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The purpose of this study was to assess the effect of computer-based cognitive training on executive dysfunction in patients with schizophrenia. Sixty-five patients with schizophrenia were randomly assigned to a training group ( n = 33) or a non-training group ( n = 32), and compared in terms of executive performance to a healthy control group ( n = 33). Executive function was assessed using the Trail Making Test, the Stroop Color and Word Test, and the Wisconsin Card Sorting Test (computer version). Cognitive training was performed using RehaCom software over a course of 16 individual sessions. Primary outcomes were training (performance at three different timepoints) and neuropsychological components (flexibility and cognitive inhibition, high executive processing, and processing speed). In both clinical groups, all aspects of executive function were found to be deficient. In the patient training group, the use of computer-based training alongside pharmacological treatment was more effective in terms of cognitive improvement than pharmacological treatment alone. However, there was no significant effect of cognitive training on processing speed. Cognitive training in schizophrenia patients was effective at improving several aspects of executive function, but did not improve processing speed.

Studies on the nature and extent of prospective memory impairment in patients with obsessive-compulsive disorder are relatively scarce. The present study examined prospective memory in patients with obsessive-compulsive disorder in comparison to patients with schizophrenia and healthy controls. Prospective memory was assessed using Memory for Intentions Screening Test (MIST). Further, the participants were administered Delis-Kaplan Executive Function System Tower Test, Wisconsin Card Sorting Test, and Stroop Test for assessing their planning ability, mental flexibility and cognitive inhibition, respectively. Monitoring was assessed by frequency of clock checking. Results indicated that as compared to healthy controls, the patients with obsessive-compulsive disorder performed poorly on both time- and event-based prospective memory tasks, whereas, patients with schizophrenia performed poorly on time-based prospective memory task only. Further, both the patient groups had comparable performance across time- and event-based tasks. Results of error analysis indicated that patients with obsessive-compulsive disorder mainly committed no response and task substitution errors, whereas patients with schizophrenia committed no response errors. Except monitoring, none of the neurocognitive variables correlated with time or event-based prospective memory in any group. The findings are discussed in the light of their implications for retraining of prospective memory deficits in patients with obsessive-compulsive disorder and schizophrenia.

Three components of cognitive inhibition were compared in patients with schizophrenia and healthy controls. Nineteen patients with schizophrenia were compared to 30 healthy controls, matched for age, sex, and educational level. Cognitive inhibition was examined by (i) access to relevant information (Reading with distraction task), (ii) suppression of no longer relevant information (Trail Making Test B), and (iii) restraint of cognitive resources to relevant information (Stroop Test, Hayling Sentence Completion Test, Go/No-Go Test). Beck Depression Inventory, and Positive and Negative Syndrome Scale were also used. Compared to healthy controls, patients with schizophrenia and stabilized for at least 6 months were slower in the inhibition condition at the Stroop task, read more distractors at the RWD, and made more perseverative errors at the TMT, even after controlling for age, Mini-Mental State Examination score, information speed processing, and accuracy. This difference remained significant after taking into account the level of depressive symptoms and the severity of psychotic symptoms. In multivariate analyses, only the Stroop interference index explained cognitive inhibition deficit in patients with schizophrenia. The abnormal cognitive inhibition process observed in patients with schizophrenia could therefore concerns the ability to restraint, rather than the access or the suppression processes.

Impairments in executive functioning have been identified as an underlying cause of Obsessive-Compulsive Disorder (OCD). Obsessive patients attempt to suppress certain unwanted thoughts through a mechanism that Wegner referred to as 'chronic thought suppression', whereas compulsive patients are unable to inhibit their rituals. We tested 51 OCD patients using the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), the White Bear Suppression Inventory (WBSI) and the Dysexecutive Questionnaire (DEX). Executive functions were tested using a cognitive test battery. We found that the total WBSI score was correlated with the Y-BOCS obsessive score but not with the Y-BOCS compulsive score. A stronger correlation was observed between the Y-BOCS obsessive score and the 'unwanted intrusive thoughts' factor based on Blumberg's 3-factor model of the WBSI. The total WBSI score was not correlated with the cognitive test results. The DEX score was significantly correlated with the Y-BOCS compulsive score; however, no correlation was found between the DEX score and the Y-BOCS obsessive score. A stronger correlation was observed between the Y-BOCS compulsive score and the 'inhibition' component of the DEX score, as defined by Burgess's 5-factor model. The DEX scores were correlated with cognitive test results measuring attention, cognitive flexibility and inhibitory processes. We conclude that obsessions indicate a failure of cognitive inhibition but do not involve significant impairment of executive functions, whereas compulsions indicate ineffective behavior inhibition and impaired executive functions.

