Observational and experimental studies on sleep duration and aggression: A systematic review and meta-analysis.

Short sleep duration has been linked to higher levels of aggression. To synthetize all available research on this association, a systematic review and meta-analysis was performed. We included observational and experimental studies, using various measures of sleep duration and aggression. Eighty eligible papers were identified, describing 82 studies comprising a total number of 76.761 participants. Meta-analysis of results was possible for 60 studies. Pooled observational results on the association between sleep duration and aggression showed a correlation estimate of -0.16 (95%CI -0.19, -0.12; I2 = 83.9%) and an odds ratio estimate of 1.83 (95%CI 1.47, 2.28; I2 = 0.0%). For experimental studies, the pooled Standardized Mean Difference after manipulation of sleep duration was -0.37 (95%CI -0.80, 0.05; I2 = 89.05%) for controlled designs and -0.34 (95%CI -0.54, -0.14; I2 = 89.05%) for pre-post designs. Effect estimates were stronger for individuals with psychological vulnerabilities and younger persons. Exclusion of studies with low methodological quality strengthened the effect estimate in experimental but not in observational studies. To conclude, short sleep duration is associated with higher levels of aggression, with observational research strongly supporting the association and experimental studies providing mixed results. More well-designed prospective and experimental studies are needed to establish causality and optimize treatment, especially for individuals with psychological vulnerabilities.

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.

Cannabis and tolerance: acute drug impairment as a function of cannabis use history.

Cannabis use history as predictor of neurocognitive response to cannabis intoxication remains subject to scientific and policy debates. The present study assessed the influence of cannabis on neurocognition in cannabis users whose cannabis use history ranged from infrequent to daily use. Drug users (N = 122) received acute doses of cannabis (300 µg/kg THC), cocaine HCl (300 mg) and placebo. Cocaine served as active control for demonstrating neurocognitive test sensitivity. Executive function, impulse control, attention, psychomotor function and subjective intoxication were significantly worse after cannabis administration relative to placebo. Cocaine improved psychomotor function and attention, impaired impulse control and increased feelings of intoxication. Acute effects of cannabis and cocaine on neurocognitive performance were similar across cannabis users irrespective of their cannabis use history. Absence of tolerance implies that that frequent cannabis use and intoxication can be expected to interfere with neurocognitive performance in many daily environments such as school, work or traffic.

Cannabis and cocaine decrease cognitive impulse control and functional corticostriatal connectivity in drug users with low activity DBH genotypes.

The dopamine ß-hydroxylase (DßH) enzyme transforms dopamine into noradrenaline. We hypothesized that individuals with low activity DBH genotypes (rs1611115 CT/TT) are more sensitive to the influence of cannabis and cocaine on cognitive impulse control and functional connectivity in the limbic 'reward' circuit because they experience a drug induced hyperdopaminergic state compared to individuals with high activity DBH genotypes (rs1611115 CC). Regular drug users (N = 122) received acute doses of cannabis (450 µg/kg THC), cocaine HCl 300 mg and placebo. Cognitive impulse control was assessed by means of the Matching Familiar Figures Test (MFFT). Resting state fMRI was measured in a subset of participants to determine functional connectivity between the nucleus accumbens (NAc) and (sub)cortical areas. The influence of cannabis and cocaine on impulsivity and functional connectivity significantly interacted with DBH genotype. Both drugs increased cognitive impulsivity in participants with CT/TT genotypes but not in CC participants. Both drugs also reduced functional connectivity between the NAc and the limbic lobe, prefrontal cortex, striatum and thalamus and primarily in individuals with CT/TT genotypes. Correlational analysis indicated a significant negative association between cognitive impulsivity and functional connectivity in subcortical areas of the brain. It is concluded that interference of cannabis and cocaine with cognitive impulse control and functional corticostriatal connectivity depends on DBH genotype. The present data provide a neural substrate and behavioral mechanism by which drug users can progress to drug seeking and may also offer a rationale for targeted pharmacotherapy in chronic drug users with high risk DBH genotypes.

Psychedelic symptoms of cannabis and cocaine use as a function of trait impulsivity.

