The acute effects of d-amphetamine and methamphetamine on attention and psychomotor performance

Trait anger as a predictor of dangerous driving behaviour amongst people who use methamphetamine

INTRODUCTION

Despite increased prevalence of methamphetamine in road trauma, it remains unclear how its use translates to an increased risk of traffic-related harm. Exploration of psychosocial factors may thus help identify relevant predictors of dangerous driving behaviour among people who regularly consume methamphetamine.

METHODS

Licenced individuals who report predominant and sustained methamphetamine use (at least 1-time/month for 6 months at heaviest use) were recruited from the Australian community and via targeted campaign (Eastern Health). Psychosocial, substance use and driving behaviour data (Dula Dangerous Driving Index, DDDI) were collected via a secure anonymous online forced-entry survey platform (Qualtrics).

RESULTS

Seventy-seven individuals (65.5 % male) aged between 20-50 years [mean = 29.7, ± Standard Deviation (SD) 6.1] were included. Most (90 %) respondents met criteria for problematic methamphetamine use [Severity of Dependency Scale (SDS) score ≥ 5], and 75 % were high-risk alcohol consumers [Alcohol Use Disorders Identification Test (AUDIT-C) score ≥ 4 for men and ≥ 3 for women]. On average, age of first methamphetamine use occurred at 23.3 years (±5.2). A best-possible subset's regression selection method with dangerous driving behaviour as the dependent variable determined the model with three predictors (alcohol use, substance dependence severity and trait anger) as most parsimonious. After controlling for substance use, trait anger strongly and positively predicted dangerous driving behaviour as measured by the DDDI ([F(3,74) = 26.06, p < .001, adjusted R2 = 0.50, Cohens f2 = 0.42).

DISCUSSION AND CONCLUSIONS

Trait anger is a strong predictor of risky driving among road users who use methamphetamine. Interactions between stable negative-emotional and situational traffic and driving-related factors may increase risk of harm through greater engagement in risk-taking behaviour.

Acetaldehyde-mediated increase in glutamatergic and N-acetylaspartate neurometabolite levels in the midcingulate cortex of ALDH2*1/*2 heterozygous young adults

BACKGROUND

To elucidate the neurobiology underlying alcohol's effect on the human brain, we examined the acute effects of moderate alcohol administration on levels of glutamatergic neurometabolites and N-acetylaspartate, an amino acid found in neurons, may reflect disordered neuronal integrity.

METHODS

Eighteen healthy Japanese participants (7 males/11 females) aged 20-30 years who were heterozygous for an inactive allele of acetaldehyde dehydrogenase-2 (ALDH/*1/*2) were included. Participants underwent an intravenous alcohol infusion using the clamp method at a target blood alcohol concentration (BAC) of 0.50 mg/mL for 90 min within a range of ±0.05 mg/mL. We examined glutamate + glutamine (Glx) and N-acetylaspartate N-acetylaspartylglutamate (NAA) levels in the midcingulate cortex (MCC) using 3 T 1 H-MRS PRESS at baseline, 90 min, and 180 min (i.e., 90 min after alcohol infusion was finished). A two-way repeated-measures analysis of variance was used to assess longitudinal changes in Glx and NAA levels, with time and sex as within- and between-subject factors, respectively. Pearson's correlation coefficients were calculated among neurometabolite levels and BAC or blood acetaldehyde concentration (BAAC).

RESULTS

Both Glx (F(2,32) = 8.15, p = 0.004, η2  = 0.15) and NAA (F(2,32) = 5.01, p = 0.04, η2  = 0.07) levels were increased after alcohol injection. There were no sex or time × sex interaction effects observed. NAA levels were positively correlated with BAAC at 90 min (r(13) = 0.77, p = 0.01). There were no associations between neurometabolite levels and BAC.

CONCLUSIONS

Both Glx and NAA levels in the MCC increased in response to the administration of moderate concentrations of alcohol. Given positive associations between NAA levels and BAAC and the hypothetical glutamate release via dopamine pathways, the effects of drinking on the MCC in the acute phase may be ascribed to acetaldehyde metabolized from alcohol.

Acute neurocognitive and subjective effects of oral methamphetamine with low doses of alcohol: A randomised controlled trial

BACKGROUND

Methamphetamine is often recreationally co-consumed with alcohol due to desirable off-target effects; however, the acute neurocognitive and subjective consequences of combined use are unclear.

METHODS

In a randomised, placebo-controlled, counterbalanced, cross-over study design, the effects of acute oral methamphetamine (0.42 mg/kg) were assessed with and without low doses of alcohol (target 0.04% blood-alcohol concentration, BAC) on subjective intoxication, alertness, physiological outcomes and neurocognition during the ascending and descending phases of the BAC curve. Sixteen healthy adults (mean age = 30.4 years, SD ± 4.4, 67% male) completed four experimental sessions over 4 weeks involving a one-week washout period.

RESULTS

Cardiovascular measures [heart rate (beats/minute), blood pressure (mmHg)] were predictably elevated following methamphetamine, but unaffected by combined alcohol use. Methamphetamine and alcohol produce divergent effects on subjective alertness and sedation across time, yet their combination produced predominantly sustained stimulative effects independent of the biphasic alcohol curve. At a peak BAC of 0.029%, alcohol alone impaired performance across most functional neurocognitive domains relative to placebo and methamphetamine only, and the addition of methamphetamine attenuated these effects. Methamphetamine alone produced isolated improvement in psychomotor speed consistent with peak drug effects.

CONCLUSION

Methamphetamine combined with alcohol does not substantially alter the physiological or metabolic profile compared to either drug alone. Strong stimulative effects of methamphetamine appear to mask the biphasic sedative and performance effects of low doses of alcohol, which may underlie motivations for co-consumption in recreational settings and increase propensity for harm.

The effects of caffeine and d-amphetamine on spatial span task in healthy participants

Studies that examined the effect of amphetamine or caffeine on spatial working memory (SWM) and verbal working memory (VWM) have used various tasks. However, there are no studies that have used spatial span tasks (SSTs) to assess the SWM effect of amphetamine and caffeine, although some studies have used digit span tasks (DST) to assess VWM. Previous reports also showed that increasing dopamine increases psychosis-like experiences (PLE, or schizotypy) scores which are in turn negatively associated with WM performance in people with high schizotypy and people with schizophrenia. Therefore, the present study aimed to examine the influence of d-amphetamine (0.45 mg/kg, PO), a dopamine releasing stimulant, on SST, DST, and on PLE in healthy volunteers. In a separate study, we examined the effect of caffeine, a nonspecific adenosine receptor antagonist with stimulant properties, on similar tasks.

METHODS

Healthy participants (N = 40) took part in two randomized, double-blind, counter-balanced placebo-controlled cross-over pilot studies: The first group (N = 20) with d-amphetamine (0.45 mg/kg, PO) and the second group (N = 20) with caffeine (200 mg, PO). Spatial span and digit span were examined under four delay conditions (0, 2, 4, 8 s). PLE were assessed using several scales measuring various aspects of psychosis and schizotypy.

RESULTS

We failed to find an effect of d-amphetamine or caffeine on SWM or VWM, relative to placebo. However, d-amphetamine increased a composite score of psychosis-like experiences (p = 0.0005), specifically: Scores on Brief Psychiatric Rating Scale, Perceptual Aberrations Scale, and Magical Ideation Scale were increased following d-amphetamine. The degree of change in PLE following d-amphetamine negatively and significantly correlated with changes in SWM, mainly at the longest delay condition of 8 s (r = -0.58, p = 0.006).

CONCLUSION

The present results showed that moderate-high dose of d-amphetamine and moderate dose of caffeine do not directly affect performances on DST or SST. However, the results indicate that d-amphetamine indirectly influences SWM, through its effect on psychosis-like experiences.

TRIAL REGISTRATION

CLINICAL TRIAL REGISTRATION NUMBER

CT-2018-CTN-02561 (Therapeutic Goods Administration Clinical Trial Registry) and ACTRN12618001292268 (The Australian New Zealand Clinical Trials Registry) for caffeine study, and ACTRN12608000610336 for d-amphetamine study.

A 6-Month Follow-Up Study: Cognitive Impairment May Predict More Frequent Use of Methamphetamine

Objectives

Methamphetamine (METH) use has been associated with impairments in a variety of cognitive functions. In this study, it was aimed to assess the relation between cognitive measures and frequency of METH use.

Methods

Ninety-eight participants with methamphetamine use disorder were assessed with Wisconsin Card Sorting Test (WCST), Victoria-Stroop Word Color Test (SWCT), Trail Making Test (TMT) A and B. Participants were followed up during 6-month period with multiple urine toxicology tests (at baseline, month 1, month 2, month 3 and month 6).

Results

Participants who had their prescriptions regularly were more likely to have higher rates of METH-negative urine results (P = .003). Participants who had more correct numbers, completed more categories and had more conceptual level responses on WCST were more likely to use lower frequency of METH (OR = 0.006, P < .01; OR = 0.171, P < .001; OR = 0.024, P < .001; respectively). The higher error numbers and perseverative error rates on WCST were associated with more frequent METH use (OR = 0.023, P < .001; OR = 0.076, P < .001). Interference factor on SWCT was related with lower frequency of METH use whereas color naming factor on SWCT was related with higher rates of urine results (OR = 0.012, P < .001; OR = 3.628, P < .001; respectively). Higher TMT B-A score was related with more frequent METH use, although the significance disappeared after adjustment (OR = 0.002, P < .001). Having psychotic symptoms predicted less frequent use, but after adjustment for other significant variables, there was no significance.