Amphetamine abuse may lead to a psychotic state, its symptomatology being very similar to what is seen in paranoid schizophrenia. Failure of attentional inhibition of irrelevant information is thought to be associated with the psychotic symptoms in schizophrenia. Negative priming (NP) paradigm is believed to measure this impairment. Several studies have shown impaired NP in schizophrenia. In the present study a spatial NP task was used to assess attentional inhibition in a group of amphetamine-induced psychosis patients. Nineteen patients with amphetamine-induced psychotic disorder and 20 healthy subjects participated in this study. Severity of psychotic symptoms was measured prior to testing using the Brief Psychiatric Rating Scale (BPRS). Patients showed no deficit in NP, and the amount of their NP effect was not significantly different from healthy subjects. Besides, we did not find any correlation between the amount of NP effect and severity of symptoms. Our results may indicate that cognitive mechanisms underlying NP might not be affected in amphetamine psychosis.

The sensory gating deficits in schizophrenia have been theorized to associate with increased distractibility. We explore the potential associations between sensory and sensorimotor gating and subjective and objective indices of distraction in healthy subjects. Forty healthy males were assessed with the P50 suppression and pre-pulse inhibition of the startle reflex (PPI) paradigms. Additionally, a neurocognitive test battery was administered in a cross-over design: with/without auditory distraction. Significant effects of distraction were found in response inhibition, and verbal working memory and attention. Parameters from the PPI and P50 suppression paradigms were significantly associated with the distractor effects on strategy formation, cognitive inhibition and flexibility, visual short-term memory, and the level of subjective distraction. Subjectively reported distraction was significantly associated with verbal working memory and attention as well as executive and supervisory processes. Sensory and sensorimotor gating efficiency do not reflect the effect of distraction across executive and attention functions i.e. we did not observe a generalized distractor effect. Gating only related to the effect of distraction on strategy formation, cognitive inhibition and flexibility, as well as visual short term memory. Future studies should investigate if gating deficits affect the distractibility of the same specific cognitive functions in patients with schizophrenia.

Deficits in memory and cognitive inhibition have been proposed as underlying mechanisms of obsessive–compulsive disorder (OCD). To test this hypothesis, an emotional variant of the retrieval-induced forgetting (RIF) paradigm was constructed which investigates whether repeated retrieval of previously learned material (Rp +) leads to enhanced forgetting of related but nonretrieved material (Rp −) in comparison to unrelated material (NRp). Paradigm (involving OCD-relevant, neutral and negative material) was presented to 21 participants with OCD and 22 healthy controls. To compare personally relevant stimuli across groups, salience ratings of the material were included. RIF was not reduced in OCD per se. Tentative evidence was found for a weakened RIF effect for personally salient OCD-relevant material in OCD patients in comparison to healthy controls.

Previous research suggests that patients with schizophrenia demonstrate deficits in a range of parameters of motor cortical and cognitive inhibition. I-wave facilitation and long-interval cortical inhibition (LICI) are two paired pulse transcranial magnetic stimulation paradigms that appear to assess aspects of cortical inhibitory function that have not previously been assessed in this patient group. Eighteen patients with schizophrenia (nine medication-free) were compared with eight control subjects. We assessed resting motor threshold (RMT) levels, LICI and I-wave facilitation. RMT levels did not differ between the three groups. There was a significant overall difference in I-wave facilitation levels. Both patient groups as compared with the control group showed increased facilitation. There were no differences between the groups in the measure of LICI. Patients with schizophrenia appear to have increased I-wave facilitation. Increased I-wave facilitation suggests deficient function of cortical inhibitory GABAergic activity. This is consistent with previous research that has found deficient cortical inhibition in patients with schizophrenia.

a Abstract Chronic methamphetamine abuse is associated with disruption of frontostriatal function involving serotonin and dopamine circuitry. Clinically, methamphetamine-dependent (MD) individuals are highly distractible and have difficulty focussing. Here, we used a computerized single-trial version of the Stroop Test to examine selective attention and priming in MD. Subject groups comprised eight MD men (31.7"7.2 years of age), who had used methamphetamine for 15.75"8.4 years but were currently abstinent for 2-4 months, and 12 controls (35.7q9.7 years of age). Compared with the control group, the MD group exhibited significantly greater interference (P-0.05) despite intact priming. Error rates did not differ between the groups. This preliminary finding of reduced cognitive inhibition in MD individuals is consistent with the distractibility they show clinically. Furthermore, the dissociation between explicit attentional performance and priming effects suggests that some attentional functions are not as affected by long-term methamphetamine use as others. 2002 Elsevier Science Ireland Ltd. All rights reserved.