Trait impulsivity has been linked to addiction in humans. It has been suggested that drug users with high trait impulsivity levels are more sensitive to subjective drug intoxication. This study assessed whether subjective response to drugs differs between drug users with normal or high levels of trait impulsivity. Regular drug users (N = 122) received doses of cocaine HCl, cannabis, and placebo in a three-way crossover study. Their mood, dissociative state, and psychedelic symptoms were measured with subjective rating scales (CADDS, Bowdle, POMS). Trait impulsivity was assessed with the Barratt Impulsiveness Scale. Cannabis increased dissociation and psychedelic state, as well as fatigue, confusion, depression and anxiety, and decreased arousal, positive mood, vigor, friendliness, and elation. Cocaine increased dissociation, psychedelic state, vigor, friendliness, elation, positive mood, anxiety and arousal, while decreasing fatigue. Only a few subjective items revealed a drug × trait impulsivity interaction, suggesting that psychedelic symptoms were most intense in high impulsivity subjects. Trait impulsiveness ratings were negatively correlated with ratings of vigor (r = -.197) and positively correlated with ratings of loss of thought control (r = .237) during cannabis intoxication. It is concluded that a broad association between trait impulsivity and psychedelic subjective drug experience appears to be absent.

Co-morbid anxiety disorders predict early relapse after inpatient alcohol treatment.

INTRODUCTION: Alcohol dependence and anxiety disorders often co-occur. Yet, the effect of co-morbid anxiety disorders on the alcohol relapse-risk after treatment is under debate. This study investigated the effect of co-morbid anxiety disorders on relapse rates in alcohol dependence. We hypothesized that co-morbid anxiety disorders would be particularly predictive for early relapse, but not late relapse. SUBJECTS AND METHODS: In a prospective design, male alcohol dependent patients (n=189) were recruited from an inpatient detoxification clinic. Psychiatric diagnoses and personality traits were assessed using the Mini International Neuropsychiatric Interview for psychiatric disorders and the Temperament and Character Inventory. The addiction severity index was used to assess addiction severity and follow-up. RESULTS: One year after detoxification, 81 patients (53%) relapsed and nine patients (7%) were deceased, due to alcohol related causes. Co-morbid anxiety disorder, marital status, addiction severity, in particular legal problems, and harm avoidance predicted relapse. Anxiety disorders specifically predicted early relapse. CONCLUSION: Alcohol dependence is a severe mental disorder, with high relapse rates and high mortality. Alcohol dependent patients with co-morbid anxiety disorders are particularly prone to relapse during the first three months of treatment. These patients may therefore require additional medical and psychological attention.

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

RATIONALE: Knowing how commonly used drugs affect performance monitoring is of great importance, because drug use is often associated with compromised behavioral control. Two of the most commonly used recreational drugs in the western world, 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy") and ethanol (alcohol), are also often used in combination. The error-related negativity (ERN), correct-related negativity (CRN), and N2 are electrophysiological indices of performance monitoring. OBJECTIVES: The present study aimed to investigate how ethanol, MDMA, and their co-administration affect performance monitoring as indexed by the electrophysiological correlates. METHODS: Behavioral and EEG data were obtained from 14 healthy volunteers during execution of a speeded choice-reaction-time task after administration of ethanol, MDMA, and combined ethanol and MDMA, in a double-blind, placebo-controlled, randomized crossover design. RESULTS: Ethanol significantly reduced ERN amplitudes, while administration of MDMA did not affect the ERN. Co-administration of MDMA and ethanol did not further impair nor ameliorate the effect of ethanol alone. No drug effects on CRN nor N2 were observed. DISCUSSION: A decreased ERN following ethanol administration is in line with previous work and offers further support for the impairing effects of alcohol intoxication on performance monitoring. This impairment may underlie maladaptive behavior in people who are under influence. Moreover, these data demonstrate for the first time that MDMA does not affect performance monitoring nor does it interact with ethanol in this process. These findings corroborate the notion that MDMA leaves central executive functions relatively unaffected.

Efficacy and safety of medical cannabinoids in older subjects: a systematic review.