Conclusion

Lower frequency of METH use in the follow-up could be predicted by neurocognitive assessments. Deficits in executive functions, attention, set-shifting and mental flexibility seems to be the most effected domains and this effect may be independent from the severity of psychotic symptoms.

Pharmacological effects of methylone and MDMA in humans

Methylone is one of the most common synthetic cathinones popularized as a substitute for 3,4-methylenedioxymethamphetamine (MDMA, midomafetamine) owing to its similar effects among users. Both psychostimulants exhibit similar chemistry (i.e., methylone is a β-keto analog of MDMA) and mechanisms of action. Currently, the pharmacology of methylone remains scarcely explored in humans. Herein, we aimed to evaluate the acute pharmacological effects of methylone and its abuse potential in humans when compared with that of MDMA following oral administration under controlled conditions. Seventeen participants of both sexes (14 males, 3 females) with a previous history of psychostimulant use completed a randomized, double-blind, placebo-controlled, crossover clinical trial. Participants received a single oral dose of 200 mg of methylone, 100 mg of MDMA, and a placebo. The variables included physiological effects (blood pressure, heart rate, oral temperature, pupil diameter), subjective effects using visual analog scales (VAS), the short form of the Addiction Research Center Inventory (ARCI), the Evaluation of Subjective Effects of Substances with Abuse Potential questionnaire (VESSPA-SSE), and the Sensitivity to Drug Reinforcement Questionnaire (SDRQ), and psychomotor performance (Maddox wing, psychomotor vigilance task). We observed that methylone could significantly increase blood pressure and heart rate and induce pleasurable effects, such as stimulation, euphoria, wellbeing, enhanced empathy, and altered perception. Methylone exhibited an effect profile similar to MDMA, with a faster overall onset and earlier disappearance of subjective effects. These results suggest that abuse potential of methylone is comparable to that of MDMA in humans. Clinical Trial Registration: https://clinicaltrials.gov/ct2/show/NCT05488171; Identifier: NCT05488171.

The prevalence of substance use among drivers with traffic injuries in Mazandaran Province, Northern Iran

Background

Motor vehicle accidents (MVAs) are one of the main causes of mortality in developing countries. Although the association between alcohol and the risk of MVA has been known for a long time, only a few studies have been conducted on driving following substance consumption in a short period of time. This is while narcotic and stimulant use seems to be a threat to traffic safety and a serious health concern for substance users. In this study, we investigated the prevalence of substance use (narcotics and stimulants) in drivers with traffic injuries admitted to the orthopedic ward of Imam Khomeini Hospital between October 2020 and June 2021.

Methods

The current research is a cross-sectional, descriptive-analytical study. The statistical population consisted of 77 patients admitted to the orthopedic ward of a training hospital (Imam Khomeini) in Mazandaran Province, northern Iran. The Shapiro-Wilk test was used to determine the quantitative variables. The sampling method is random and consecutive. The method of data collection was through questionnaire tools. The software used was SPSS 26 with an independent t-test, Mann–Whitney U test, Chi-square or Fisher's exact test.

Results

In this study, the frequency of substance use was 18.18%. The prevalence of opioid usage was 35.7% and for stimulants it was 64.28%. There was no case of concomitant use of opioids and stimulants. In the opioid group, 60% of patients used opium, 20% methadone, and 20% tramadol. In the stimulant and alcohol groups, 12.12% utilized methamphetamine and 88.88% drank alcohol. The average age of consumers was 39 years, which was significantly higher in the opioid group (P = 0.040). The education level of substance users was remarkably lower (P < 0.05) and, occupationally, there was no statistically significant difference between groups of substance users (P = 0.290). Considerably, the unemployed population consumed more substances (P = 0.001). Multiple fractures (P < 0.05) and surgical treatment (P = 0.012) were more common in the user group.

Conclusion

Users of stimulants and alcohol were younger than opioid users, according to our results. There is an association between drug use and the incidence of traffic accidents, as well as lower educational levels, masculinity, fracture type, and patient complication type.

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Association between drug use and the incidence of traffic accidents.

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Substance use has the ability to disrupt attention.

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Most drivers who suffer from severe accidents can be caused by the Substance use.

Human behavioral pharmacology of stimulant drugs: An update and narrative review

Stimulant use disorders present an enduring public health concern. Chronic stimulant use is associated with a range of health problems, with notable increases in stimulant overdose that disproportionately affect marginalized populations. With these persistent problems, it is important to understand the behavioral and pharmacological factors that contribute to stimulant use in humans. The purpose of this chapter is to provide an update and narrative review on recent human laboratory research that has evaluated the behavioral pharmacology of stimulant drugs. We focus on two prototypic stimulants: cocaine as a prototype monoamine reuptake inhibitor and d-amphetamine as a prototype monoamine releaser. As such, placebo controlled human laboratory studies that involved administration of doses of cocaine or d-amphetamine and were published in peer reviewed journals within the last 10 years (i.e., since 2011) are reviewed. Primary outcomes from these studies are subjective effects, reinforcing effects, cognitive/behavioral effects, and discriminative stimulus effects. Both cocaine and d-amphetamine produce classical stimulant-like behavioral effects (e.g., increase positive subjective effects, function as reinforcers), but there are notable gaps in the literature including understanding sex differences in response to stimulant drugs, cognitive-behavioral effects of stimulants, and influence of use history (e.g., relatively drug naïve vs drug experienced) on stimulant effects.

Driving under the influence of drugs: Correlation between blood psychoactive drug concentrations and cognitive impairment. A narrative review taking into account forensic issues

Driving under the influence of alcohol has been shown to increase the risk of involvement in road traffic collisions (RTCs) however, less is known about the effects of illicit drugs, and a clear correlation between drug concentrations and RTC risk is still debated. The goal of this narrative review is to assess the current literature regarding the most detected psychoactive drugs in RTC (ethanol, amphetamines, cannabis, opioids and cocaine), in relation to driving performance. Evidence on impaired driving due to psychoactive substances, forensic issues relating to the assessment of the impact of drugs, blood cut-off values proposed to date as well as scientific basis for proposed legislative limits are discussed. At present there is no unequivocal evidence demonstrating a clear dose/concentration dependent impairment in many substances. Per se and zero tolerance approaches seem to have negative effect on drugged driving fatalities. However, the weight of these approaches needs further investigation.

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Driving under the influence of psychotropic substances has become a widespread phenomenon.

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Only a few substances have been reported to have a clear dose/concentration dependent impairment.

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Statistically significant differences should not be considered as clinically significant per se

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There is wide variability in legislative cut-offs.

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Detection limits seems to be the most public safety-oriented legislative approach.

Methamphetamine and Modulation Functionality of the Prelimbic Cortex for Developing a Possible Treatment of Alzheimer's Disease in an Animal Model

Alzheimer’s disease (AD) is a progressive neurodegenerative condition that causes cognitive impairment and other neuropsychiatric symptoms. Previously, little research has thus far investigated whether methamphetamine (MAMPH) can enhance cognitive function or ameliorate AD symptoms. This study examined whether a low dose of MAMPH can induce conditioned taste aversion (CTA) learning, or can increase plasma corticosterone levels, neural activity, and neural plasticity in the medial prefrontal cortex (mPFC) (responsible for cognitive function), the nucleus accumbens (NAc) and the amygdala (related to rewarding and aversive emotion), and the hippocampus (responsible for spatial learning). Furthermore, the excitations or lesions of the prelimbic cortex (PrL) can affect MAMPH-induced CTA learning, plasma corticosterone levels, and neural activity or plasticity in the mPFC [i.e., PrL, infralimbic cortex (IL), cingulate cortex 1 (Cg1)], the NAc, the amygdala [i.e., basolateral amygdala (BLA) and central amygdala (CeA)], and the hippocampus [i.e., CA1, CA2, CA3, and dentate gyrus (DG)]. In the experimental procedure, the rats were administered either saline or NMDA solutions, which were injected into the PrL to excite or destroy PrL neurons. Additionally, rats received 0.1% saccharin solution for 15 min, followed by intraperitoneal injections of either normal saline or 1 mg/kg MAMPH to induce CTA. A one-way ANOVA was performed to analyze the effects of saccharin intake on CTA, plasma corticosterone levels, and the expression of c-Fos and p-ERK. The results showed that the MAMPH induced CTA learning and increased plasma corticosterone levels. The mPFC, and particularly the PrL and IL and the DG of the hippocampus, appeared to show increased neural activity in c-Fos expression or neural plasticity in p-ERK expression. The excitation of the PrL neurons upregulated neural activity in c-Fos expression and neural plasticity in p-ERK expression in the PrL and IL. In summary, MAMPH may be able to improve cognitive and executive function in the brain and reduce AD symptoms. Moreover, the excitatory modulation of the PrL with MAMPH administration can facilitate MAMPH-induced neural activity and plasticity in the PrL and IL of the mPFC. The present data provide clinical implications for developing a possible treatment for AD in an animal model.

Examining the effects of psychoactive drugs on complex behavioral processes in laboratory animals

Behavioral pharmacology has been aided significantly by the development of innovative cognitive tasks designed to examine complex behavioral processes in laboratory animals. Performance outcomes under these conditions have provided key metrics of drug action which serve to supplement traditional in vivo assays of physiologic and behavioral effects of psychoactive drugs. This chapter provides a primer of cognitive tasks designed to assay different aspects of complex behavior, including learning, cognitive flexibility, memory, attention, motivation, and impulsivity. Both capstone studies and recent publications are highlighted throughout to illustrate task value for two distinct but often interconnected translational strategies. First, task performance in laboratory animals can be utilized to elucidate how drugs of abuse affect complex behavioral processes. Here, the expectation is that adverse effects on such processes will have predictive relevance to consequences that will be experienced by humans. Second, these same task outcomes can be used to evaluate candidate therapeutics. In this case, the extent to which drug doses with medicinal value perturb task performance can contribute critical information for a more complete safety profile appraisal and advance the process of medications development. Methodological and theoretical considerations are discussed and include an emphasis on determining selectivity in drug action on complex behavioral processes.

