No effects of l-dopa and bromocriptine on psychophysiological parameters of human selective attention

Patients with schizophrenia exhibit diverse cognitive deficits, one of which is a loss of the ability to focus attention. According to the revised dopamine hypothesis of schizophrenia both an increased mesolimbic and a decreased prefrontal dopaminergic activity is suggested to be involved in schizophrenia. The current study was designed to explore the relationship between dopamine and two psychophysiological parameters of selective attention, i.e. P300 amplitude and processing negativity (PN) in healthy volunteers. In two separate experiments, with a double-blind, balanced and placebo-controlled crossover design, 18 healthy male volunteers were orally administered either 300 mg l-dopa (precursor of dopamine) or placebo (experiment I), or 1.25mg bromocriptine (D2 agonist) or placebo (experiment II). Following this treatment they were tested in an auditory, dichotic selective attention paradigm. An increase in P300 amplitude was found following deviant stimuli when compared to standard stimuli and following attended stimuli when compared to unattended stimuli, regardless of treatment. Similarly, PN was found regardless of treatment. Neither l-dopa nor bromocriptine affected task performance or the amplitudes of PN or P300. In the present study neither l-dopa nor bromocriptine affected PN, P300 amplitude or task performance in healthy controls, phenomena which are usually found to be disrupted in schizophrenia. This indicates that P300 amplitude and PN are neither affected by a global (l-dopa) increased dopaminergic activity, nor by a more selectively towards striatal areas targeted (bromocriptine) increase in dopaminergic activity.

Brain volume changes in the first year of illness and 5-year outcome of schizophrenia

Progressive brain volume changes have been reported in first-episode schizophrenia, but their relationship to the disease process or to other factors remains unclear. We examined such changes in the first year of illness, and related them to 5-year outcome. Progressive brain volume changes, in particular of grey matter, during the first year of illness were found to be significantly associated with clinical and functional outcome 5 years after the first episode. These findings suggest that early dynamic brain volume changes are related to the disease process and predict the longer-term outcome of schizophrenia.

Effects of aging on BOLD fMRI during prosaccades and antisaccades

Age affects the ability to inhibit saccadic eye movements. According to current theories, this may be associated with age-induced neurophysiological changes in the brain and with compensatory activation in frontal brain areas. In the present study, the effects of aging are assessed on brain systems that subserve generation and inhibition of saccadic eye movements. For this purpose, an event-related functional magnetic resonance imaging design was used in adults covering three age ranges (18-30, 30-55, and 55-72 years). Group differences were controlled for task performance. Activity associated with saccadic inhibition was represented by the contrast between prosaccade and antisaccade activation. The tasks activated well-documented networks of regions known to be involved in generation and inhibition of saccadic eye movements. There was an age-related shift in activity from posterior to frontal brain regions after young adulthood. In addition, old adults demonstrated an overall reduction in the blood oxygenation level dependent (BOLD) signal in the visual and oculomotor system. Age, however, did not affect saccade inhibition activity. Mid and old adults appear to increase frontal activation to maintain performance even during simple prosaccades. The global reduction of the BOLD response in old adults could reflect a reduction in neural activity, as well as changes in the neuronal-vascular coupling. Future research should address the impact of altered vascular dynamics on neural activation and the BOLD signal.

Olanzapine and haloperidol in first episode psychosis: two-year data

Few studies have assessed the comparative efficacy and safety of atypical and typical antipsychotic medications in patients within their first episode of psychosis. This study examined the effectiveness of the atypical antipsychotic olanzapine and the typical antipsychotic haloperidol in patients experiencing their first episode of a schizophrenia-related psychotic disorder over a 2-year treatment period. Two hundred and sixty-three patients were randomized to olanzapine or haloperidol in a doubleblind, multisite, international 2-year study. Clinical symptoms and side effects were assessed at baseline and longitudinally following randomization for the duration of the study. Olanzapine and haloperidol treatment were both associated with substantial and comparable reductions in symptom severity (the primary outcome measure) over the course of the study. However, the treatment groups differed on two secondary efficacy measures. Patients were less likely to discontinue treatment with olanzapine than with haloperidol: mean time (in days) in the study was significantly greater for those treated with olanzapine compared to haloperidol (322.09 vs. 230.38, p<0.0085). Moreover, remission rates were greater in patients treated with olanzapine as compared to those treated with haloperidol (57.25% vs. 43.94%, p<0.036). While extrapyramidal side effects were greater in those treated with haloperidol, weight gain, cholesterol level and liver function values were greater in patients treated with olanzapine. The data from this study suggest some clinical benefits for olanzapine as compared to haloperidol in first episode patients, which must be weighed against those adverse effects that are more likely with olanzapine.