This systematic review aims to integrate the evidence on indications, efficacy, safety and pharmacokinetics of medical cannabinoids in older subjects. The literature search was conducted using PubMed, EMBASE, CINAHL and Cochrane Library. We selected controlled trials including solely older subjects (≥65 years) or reporting data on older subgroups. 105 (74%) papers, on controlled intervention trials, reported the inclusion of older subjects. Five studies reported data on older persons separately. These were randomized controlled trials, including in total 267 participants (mean age 47-78 years). Interventions were oral tetrahydrocannabinol (THC) (n=3) and oral THC combined with cannabidiol (n=2). The studies showed no efficacy on dyskinesia, breathlessness and chemotherapy induced nausea and vomiting. Two studies showed that THC might be useful in treatment of anorexia and behavioral symptoms in dementia. Adverse events were more common during cannabinoid treatment compared to the control treatment, and were most frequently sedation like symptoms. Although trials studying medical cannabinoids included older subjects, there is a lack of evidence of its use specifically in older patients. Adequately powered trials are needed to assess the efficacy and safety of cannabinoids in older subjects, as the potential symptomatic benefit is especially attractive in this age group.

[Dopamine and excessive alcohol consumption: how genes interact with their environment]. / Dopamine en overmatig alcoholgebruik: genen in interactie met hun omgeving.

BACKGROUND: Hereditary factors account for approximately 50% of the risk of developing alcohol dependence. Genes that affect the dopamine function in the brain have been extensively studied as candidate genes. AIM: To present the results of recent Dutch studies on the interaction between genes and their environment in relation to dopamine function and excessive alcohol use. METHOD: Two large scale research projects were recently carried out in order to study the relation between dopamine genes and excessive alcohol use in the Netherlands. The first study investigated excessive alcohol use among adolescents. The second studied alcohol dependence among adult males. RESULTS: Genes that affect the dopamine function in the brain were not directly linked to excessive alcohol use or dependence. Dopamine genes, however, do influence sensitivity to environmental risk factors for excessive alcohol use. CONCLUSION: These studies show that genetically determined dopamine function increases the risk of excessive alcohol use in the context of an adverse environment. Traumatic experiences and parenting style were both shown to be important environmental factors.

Feedback-related negativity codes outcome valence, but not outcome expectancy, during reversal learning.

Optimal behavior depends on the ability to assess the predictive value of events and to adjust behavior accordingly. Outcome processing can be studied by using its electrophysiological signatures--that is, the feedback-related negativity (FRN) and the P300. A prominent reinforcement-learning model predicts an FRN on negative prediction errors, as well as implying a role for the FRN in learning and the adaptation of behavior. However, these predictions have recently been challenged. Notably, studies so far have used tasks in which the outcomes have been contingent on the response. In these paradigms, the need to adapt behavioral responses is present only for negative, not for positive feedback. The goal of the present study was to investigate the effects of positive as well as negative violations of expectancy on FRN amplitudes, without the usual confound of behavioral adjustments. A reversal-learning task was employed in which outcome value and outcome expectancy were orthogonalized; that is, both positive and negative outcomes were equally unexpected. The results revealed a double dissociation, with effects of valence but not expectancy on the FRN and, conversely, effects of expectancy but not valence on the P300. While FRN amplitudes were largest for negative-outcome trials, irrespective of outcome expectancy, P300 amplitudes were largest for unexpected-outcome trials, irrespective of outcome valence. These FRN effects were interpreted to reflect an evaluation along a good-bad dimension, rather than reflecting a negative prediction error or a role in behavioral adaptation. By contrast, the P300 reflects the updating of information relevant for behavior in a changing context.

Single doses of THC and cocaine decrease proficiency of impulse control in heavy cannabis users.