Methamphetamine and alcohol detection in vehicle-driver fatalities in South Australia: A 10-year survey (2008-2018)

Motor vehicle driver fatalities (≥18 years) from the files at Forensic Science South Australia were reviewed from January 2008 to December 2018 for cases in which either positive blood sample for methamphetamine (MA) or an illegal blood alcohol concentration (BAC) >0.05g/100 ml were found. Three hundred driver deaths were found with MA detected in 28 cases (age range 21-62 years; ave. 37.8 years; M:F 23:5). Hundred and fifteen cases with a BAC > 0.05 g/100 ml were identified (age range 18-67 years; ave 35.7 years; M:F 95:20). No change was found in numbers of MA cases, although alcohol cases showed a significant decline (p < 0.001). Drunk driving-related fatal crashes tended to occur in the evening (5 p.m. to 11 p.m.), while MA-related fatal crashes had a longer peak extending from late evening until late morning (11 p.m. to 8 a.m.). This study has demonstrated that while roadside breath testing, legislative changes, and increased monitoring have resulted in reduced levels of drunk driving, similar safety countermeasures have had negligible effects on MA use in drivers. Continued monitoring of MA use by drivers will, therefore, be necessary to assess the possible effects, or not, of new countermeasures.

What is reinforcement sensitivity? Neuroscience paradigms for approach‐avoidance process theories of personality

Reinforcement sensitivity is a concept proposed by Gray (1973) to describe the biological antecedents of personality, and has become the common mechanism among a family of personality theories concerning approach and avoidance processes. These theories suggest that 2–3 biobehavioural systems mediate the effects of reward and punishment on emotion and motivation, and that individual differences in the functioning of these systems manifest as personality. Identifying paradigms for operationalising reinforcement sensitivity is therefore critical for testing and developing these theories, and evaluating their footprint in personality space. In this paper I suggest that, while traditional self‐report paradigms in personality psychology may be less‐than‐ideal for this purpose, neuroscience paradigms may offer operations of reinforcement sensitivity at multiple levels of approach and avoidance processes. After brief reflection on the use of such methods in animal models—which first spawned the concept of reinforcement sensitivity—recent developments in four domains of neuroscience are reviewed. These are psychogenomics, psychopharmacology, neuroimaging and category‐learning. By exploring these paradigms as potential operations of reinforcement sensitivity we may enrich our understanding of the putative biobehavioural bases of personality. Copyright © 2008 John Wiley & Sons, Ltd.

Amphetamine-induced alteration to gaze parameters: A novel conceptual pathway and implications for naturalistic behavior

Amphetamine produces a multiplicity of well-documented end-order biochemical, pharmacological and biobehavioural effects. Mechanistically, amphetamine downregulates presynaptic and postsynaptic striatal monoamine (primarily dopaminergic) systems, producing alterations to key brain regions which manifest as stereotyped ridged behaviour which occurs under both acute and chronic dosing schedules and persists beyond detoxification. Despite evidence of amphetamine-induced visual attentional dysfunction, no conceptual synthesis has yet captured how characteristic pharmaco-behavioural processes are critically implicated via these pathways, nor described the potential implications for safety-sensitive behaviours. Drawing on known pathomechanisms, we propose a cross-disciplinary, novel conceptual functional system framework for delineating the biobehavioural consequences of amphetamine use on visual attentional capacity and discuss the implications for functional and behavioural outcomes. Specifically, we highlight the manifest implications for behaviours that are conceptually driven and highly dependent on visual information processing for timely execution of visually-guided movements. Following this, we highlight the potential impact on safety-sensitive, but common behaviours, such as driving a motor vehicle. The close pathophysiological relationship between oculomotor control and higher-order cognitive processes further suggests that dynamic measurement of movement related to the motion of the eye (gaze behaviour) may be a simple, effective and direct measure of behavioural performance capabilities in naturalistic settings. Consequently, we discuss the potential efficacy of ocular monitoring for the detection and monitoring of driver states for this drug user group, and potential wider application. Significance statement: We propose a novel biochemical-physiological-behavioural pathway which delineates how amphetamine use critically alters oculomotor function, visual-attentional performance and information processing capabilities. Given the manifest implications for behaviours that are conceptually driven and highly dependent on these processes, we recommend oculography as a novel means of detecting and monitoring gaze behaviours during naturalistic tasks such as driving. Real-word examination of gaze behaviour therefore present as an effective means to detect driver impairment and prevent performance degradation due to these drugs.

How effective are pharmaceuticals for cognitive enhancement in healthy adults? A series of meta-analyses of cognitive performance during acute administration of modafinil, methylphenidate and D-amphetamine

Modafinil, methyphenidate (MPH) and d-amphetamine (d-amph) are putative cognitive enhancers. However, efficacy of cognitive enhancement has yet to be fully established. We examined cognitive performance in healthy non-sleep-deprived adults following modafinil, MPH, or d-amph vs placebo in 3 meta-analyses, using subgroup analysis by cognitive domain; executive functions (updating, switching, inhibitory control, access to semantic/long term memory), spatial working memory, recall, selective attention, and sustained attention. We adhered to PRISMA. We identified k = 47 studies for analysis; k = 14 studies (64 effect sizes) for modafinil, k = 24 studies (47 effect sizes) for Methylphenidate, and k = 10 (27 effect sizes) for d-amph. There was an overall effect of modafinil (SMD=0.12, p=.01). Modafinil improved memory updating (SMD=0.28, p=.03). There was an overall effect of MPH (SMD=0.21, p=.0004) driven by improvements in recall (SMD=0.43, p=.0002), sustained attention (SMD=0.42, p=.0004), and inhibitory control (SMD=0.27, p=.03). There were no effects for d-amph. MPH and modafinil show enhancing effects in specific sub-domains of cognition. However, data with these stimulants is far from positive if we consider that effects are small, in experiments that do not accurately reflect their actual use in the wider population. There is a user perception that these drugs are effective cognitive enhancers, but this is not supported by the evidence so far.

Amphetamine reduces reward encoding and stabilizes neural dynamics in rat anterior cingulate cortex

Psychostimulants such as d-amphetamine (AMPH) often have behavioral effects that appear paradoxical within the framework of optimal choice theory. AMPH typically increases task engagement and the effort animals exert for reward, despite decreasing reward valuation. We investigated neural correlates of this phenomenon in the anterior cingulate cortex (ACC), a brain structure implicated in signaling cost-benefit utility. AMPH decreased signaling of reward, but not effort, in the ACC of freely-moving rats. Ensembles of simultaneously recorded neurons generated task-specific trajectories of neural activity encoding past, present, and future events. Low-dose AMPH contracted these trajectories and reduced their variance, whereas high-dose AMPH expanded both. We propose that under low-dose AMPH, increased network stability balances moderately increased excitability, which promotes accelerated unfolding of a neural 'script' for task execution, despite reduced reward valuation. Noise from excessive excitability at high doses overcomes stability enhancement to drive frequent deviation from the script, impairing task execution.

Alcohol and illicit substances associated with fatal crashes in Queensland: An examination of the 2011 to 2015 Coroner's findings

PROBLEM

The problem of impaired driving is well documented in the literature but is heavily dependent upon self-report studies and/or databases that do not include in-depth information about the contributing origins of fatalities.

AIM

This study aimed to conduct an in-depth analysis of Coroner's findings for all fatally injured drivers in the state of Queensland in order to explore the prevalence of alcohol and different types of illicit substances (including drug combinations) in fatal crash reports.

METHOD

A total of 701 Coroner's reports related to drivers or controllers of vehicles involved in traffic related fatalities for the period of 2011-2015 were analysed, revealing 306 controllers (43.6%) were detected with either alcohol or illegal drugs (e.g., methylamphetamine, Δ9-tetrahydrocannabinol, cocaine or MDMA) RESULTS: Alcohol was the most commonly detected substance identified with 223 cases (72.9% of the drug and alcohol sample). Illicit drug detections totalled 147 cases (48% of the drug and alcohol sample) with Δ9-tetrahydrocannabinol the most commonly detected illicit substance (109 cases; 35.6% of the drug and alcohol sample) followed by methylamphetamine (total of 63 cases; 20.6% of the drug and alcohol sample). An important theme to emerge was the prevalence of polysubstance use among fatally injured drivers, not just for alcohol and one drug type, but also multiple drug combinations. Fatality trends revealed a decrease in both non-substance and alcohol-related fatalities across the study period. However, road fatalities where an illicit substance was detected increased by approximately 57%. Males were overrepresented as a proportion of total fatalities (82.4%) and there were no significant sex or age differences regarding illicit substance related deaths. Drivers of passenger vehicles were most commonly identified in the data (66.2%), but motorcycle operators were disproportionately represented (28.1% of the total controller sample compared to 4% of vehicle registrations in Queensland) CONCLUSION: This case study analysis of fatal crashes not only confirms the ongoing problem of alcohol and driving, but also illuminates the emerging (and escalating) issue of illicit substances detected in fatally injured drivers.