The rs1344706 single nucleotide polymorphism within intron 2 of the ZNF804A gene is strongly associated with schizophrenia and bipolar disorder. This variant has also been associated in some studies with a range of cognitive and neuroimaging phenotypes, but several studies have reported no effect on the same phenotypes in other samples. Here, we genotyped 670 healthy adult Norwegian subjects and 1753 healthy adult Swedish subjects for rs1344706, and tested for associations with cognitive phenotypes including general intellectual abilities, memory functions and cognitive inhibition. We also tested whether rs1344706 is associated with white matter microstructural properties using diffusion tensor imaging (DTI) data from 250 to 340 of the Norwegian and Swedish subjects, respectively. Whole-brain voxel-wise statistical modeling of the effect of the ZNF804A variant on two DTI indices, fractional anisotropy (FA) and radial diffusivity (RD), was performed using tract-based spatial statistics (TBSS), and commonly reported effect sizes were calculated within several large-scale white matter pathways based on neuroanatomical atlases. No significant associations were found between rs1344706 and the cognitive traits or white matter microstructure. We conclude that the rs1344706 SNP has no significant effect on these phenotypes in our two reasonably powered samples.

The presence of obsessive-compulsive symptoms (OCS) and obsessive-compulsive disorder (OCD) is frequent in patients with schizophrenia and has been associated with greater functional impairment. The impact of these features on cognitive function is unclear. In this article, we performed a systematic review and meta-analysis to assess the effect of OCS/OCD on executive functions in schizophrenia patients. Results indicate that schizophrenia patients with OCS/OCD were more impaired in abstract thinking than schizophrenia patients without OCS/OCD. This finding provides support to the double jeopardy hypothesis and may partially explain the greater functional impairment shown in schizo-obsessive patients compared to those with schizophrenia. Inconsistent results were found for set-shifting, cognitive flexibility, cognitive inhibition and verbal fluency, as indicated by the high statistical heterogeneity found. Potential sources of heterogeneity such as definition of OCS/OCD, age of onset, severity of negative symptoms and premorbid intelligence were planned to be explored but there was an insufficient number of studies to perform these analyses. Our findings highlight the complexity of the relationship between OCS/OCD and schizophrenia and warrant further investigation of the cognitive function of schizo-obsessive patients.

Deficits in inhibitory control have been reported in euthymic bipolar disorder patients. To date, data on the neuroanatomical correlates of these deficits are exclusively related to cognitive inhibition. This study aimed to examine the neural substrates of motor inhibitory control in euthymic bipolar patients. Groups of 20 patients with euthymic bipolar disorder and 20 demographically matched healthy subjects underwent event-related functional magnetic resonance imaging while performing a Go-NoGo task. Between-group differences in brain activation associated with motor response inhibition were assessed by using random-effects analyses. Although euthymic bipolar patients and healthy subjects performed similarly on the Go-NoGo task, they showed different patterns of brain activation associated with response inhibition. Specifically, patients exhibited significantly decreased activation in the left frontopolar cortex and bilateral dorsal amygdala compared with healthy subjects. There were no brain regions that were significantly more activated in patients than in healthy subjects. The findings suggest that euthymic bipolar patients have deficits in their ability to engage the left frontopolar cortex and bilateral dorsal amygdala during response inhibition. Further research should ascertain the role that such deficits may play in the emergence of impulsive behaviors that characterize bipolar disorder.

Difficulty inhibiting irrelevant information may play a central role in the aetiology of obsessive-compulsive disorder (OCD). The aim of the present study was to determine whether OCD subjects (n=20) exhibit deficits in behavioural and cognitive inhibition compared with a clinical control group diagnosed with panic disorder (n=20). All subjects were administered a Go/Nogo task (a measure of behavioural inhibition) and a Stroop test (a measure of cognitive inhibition). OCD subjects made more commission errors on the Go/Nogo task, and they made more errors and displayed longer reaction times on the interference trial of the Stroop task. Trends towards correlations were observed between OCD severity scores and Stroop reaction time, where the more severe the OCD symptoms the faster was the response. No correlations between clinical symptomatology or subject demographics and the Go/Nogo task were observed. It was demonstrated that OCD subjects exhibit deficits in behavioural and cognitive inhibition, which together may underlie the repetitive symptomatic behaviours of the disorder, such as compulsions and obsessions.