Comparison of neurocognition between drug-free patients with schizophrenia and bipolar disorder

Pareidolia in Schizophrenia and Bipolar Disorder

While there are many studies on pareidolia in healthy individuals and patients with schizophrenia, to our knowledge, there are no prior studies on pareidolia in patients with bipolar disorder. Accordingly, in this study, we, for the first time, measured pareidolia in patients with bipolar disorder (N = 50), and compared that to patients with schizophrenia (N = 50) and healthy controls (N = 50). We have used (a) the scene test, which consists of 10 blurred images of natural scenes that was previously found to produce illusory face responses and (b) the noise test which had 32 black and white images consisting of visual noise and 8 images depicting human faces; participants indicated whether a face was present on these images and to point to the location where they saw the face. Illusory responses were defined as answers when observers falsely identified objects that were not on the images in the scene task (maximum illusory score: 10), and the number of noise images in which they reported the presence of a face (maximum illusory score: 32). Further, we also calculated the total pareidolia score for each task (the sum number of images with illusory responses in the scene and noise tests). The responses were scored by two independent raters with an excellent congruence (kappa > 0.9). Our results show that schizophrenia patients scored higher on pareidolia measures than both healthy controls and patients with bipolar disorder. Our findings are agreement with prior findings on more impaired cognitive processes in schizophrenia than in bipolar patients.

Is Schizophrenia a Disorder of Consciousness? Experimental and Phenomenological Support for Anomalous Unconscious Processing

Decades ago, several authors have proposed that disorders in automatic processing lead to intrusive symptoms or abnormal contents in the consciousness of people with schizophrenia. However, since then, studies have mainly highlighted difficulties in patients' conscious experiencing and processing but rarely explored how unconscious and conscious mechanisms may interact in producing this experience. We report three lines of research, focusing on the processing of spatial frequencies, unpleasant information, and time-event structure that suggest that impairments occur at both the unconscious and conscious level. We argue that focusing on unconscious, physiological and automatic processing of information in patients, while contrasting that processing with conscious processing, is a first required step before understanding how distortions or other impairments emerge at the conscious level. We then indicate that the phenomenological tradition of psychiatry supports a similar claim and provides a theoretical framework helping to understand the relationship between the impairments and clinical symptoms. We base our argument on the presence of disorders in the minimal self in patients with schizophrenia. The minimal self is tacit and non-verbal and refers to the sense of bodily presence. We argue this sense is shaped by unconscious processes, whose alteration may thus affect the feeling of being a unique individual. This justifies a focus on unconscious mechanisms and a distinction from those associated with consciousness.

The neurocognitive functioning in bipolar disorder: a systematic review of data

BACKGROUND

During the last decades, there have been many different opinions concerning the neurocognitive function in Bipolar disorder (BD). The aim of the current study was to perform a systematic review of the literature and to synthesize the data in a comprehensive picture of the neurocognitive dysfunction in BD.

METHODS

Papers were located with searches in PubMed/MEDLINE, through June 1st 2015. The review followed a modified version of the recommendations of the Preferred Items for Reporting of Systematic Reviews and Meta-Analyses statement.

RESULTS

The initial search returned 110,403 papers. After the deletion of duplicates, 11,771 papers remained for further evaluation. Eventually, 250 were included in the analysis.

CONCLUSION

The current review supports the presence of a neurocognitive deficit in BD, in almost all neurocognitive domains. This deficit is qualitative similar to that observed in schizophrenia but it is less severe. There are no differences between BD subtypes. Its origin is unclear. It seems it is an enduring component and represents a core primary characteristic of the illness, rather than being secondary to the mood state or medication. This core deficit is confounded (either increased or attenuated) by the disease phase, specific personal characteristics of the patients (age, gender, education, etc.), current symptomatology and its treatment (especially psychotic features) and long-term course and long-term exposure to medication, psychiatric and somatic comorbidity and alcohol and/or substance abuse.

