Auditory verbal hallucinations and childhood trauma subtypes across the psychosis continuum: a cluster analysis.

Introduction: A strong link between voice-hearing experience and childhood trauma has been established. The aim of this study was to identify whether there were unique clusters of childhood trauma subtypes in a sample across the clinical spectrum of auditory verbal hallucinations (AVH) and to examine clinical and phenomenological features across these clusters.Methods: Combining two independent international datasets (the Netherlands and Australia), childhood trauma subtypes were examined using hierarchical cluster analysis. Clinical and phenomenological characteristics were compared across emerging clusters using MANOVA and chi-squared analyses.Results: The total sample (n = 413) included 166 clinical individuals with a psychotic disorder and AVH, 122 non-clinical individuals with AVH and 125 non-clinical individuals without AVH. Three clusters emerged: (1) low trauma (n = 299); (2) emotion-focused trauma (n = 71); (3) multi-trauma (n = 43). The three clusters differed significantly on their AVH ratings of amount of negative content, with trend-level effects for loudness, degree of negative content and degree of experienced distress. Furthermore, perceptions of voices being malevolent, benevolent and resistance towards voices differed significantly.Conclusion: The data revealed different types of childhood trauma had different relationships between clinical and phenomenological features of voice-hearing experiences. Thus, implicating different mechanistic pathways and a need for tailored treatment approaches.

Identifying the cognitive underpinnings of voice-hearing by comparing never, past and current voice-hearers.

OBJECTIVE: The current study aimed to compare specific cognitive profiles corresponding to auditory verbal hallucinations (AVH) status and elucidate which pattern of cognitive deficits may predict voice-hearing status. METHOD: Clinical participants with schizophrenia spectrum disorders were partitioned into: (i) current voice-hearers (n = 46), (ii) past voice-hearers (n = 37) and (iii) never voice-hearers (n = 40), and compared with 319 non-clinical controls. Cognitive assessment employed the MATRICS Consensus Cognitive Battery (MCCB), supplemented by the Delis-Kaplan Executive Function System (D-KEFS) Colour-Word Interference Test (Stroop) as a robust measure of executive function. RESULTS: On the Visual Learning domain, current and past voice-hearers had significantly poorer performance relative to never voice-hearers, who in turn had significantly poorer performance than non-clinical controls. Current and never voice-hearers had significantly poorer performance on the Social Cognition domain relative to non-clinical controls. Current voice-hearers also had significantly poorer performance on the Inhibition domain relative to non-clinical controls. Binary logistic regression revealed that Visual Learning was the only significant cognitive predictor of AVH presence. CONCLUSION: Visual learning, and potentially inhibition, may be viable therapeutic targets when addressing cognitive mechanisms associated with AVHs. Future research should focus on investigating additional cognitive mechanisms, employing diverse voice-hearing populations and embarking on related longitudinal studies.

Characterizing cognitive heterogeneity on the schizophrenia-bipolar disorder spectrum.

BACKGROUND: Current group-average analysis suggests quantitative but not qualitative cognitive differences between schizophrenia (SZ) and bipolar disorder (BD). There is increasing recognition that cognitive within-group heterogeneity exists in both disorders, but it remains unclear as to whether between-group comparisons of performance in cognitive subgroups emerging from within each of these nosological categories uphold group-average findings. We addressed this by identifying cognitive subgroups in large samples of SZ and BD patients independently, and comparing their cognitive profiles. The utility of a cross-diagnostic clustering approach to understanding cognitive heterogeneity in these patients was also explored. METHOD: Hierarchical clustering analyses were conducted using cognitive data from 1541 participants (SZ n = 564, BD n = 402, healthy control n = 575). RESULTS: Three qualitatively and quantitatively similar clusters emerged within each clinical group: a severely impaired cluster, a mild-moderately impaired cluster and a relatively intact cognitive cluster. A cross-diagnostic clustering solution also resulted in three subgroups and was superior in reducing cognitive heterogeneity compared with disorder clustering independently. CONCLUSIONS: Quantitative SZ-BD cognitive differences commonly seen using group averages did not hold when cognitive heterogeneity was factored into our sample. Members of each corresponding subgroup, irrespective of diagnosis, might be manifesting the outcome of differences in shared cognitive risk factors.

A systematic review of visual processing and associated treatments in body dysmorphic disorder.