Pharmacological Treatment of Methamphetamine/Amphetamine Dependence: A Systematic Review

BACKGROUND

Stimulant drugs are second only to cannabis as the most widely used class of illicit drug globally, accounting for 68 million past-year consumers. Dependence on amphetamines (AMPH) or methamphetamine (MA) is a growing global concern. Yet, there is no established pharmacotherapy for AMPH/MA dependence. A comprehensive assessment of the research literature on pharmacotherapy for AMPH/MA dependence may inform treatment guidelines and future research directions.

METHODS

We systematically reviewed the peer-reviewed literature via the electronic databases PubMed, EMBASE, CINAHL and SCOPUS for randomised controlled trials reported in the English language examining a pharmacological treatment for AMPH/MA dependence or use disorder. We included all studies published to 19 June 2019. The selected studies were evaluated for design; methodology; inclusion and exclusion criteria; sample size; pharmacological and (if included) psychosocial interventions; length of follow-up and follow-up schedules; outcome variables and measures; results; overall conclusions and risk of bias. Outcome measures were any reported impact of treatment related to AMPH/MA use.

RESULTS

Our search returned 43 studies that met our criteria, collectively enrolling 4065 participants and reporting on 23 individual pharmacotherapies, alone or in combination. Disparate outcomes and measures (n = 55 for the primary outcomes) across studies did not allow for meta-analyses. Some studies demonstrated mixed or weak positive signals (often in defined populations, e.g. men who have sex with men), with some variation in efficacy signals dependent on baseline frequency of AMPH/MA use. The most consistent positive findings have been demonstrated with stimulant agonist treatment (dexamphetamine and methylphenidate), naltrexone and topiramate. Less consistent benefits have been shown with the antidepressants bupropion and mirtazapine, the glutamatergic agent riluzole and the corticotropin releasing factor (CRF-1) antagonist pexacerfont; whilst in general, antidepressant medications (e.g. selective serotonin reuptake inhibitors [SSRIs], tricyclic antidepressants [TCAs]) have not been effective in reducing AMPH/MA use.

CONCLUSIONS

No pharmacotherapy yielded convincing results for the treatment of AMPH/MA dependence; mostly studies were underpowered and had low treatment completion rates. However, there were positive signals from several agents that warrant further investigation in larger scale studies; agonist therapies show promise. Common outcome measures should include change in use days. Future research must address the heterogeneity of AMPH/MA dependence (e.g. coexisting conditions, severity of disorder, differences between MA and AMPH dependence) and the role of psychosocial intervention.

Intoxicated aggression: Do alcohol and stimulants cause dose-related aggression? A review

RATIONALE

Violence and drug use are significant public health challenges that are strongly linked. It is known that alcohol plays a major role in the causation of unnatural deaths and that stimulants like cocaine and amphetamine are often implicated in aggressive acts or violence. However, a clear causal relationship between these substances and aggression, and more specifically a blood concentration threshold at which intoxicated aggression emerges is lacking. In case of a crime and subsequent law enforcement, knowledge about dose-response relationships could be of pivotal importance when evaluating the role of alcohol and drugs in aggressive offences.

AIMS

The present review aimed to determine whether there is a causal relation between intoxication with these psychoactive substances and aggression, and to define blood concentration thresholds above which these substances elicit aggression.

METHODS

Empirical articles published between 2013 and 2017 and review papers containing the predefined search strings were identified through searches in the PubMed and Embase databases and additional reference list searches. The complete search query yielded 1578 publications. Initially all articles were manually screened by title and abstract. Articles with irrelevant titles, given the selected search terms and review aims were discarded. Remaining articles were carefully studied and those that did not comply with the main objectives of this review were discarded. At the end of this process, 167 titles were found eligible for review.

FINDINGS AND CONCLUSION

While placebo-controlled experimental studies clearly showed a causal link between alcohol and aggression, it is evident that such a link has not yet been established for cocaine and amphetamines. In case of alcohol, it is clear that there are various individual and contextual factors that may contribute to the occurrence of an aggressive act during intoxication. A clear threshold blood alcohol concentration has not been defined yet for alcohol, but a statistically significant increase of aggression has been demonstrated at a dose of 0.75 g/kg and higher. Future studies into intoxicated aggression should include multiple doses of alcohol and stimulants and take into account individual and contextual factors.

Bias Toward Drug-Related Stimuli Is Affected by Loading Working Memory in Abstinent Ex-Methamphetamine Users

Background: There is a trade-off between drug-related impulsive process and cognitive reflective process among ex-drug abusers. The present study aimed to investigate the impulsive effects of methamphetamine-related stimuli on working memory (WM) performance by manipulating WM load in abstinent ex-methamphetamine users. Methods: Thirty abstinent ex-methamphetamine users and 30 nonaddict matched control participants were recruited in this study. We used a modified Sternberg task in which participants were instructed to memorize three different sets of methamphetamine-related and non-drug-related words (three, five, or seven words) while performing a secondary attention-demanding task as an interference. Results: Repeated-measures ANOVA revealed that reaction times of abstinent ex-methamphetamine users increased during low WM load (three words) compared to the control group (p = 0.01). No significant differences were observed during high WM loads (five or seven words) (both p's > 0.1). Besides, reaction times of the experimental group during trials with high interference (three, five, or seven words) were not significantly different compared to the control group (p > 0.2). Conclusion: These findings imply that increasing WM load may provide an efficient buffer against attentional capture by salient stimuli (i.e., methamphetamine-related words). This buffer might modify the effect of interference bias. Besides, presenting methamphetamine-related stimuli might facilitate the encoding phase due to bias toward task-relevant stimuli. This finding has an important implication, suggesting that performing concurrent demanding tasks may reduce the power of salient stimuli and thus improve the efficiency of emotional regulation strategies.

Independent elevation of peripheral oxytocin concentrations and reduction in cognitive empathy during 4-fluoroamphetamine intoxication

OBJECTIVES

4-Fluoroamphetamine (4-FA) is a novel psychoactive substance with a pharmacological profile and reported subjective effects (e.g., empathy) intermediate between 3,4-methylenedioxymethamphetamine (MDMA) and amphetamine. Studies have shown that MDMA and amphetamine increase emotional empathy without affecting cognitive empathy; MDMA simultaneously leads to elevated levels of oxytocin, unrelated to its behavioral effects. The aim of the present study was to assess the reported enhancement of empathy by 4-FA, to assess its effects on oxytocin, and to test potential associations between both.

METHODS

Twelve healthy poly-drug users were included in a double-blind placebo-controlled two-way crossover study. Treatments were 4-FA (100 mg) and placebo; empathy was assessed by means of the multifaceted empathy test, and blood samples were taken before and after treatment administration to determine oxytocin concentrations.

RESULTS

4-FA reduced cognitive empathy, whereas emotional empathy was left unaffected. One hour after treatment, plasma oxytocin levels were significantly increased compared with placebo. Behavioral and hormonal effects were unrelated.

CONCLUSION

Although 4-FA shares its pharmacological mechanism with MDMA and amphetamine, current findings seem to indicate that it affects empathy differently. The 4-FA-induced increase in oxytocin levels was independent of behavioral effects, which confirms previous findings that drug-induced effects on peripheral oxytocin levels are not associated with empathy.

Downregulation of HCN1 channels in hippocampus and prefrontal cortex in methamphetamine re-exposed mice with enhanced working memory

The hyperpolarization-activated cyclic-nucleotide-gated non-selective cation (HCN) channels play a potential role in the neurological basis underlying drug addiction. However, little is known about the role of HCN channels in methamphetamine (METH) abuse. In the present study, we examined the changes in working memory functions of METH re-exposed mice through Morris water maze test, and investigated the protein expression of HCN1 channels and potential mechanisms underlying the modulation of HCN channels by Western blotting analysis. Mice were injected with METH (1 mg/kg, i.p.) once per day for 6 consecutive days. After 5 days without METH, mice were re-exposed to METH at the same concentration. We found that METH re-exposure caused an enhancement of working memory, and a decrease in the HCN1 channels protein expression in both hippocampus and prefrontal cortex. The phosphorylated extracellular regulated protein kinase 1/2 (p-ERK1/2), an important regulator of HCN channels, was also obviously reduced in hippocampus and prefrontal cortex of mice with METH re-exposure. Meanwhile, acute METH exposure did not affect the working memory function and the protein expressions of HCN1 channels and p-ERK1/2. Overall, our data firstly showed the aberrant protein expression of HCN1 channels in METH re-exposed mice with enhanced working memory, which was probably related to the down-regulation of p-ERK1/2 protein expression.

DARK Classics in Chemical Neuroscience: Methamphetamine

Methamphetamine has the second highest prevalence of drug abuse after cannabis, with estimates of 35 million users worldwide. The ( S)-(+)-enantiomer is the illicit drug, active neurostimulant, and eutomer, while the ( R)-(-)-enantiomer is contained in over the counter decongestants. While designated a schedule II drug in 1970, ( S)-(+)-methamphetamine is available by prescription for the treatment of attention-deficit disorder and obesity. The illicit use of ( S)-(+)-methamphetamine results in the sudden "rush" of stimulation to the motivation, movement, pleasure, and reward centers in the brain, caused by rapid release of dopamine. In this review, we will provide an overview of the synthesis, pharmacology, adverse effects, and drug metabolism of this widely abused psychostimulant that distinguish it as a DARK classic in Chemical Neuroscience.