A preliminary validity study of the cambridge neuropsychological test automated battery for the assessment of executive function in schizophrenia and bipolar disorder

OBJECTIVE

Although the executive function subtests of the Cambridge Neuropsychological Test Automated Battery (CANTAB) have been used to assess cognitive function in diverse psychiatric illnesses, few studies have verified the validity of this battery for Korean psychiatric patients. Therefore, this preliminary study evaluated the construct and concurrent validity of the executive function subtests of the CANTAB for Korean psychiatric patients by comparing it with subtests of the Computerized Neuropsychological Test (CNT).

METHODS

Three subtests of the CANTAB and three subtests of the CNT were administered to 36 patients diagnosed with either schizophrenia or bipolar disorder. Subtests of the CANTAB included the Intra/Extra-Dimensional Set Shift (IED), Stockings of Cambridge (SOC), and Spatial Working Memory (SWM). Differences between groups on each subtest as well as correlations between the subtests of the CANTAB and the CNT were assessed.

RESULTS

The schizophrenia group performed significantly more poorly on the IED and the Wisconsin Card Sorting Test (WCST) compared with the bipolar disorder group. Additionally, correlation analyses revealed a significant correlation between the IED and the WCST; a positive correlation between the SOC and the Trail Making Test, Part B and the Stroop test; and a significant correlation between the SWM and the Stroop test.

CONCLUSION

This study verified the construct and concurrent validity of the executive function subtests of the CANTAB for Korean psychiatric patients and suggests that the subtests of this battery would be useful and appropriate for assessing deficits in executive function in Korean clinical settings.

Generalized and specific neurocognitive deficits in psychotic disorders: utility for evaluating pharmacological treatment effects and as intermediate phenotypes for gene discovery

A growing body of research suggests that schizophrenia and bipolar disorder share overlapping clinical, neurobiological, and genetic features, raising important questions about the boundaries and distinctiveness of these 2 major psychiatric disorders. A generalized cognitive impairment has long been understood to be a core feature of schizophrenia. More recently, it has become apparent that cognitive impairment also occurs in bipolar disorder, particularly in those patients with a history of psychotic symptoms. Whether a generalized deficit exists across a spectrum of psychotic disorders is less clearly established. Additionally, in the context of a broad impairment, it remains a significant challenge to identify deficits in specific cognitive processes that may have distinct neurochemical or regional brain substrates and linkages to particular risk-associated genetic factors. In this article, we review the findings from neuropsychological studies across a spectrum that includes schizophrenia, schizoaffective and bipolar disorders, and conclude the available evidence strongly supports that a generalized deficit is present across psychotic disorders that differs in severity more so than form. We then consider the implications of generalized and specific deficits in psychosis for 2 areas of research--the evaluation of pharmacological treatments targeting cognitive deficits, and the investigation of cognitive intermediate phenotypes in family genetic studies. Examples from the literature that touch on the relevance of the generalized deficit in these contexts are provided, as well as consideration for the continued need to identify specific impairments that are separable from the generalized deficit in order to advance drug and gene discovery.

Schizophrenia and the paranormal: more psi belief and superstition, and less déjà vu in medicated schizophrenic patients

OBJECTIVE

The present study examined the relation between déjà vu experiences and paranormal beliefs in schizophrenic patients.

METHODS

A total of 522 participants (54.5% female; mean age=33.3, SD=16.02) were recruited, including 422 healthy adults (60.9% female; mean age=29.48, SD=15.07) and 100 medicated adult schizophrenic patients (27.3% female; mean age=48.98, SD=8.57). The Chinese version of the Inventory of Déjà-vu Experiences Assessment was created via back translation. Chinese versions of the Revised Paranormal Belief Scale (CRPB), Beck Anxiety Inventory (CBAI), and Perceived Stress Scale (CPSS) were also used.

RESULTS AND CONCLUSION

After controlling for age, gender, education, and anxiety, the results supported the following three hypotheses. Schizophrenic persons have fewer déjà vu experiences than normal persons. These experiences are positively related to paranormal beliefs in healthy adults but not in schizophrenic patients. Schizophrenic patients have higher scores than healthy adults on the psi and superstitious subscales of the CRPB.