BACKGROUND AND PURPOSE: Cannabis is the most popular drug used in the European Union, closely followed by cocaine. Whereas cannabis impairs neurocognitive function in occasional cannabis users, such impairments appear less prominent in heavy users, possibly as a result of tolerance. The present study was designed to assess whether the impairing effects of Δ(9) -tetrahydrocannabinol (THC) in heavy cannabis users would present in a wide range of neuropsychological functions or selectively affect specific performance domains. We also assessed the acute effects of cocaine on neurocognitive functions of heavy cannabis users. EXPERIMENTAL APPROACH: Heavy cannabis users, who had a history of cocaine use (n = 61), participated in a double-blind, placebo-controlled, three-way crossover study. Subjects received single doses of cocaine HCl (300 mg), cannabis (THC µg·kg(-1) ) and placebo, and completed a number of tests measuring impulse control and psychomotor function. KEY RESULTS: Single doses of cannabis impaired psychomotor function and increased response errors during impulsivity tasks. Single doses of cocaine improved psychomotor function and decreased response time in impulsivity tasks, but increased errors. CONCLUSIONS AND IMPLICATIONS: Heavy cannabis users display impairments in a broad range of neuropsychological domains during THC intoxication. Impairments observed in psychomotor tasks, but not in impulsivity tasks, appeared smaller in magnitude as compared with those previously reported in occasional cannabis users. Heavy cannabis users were sensitive to the stimulating and inhibitory effects of cocaine on psychomotor function and impulsivity respectively. The reduction in proficiency in impulse control may put drug users at increased risk of repeated drug use and addiction.

DBH -1021C>T and COMT Val108/158Met genotype are not associated with the P300 ERP in an auditory oddball task.

OBJECTIVE: The amplitude and latency of the P300 may be associated by variations in dopaminergic genes. The current study was conducted to determine whether functional variants of the catechol-O-methyltransferase (COMT) and dopamine beta-hydroxylase (DBH) gene were associated with P300 amplitude and latency in an auditory oddball task. METHODS: The P300 ERP was assessed by a two-tone auditory oddball paradigm in a large sample of 320 healthy volunteers. The Val108/158Met polymorphism (rs4680) of the COMT gene and the -1021C>T polymorphism (rs1611115) of the DBH gene were genotyped. P300 amplitude and latency were compared across genotype groups using analysis of variance. RESULTS: There were no differences in demographic characteristics in subjects for genotypic subgroups. No genotype associations were observed for the P300 amplitude and latency on frontal, central and parietal electrode positions. CONCLUSIONS: COMT Val108/158Met and DBH -1021C>T polymorphisms do not show evidence of association with characteristics of the P300 ERP in an auditory oddball paradigm in healthy volunteers. SIGNIFICANCE: We failed to find evidence for the association between dopaminergic enzymatic polymorphisms and the P300 ERP in healthy volunteers, in the largest study undertaken to date.

Neural basis of emotion recognition deficits in first-episode major depression.

BACKGROUND: Depressed individuals demonstrate a poorer ability to recognize the emotions of others, which could contribute to difficulties in interpersonal behaviour. This emotion recognition deficit appears related to the depressive state and is particularly pronounced when emotions are labelled semantically. Here, we investigated its neural basis by comparing emotion recognition processing between depressed, recovered and healthy individuals. METHOD: Medication-naive patients with a first major depressive episode, medication-free patients who had recovered from a first episode, and a group of matched healthy individuals participated. They were requested to identify the emotion of angry and fearful face stimuli, either by matching them to other emotional faces on a perceptual basis or by matching them to a semantic label, while their brain activity was measured with functional magnetic resonance imaging. RESULTS: The depressed individuals performed worse than recovered and healthy individuals on the emotion-labelling but not the emotion-matching task. The labelling deficit was related to increased recruitment of the right amygdala, left inferior frontal gyrus and anterior cingulate cortex. CONCLUSIONS: Deficits in semantic labelling of negative emotions are related to increased activation in specific brain regions and these abnormalities are mood state-dependent. These results indicate that accessing semantic knowledge about negative information triggers increased amygdala and left inferior frontal gyrus processing, which subsequently impairs task-relevant behaviour. We propose that this may reflect the activation of negative schemas.

Acute psychomotor, memory and subjective effects of MDMA and THC co-administration over time in healthy volunteers.