OBJECTIVE: Recent advances in body dysmorphic disorder (BDD) have explored abnormal visual processing, yet it is unclear how this relates to treatment. The aim of this study was to summarize our current understanding of visual processing in BDD and review associated treatments. METHOD: The literature was collected through PsycInfo and PubMed. Visual processing articles were included if written in English after 1970, had a specific BDD group compared to healthy controls and were not case studies. Due to the lack of research regarding treatments associated with visual processing, case studies were included. RESULTS: A number of visual processing abnormalities are present in BDD, including face recognition, emotion identification, aesthetics, object recognition and gestalt processing. Differences to healthy controls include a dominance of detailed local processing over global processing and associated changes in brain activation in visual regions. Perceptual mirror retraining and some forms of self-exposure have demonstrated improved treatment outcomes, but have not been examined in isolation from broader treatments. CONCLUSION: Despite these abnormalities in perception, particularly concerning face and emotion recognition, few BDD treatments attempt to specifically remediate this. The development of a novel visual training programme which addresses these widespread abnormalities may provide an effective treatment modality.

Sustained brain activation supporting stop-signal task performance.

Stop-signal paradigms operationalize a basic test of goal-directed behaviour whereby an overarching stop goal that is performed intermittently must be maintained throughout ongoing performance of a reaction time go task (go goal). Previous studies of sustained brain activation during stop-signal task performance in humans did not observe activation of the dorsolateral prefrontal cortex (DLPFC) that, in concert with the parietal cortex, is known to subserve goal maintenance. Here we explored the hypothesis that a DLPFC and parietal network has a key role in supporting ongoing stop-signal task performance. We used a blocked functional magnetic resonance imaging design that included blocks of trials containing typical stop-signal paradigm stimuli that were performed under three conditions: Stop condition, which required reaction time responding to go stimuli and inhibition of cued responses upon presentation of a stop signal; Go condition, identical except that the tone was ignored; and Passive condition, which required only quiescent attention to stimuli. We found that, whereas a distributed corticothalamic network was more active in Stop compared with Go, only the right DLPFC and bilateral parietal cortex survived after masking that contrast with Stop compared with Passive. These findings indicate that sustained activation of a right dominant frontoparietal network supports stop goal processes during ongoing performance of the stop-signal task.

Pathways between neurocognition, social cognition and emotion regulation in bipolar disorder.

OBJECTIVE: Converging evidence suggests that in bipolar disorder (BD), social cognition and emotion regulation are affected by the capacity for effective neurocognitive function. Adaptive emotion regulation may also rely on intact social cognition, and it is possible that social cognition acts as a mediator in its relationship with neurocognition. We aimed to address this hypothesis by explicitly examining interrelationships among neurocognition, social cognition and emotion regulation in an out-patient sample meeting criteria for a DSM-IV-TR diagnosis of BD compared with controls. METHOD: Fifty-one BD patients and 52 healthy controls completed a battery of tests assessing neurocognition, social cognition (emotion perception and theory of mind) and emotion regulation. RESULTS: Path analysis revealed that in BD, neurocognition was associated with social cognition, but social cognition was not associated with emotion regulation as expected. In contrast, a component of social cognition was found to mediate the relationship between neurocognition and emotion regulation in healthy controls. CONCLUSION: These findings highlight differences in the pattern of associations between neurocognition, social cognition and emotion regulation across BD patients and controls. In the present data, these results appear to indicate that neurocognitive and social cognitive abilities generally operate in isolation from emotion regulation in BD.

Brain connectivity in body dysmorphic disorder compared with controls: a diffusion tensor imaging study.

BACKGROUND: Several neuroimaging studies have investigated brain grey matter in people with body dysmorphic disorder (BDD), showing possible abnormalities in the limbic system, orbitofrontal cortex, caudate nuclei and temporal lobes. This study takes these findings forward by investigating white matter properties in BDD compared with controls using diffusion tensor imaging. It was hypothesized that the BDD sample would have widespread significantly reduced white matter connectivity as characterized by fractional anisotropy (FA). METHOD: A total of 20 participants with BDD and 20 healthy controls matched on age, gender and handedness underwent diffusion tensor imaging. FA, a measure of water diffusion within a voxel, was compared between groups on a voxel-by-voxel basis across the brain using tract-based spatial statistics within the FSL package. RESULTS: Results showed that, compared with healthy controls, BDD patients demonstrated significantly lower FA (p < 0.05) in most major white matter tracts throughout the brain, including in the superior longitudinal fasciculus, inferior fronto-occipital fasciculus and corpus callosum. Lower FA levels could be accounted for by increased radial diffusivity as characterized by eigenvalues 2 and 3. No area of higher FA was found in BDD. CONCLUSIONS: This study provided the first evidence of compromised white matter integrity within BDD patients. This suggests that there are inefficient connections between different brain areas, which may explain the cognitive and emotion regulation deficits within BDD patients.