No evidence for prolonged visible persistence in patients with schizophrenia

BACKGROUND

Temporal visual processing is strongly deteriorated in patients with schizophrenia. For example, the interval required between a visual stimulus and a subsequent mask has to be much longer in schizophrenic patients than in healthy controls. We investigated whether this deficit in temporal resolution is accompanied by prolonged visual persistence and/or deficient temporal precision (temporal asynchrony perception).

METHODOLOGY/PRINCIPAL FINDINGS

We investigated visual persistence in three experiments. In the first, measuring temporal processing by so-called backward masking, prolonged visible persistence is supposed to decrease performance. In the second experiment, requiring temporal integration, prolonged persistence is supposed to improve performance. In the third experiment, we investigated asynchrony detection, as another measure of temporal resolution. Eighteen patients with schizophrenia and 15 healthy controls participated. Asynchrony detection was intact in the patients. However, patients' performance was inferior compared to healthy controls in the first two experiments. Hence, temporal processing in schizophrenic patients is indeed significantly impaired but this impairment is not caused by prolonged temporal integration.

CONCLUSIONS/SIGNIFICANCE

Our results argue against a generally prolonged visual persistence in patients with schizophrenia. Together with the preserved ability of patients, to detect temporal asynchronies in permanently presented stimuli, the results indicate a more specific deficit in temporal processing of schizophrenic patients.

Attention and masking in schizophrenia

BACKGROUND

Patients with schizophrenia are known to be impaired in masking tasks, but the mechanisms underlying their deficits are still elusive. Our study was intended to examine attentional effects, which have a known impact on masking in healthy volunteers but have only rarely been explored in relation to masking in patients.

METHODS

We compared focused versus divided attention in 18 control subjects and 18 patients using forward and backward masking tasks. In the conventional masking task, subjects had to locate one target among four possible locations. Presentation of one target allows attention to be focused, in contrast with the divided attention task in which two targets were presented either in the same hemifield or different hemifields.

RESULTS

Our results reproduce patients' deficits in forward and backward masking tasks but only when one target is presented. We show that control subjects benefit from focused attention, much more so than patients. Furthermore, patients' performance is identical to that of control subjects in backward masking when targets are presented across hemifields. This performance equalization was checked to ensure it was not due solely to the redundancy of signals (two vs. one). We achieved this by comparing performance when two targets were presented in the same vs. across hemifields, the latter yielding a greater redundancy gain.

CONCLUSIONS

From the results, it is unlikely that redundancy can account for the whole pattern of results, which suggest instead that attention deficits play a role in backward masking impairments in patients.

Relationship of neurocognitive deficits to diagnosis and symptoms across affective and non-affective psychoses

INTRODUCTION

Neurocognitive dysfunction is believed to be a core feature of schizophrenia and is increasingly recognized as a common symptom dimension in bipolar disorder. Despite a copious literature on neurocognition in these disorders, the relationship amongst neurocognition, symptoms, and diagnosis remains unclear. We examined neurocognitive functioning in a cross-diagnostic sample of patients with psychotic disorders. Based on previous findings, it was hypothesized that neurocognitive functioning would be impaired in all three patient groups, and that groups would be similarly impaired on all neuropsychological measures. Additionally, we predicted that negative symptoms but not positive, general, or mood symptoms, would be associated with neurocognitive functioning.

METHOD

Neurocognitive functioning and symptoms were assessed in participants with schizophrenia (n=25), schizoaffective disorder (n=29), or bipolar disorder with psychosis (n=31), and in healthy controls (n=20).

RESULTS

Neurocognitive functioning was significantly impaired in all patient groups, and groups did not differ by diagnosis on most measures. A series of linear regressions revealed that negative symptoms (but no other clinical symptom) predicted poorer executive functioning across groups. Diagnosis was not a significant predictor of any neurocognitive variable.