Impact of aerobic exercise on cognitive impairment and oxidative stress markers in methamphetamine-dependent patients

This study aimed to investigate whether 12-week moderate-intensity aerobic exercise has beneficial effects on oxidative stress markers in blood and on cognitive functions in patients who have methamphetamine dependence. Serum levels of oxidative stress markers, including total anti-oxidation capability, super oxide dismutase (SOD), catalase (CAT), and methane dicarboxylic aldehyde (MDA), were measured at baseline (all participants) and the 12-week follow-up (methamphetamine-dependent patients). Serum levels of CAT and MDA in methamphetamine-dependent patients (n = 68) were higher than those in healthy controls (n = 35) at baseline. Furthermore, the international shopping list (ISL) task scores of methamphetamine-dependent patients were significantly lower than those of the controls, indicating verbal memory deficits in methamphetamine-dependent patients. Although there were no significant interactions for all cognitive function scores, aerobic exercise improved the processing speed in methamphetamine-dependent patients. Of interest, aerobic exercise significantly attenuated a spontaneous increase in serum MDA levels in methamphetamine-dependent patients after 12-weeks of abstinence. In conclusion, this study showed that methamphetamine-dependent patients with verbal learning and memory deficits have higher serum levels of MDA, and that a 12-week aerobic exercise program may have beneficial effects on the processing speed as well as blood lipid peroxidation in methamphetamine-dependent patients.

Safety Profile and Neurocognitive Function Following Acute 4-Fluoroamphetamine (4-FA) Administration in Humans

Availability of novel psychoactive substances (NPS) exponentially increased over the last years. Risk evaluations of NPS are hampered by the lack of pharmacological studies in humans on health parameters. The aim of the present study was to evaluate safety and neurocognitive function of healthy volunteers (N = 12) who received single doses of 100 and 150 mg 4-fluoroamphetamine (4-FA), a phenethylamine that has been associated with severe cardiovascular and cerebrovascular complications. The study was set-up as a placebo controlled, within subject, phase 1 trial as it was the first to administer 4-FA to humans under controlled conditions. Overall, 4-FA produced a strong elevation in blood pressure up until 4–5 h after administration that was followed by a sustained increase in heart rate. After an interim review of safety data from five participants, a decision was taken to cancel administration of 150 mg. We subsequently obtained complete datasets for placebo and 100 mg 4-FA treatments only. Effects of 4-FA on mood and neurocognitive function were most distinct at 1 h post drug and included significant elevations of vigor, friendliness, elation, arousal, positive mood, as well as improvements in attention and motor performance. Negative affect was also reported as time progressed in the acute phase and even more so during the subacute phase. Overall, the influence of 4-FA on vital signs, mood, and neurocognition was similar to that observed with other stimulants. Present findings confirm clinical observations of acute toxicity among 4-FA users and warrant warnings about potential health risks associated with 4-FA use.

Caffeine and Selective Adenosine Receptor Antagonists as New Therapeutic Tools for the Motivational Symptoms of Depression

Major depressive disorder is one of the most common and debilitating psychiatric disorders. Some of the motivational symptoms of depression, such anergia (lack of self-reported energy) and fatigue are relatively resistant to traditional treatments such as serotonin uptake inhibitors. Thus, new pharmacological targets are being investigated. Epidemiological data suggest that caffeine consumption can have an impact on aspects of depressive symptomatology. Caffeine is a non-selective adenosine antagonist for A1/A2A receptors, and has been demonstrated to modulate behavior in classical animal models of depression. Moreover, selective adenosine receptor antagonists are being assessed for their antidepressant effects in animal studies. This review focuses on how caffeine and selective adenosine antagonists can improve different aspects of depression in humans, as well as in animal models. The effects on motivational symptoms of depression such as anergia, fatigue, and psychomotor slowing receive particular attention. Thus, the ability of adenosine receptor antagonists to reverse the anergia induced by dopamine antagonism or depletion is of special interest. In conclusion, although further studies are needed, it appears that caffeine and selective adenosine receptor antagonists could be therapeutic agents for the treatment of motivational dysfunction in depression.

Acute effects of lisdexamfetamine and D-amphetamine on social cognition and cognitive performance in a placebo-controlled study in healthy subjects

RATIONALE

Amphetamines are used as medications but are also misused as cognitive enhancers by healthy subjects and may have additional effects on social cognition.

METHODS

We investigated the acute effects of single, high, equimolar doses of D-amphetamine (40 mg) and lisdexamfetamine (100 mg) on social cognition and cognitive performance using a randomized, placebo-controlled, double-blind, cross-over design in 24 healthy volunteers. Effects on social cognition were assessed using the Facial Emotion Recognition Task (FERT), Multifaceted Empathy Test (MET), and Sexual Arousal Task (SAT). Cognitive performance was measured using the Digit Symbol Substitution Test (DSST), Digit Span (DS), Stop-Signal Task (SST), and Mackworth Clock Test (MCT).

RESULTS

D-Amphetamine and lisdexamfetamine had small effects on measures of social cognition. There were no effects on emotion recognition on the FERT. D-Amphetamine increased direct empathy on the MET, but only for positive stimuli. Both amphetamines increased ratings of pleasantness and attractiveness on the SAT in response to sexual but also to neutral stimuli. D-Amphetamine and lisdexamfetamine increased cognitive performance (go-accuracy and vigilance on the SST and MCT, respectively). Lisdexamfetamine increased processing speed on the DSST. Neither drug had an effect on the DS.

CONCLUSION

Single, high, equimolar doses of D-amphetamine and lisdexamfetamine enhanced certain aspects of cognitive performance in healthy non-sleep-deprived subjects. Both amphetamines also slightly altered aspects of social cognition. Whether these small effects also influence social interaction behavior in amphetamine users remains to be investigated.

TRIAL REGISTRATION

The study was registered at ClinicalTrials.gov (NCT02668926).

Individual differences in the energizing effects of caffeine on effort-based decision-making tests in rats

Motivated behavior is characterized by activation and high work output. Nucleus accumbens (Nacb) modulates behavioral activation and effort-based decision-making. Caffeine is widely consumed because of its energizing properties. This methylxanthine is a non-selective adenosine A₁/A_2A receptor antagonist. Adenosine receptors are highly concentrated in Nacb. Adenosine agonists injected into Nacb, shift preference towards low effort alternatives. The present studies characterized effort-related effects of caffeine in a concurrent progressive ratio (PROG)/free reinforcer choice procedure that requires high levels of work output, and generates great variability among different animals. Male Sprague-Dawley rats received an acute dose of caffeine (2.5-20.0 mg/kg, IP) and 30 min later were tested in operant boxes. One group was food-restricted and had to lever pressed for high carbohydrate pellets, another group was non-food-restricted and lever pressed for a high sucrose solution. Caffeine (2.5 and 5.0 mg/kg) increased lever pressing in food-restricted animals that were already high responders. However, in non-restricted animals, caffeine (5.0 and 10.0 mg/kg) increased work output only among low responders. In fact, caffeine (10.0 and 20.0 mg/kg) in non-restricted animals, reduced lever pressing among high responders in the PROG task, and also in a different group of animals lever pressing in an easy task (fixed ratio 7 schedule) that uniformly generates high levels of responding. Caffeine did not modify sucrose preference or consumption under free access conditions. Thus, when animals do not have a homeostatic need, caffeine can help those not very intrinsically motivated to work harder for a more palatable reward. However, caffeine can disrupt performance of animals intrinsically motivated to work hard for a better reward.

Correlation between Blood and Oral Fluid Psychoactive Drug Concentrations and Cognitive Impairment in Driving under the Influence of Drugs

BACKGROUND

The effects of drugs on driving performance should be checked with drug concentration in the brain and at the same time with the evaluation of both the behavioural and neurophysiological effects. The best accessible indicator of this information is the concentration of the drug and/or metabolites in blood and, to a certain extent, oral fluid. We sought to review international studies on correlation between blood and oral fluid drug concentrations, neurological correlates and cognitive impairment in driving under the influence of drugs.

METHODS

Relevant scientific articles were identified from PubMed, Cochrane Central, Scopus, Web of Science, Science Direct, EMBASE up to April 2017.

RESULTS

Up to 2010, no epidemiological studies were available on this matter and International scientists suggested that even minimal amounts of parent drugs in blood and oral fluid could affect driving impairment. More recently, epidemiological data, systematic reviews and meta-analysis on drugged drivers allowed the suggestion of impairment concentration limits for the most common illicit drugs. These values were obtained comparing driving disability induced by psychotropic drugs with that of established blood alcohol limits. Differently from ethyl alcohol where both detection methods and concentration limits have been well established even with inhomogeneity of ranges within different countries, in case of drugs of abuse no official cut-offs have yet been established, nor any standardized analytical protocols.

CONCLUSION

Multiple aspects of driving performance can be differently affected by illicit drugs, and even if for few of them some dose/concentration dependent impairment has been reported, a wider knowledge on concentration/impairment relationship is still missing.