Is the non-verbal behavioural emotion-processing profile of bipolar disorder impaired? A critical review.

OBJECTIVE: Growing evidence suggests that patients with bipolar disorder (BD) are impaired in their ability to process non-verbal emotion, although few comprehensive reviews of the behavioural literature exist, and there has been little consideration of methodological issues that may account for discrepant empirical findings. This review examines the behavioural facial, prosodic and multimodal processing literature in BD and discusses methodological issues in the context of this evidence. METHOD: Major computer databases including Google Scholar and PsychINFO were consulted to conduct a comprehensive review of quantitative behavioural differences in the emotion-processing literature in BD. Articles were accepted only if the target population sample met criteria for a DSM-III, DSM-IV or ICD-10 diagnosis, and they contained a healthy control group. RESULTS: The current literature suggests that facial emotion processing is impaired, and there is preliminary evidence for some behavioural impairment in the processing of emotional prosody. CONCLUSION: The specificity or generalisability of impairments in facial emotion processing and the effects of mood state are unclear. Similarly, the lack of clarity around the impact of auditory processes on emotional prosody processing warrants a comprehensive examination of the auditory profile in BD.

Pet ownership and mental health during COVID-19 lockdown.

Owning a pet has often been associated with improved mental health among owners, including enhanced quality of life, and decreased levels of depression and loneliness. The aim of this study was to identify whether owning a cat and/or dog was associated with better psychological wellbeing during a strict lockdown period in Victoria, Australia, during the COVID-19 pandemic. Data were analysed from a large-scale mental health study: the COvid-19 and you: mentaL heaLth in AusTralia now survEy (COLLATE). The impact of pet ownership on levels of resilience, loneliness and quality of life were examined in a sample of 138 pet owners and 125 non-pet owners. Hierarchical linear regression analyses indicated that pet ownership was significantly associated with poorer quality of life, but not significantly associated with resilience or loneliness, after accounting for situational factors (e.g. job loss) and mood states. Contrary to expectations, the findings suggest that during a specific situation such as a pandemic, pets may contribute to increased burden among owners and contribute to poorer quality of life.

Executive function in body dysmorphic disorder.

BACKGROUND: Body dysmorphic disorder (BDD) is a poorly understood disorder that involves a preoccupation with imagined or minor bodily defects. Only a few studies of neuropsychological function have been conducted. Two previous studies have indicated executive dysfunction in BDD. The current study sought to further define these executive deficits. METHOD: Fourteen DSM-IV BDD patients and 14 age- and sex-matched control participants took part. Because of the high incidence of co-morbidity in BDD, patients with co-morbid Axis I disorders were not excluded. Control participants had no history of psychiatric illness. All participants completed the following executive function (EF) tests: Spatial Span (SS), Spatial Working Memory (SWM) and the Stockings of Cambridge (SOC) task. They also completed the Pattern Recognition (PR) test, a test of visual memory (VM). RESULTS: BDD participants made significantly more between-search errors on the SWM task, an effect that increased with task difficulty. Between-search errors are an example of poor maintenance and manipulation of information. SOC results indicated slower subsequent thinking times (i.e. the time taken to plan) in BDD participants. There were no group differences in SS or PR scores. The severity of BDD, depressive or anxiety symptoms was not correlated with performance on any of the cognitive tasks. CONCLUSIONS: The results of this study indicate that BDD patients have EF deficits in on-line manipulation, planning and organization of information. By contrast, spatial memory capacity, motor speed and visual memory were intact. Considered with evidence from lesion and neuroimaging studies, these results suggest frontal lobe dysfunction in BDD.

The impact of intrinsic motivation on session attendance and reliable cognitive improvement in cognitive remediation in schizophrenia.