DISCUSSION

Neurocognitive deficits were pronounced in this cross-diagnostic sample of patients with psychotic disorders, and did not differ by diagnosis. Neurocognitive dysfunction may represent a symptom dimension that spans diagnostic categories, and may reflect shared pathogenic processes. As neurocognitive dysfunction is among the strongest predictors of outcome in patients, efforts to treat these deficits, which have shown promise in schizophrenia, should be extended to all patients with psychosis.

Evolution of neuropsychological dysfunction during the course of schizophrenia and bipolar disorder

BACKGROUND

Neurocognitive dysfunction in schizophrenia (SZ), bipolar (BD) and related disorders represents a core feature of these illnesses, possibly a marker of underlying pathophysiology. Substantial overlap in domains of neuropsychological deficits has been reported among these disorders after illness onset. However, it is unclear whether deficits follow the same longitudinal pre- and post-morbid course across diagnoses. We examine evidence for neurocognitive dysfunction as a core feature of all idiopathic psychotic illnesses, and trace its evolution from pre-morbid and prodromal states through the emergence of overt psychosis and into chronic illness in patients with SZ, BD and related disorders.

METHOD

Articles reporting on neuropsychological functioning in patients with SZ, BD and related disorders before and after illness onset were reviewed. Given the vast literature on these topics and the present focus on cross-diagnostic comparisons, priority was given to primary data papers that assessed cross-diagnostic samples and recent meta-analyses.

RESULTS

Patients with SZ exhibit dysfunction preceding the onset of illness, which becomes more pronounced in the prodrome and early years following diagnosis, then settles into a stable pattern. Patients with BD generally exhibit typical cognitive development pre-morbidly, but demonstrate deficits by first episode that are amplified with worsening symptoms and exacerbations.

CONCLUSIONS

Neuropsychological deficits represent a core feature of SZ and BD; however, their onset and progression differ between diagnostic groups. A lifetime perspective on the evolution of neurocognitive deficits in SZ and BD reveals distinct patterns, and may provide a useful guide to the examination of the pathophysiological processes underpinning these functions across disorders.

Rapid computerized assessment of neurocognitive deficits in bipolar disorder

The purpose of this study is to illustrate the clinical usefulness of a computerized neuropsychological battery for identifying neurocognitive deficits in adults with bipolar disorder. Participants were 47 outpatients with bipolar disorder who were individually matched on age, education, sex, and ethnicity to 47 control subjects from the Central Nervous System (CNS) Vital Signs normative database. CNS Vital Signs is comprised of seven common neuropsychological measures, and it generates 15 primary scores that are used to calculate five domain scores (Memory, Psychomotor Speed, Reaction Time, Cognitive Flexibility, and Complex Attention). There was a significant multivariate effect and statistically significantly worse scores for those in the bipolar group on all five domain scores (medium to large effect sizes). When using two or more scores below the fifth percentile as a cutoff for neurocognitive impairment, 42.6% of the bipolar sample and only 6.4% of the control sample scored in this range. A subset of outpatients with bipolar disorder has frank neurocognitive impairments identifiable with this 30-40-minute computerized assessment battery.

Alterações cognitivas na esquizofrenia: atualização

As alterações cognitivas são características centrais na esquizofrenia. Elas permanecem relativamente estáveis durante todo o curso da doença, não sendo secundárias a outros sintomas ou a efeitos colaterais de psicofármacos. Estão diretamente ligadas a prejuízo funcional e a pior qualidade de vida dos pacientes. Diversos estudos vêm sendo realizados no sentido de caracterizar as principais alterações cognitivas na esquizofrenia, identificar suas bases neurobiológicas e padronizar instrumentos de pesquisa, fundamentais para o advento de novos alvos para intervenções farmacológicas na esquizofrenia. O objetivo deste trabalho foi fazer uma atualização sobre o assunto.