In Western societies a considerable percentage of young people expose themselves to the combination of 3,4-methylenedioxymethamphetamine (MDMA or 'ecstasy') and cannabis. The aim of the present study was to assess the acute effects of co-administration of MDMA and THC (the main psychoactive compound of cannabis) on pharmacokinetics, psychomotor performance, memory and subjective experience over time. We performed a four-way, double blind, randomized, crossover, placebo-controlled study in 16 healthy volunteers (12 male, four female) between the ages of 18 and 27. MDMA (100 mg) was given orally, THC (4, 6, and 6 mg, interval of 90 min) was vaporized and inhaled. THC induced more robust cognitive impairment compared with MDMA, and co-administration did not exacerbate single drug effects on cognitive function. However, co-administration of THC with MDMA increased desired subjective drug effects and drug strength compared with the MDMA condition, which may explain the widespread use of this combination.

Ziprasidone vs olanzapine in recent-onset schizophrenia and schizoaffective disorder: results of an 8-week double-blind randomized controlled trial.

INTRODUCTION: Head-to-head comparisons of antipsychotics have predominantly included patients with chronic conditions. The aim of the present study was to compare the efficacy and tolerability of ziprasidone and olanzapine in patients with recent-onset schizophrenia. METHODS: The study was an 8-week, double-blind, parallel-group, randomized, controlled multicenter trial (NCT00145444). Seventy-six patients with schizophreniform disorder, schizophrenia or schizoaffective disorder (diagnosis < 5 y), and a maximum lifetime antipsychotic treatment < 16 weeks participated in the study. Efficacy of ziprasidone (80-160 mg/d) and olanzapine 10-20 mg was measured using the Positive and Negative Syndrome Scale (PANSS), the Clinical Global Impression (CGI) Scale, the Calgary Depression Scale for Schizophrenia (CDSS), and the Heinrich Quality of Life Scale (HQLS); tolerability assessments included laboratory assessments, body weight, and electroencephalogram. RESULTS: Olanzapine (n = 34) and ziprasidone (n = 39) showed equal efficacy as measured by the PANSS, CDSS, CGI, and HQLS. However, mean weight gain was significantly higher in the olanzapine group (6.8 vs 0.1 kg, P < .001). Ziprasidone was associated with decreasing levels of triglycerides, cholesterol, and transaminases, while these parameters increased in the olanzapine group (all P values < .05). There were no significant differences in fasting glucose and prolactin levels or in cardiac or sexual side effects. Patients on ziprasidone used biperiden for extrapyramidal side effects more frequently (P < .05). DISCUSSION: The results of this study indicate that ziprasidone and olanzapine have comparable therapeutic efficacy but differ in their side effect profile. However, there is a risk of a type II error with this sample size. Clinically significant weight gain and laboratory abnormalities appear early after initiating treatment and are more prominent with olanzapine, while more patients on ziprasidone received anticholinergic drugs to treat extrapyramidal symptoms.

Effects on cognitive functioning after olanzapine-ziprasidone crossover in recent-onset schizophrenia.

INTRODUCTION: To enhance functional outcome in schizophrenia improvement of cognitive symptoms is crucial. EXPERIMENTAL PROCEDURES: Using a comprehensive test battery, this follow-up examines cognitive effects in patients with recent-onset schizophrenia after a change of medication following insufficient clinical response and intolerance. RESULTS: After eight weeks cognitive outcomes had not improved in the patients having switched from olanzapine to ziprasidone (n=11; mean dose 136 mg) nor in those having switched from ziprasidone to olanzapine (n=10; mean 16 mg), while the symptoms of patients maintaining olanzapine (n=18; mean 10.9 mg) or ziprasidone (n=18; mean 88.9 mg) treatment had not improved further. DISCUSSION: The findings suggest that also in early-stage schizophrenia the antipsychotics tested affect cognitive symptoms similarly.

Short term neurocognitive effects of treatment with ziprasidone and olanzapine in recent onset schizophrenia.