OBJECTIVE: Cognitive remediation (CR) is considered a potentially effective method of improving cognitive function in people with schizophrenia. Few studies, however, have explored the role of intrinsic motivation on treatment utilization or training outcomes in CR in this population. This study explored the impact of task-specific intrinsic motivation on attendance and reliable cognitive improvement in a controlled trial comparing CR with a computer game (CG) playing control. METHODS: Forty-nine participants with schizophrenia or schizoaffective disorder, allocated to 10 weeks of group-based CR (n = 25) or CG control (n = 24), provided complete outcome data at baseline. Forty-three participants completed their assigned intervention. Cognition, psychopathology and intrinsic motivation were measured at baseline and end-treatment. Regression analyses explored the relative contribution of baseline motivation and other clinical factors to session attendance as well as the association of baseline and change in intrinsic motivation with the odds of reliable cognitive improvement (calculated using reliable change indices). RESULTS: Baseline reports of perceived program value were the only significant multivariable predictor of session attendance when including global cognition and psychiatric symptomatology. The odds of reliable cognitive improvement significantly increased with greater improvements in program interest and value from baseline to end-treatment. Motivational changes over time were highly variable between participants. CONCLUSION: Task-specific intrinsic motivation in schizophrenia may represent an important patient-related factor that contributes to session attendance and cognitive improvements in CR. Regular evaluation and enhancement of intrinsic motivation in cognitively enhancing interventions may optimize treatment engagement and the likelihood of meaningful training outcomes.

Emotional prosodic processing in auditory hallucinations.

Deficits in emotional prosodic processing, the expression of emotions in voice, have been widely reported in patients with schizophrenia, not only in comprehending emotional prosody but also expressing it. Given that prosodic cues are important in memory for voice and speaker identity, Cutting has proposed that prosodic deficits may contribute to the misattribution that appears to occur in auditory hallucinations in psychosis. The present study compared hallucinating patients with schizophrenia, non-hallucinating patients and normal controls on an emotional prosodic processing task. It was hypothesised that hallucinators would demonstrate greater deficits in emotional prosodic processing than non-hallucinators and normal controls. Participants were 67 patients with a diagnosis of schizophrenia or schizoaffective disorder (hallucinating=38, non-hallucinating=29) and 31 normal controls. The prosodic processing task used in this study comprised a series of semantically neutral sentences expressed in happy, sad and neutral voices which were rated on a 7-point Likert scale from sad (-3) through neutral (0) to happy (+3). Significant deficits in the prosodic processing tasks were found in hallucinating patients compared to non-hallucinating patients and normal controls. No significant differences were observed between non-hallucinating patients and normal controls. In the present study, patients experiencing auditory hallucinations were not as successful in recognising and using prosodic cues as the non-hallucinating patients. These results are consistent with Cutting's hypothesis, that prosodic dysfunction may mediate the misattribution of auditory hallucinations.

Evidence of semantic disorganisation using semantic priming in individuals with high schizotypy.

Semantic processing deficits are present in schizophrenia and are particularly evident on semantic priming tasks. Using high schizotypes (psychosis-prone individuals) can overcome some confounds involved in studying actively symptomatic schizophrenics. In the current study, 26 high and 32 low scorers on the O-LIFE schizotypy scale (from a sample of 251 students) were selected for testing. All subjects were administered a lexical-decision semantic priming task where half the stimuli had a short 200 ms stimulus onset asynchrony (SOA, length of time from onset of prime to onset of target) and half the stimuli had a long 750 ms SOA. In addition, half the words were of high frequency and half of a low frequency. There were no group differences in priming for words of different frequencies. Low schizotypes showed greater priming at the 200 ms SOA than at the 750 ms SOA, whilst individuals with high schizotypy showed the opposite pattern. The pattern shown by the low schizotypes replicates earlier work by the authors using other normal control samples; establishing that there is greater priming under conditions of automatic spreading of activation. Furthermore, the data shows there is not an increase in automatic spreading of activation in individuals with high schizotypy. There has been controversy in the schizophrenia literature over whether there is increased priming under automatic conditions. The current study suggests that, when confounds are controlled for, schizophrenia-like symptoms are not related to an increase in automatic spreading of activation.

Dopamine and cognitive control: sex-by-genotype interactions influence the capacity to switch attention.