Effects of drugs of abuse on hippocampal plasticity and hippocampus-dependent learning and memory: contributions to development and maintenance of addiction

It has long been hypothesized that conditioning mechanisms play major roles in addiction. Specifically, the associations between rewarding properties of drugs of abuse and the drug context can contribute to future use and facilitate the transition from initial drug use into drug dependency. On the other hand, the self-medication hypothesis of drug abuse suggests that negative consequences of drug withdrawal result in relapse to drug use as an attempt to alleviate the negative symptoms. In this review, we explored these hypotheses and the involvement of the hippocampus in the development and maintenance of addiction to widely abused drugs such as cocaine, amphetamine, nicotine, alcohol, opiates, and cannabis. Studies suggest that initial exposure to stimulants (i.e., cocaine, nicotine, and amphetamine) and alcohol may enhance hippocampal function and, therefore, the formation of augmented drug-context associations that contribute to the development of addiction. In line with the self-medication hypothesis, withdrawal from stimulants, ethanol, and cannabis results in hippocampus-dependent learning and memory deficits, which suggest that an attempt to alleviate these deficits may contribute to relapse to drug use and maintenance of addiction. Interestingly, opiate withdrawal leads to enhancement of hippocampus-dependent learning and memory. Given that a conditioned aversion to drug context develops during opiate withdrawal, the cognitive enhancement in this case may result in the formation of an augmented association between withdrawal-induced aversion and withdrawal context. Therefore, individuals with opiate addiction may return to opiate use to avoid aversive symptoms triggered by the withdrawal context. Overall, the systematic examination of the role of the hippocampus in drug addiction may help to formulate a better understanding of addiction and underlying neural substrates.

Neurocognitive enhancement or impairment? A systematic meta-analysis of prescription stimulant effects on processing speed, decision-making, planning, and cognitive perseveration

Increasing numbers of adults, particularly college students, are misusing prescription stimulants primarily for cognitive/academic enhancement, so it is critical to explore whether empirical findings support neurocognitive benefits of prescription stimulants. Previous meta-analytic studies have supported small benefits from prescription stimulants for the cognitive domains of inhibitory control and memory; however, no meta-analytic studies have examined the effects on processing speed or the potential impairment on other domains of cognition, including planning, decision-making, and cognitive perseveration. Therefore, the present study conducted a meta-analysis of the available literature examining the effects of prescription stimulants on specific measures of processing speed, planning, decision-making, and cognitive perseveration among healthy adult populations. The meta-analysis results indicated a positive influence of prescription stimulant medication on processing speed accuracy, with an overall mean effect size of g = 0.282 (95% CI [0.077, 0.488]; n = 345). Neither improvements nor impairments were revealed for planning time, planning accuracy, advantageous decision-making, or cognitive perseveration; however, findings are limited by the small number of studies examining these outcomes. Findings support that prescription stimulant medication may indeed act as a neurocognitive enhancer for accuracy measures of processing speed without impeding other areas of cognition. Considering that adults are already engaging in illegal use of prescription stimulants for academic enhancement, as well as the potential for stimulant misuse to have serious side effects, the establishment of public policies informed by interdisciplinary research surrounding this issue, whether restrictive or liberal, is of critical importance. (PsycINFO Database Record

Long-Term Treatment with Low Doses of Methamphetamine Promotes Neuronal Differentiation and Strengthens Long-Term Potentiation of Glutamatergic Synapses onto Dentate Granule Neurons

Methamphetamine (METH) is a psychostimulant, affecting hippocampal function with disparate cognitive effects, which depends on the dose and time of administration, ranging from improvement to impairment of memory. Importantly, in the United States, METH is approved for the treatment of attention deficit hyperactivity disorder. Modifications of long-term plasticity of synapses originating from the entorhinal cortex onto dentate granule cells (DGCs) have been proposed to underlie cognitive alterations similar to those seen in METH users. However, the effects of METH on synaptic plasticity of the dentate gyrus are unknown. Here, we investigated the impact of long-term administration of METH (2 mg/kg/d) on neurogenesis and synaptic plasticity of immature and mature DGCs of juvenile mice. We used a mouse model of neurogenesis (the G42 line of GAD67-GFP), in which GFP is expressed by differentiating young DGCs. METH treatment enhanced the differentiation of GFP(+) cells, as it increased the fraction of GFP(+) cells expressing the neuronal marker NeuN, and decreased the amount of immature DGCs coexpressing doublecortin. Interestingly, METH did not change the magnitude of long-term potentiation (LTP) in more immature neurons, but facilitated LTP induction in more differentiated GFP(+) and strengthened plasticity in mature GFP(-) DGCs. The METH-induced facilitation of LTP in GFP(+) neurons was accompanied with spine enlargement. Our results reveal a specific action of long-term use of METH in the long-term plasticity of excitatory synapses onto differentiating DGCs and might have important implications toward the understanding of the synaptic basis of METH-induced cognitive alterations.

Effects of d-amphetamine upon psychosocial stress responses

Psychostimulant drugs alter the salience of stimuli in both laboratory animals and humans. In animals, stimulants increase rates of responding to conditioned incentive stimuli, and in humans, amphetamine increases positive ratings of emotional images. However, the effects of stimulants on real-life emotional events have not been studied in humans. In this study, we examined the effect of d-amphetamine on responses to acute psychosocial stress using a public speaking task. Healthy volunteers (N=56) participated in two experimental sessions, one with a psychosocial stressor (the Trier Social Stress Test) and one with a non-stressful control task. They were randomly assigned to receive d-amphetamine (5 mg n=18, 10 mg n=20) or placebo (n=18) on both sessions under double blind conditions. Salivary cortisol, subjective mood, and vital signs were measured at regular intervals during the session. Subjects also provided cognitive appraisals of the tasks before and after their performances. Amphetamine produced its expected mood and physiological effects, and the Trier Social Stress Test produced its expected effects on cortisol and mood. Although neither dose of amphetamine altered cardiovascular or hormonal responses to stress, amphetamine (10 mg) increased participants' pre-task appraisals of how challenging the task would be, and it increased post-task ratings of self-efficacy. Paradoxically, it also increased ratings of how stressful the task was, and prolonged aversive emotional responses. These findings suggest that amphetamine differentially affects stress response components: it may increase participants' appraisals of self-efficacy without dampening the direct emotional or physiological responses to the stress.

A rodent model of the human psychomotor vigilance test: Performance comparisons

BACKGROUND

The human Psychomotor Vigilance Test (PVT) is commonly utilized as an objective risk assessment tool to quantify fatigue and sustained attention in laboratory, clinical, and operational settings.

NEW METHOD

Recent studies have employed a rodent version of the PVT (rPVT) to measure various aspects of attention (lapses in attention, reaction times) under varying experimental conditions.

RESULTS

Data are presented here to evaluate the short- and long-term utility of the rPVT adapted for laboratory rats designed to track the same types of performance variables as the human PVT-i.e., motor speed, inhibitory control ("impulsivity"), and attention/inattention. Results indicate that the rPVT is readily learned by rats and requires less than two weeks of training to acquire the basic procedure. Additional data are also presented on the effects of radiation exposure on these performance measures that indicate the utility of the procedure for assessing changes in neurobehavioral function in rodents across their lifespans.

COMPARISON WITH EXISTING METHOD(S)

Once stable performances are obtained, rats evidence a high degree of similarity to human performance measures, and include similarities in terms of lapses and reaction times, in addition to percent correct and premature responding. Similar to humans, rats display both a vigilance decrement across time on task and a response-stimulus interval effect.

CONCLUSIONS

The rPVT is a useful tool in the investigation of the effects of a wide range of variables on vigilance performance that compares favorably to the human PVT and for developing potential prophylactics, countermeasures, and treatments for neurobehavioral dysfunctions.

The Standardized Field Sobriety Tests (SFST) and measures of cognitive functioning

OBJECTIVE

The Standardized Field Sobriety Tests (SFST) are utilised widely to assess fitness to drive when law enforcement suspects a driver's ability to drive is impaired, whether by drugs or alcohol. The SFST ostensibly achieve this through assessment of the level of drivers' cognitive and psychomotor impairment, although no studies have explicitly assessed the relatedness of cognitive ability and performance on the SFST. The current study aimed to assess the relationship between the three components of the SFST with a well validated computerised cognitive battery.

METHOD

A sub-set of 61 placebo condition participants comprised the sample, with 33 females and 28 males (mean age 25.45 years). Correlations between the individual SFST subscales 'Horizontal Gaze Nystagmus' (HGN), the 'One Leg Stand' (OLS) and the 'Walk and Turn' test (WAT) and Cognitive Drug Research (CDR) sub-scales of 'Quality of Working Memory', 'Power of Attention' and 'Continuity of Attention' were analysed using point-biserial correlation.

RESULTS

Sixty participants were included for analyses. A weak-moderate positive (five subscales) and a moderate-strong negative (two subscales) association was noted between seven of the nine individual CDR subscales and the SFST subscale of the WAT test (all p<0.05). Individually, a moderate positive association was noted between the sub-scale 'Nystagmus lack of smooth pursuit' and 'digit vigilance reaction time' and 'choice reaction time; reaction time' (both p<0.05) and 'Nystagmus head move and/or jerk' and 'simple reaction time' (p<0.001). When assessed as a partially composite factor, a comparable association was also noted between the composite score of the SFST subscale 'Nystagmus head move and/or jerk' and both (a) simple and (b) digit vigilance reaction time (both p<0.05). No association was noted between any of the individual cognitive variables and the SFST subscale 'OLS', or between composite cognitive scores 'Quality of Working Memory', 'Power of Attention' and 'Continuity of Attention' and total SFST scores.

DISCUSSION

Variation in some aspects of cognitive performance was found to be moderately and positively correlated with some individual aspects of the SFST; particularly among tasks which assess reaction time. Impairment of these cognitive processes can also contribute to the completion of complex tasks such as driving or the SFST. Complex behavioural tasks such as driving are often severely impaired due to intoxication, and thus in a practical sense, the SFST can still be considered a useful screening tool to identify drug or alcohol impaired drivers.