Long-term effects of frequent cannabis use on working memory and attention: an fMRI study

RATIONALE

Excessive use of cannabis may have long-term effects on cognitive abilities. Mild impairments have been found in several cognitive domains, particularly in memory and attention. It is not clear, however, whether these effects also occur with moderate, recreational use of cannabis. Furthermore, little is known about underlying brain correlates.

OBJECTIVES

The aim of this study is to assess brain function in frequent but relatively moderate cannabis users in the domains of working memory and selective attention.

METHODS

Functional magnetic resonance imaging was used to examine verbal working memory and visuo-auditory selective attention in ten frequent cannabis users (after 1 week of abstinence) and ten non-using healthy controls. Groups were similar in age, gender and estimated IQ.

RESULTS

Cannabis users and controls performed equally well during the working memory task and the selective attention task. Furthermore, cannabis users did not differ from controls in terms of overall patterns of brain activity in the regions involved in these cognitive functions. However, for working memory, a more specific region-of-interest analysis showed that, in comparison to the controls, cannabis users displayed a significant alteration in brain activity in the left superior parietal cortex.

CONCLUSION

No evidence was found for long-term deficits in working memory and selective attention in frequent cannabis users after 1 week of abstinence. Nonetheless, frequent cannabis use may affect brain function, as indicated by altered neurophysiological dynamics in the left superior parietal cortex during working memory processing.

Brain activation during antisaccades in unaffected relatives of schizophrenic patients

BACKGROUND

Schizophrenia patients have difficulty inhibiting automatic saccades. Many studies have failed to resolve whether healthy first-degree relatives share the same deficit. Measures of brain activity may be more sensitive than behavioral measures. In patients, the saccadic inhibition deficit has been related to impaired frontostriatal functioning. This study attempts to establish whether this abnormality is also present in unaffected relatives of patients.

METHODS

Functional brain images were acquired during prosaccades and antisaccades in 16 control subjects and 16 unaffected siblings of schizophrenia patients using an event-related functional magnetic resonance imaging design. Eye movements were measured during scanning.

RESULTS

The task activated a network of regions corresponding to the oculomotor system. Siblings and control subjects did not differ during execution of prosaccades. During antisaccades, siblings did not activate the caudate nucleus. Siblings and control subjects did not differ on the percentage of antisaccade errors.

CONCLUSIONS

Siblings did not appropriately activate the striatum during antisaccades, similar to what has been reported in patients. Siblings, however, did not make significantly more errors during antisaccades, indicating that they were able to compensate for the inactive caudate. Future research is needed to assess the potential of this striatal deficit as (genetic) risk factor for schizophrenia.

Predictors of antipsychotic medication adherence in patients recovering from a first psychotic episode

BACKGROUND

Many patients recovering from a first psychotic episode will discontinue medication against medical advice, even before a 1-year treatment course is completed. Factors associated with treatment adherence in patients with chronic schizophrenia include beliefs about severity of illness and need for treatment, treatment with typical versus atypical antipsychotic and medication side effects.

METHOD

In this 2-year prospective study of 254 patients recovering from a first episode of schizophrenia, schizophreniform, or schizoaffective disorder we examined the relationship between antipsychotic medication non-adherence and patient beliefs about: need for treatment, antipsychotic medication benefits, and negative aspects of antipsychotic medication treatment. We also examined the relationship between medication non-adherence and treatment with either haloperidol or olanzapine, and objective measures of symptom response and side effects.

RESULTS

The likelihood of becoming medication non-adherent for 1 week or longer was greater in subjects whose belief in need for treatment was less (HR=1.75, 95% CI 1.16, 2.65, p=0.0077) or who believed medications were of low benefit (HR=2.88, 95 CI 1.79-4.65, p<0.0001). Subjects randomized to haloperidol were more likely to become medication non-adherent for >or=1 week than subjects randomized to olanzapine (HR-1.51, 95% CI 1.01, 2.27, p=0.045).

CONCLUSION

Beliefs about need for treatment and the benefits of antipsychotic medication may be intervention targets to improve likelihood of long-term medication adherence in patients recovering from a first episode of schizophrenia, schizoaffective, or schizophreniform disorder.

An Intervention Study to Prevent Relapse in Patients With Schizophrenia

PURPOSE

To determine whether the use of relapse prevention plans (RPPs) in nursing practice is an effective intervention in reducing relapse rates among patients with schizophrenia.

DESIGN AND METHODS

Experimental design. Patients with schizophrenia (or a related psychotic disorder) and nurses from three mental health organizations were randomly assigned to either an experimental (RPP) or control condition (care as usual). The primary outcome measure was the psychotic relapses in the research groups.

RESULTS

The relapse rates in the experimental and control groups after 1-year follow-up were 12.5% and 26.2%, respectively (p=. 12, ns). The relative risk of a relapse in the experimental versus the control group was 0.48 (ns).

CONCLUSIONS

In this study no statistically significant effects of the intervention were found. Effectiveness research in this area should be continued with larger sample sizes and longer follow-up periods.