Comparative study of neurocognitive function in euthymic bipolar patients and stabilized schizophrenic patients

Few studies have compared neurocognitive performance in euthymic patients with bipolar disorder (BD), stabilized patients with schizophrenia (SC) and normal controls (NC) using a comprehensive neuropsychological battery, and those that have been conducted have yielded discrepant results. We evaluated the neurocognitive profile shown by 73 euthymic patients with BD, 89 stabilized patients with SC and 67 NC. All participants completed a cognitive battery in which the domains evaluated were executive functioning, sustained attention, and verbal and visual memory. Individuals with BD were administered the Quality of Life Scale (QLS). Patients with BD manifested dysfunction in executive functioning (moderate-to-large effect size), sustained attention (moderate effect size) and verbal/visual memory (large effect size) compared with NC. Verbal memory deficit in patients with BD was related to poor functional outcome on the QLS and Global Assessment of Functioning (GAF). Patients with BD performed significantly better than patients with SC on the Trail Making Test (TMT) part B, backward digit span, and California Verbal Learning Test (CVLT) learning trials. Other neuropsychological measures showed no significant differences between the two patient groups. These findings support the notion that euthymic BD patients suffer from an extensive neurocognitive deficit that affects all cognitive domains and is qualitatively similar to that in SC patients. Persistent verbal memory impairment in BD has clinical relevance because it is associated with poor psychosocial function.

Are masking abnormalities in schizophrenia limited to backward masking?

Schizophrenia, it has been proposed, is associated with deficits in the magnocellular part of the visual system. In support of this suggestion, it has been claimed that schizophrenic subjects have abnormal backward masking. However, if this abnormality is to be linked specifically to magnocellular defects, then it must be specific to backward masking, and not, also effect, for example, forward masking. We examined this issue by reviewing the studies of masking in schizophrenic subjects. We find: (i) Most studies (56 out of 67) of backward masking have researched only backward masking. This makes it impossible to determine if the abnormalities found in these studies are exclusively confined to backward masking. (ii) Of those studies (11) that have included both forward and backward masking conditions, the majority found some degree of abnormality under both forward and backward masking conditions. It is concluded that the evidence for linking the abnormalities found in those with schizophrenia specifically to backward masking, rather than masking in general, or more general visual impairments, is at present relatively weak. Given the rationale for using backward masking as a test of magnocellular sensitivity, research in this area does not point to a deficit specific to the magnocellular system.

P300 event-related potential in euthymic patients with bipolar disorder

Auditory P300 event-related potential (ERP) and performance on Sustained Attention were evaluated in 24 euthymic bipolar patients and 38 healthy volunteers. There were no significant differences between groups, and performance in sustained attention had no significant influence in the P300 responses. P300 response might be driven by the presence of mood symptoms.

Theory of mind deficit in bipolar disorder: is it related to a previous history of psychotic symptoms?

It has been hypothesized that a Theory of Mind (ToM) deficit could be a vulnerability marker for psychosis. Recent studies, however, have shown ToM deficits in affective relapses of bipolar disorder as well as in the euthymic phase. This study analyzes the relationship between ToM and a previous history of psychotic symptoms in bipolar disorder. ToM, sustained attention and executive functions were analyzed in 75 bipolar euthymic patients with three or more previous relapses (42 of them had a history of psychotic symptoms and 33 did not) and 48 healthy subjects. ToM was assessed with the Advanced Test by Happé. ToM performance was similar in bipolar patients with or without a history of psychotic symptoms, and in both cases it was significantly reduced as compared with the healthy control group. Similarly, both bipolar groups showed impaired sustained attention and executive functions. This general cognitive deficit partially explains the differences obtained in ToM. The ToM instrument used shows low sensitivity for assessing ToM in bipolar patients and it could partially reflect general cognitive functioning rather than a specific deficit in psychosis. ToM deficit is not a trait marker for psychosis, given that it is present in bipolar disorder regardless of a previous history of psychotic symptoms.

Cognitive functions in euthymic patients with bipolar disorder

BACKGROUND

Recent studies have focused on the nature of cognitive dysfunction in bipolar patients. The purpose of the current study was to investigate cognitive performance of individuals with bipolar disorder compared to healthy control subjects during a well-established euthymic period.

METHODS

The sample consisted of 27 bipolar euthymic patients and 21 control subjects. Verbal and visual memory performance, attention, executive functions and psychosocial functions were evaluated for each participant.