The effect of banning MDPV on the incidence of MDPV-positive findings among users of illegal drugs and on court decisions in traffic cases in Finland

In this study, we sought to determine what impact the banning of 3, 4- methylenedioxypyrovalerone (MDPV) had on the incidence of MDPV-positive findings and on user profiles in driving under the influence of drugs (DUID) and postmortem (PM) investigations in Finland. All MDPV-positive cases and a selection of corresponding court cases between 2009 and 2012 were examined. The median serum concentration of MDPV in DUID cases was 0.030 mg/L and in PM blood 0.12 mg/L. The number of MDPV-positive cases decreased both in DUID and PM investigations after the drug was banned. The decrease in the mean monthly numbers of MDPV-positive DUID cases was 51.1%. In court cases, MDPV was rarely mentioned until banned and frequently mentioned thereafter. Of the convicted, 37% were without a fixed abode, 98% had other charges besides that of DUID, and 13% appeared in the study material more than once. In MDPV-positive PM cases, the proportion of suicides was very high (24%). Research on new psychoactive substances is required not only to support banning decisions but more importantly to be able to provide a scientific assessment of the risks of these new substances to the public and potential users.

Prescription Stimulants' Effects on Healthy Inhibitory Control, Working Memory, and Episodic Memory: A Meta-analysis

The use of prescription stimulants to enhance healthy cognition has significant social, ethical, and public health implications. The large number of enhancement users across various ages and occupations emphasizes the importance of examining these drugs' efficacy in a nonclinical sample. The present meta-analysis was conducted to estimate the magnitude of the effects of methylphenidate and amphetamine on cognitive functions central to academic and occupational functioning, including inhibitory control, working memory, short-term episodic memory, and delayed episodic memory. In addition, we examined the evidence for publication bias. Forty-eight studies (total of 1,409 participants) were included in the analyses. We found evidence for small but significant stimulant enhancement effects on inhibitory control and short-term episodic memory. Small effects on working memory reached significance, based on one of our two analytical approaches. Effects on delayed episodic memory were medium in size. However, because the effects on long-term and working memory were qualified by evidence for publication bias, we conclude that the effect of amphetamine and methylphenidate on the examined facets of healthy cognition is probably modest overall. In some situations, a small advantage may be valuable, although it is also possible that healthy users resort to stimulants to enhance their energy and motivation more than their cognition.

Methamphetamine-induced short-term increase and long-term decrease in spatial working memory affects protein Kinase M zeta (PKMζ), dopamine, and glutamate receptors

Methamphetamine (MA) is a toxic, addictive drug shown to modulate learning and memory, yet the neural mechanisms are not fully understood. We investigated the effects of 2 weekly injections of MA (30 mg/kg) on working memory using the radial 8-arm maze (RAM) across 5 weeks in adolescent-age mice. MA-treated mice show a significant improvement in working memory performance 1 week following the first MA injection compared to saline-injected controls. Following 5 weeks of MA abstinence mice were re-trained on a reference and working memory version of the RAM to assess cognitive flexibility. MA-treated mice show significantly more working memory errors without effects on reference memory performance. The hippocampus and dorsal striatum were assessed for expression of glutamate receptors subunits, GluA2 and GluN2B; dopamine markers, dopamine 1 receptor (D1), dopamine transporter (DAT) and tyrosine hydroxylase (TH); and memory markers, protein kinase M zeta (PKMζ) and protein kinase C zeta (PKCζ). Within the hippocampus, PKMζ and GluA2 are both significantly reduced after MA supporting the poor memory performance. Additionally, a significant increase in GluN2B and decrease in D1 identifies dysregulated synaptic function. In the striatum, MA treatment increased cytosolic DAT and TH levels associated with dopamine hyperfunction. MA treatment significantly reduced GluN2B while increasing both PKMζ and PKCζ within the striatum. We discuss the potential role of PKMζ/PKCζ in modulating dopamine and glutamate receptors after MA treatment. These results identify potential underlying mechanisms for working memory deficits induced by MA.

The neurobiology of methamphetamine induced psychosis

Chronic methamphetamine abuse commonly leads to psychosis, with positive and cognitive symptoms that are similar to those of schizophrenia. Methamphetamine induced psychosis (MAP) can persist and diagnoses of MAP often change to a diagnosis of schizophrenia over time. Studies in schizophrenia have found much evidence of cortical GABAergic dysfunction. Methamphetamine psychosis is a well studied model for schizophrenia, however there is little research on the effects of methamphetamine on cortical GABAergic function in the model, and the neurobiology of MAP is unknown. This paper reviews the effects of methamphetamine on dopaminergic pathways, with focus on its ability to increase glutamate release in the cortex. Excess cortical glutamate would likely damage GABAergic interneurons, and evidence of this disturbance as a result of methamphetamine treatment will be discussed. We propose that cortical GABAergic interneurons are particularly vulnerable to glutamate overflow as a result of subcellular location of NMDA receptors on interneurons in the cortex. Damage to cortical GABAergic function would lead to dysregulation of cortical signals, resulting in psychosis, and further support MAP as a model for schizophrenia.

Evaluation of the effects of anti-motion sickness drugs on subjective sleepiness and cognitive performance of healthy males

This study aimed to investigate the clinical and cognitive side effects of baclofen (10 mg), meclizine (25 mg), dimenhydrinate (40 mg) plus cinnarizine (25 mg) and promethazine (25 mg) plus d-amphetamine (10 mg). The study had a double-blind, placebo controlled, repeated measures design and was conducted on healthy male volunteers. The psychomotor vigilance test, the Sternberg working memory task, the implicit memory test and the automated Operation Span (Ospan) task were performed. The Stanford, the Karolinska and the Epworth Sleepiness scale determined the degree of sleepiness. The Profile of Mood States (POMS) evaluated mood states and adverse effects were reported on a 22-item questionnaire. Letter recalls and time for solving mathematical problems, recorded during the Ospan task, were impaired by baclofen and dimenhydrinate-cinnarizine respectively, suggesting an influence of these drugs on the working memory. Significant side effects for baclofen were: sleepiness, tiredness, blurred vision, concentration problems and dizziness whereas for dimenhydrinate-cinnarizine only sleepiness and blurred vision were reported. Meclizine decreased the accuracy on the Sternberg working memory task and thus seemed to affect short-term memory. A reported side effect was increased sleepiness. Promethazine plus d-amphetamine did not affect any of the tested cognitive functions. However, many side effects such as sleepiness, dry mouth, dizziness, vertigo, confusion, insomnia and tremors were reported. The results show that meclizine and dimenhydrinate combined with cinnarizine were the two drugs with the most acceptable combination of side effects.

Do negative stimulant-related attitudes vary for prescription stimulants and cocaine among college students?

Nonmedical prescription stimulant use (NPS) has become an increasing problem for college students across the United States. Many engage in NPS due to the belief that their academic functioning will improve - a belief that rarely extends to other illicit stimulants. Because positive attitudes toward substances potentially predict the maintenance of current and future use, the aim of the current study was to directly compare attitudes toward different stimulants of abuse (prescription stimulants and cocaine) to ascertain whether attitudes were generally more positive as a function of both drug and drug user type. Ninety-one participants completed a brief attitudinal index assessing attitudes for both prescription stimulants and cocaine. Participants held stronger positive attitudes toward prescription stimulants than cocaine on a variety of items. NPS users reported more positive attitudes toward prescription stimulants than both nonusers and cocaine users. Nonusers reported more negative cocaine-related attitudes than cocaine users and polydrug users (users of both prescription stimulants and cocaine). Intervention programs may benefit from highlighting the negative consequences of NPS, particularly by way of comparisons to cocaine. Doing so may heighten awareness on the overlap of adverse outcomes resulting from use between these stimulants.

Humility pills: building an ethics of cognitive enhancement

The use of cognition-enhancing drugs (CEDs) appears to be increasingly common in both academic and workplace settings. But many universities and businesses have not yet engaged with the ethical challenges raised by CED use. This paper considers criticisms of CED use with a particular focus on the Accomplishment Argument: an influential set of claims holding that enhanced work is less dignified, valuable, or authentic, and that cognitive enhancement damages our characters. While the Accomplishment Argument assumes a view of authorship based on individual credit-taking, an impersonal or collaborative view is just as possible. This paper considers the benefits of this view-including humility, a value often claimed by critics of enhancement-and argues that such a view is consistent with open CED use. It proposes an ethics of cognitive enhancement based on toleration, transparency, and humility, and it discusses how institutions and individuals can build a culture of open cognitive enhancement.

Concurrent use of khat and tobacco is associated with verbal learning and delayed recall deficits

AIMS

The present study assessed whether cigarette smokers who are also regular khat users would demonstrate greater impairments in verbal learning and recall compared to both non-smokers who are khat users and control subjects.

DESIGN

An independent-measures, between-subjects design with two covariates.

SETTING

An out-patient, university research center in Taiz, Yemen.

PARTICIPANTS

Subjects were 175 Yemeni college students (90 men, 85 women) ranging in age from 18 to 38 years. Seventy-five subjects were self-reported chronic cigarette smokers and khat users, 48 non-smoking subjects were self-reported to be chronic khat users and 52 non-smoking subjects reported no current use or history of khat use.

MEASUREMENTS

Verbal learning and verbal memory recall was assessed by subject performance on the Arabic version of the Rey Auditory Verbal Learning Test (RAVLT).

FINDINGS

Statistically significant differences (P < 0.05) were observed in RAVLT acquisition learning trials 2-5 and on delayed recall measures between concurrent khat and cigarette users compared to both the khat-only group and the control group of non-users of khat and cigarettes. On each of these trials, concurrent users recalled fewer words, demonstrating a slowed rate of verbal learning. This same pattern of performance was also seen on delayed recall measures. Khat use alone did not affect immediate or delayed recall of previously learned words.

