BAC, >0.05 %). For each part of the study, two levels of ∆9-tetrahydrocannabinol (THC) were administered (1.8 and 3 % THC) or a matching placebo cigarette (0 % THC) in combination with alcohol. Performance on the SFST was assessed 30 min post-dosing. RESULTS: A number of significant differences in SFST performance were identified with 28 % of the sample failing the test (when the head movement and jerks sign was included) when low alcohol and low THC were administered together. When a higher dose of alcohol was administered with a low dose of THC, 38 % of the sample failed the test, and 35 % also failed when the high dose of alcohol was combined with a higher dose of THC. CONCLUSIONS: The current results highlight the limited ability of the SFST to identify drug consumption in the absence of any evidence of driving impairment or physiological indicators.

Examining the effect of dl-3,4-methylenedioxymethamphetamine (MDMA) and methamphetamine on the Standardized Field Sobriety Tests.

dl-3,4-methylenedioxymethamphetamine (MDMA) and methamphetamine are commonly used illicit drugs that are thought to impair driving ability. The Standardized Field Sobriety Tests (SFSTs) are utilized widely to detect impairment associated with drugs other than alcohol in drivers, although limited evidence concerning MDMA and methamphetamine consumption on SFST performance exists. The aim of this study was to evaluate whether the SFSTs were a sensitive measure for identifying the presence of the specific isomer d-methamphetamine and MDMA. In a double-blind, within-subject, counter-balanced and placebo-controlled study, 58 healthy and abstinent recreational drugs users were administered three treatments: 100mg of MDMA, 0.42 mg/kg d-methamphetamine, and placebo. For each condition the SFSTs were administered at 4 and 25 h post treatment. d-methamphetamine was not found to significantly impair SFST performance unlike MDMA, which significantly impaired SFST performance in comparison to placebo with 22% of the sample failing the test at the 4h testing time-point. No differences were observed at the 25 h testing time-point for any of the conditions. It was concluded that the SFSTs are not efficient in identifying the presence of low level d-methamphetamine, and are significantly better at detecting the presence of MDMA at the levels assessed.

The acute effects of 3,4-methylenedioxymethamphetamine and methamphetamine on driving: a simulator study.

OBJECTIVES: Illicit drugs such as MDMA and methamphetamine are commonly abused drugs that have also been observed to be prevalent in drivers injured in road accidents. Their exact effect on driving and driving behavior has yet to be thoroughly investigated. METHODS: Sixty-one abstinent recreational users of illicit drugs comprised the participant sample, with 33 females and 28 males, mean age 25.45 years. The three testing sessions involved oral consumption of 100 mg MDMA, 0.42 mg/kg methamphetamine, or a matching placebo. The drug administration was counter-balanced, double-blind, and medically supervised. At each session driving performance was assessed 3 h and 24 h post drug administration on a computerized driving simulator. RESULTS: At peak concentration overall impairment scores for driving (F(2,118)=9.042, p<0.001) and signaling (F(2,118)=4.060, p=0.020) were significantly different for the daytime simulations. Performance in the MDMA condition was worse than both the methamphetamine (p=0.023) and placebo (p<0.001) conditions and the methamphetamine condition was also observed to be worse in comparison to the placebo (p=0.055). For signaling adherence, poorer signaling adherence occurred in both the methamphetamine (p=0.006) and MDMA (p=0.017) conditions in comparison to placebo in the daytime simulations. CONCLUSIONS: The findings of this study have for the first time illustrated how both MDMA and methamphetamine effect driving performance, and provide support for legislation regarding testing for the presence of illicit drugs in impaired or injured drivers as deterrents for driving under the influence of illicit drugs.

The effect of d,l-methamphetamine on simulated driving performance.

RATIONALE: Illicit drugs such as methamphetamine are commonly abused drugs that have also been observed to be prevalent in drivers injured in road accidents. The exact effect of methamphetamine or its specific isomers on driving and driving behaviour have yet to be thoroughly investigated. METHODS: Twenty healthy recreational illicit stimulant users (ten males, ten females), aged between 21 and 34 years (mean = 24.3 years, SD = 3.4 years), attended two testing sessions involving oral consumption of 0.42 mg/kg d,l-methamphetamine or a matching placebo. The drug administration was counterbalanced, double-blind, and medically supervised. At each session, driving performance was assessed 2.5 h post-drug administration. RESULTS: Mean blood and saliva d,l-methamphetamine concentrations of approximately 90 and 400 ng/ml, respectively, at 2 h and 95 and 475 ng/ml at 3 h were observed. These levels of d,l-methamphetamine were found not to significantly impair, or improve, driving performance at the 2.5-h post-drug administration time point. CONCLUSIONS: The findings of this study illustrate that d,l-methamphetamine has no significant effect on simulated driving performance.

The acute effects of 3,4-methylenedioxymethamphetamine and d-methamphetamine on human cognitive functioning.

RATIONALE: This study investigated the acute (3-h) and 24-h post-dose cognitive effects of oral 3,4-methylenedioxymethamphetamine (MDMA), d-methamphetamine, and placebo in a within-subject double-blind laboratory-based study in order to compare the effect of these two commonly used illicit drugs on a large number of recreational drug users. METHODS: Sixty-one abstinent recreational users of illicit drugs comprised the participant sample, with 33 females and 28 males, mean age 25.45 years. The three testing sessions involved oral consumption of 100 mg MDMA, 0.42 mg/kg d-methamphetamine, or a matching placebo. The drug administration was counter-balanced, double-blind, and medically supervised. Cognitive performance was assessed during drug peak (3 h) and at 24 h post-dosing time-points. Blood samples were also taken to quantify the levels of drug present at the cognitive testing time-points. RESULTS: Blood concentrations of both methamphetamine and MDMA at drug peak samples were consistent with levels observed in previous studies. The major findings concern poorer performance in the MDMA condition at peak concentration for the trail-making measures and an index of working memory (trend level), and more accurate performance on a choice reaction task within the methamphetamine condition. Most of the differences in performance between the MDMA, methamphetamine, and placebo treatments diminished by the 24-h testing time-point, although some performance improvements subsisted for choice reaction time for the methamphetamine condition. CONCLUSIONS: Further research into the acute effects of amphetamine preparations is necessary to further quantify the acute disruption of aspects of human functioning crucial to complex activities such as attention, selective memory, and psychomotor performance.