RESULTS

Bipolar patients showed significant attentional deficit and executive dysfunction and also poor performance on verbal and visual memory tasks compared to the controls. Illness duration and lifetime total episode number and previous episode with psychotic features was associated with worsened performance on attention, executive and memory tasks. Psychosocial functioning was not associated with cognitive deficit.

CONCLUSIONS

The present study showed persistent cognitive impairment on inhibitory control and selective attention as well as poor performance on verbal and visual memory tests in a group of bipolar euthymic patients. The impaired neuropsychological performance was associated with duration of illness, total number of episodes per lifetime, and previous episodes with psychotic features. Attentional dysfunction seemed to be a trait abnormality for the sample studied.

Vernier threshold and the parallel visual pathways in bipolar disorder: a follow-up study

Magnocellular (M) and parvocellular (P) visual pathways participate in the processing of low contrast and colors of objects, respectively. The aim of this study was to investigate M and P pathway functions in bipolar disorder during a depressive episode and after the amelioration of symptoms. Participants (17 patients with type I bipolar disorder and 20 matched healthy controls) received two vernier tasks. During the M pathway test, stimuli were dots with low luminance-contrast (5%), whereas during the P pathway test, isoluminant blue dots were presented against a yellow background. Participants were asked to detect the direction of the horizontal displacement of the dots (left or right). The assessment was performed during a depressive state and during a clinically improved state after 2 months. During the depressive state, the patients showed significantly impaired M and P pathway functions, whereas during the clinically improved state, their performance was better and was statistically indistinguishable from that of the controls. In conclusion, M and P pathways are impaired in depressed bipolar patients. This deficit is ameliorated along with clinical improvement. Further studies are necessary to separately assess cortical and precortical stages of information-processing, and to exclude the possibility of general motivational and attentional impairments.

Classification of adolescent psychotic disorders using linear discriminant analysis

BACKGROUND

The differential diagnosis between schizophrenia and bipolar disorder during adolescence presents a major clinical problem. Can these two diagnoses be differentiated objectively early in the courses of illness?

METHODS

We used linear discrimination analysis (LDA) to classify 28 adolescent subjects into one of three diagnostic categories (healthy, N=8; schizophrenia, N=10; bipolar, N=10) using subsets from a pool of 45 variables as potential predictors (22 neuropsychological test scores and 23 quantitative structural brain measurements). The predictor variables were adjusted for age, gender, race, and psychotropic medication. All possible subsets composed of k=2-12 variables, from the set of 45 variables available, were evaluated using the robust leaving-one-subject-out method.

RESULTS

The highest correct classification (96%) of the 3 diagnostic categories was yielded by 9 sets of k=12 predictors, comprising both neuropsychological and brain structural measures. Although each one of these sets misclassified one case, each set correctly classified (100%) at least one group, such that a fully correct diagnosis could be reached by a tree-type decision procedure.

CONCLUSIONS

We conclude that LDA with 12 predictor variables can provide correct and robust classification of subjects into the three diagnostic categories above. This robust classification relies upon both neuropsychological and brain structural information. Our results demonstrate that, despite overlapping clinical symptoms, schizophrenia and bipolar disorder can be differentiated early in the course of disease. This finding has two important implications. Firstly, schizophrenia and bipolar disorder are different illnesses. If schizophrenia and bipolar are dissimilar clinical manifestations of the same disease, we would not be able to use non-clinical information to classify ('diagnose') schizophrenia and bipolar disorder. Secondly, if this study's findings are replicated, brain structure (MRI) and brain function (neuropsychological) used together may be useful in the diagnosis of new patients.

Specificity of cognitive deficits in bipolar disorder versus schizophrenia. A systematic review

BACKGROUND

More and more epidemiological, genetic and neuroimaging studies show similarities between bipolar disorder (BD) and schizophrenia (SZ). Cognitive functions are known to be highly impaired in SZ and are increasingly studied in BD. When both populations are compared, the conclusions appear to be contradictory. The purpose of this review is to help define the profile of cognitive deficits in BD and in SZ.