CONCLUSIONS

Khat users who smoke cigarettes have a lower rate of verbal learning and delayed recall of previously learned verbal material than khat users who do not smoke cigarettes. This may be due to pre-existing differences between these groups of subjects.

Working memory capacity predicts effects of methylphenidate on reversal learning

Increased use of stimulant medication, such as methylphenidate, by healthy college students has raised questions about its cognitive-enhancing effects. Methylphenidate acts by increasing extracellular catecholamine levels and is generally accepted to remediate cognitive and reward deficits in patients with attention deficit hyperactivity disorder. However, the cognitive-enhancing effects of such 'smart drugs' in the healthy population are still unclear. Here, we investigated effects of methylphenidate (Ritalin, 20  mg) on reward and punishment learning in healthy students (N=19) in a within-subject, double-blind, placebo-controlled cross-over design. Results revealed that methylphenidate effects varied both as a function of task demands and as a function of baseline working memory capacity. Specifically, methylphenidate improved reward vs punishment learning in high-working memory subjects, whereas it impaired reward vs punishment learning in low-working memory subjects. These results contribute to our understanding of individual differences in the cognitive-enhancing effects of methylphenidate in the healthy population. Moreover, they highlight the importance of taking into account both inter- and intra-individual differences in dopaminergic drug research.

Dopaminergic involvement in effort-based but not impulsive reward processing in smokers

BACKGROUND

A reduction in reward responsivity and an increase in temporal discounting of rewards are both evident in smokers during acute abstinence compared to satiation. However, it is not yet known whether these processes can be modulated pharmacologically in smokers, other than with nicotine or tobacco.

METHODS

A double-blind placebo controlled crossover design assessed the effects of 0.5 mg pramipexole, a dopamine D₂/D₃ agonist, in smokers following 2 h of abstinence. Reward responsivity was measured using an effort-based card sorting task. Temporal discounting of monetary reward was assessed using Area Under the Curve (AUC) analysis, and affective and subjective effects were indexed.

RESULTS

On placebo, smokers showed an equivalent speed of card sorting when a financial incentive was provided compared to when it was not. Conversely, more cards were sorted under rewarded compared to non-rewarded trials after pramipexole, indicating an improvement in reward responsivity. Temporal discounting of monetary reward was not affected by pramipexole. Drug treatment also decreased positive affect and increased drowsiness.

CONCLUSIONS

A single dose of pramipexole can enhance effort-based reward responsivity, but does not alter temporal discounting in smokers. These findings highlight pharmacological correlates of reward processing deficits in nicotine dependence and offer potential targets for their treatment.

Amphetamine abuse in Sweden: subject demographics, changes in blood concentrations over time, and the types of coingested substances

Amphetamine is a major drug of abuse in Sweden and in the other Nordic countries. The demographics of amphetamine abusers in Sweden and the concentrations of this stimulant in blood are reported for 10 years of forensic blood samples (2001-2010). Using a forensic toxicology database (TOXBASE), we studied 1183 amphetamine-related deaths, 20,452 users of illicit drugs, and 47,366 people arrested for driving under the influence of drugs (DUID). Most amphetamine abusers were male (82%-87%), and their average age was 33 to 39 years with males being 2 to 3 years older than females (P < 0.001). Mean (median) concentrations of amphetamine in blood were 1.25 (0.40) mg/L in autopsy cases, 0.61 (0.40) mg/L in users of illicit drugs, and 0.76 (0.58) mg/L in DUID suspects. Median concentration in DUID suspects was significantly higher than in the other forensic materials (P < 0.001). Women also had higher median concentrations of amphetamine in blood than male abusers of this central stimulant (P < 0.001). The major coingested drugs were benzodiazepines (41%), cannabis (26%), opiates (21%), and alcohol (18%) in autopsy cases. Polydrug use was less common in DUID suspects and users of illicit drugs, although benzodiazepines (13%), tetrahydrocannabinol (12%), and opiates (5%) were often identified along with amphetamine. Because median concentration of amphetamine was higher in living subjects (DUID suspects) compared with amphetamine-related deaths, this points toward toxicity of coingested drugs or adverse drug-drug interaction as being responsible for death.

The influence of stimulants on truck driver crash responsibility in fatal crashes

INTRODUCTION

Given the monotony and extended driving periods inherent in transport truck driving, drivers might rely on stimulants to sustain attention and combat fatigue. Research indicates that stimulant use improves some cognitive functions but impairs driving ability and is linked to crashes. The research on crash responsibility among stimulant-positive truck drivers is inconclusive due to small sample sizes and a lack of control over confounding variables. The present study investigated the influence of stimulants on unsafe driving actions (UDAs) in fatal crashes contained in the Fatality Analysis Reporting System (FARS) database.

METHODS

Logistic regression was used to calculate the odds ratio of an UDA (cases committed an UDA; controls did not) by stimulant status (present; absent) while accounting for the influence of confounding variables (age, previous driving record, and other drug use).

RESULTS

For all truck drivers, we found that 372 truck drivers tested stimulant-positive representing 0.57% of the entire truck driver sample and 3.7% of truck drivers who were actually tested for drug use. Stimulant-positive truck drivers had a greater proportion of driving record infractions and narcotic drug use compared to stimulant-negative truck drivers. The adjusted odds of committing an UDA were 78% greater for truck drivers who were stimulant-positive (OR: 1.78, 95% CI: 1.41-2.26) compared to truck drivers stimulant-negative.

CONCLUSION

The results suggest stimulants are associated with crash responsibility and warrant further study into their impact on truck drivers.

Driving on ice: impaired driving skills in current methamphetamine users

RATIONALE

Previous research indicates a complex link between methamphetamine (METH) and driving performance. Acute dosing with amphetamines has improved driving-related performance in some laboratory studies, while epidemiological studies suggest an association between METH use, impaired driving, and accident culpability.

METHODS

Current METH users were compared to a control group of nonusers on driving simulator performance. Groups were matched for age, gender, and driving experience. Subjects were assessed for current drug use, drug dependence, and drug levels in saliva/blood as well as personality variables, sleepiness, and driving performance.

RESULTS

METH users, most of whom met the criteria for METH dependence, were significantly more likely to speed and to weave from side to side when driving. They also left less distance between their vehicle and oncoming vehicles when making a right-hand turn. This risky driving was not associated with current blood levels of METH or its principal metabolite, amphetamine, which varied widely within the METH group. Other drugs were detected (principally low levels of THC or MDMA) in some METH users, but at levels that were unlikely to impair driving performance. There were higher levels of impulsivity and antisocial personality disorder in the METH-using cohort.

CONCLUSIONS

These findings confirm indications from epidemiological studies of an association between METH use and impaired driving ability and provide a platform for future research to further explore the factors contributing to increased accident risk in this population.

Does COMT genotype influence the effects of d-amphetamine on executive functioning?

In a widely cited study, Mattay et al. reported that amphetamine (0.25 mg/kg oral, or 17 mg for a 68 kg individual) impaired behavioral and brain indices of executive functioning, measured using the Wisconsin Card Sorting Task (WCST) and N-Back working memory task, in 6 individuals homozygous for the met allele of the val158met polymorphism in the catechol-O-methyltransferase (COMT) gene, whereas it improved executive functioning in 10 individuals homozygous for the more active val allele. We attempted to replicate their behavioral findings in a larger sample, using similar executive functioning tasks and a broader range of amphetamine doses. Over four sessions, n = 200 healthy normal adults received oral placebo, d-amphetamine 5, 10, and 20 mg (average of 0.07, 0.15 and 0.29 mg/kg), under counterbalanced double-blind conditions and completed WCST and N-back tests of executive functioning. Amphetamine had typical effects on blood pressure and processing speed but did not affect executive functioning. COMT genotype (val158met) was not related to executive functioning under placebo or amphetamine conditions, even when we compared only the homozygous val/val and met/met genotypes at the highest dose of amphetamine (20 mg). Thus, we were not able to replicate the behavioral interaction between COMT and amphetamine seen in Mattay et al. We discuss possible differences between the studies and the implications of our findings for the use of COMT genotyping to predict clinical responses to dopaminergic drugs, and the use of intermediate phenotypes in genetic research.

Distinct roles of methamphetamine in modulating spatial memory consolidation, retrieval, reconsolidation and the accompanying changes of ERK and CREB activation in hippocampus and prefrontal cortex

Drugs of abuse modulated learning and memory in humans yet the underlying mechanism remained unclear. The extracellular signal-regulated kinase (ERK) and the transcription factor cAMP response element-binding protein (CREB) were involved in neuroplastic changes associated with learning and memory. In the current study, we used a Morris water maze to examine the effect of methamphetamine (METH) on different processes of spatial memory in mice. We then investigated the status of ERK and CREB in the hippocampus and prefrontal cortex (PFC). We found that 1.0 mg/kg dose of METH facilitated spatial memory consolidation when it was injected immediately after the last learning trial. In contrast, the same dose of METH had no effect on spatial memory retrieval when it was injected 30 min before the test. Furthermore, 1.0 mg/kg dose of METH injected immediately after retrieval had no effect on spatial memory reconsolidation. Activation of both ERK and CREB in the hippocampus was found following memory consolidation but not after retrieval or reconsolidation in METH-treated mouse groups. In contrast, activation of both ERK and CREB in the PFC was found following memory retrieval but not other processes in METH-treated mouse groups. These results suggested that METH facilitated spatial memory consolidation but not retrieval or reconsolidation. Moreover, activation of the ERK and CREB signaling pathway in the hippocampus might be involved in METH-induced spatial memory changes.