Cognitive performance in healthy persons varies widely between individuals. Sex differences in cognition are well reported, and there is an emerging body of evidence suggesting that the relationship between dopaminergic neurotransmission, implicated in many cognitive functions, is modulated by sex. Here, we examine the influence of sex and genetic variations along the dopaminergic pathway on aspects of cognitive control. A total of 415 healthy individuals, selected from an international consortium linked to Brain Research and Integrative Neuroscience Network (BRAINnet), were genotyped for two common and functional genetic variations of dopamine regulating genes: the catechol-O-methyltransferase [COMT] gene (rs4680) and the dopamine receptor D2 [DRD2] gene (rs6277). Cognitive measures were selected to explore sustained attention (using a continuous performance task), switching of attention (using a Trails B adaptation) and working memory (a visual computerised adaptation of digit span). While there were no main effects for genotype across any tasks, analyses revealed significant sex by genotype interactions for the capacity to switch attention. In relation to COMT, superior performance was noted in females with the Val/Val genotype and for DRD2, superior performance was seen for TT females and CC males. These findings highlight the importance of considering genetic variation in baseline dopamine levels in addition to sex, when considering the impact of dopamine on cognition in healthy populations. These findings also have important implications for the many neuropsychiatric disorders that implicate dopamine, cognitive changes and sex differences.

Are auditory hallucinations the consequence of abnormal cerebral lateralization? A morphometric MRI study of the sylvian fissure and planum temporale.

BACKGROUND: Auditory verbal hallucinations (AVHs) are a characteristic feature of schizophrenia. Patients with schizophrenia have been found to have reduced volumes of a variety of brain structures as well as a reduction in right-left asymmetries, using postmortem and magnetic resonance imaging (MRI) measures. There is also evidence that patients with AVHs differ in these structural asymmetries, relative to those patients who do not hallucinate. The aim of this study was to examine whether patients with and without a prominent history of AVHs differ, both from each other and in comparison with normal subjects, in the asymmetry of the sylvian fissure (SF) and planum temporale (PT). METHODS: We recruited 74 DSM-IV male patients with schizophrenia (on the basis of their AVH history) and 32 matched normal control subjects. Thirty patients had no history of AVHs and 44 had a strong definitive history of AVHs. The SF length and PT area and volume were measured on a three-dimensional MRI spoiled GRASS volume sequence. Absolute measures and laterality coefficients were calculated. RESULTS: : All groups had the normal leftward asymmetry in both the SF and PT. Planum temporale volume and surface area and SF length were all larger in the left hemisphere. There were no significant differences in any measures between the two patient groups or between schizophrenic patients and control subjects. Greater leftward asymmetry of the SF correlated with hallucinations and thought disorder within the prominent hallucinator group. An association was found between handedness and brain size, but this did not interact with diagnosis. CONCLUSIONS: The results of this study do not confirm reports, based on smaller samples, of reduced structural asymmetries of either the SF or PT in schizophrenia, nor do they indicate a specific relationship to a propensity to experience AVHs. A modest correlation between leftward asymmetry of the SF and some positive symptomatology was found.

Brain activation during automatic and controlled processing of semantic relations: a priming experiment using lexical-decision.

Semantic relations may be studied using the experimental technique known as semantic priming, in which a word 'primes' the processing of a related target (e.g. lion-tiger), following a short delay. Priming may be automatic or, with longer delays, under more controlled processing. This study used functional magnetic resonance imaging (fMRI) to examine the cerebral activation during two lexical-decision semantic priming experiments, with a short and long delay, representing automatic and controlled processing, respectively. A further two un-primed lexical-decision tasks were performed to distinguish cerebral activation specific to semantic priming itself from those utilised during lexical-decision processes. Distinct regions of anterior cingulate cortex (ACC) were critical to automatic and controlled semantic priming, whilst the putamen and hippocampal complex responded differently to unrelated and semantically related prime-target pairs. Lexical-decision alone revealed activation in posterior temporal cortex especially on the left, in agreement with previous neuroimaging studies. The results provide a plausible neural substrate for common semantic relations independent of task demands and further emphasise the regional functional specialisation of the ACC.

Improving performance on the WCST: variations on the original procedure. Wisconsin Card Sorting Test.