METHODS

A systematic review of the literature of neuropsychological studies comparing BD and SZ was made, beginning in January 1990 and ending in January 2005. Thirty-eight studies met the required quality criteria and were included in this review.

RESULTS

Bipolar patients exhibit extensive cognitive abnormalities with a pattern of deficits that is not unique to this disease. However, when compared to schizophrenic patients, bipolar patients demonstrate a lesser degree of deficits, particularly concerning premorbid and current intelligence quotient and perhaps attention, verbal memory and executive functions. When looking into effect sizes, there seem to be different profiles even in studies finding no significant differences.

CONCLUSIONS

The neuropsychological differences reported between both groups could be due to the presence of psychotic features, to environmental factors (stressful events, duration of the disease and number of hospitalisations) and could also be related to differences during the neurodevelopmental phase. Further studies should confirm whether these results are truly related to different neurobiological backgrounds.

Cognitive functioning in patients with schizophrenia and bipolar disorder: a quantitative review

OBJECTIVE

Evidence suggests that cognitive functioning in bipolar disorder may be impaired even in euthymic states, but it is unclear if the pattern of deficits is similar to the deficits found in schizophrenia. The aim of this study was to review quantitatively the studies on cognitive performance in schizophrenia and bipolar disorder.

METHODS

Articles for consideration were identified through a literature search in MEDLINE and PsycLIT in the period between 1985 and October 2004, using the keywords "schizophrenia" combined with "bipolar disorder", or "manic-depress*" or "manic" combined with "cogniti*" or "neuropsycholog*". Thirty-one studies were included that: i) evaluated cognitive performance using standardized and reliable neuropsychological testing procedures; ii) compared adult patients with schizophrenia and with bipolar disorder; iii) reported test scores of both patient groups, or exact p-values, t-values, or F-values; and iv) were published as an original article in a peer-reviewed English language journal.

RESULTS

Meta-analyses of all studies indicated that patients with bipolar disorder generally perform better than patients with schizophrenia, but the distribution of effect sizes showed substantial heterogeneity. Results based on a more homogeneous subset of studies that matched patient groups on clinical and demographic characteristics pointed in the same direction, with effect sizes in the moderate range.

CONCLUSIONS

Patients with bipolar disorder show better cognitive performance than patients with schizophrenia, even when matched for clinical and demographic characteristics.

Differential effects of chronic lithium and valproate on brain activation in healthy volunteers

RATIONALE

Previous functional imaging studies have shown altered brain activity during cognitive task performance in bipolar patients. However, the fact that these patients are often on medication makes it unclear to what extent these changes reflect treatment effects.

OBJECTIVES

This study aims to identify regional brain activity changes occurring following lithium and valproate treatment in healthy volunteers.

METHODS

This was a double-blind, placebo-controlled, study in which volunteers received either 1000 mg sodium valproate (n = 12), 900 mg lithium (n = 9), or placebo (n = 12). Functional images were acquired using functional magnetic resonance imaging (fMRI) while subjects performed three cognitive tasks, a word generation paradigm, a spatial attention task and a working memory task. fMRI was carried out both before and after 14 days of treatment with valproate, lithium or placebo. The changes in the magnitude of the blood-oxygen-level-dependent (BOLD) signal after treatment were compared between the groups using a one-way ANOVA for each task followed by a post-hoc multiple comparisons correction.

RESULTS

A significant group effect was noted in the change in BOLD signal magnitude from baseline to post-treatment, in all three tasks (working memory p< 0.000; spatial attention task p = 0.003; word generation paradigm p = 0.030). In the working memory task, the lithium group had a significant decrease in BOLD signal change, compared with the control group (p< 0.000). A decrease in BOLD signal change was also noted in the valproate group, in the spatial attention task (p = 0.004). Both lithium and valproate groups had a decreased BOLD signal in the verbal task, following treatment, compared with the placebo group (p = 0.061 (lithium approached significance); p = 0.050 (valproate)).

CONCLUSIONS

These findings suggest that lithium and valproate have independent effects on brain activation that vary in a task and region-dependent manner.