BACKGROUND: Cognitive deficits are a core feature in schizophrenia. Cognitive deficits appear to be present at the onset of schizophrenia and persist after remission of psychotic symptoms. As cognitive deficits are associated with poor functional outcome, they form an important focus of treatment. There are relatively few head-to-head comparisons of the effects of second generation antipsychotics on cognition in recent onset schizophrenia. This is the first study to compare the effects of a short term treatment of olanzapine versus ziprasidone on cognitive functioning in recent onset schizophrenia. An earlier study conducted in chronic patients revealed an enhancement of cognition after treatment for both agents, but the extent of improvement was not significantly different between ziprasidone and olanzapine. METHOD: Patients with recent onset schizophrenia with limited previous exposure to medical treatment underwent a double blind randomized controlled treatment trial. Fifty-six patients completed the neuropsychological testing procedure prior to randomization and after eight weeks of treatment and were included in the analysis. We tested cognitive functioning in general and verbal memory in particular. We calculated a single unweighted composite score based on nine cognitive tests to determine general cognitive functioning. RESULTS: Cognition appeared enhanced after treatment, but was not significantly different between treatment groups, neither for the verbal memory measures, nor for the neurocognitive composite score. Furthermore, cognitive enhancement did not correlate to clinical improvement. CONCLUSION: Cognitive deficits are not a reason for preferentially prescribing one of the two second generation antipsychotics tested over the other.

Treatment of unipolar psychotic depression: a randomized, double-blind study comparing imipramine, venlafaxine, and venlafaxine plus quetiapine.

OBJECTIVE: It remains unclear whether unipolar psychotic depression should be treated with an antidepressant and an antipsychotic or with an antidepressant alone. METHOD: In a multi-center RCT, 122 patients (18-65 years) with DSM-IV-TR psychotic major depression and HAM-D-17 > or = 18 were randomized to 7 weeks imipramine (plasma-levels 200-300 microg/l), venlafaxine (375 mg/day) or venlafaxine-quetiapine (375 mg/day, 600 mg/day). Primary outcome was response on HAM-D-17. Secondary outcomes were response on CGI and remission (HAM-D-17). RESULTS: Venlafaxine-quetiapine was more effective than venlafaxine with no significant differences between venlafaxine-quetiapine and imipramine, or between imipramine and venlafaxine. Secondary outcomes followed the same pattern. CONCLUSION: That unipolar psychotic depression should be treated with a combination of an antidepressant and an antipsychotic and not with an antidepressant alone, can be considered evidence based with regard to venlafaxine-quetiapine vs. venlafaxine monotherapy. Whether this is also the case for imipramine monotherapy is likely, but cannot be concluded from the data.

Effect of apomorphine on cognitive performance and sensorimotor gating in humans.

INTRODUCTION: Dysfunction of brain dopamine systems is involved in various neuropsychiatric disorders. Challenge studies with dopamine receptor agonists have been performed to assess dopamine receptor functioning, classically using the release of growth hormone (GH) from the hindbrain as primary outcome measure. The objective of the current study was to assess dopamine receptor functioning at the forebrain level. METHODS: Fifteen healthy male volunteers received apomorphine sublingually (2 mg), subcutaneously (0.005 mg/kg), and placebo in a balanced, double-blind, cross-over design. Outcome measures were plasma GH levels, performance on an AX continuous performance test, and prepulse inhibition of the acoustic startle. The relation between central outcome measures and apomorphine levels observed in plasma and calculated in the brain was modeled using a two-compartmental pharmacokinetic-pharmacodynamic analysis. RESULTS: After administration of apomorphine, plasma GH increased and performance on the AX continuous performance test deteriorated, particularly in participants with low baseline performance. Apomorphine disrupted prepulse inhibition (PPI) on high-intensity (85 dB) prepulse trials and improved PPI on low intensity (75 dB) prepulse trials, particularly in participants with low baseline PPI. High cognitive performance at baseline was associated with reduced baseline sensorimotor gating. Neurophysiological measures correlated best with calculated brain apomorphine levels after subcutaneous administration. CONCLUSION: The apomorphine challenge test appears a useful tool to assess dopamine receptor functioning at the forebrain level. Modulation of the effect of apomorphine by baseline performance levels may be explained by an inverted U-shape relation between prefrontal dopamine functioning and cognitive performance, and mesolimbic dopamine functioning and sensorimotor gating. Future apomorphine challenge tests preferentially use multiple outcome measures, after subcutaneous administration of apomorphine.