There have been several studies on WCST training in schizophrenia. However, it is still unclear what aspects of the test schizophrenic patients find most difficult: are they failing because of impaired attention, memory or planning, to name a few possibilities? To address this, seven different versions of the WCST were developed, including a range of alternative stimuli and training techniques. The subjects were 24 schizophrenics and 24 elderly controls, divided into eight groups of three pairs (one group merely repeating the standard version), matched on their poor performance of the WCST (< 3 categories). Results on retesting with the standard WCST after carrying out a modified version, suggest levels of test performance are not fixed, and that modifications which promote planning, pacing and error detection are the most successful in improving WCST score, especially in schizophrenics. Additionally, performance was improved in controls, but not schizophrenic patients by increasing the verbal information contained in the task. The results indicate that WCST deficits in elderly controls are due to limited capacity, whereas in patient with schizophrenia, the problem may be due to the impaired monitoring of responses.

Corpus callosum area and functioning in schizophrenic patients with auditory--verbal hallucinations.

Auditory--verbal hallucinations (AVH) are a characteristic feature of schizophrenia. Patients with AVHs have been found to differ from non-hallucinating patients in volumes of certain asymmetrical brain structures on MRI, and on certain neuropsychological measures. There is also evidence of corpus callosum (CC) abnormalities in schizophrenia, and it has been proposed that abnormalities of inter-hemispheric transmission may underlie hallucinations and other symptoms. The aim of this study was to examine whether patients with AVHs have smaller corpora callosa than those without AVH, and whether CC size is related to performance on neuropsychological tests of functional cerebral asymmetry. Seventy-one DSM-IV male schizophrenics were recruited on the basis of their hallucination history plus 33 matched normal controls. Twenty-nine patients had no history of AVH, and 42 had a strong history of AVH. The mid-sagittal surface area and longitudinal length of the CC were measured from T(1)-weighted spin echo images. Callosal area was divided into four sections. There were no significant differences in any of the measurements between the two patient groups, or between patients with schizophrenia and controls. There was no association between CC measures and handedness, or performance on dichotic listening or finger tapping tasks. The results of this study do not lend support for there being a major morphological abnormality of the corpus callosum in schizophrenic patients, or for a specific relationship to AVH. However, a significant association between CC area and overall grey and white matter volumes was noted in the hallucinating patients and, to a lesser extent, in the non-hallucinators, which may point to differing influences on brain development or degeneration in such patients compared with normal controls.

Building a neurocognitive profile of thought disorder in schizophrenia using a standardized test battery.

A core symptom of schizophrenia is thought disorder (TD). The cognitive abilities of semantic processing and executive function are argued to be etiologically linked to TD. However, there has been no comprehensive investigation of neurocognition in TD to date. The neurocognitive profile of 58 schizophrenia patients and 48 healthy controls was examined using the MATRICS Consensus Cognitive Battery and the D-KEFS Color-Word Interference Test. TD patients performed more poorly than non-TD patients on the cognitive domains of Verbal Learning and Inhibition, reflective of semantic and executive function respectively, confirming their critical roles over and above other cognitive deficits in schizophrenia.

Genetic variations in dopamine and inhibitory control: lack of influence on action restraint.

Failures of inhibitory control can severely affect everyday life in healthy individuals and represent a common feature of many neuropsychiatric conditions, particularly disorders with dopaminergic disturbances implicated. This study's aim was to examine the interacting influences of three common and functional gene variants that influence dopaminergic pathways on an aspect of inhibitory control (action restraint). Three hundred and twenty two healthy adults were selected from an international consortium linked to Brain Research and Integrative Neuroscience (BRAINnet). DNA was extracted from cheek swab samples and participants were genotyped for the Val158Met single nucleotide polymorphism on COMT (rs 4680), C957T on DRD2 (rs 6277) and the 40bp variable number of tandem repeat on the DAT1 (SLC6A3, 10/10 vs 9+). Response inhibition was measured using a computerised Go/No-Go task. Main effects and interactions between genotypes were explored. We did not observe a genotype effect on fundamental measures of response inhibition, i.e. reaction time (RT) and commission errors. RT variability was significantly increased in DRD2 C957T heterozygotes. In conclusion, this large, non-clinical study reveals that the selected genetic polymorphisms regulating dopamine (COMT, DRD2 and DAT1) do not influence one aspect of response inhibition, action restraint, as measured by the Go/No-Go task, reinforcing the neuropharmacological dissociation between stop-signal and Go/No-Go tasks. Genetic variation in striatal dopamine may, however, contribute to intraindividual RT variability.