Homocysteine, methylenetetrahydrofolate reductase and risk of schizophrenia: a meta-analysis

Elevated plasma homocysteine concentration has been suggested as a risk factor for schizophrenia, but the results of epidemiological studies have been inconsistent. The most extensively studied genetic variant in the homocysteine metabolism is the 677C>T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene, resulting in reduced enzyme activity and, subsequently, in elevated homocysteine. A meta-analysis of eight retrospective studies (812 cases and 2113 control subjects) was carried out to examine the association between homocysteine and schizophrenia. In addition, a meta-analysis of 10 studies (2265 cases and 2721 control subjects) on the homozygous (TT) genotype of the MTHFR 677C>T polymorphism was carried out to assess if this association is causal. A 5 micromol/l higher homocysteine level was associated with a 70% (95% confidence interval, CI: 27-129) higher risk of schizophrenia. The TT genotype was associated with a 36% (95% CI: 7-72) higher risk of schizophrenia compared to the CC genotype. The performed meta-analyses showed no evidence of publication bias or excessive influence attributable to any given study. In conclusion, our study provides evidence for an association of homocysteine with schizophrenia. The elevated risk of schizophrenia associated with the homozygous genotype of the MTHFR 677C>T polymorphism provides support for causality between a disturbed homocysteine metabolism and risk of schizophrenia.

Negative priming in schizophrenia revisited

Reduced spatial negative priming (SNP) in schizophrenia is commonly attributed to the inability to filter out irrelevant information. However, some investigators have suggested that reduced SNP in patients is caused by either perceptual mismatching or salience of the distracter. The goal of the present study was to determine the influence of these perceptual processes. In this preliminary report, we present data of 15 schizophrenia patients on atypical medication and 15 matched healthy controls. Compared to controls, patients showed a reduced SNP effect, even when controlled for perceptual mismatching. This reduced effect was not affected by distracter salience.

Brain MRI abnormalities in schizophrenia: same genes or same environment?

BACKGROUND

Structural brain volume abnormalities are among the most extensively studied endophenotypes in schizophrenia. Bivariate genetic model fitting (adjusted to account for selection) was used to quantify the genetic relationship between schizophrenia and brain volumes and to estimate the heritability of these volumes.

METHOD

We demonstrated by simulation that the adjusted genetic model produced unbiased estimates for endophenotype heritability and the genetic and environmental correlations. The model was applied to brain volumes (whole brain, hippocampus, third and lateral ventricles) in a sample of 14 monozygotic (MZ) twin pairs concordant for schizophrenia, 10 MZ discordant pairs, 17 MZ control pairs, 22 discordant sibling pairs, three concordant sibling pairs, and 114 healthy control subjects.

RESULTS

Whole brain showed a substantial heritability (88%) and lateral ventricles substantial common environmental effects (67%). Whole brain showed a significant genetic correlation with schizophrenia, whereas lateral ventricles showed a significant individual specific correlation with schizophrenia. There were significant familial effects for hippocampus and third ventricle, but the analyses could not resolve whether these were genetic or environmental in origin (around 30%each).

CONCLUSIONS

Using genetic model fitting on twin and sibling data we have demonstrated differential sources of covariation between schizophrenia and brain volumes, genetic in the case of whole brain volume and individual specific environment in the case of lateral ventricles.

The incidence of cognitive decline after (not) undergoing coronary artery bypass grafting: the impact of a controlled definition

BACKGROUND

After coronary artery bypass grafting (CABG), 20-30% of patients are reported to suffer from cognitive decline. Studies reporting these high incidences, however, have not included an appropriate control group.

METHODS

We repeatedly administered a series of neuropsychological tests to 112 healthy middle-aged volunteers not undergoing surgery, and applied two widely used definitions of cognitive decline to their test results. In addition, we re-analysed the neuropsychological test data of 281 CABG patients with a definition of cognitive decline that takes into account the natural variability of test performance that was found in the volunteers.

RESULTS

Three months after their first assessment, 14-28% of the volunteers suffered from cognitive decline according to the definitions of cognitive decline after CABG. Using the controlled definition of cognitive decline that takes the natural variability in test performance into account, we found that only 7.7% of the CABG patients suffered from cognitive decline at 3 months after their operation.

CONCLUSION

These data suggest that the incidence of cognitive dysfunction after CABG has previously been greatly overestimated.

Differential effects of DRD4 and DAT1 genotype on fronto-striatal gray matter volumes in a sample of subjects with attention deficit hyperactivity disorder, their unaffected siblings, and controls

Genetic influences on behavior are complex and, as such, the effect of any single gene is likely to be modest. Neuroimaging measures may serve as a biological intermediate phenotype to investigate the effect of genes on human behavior. In particular, it is possible to constrain investigations by prior knowledge of gene characteristics and by including samples of subjects where the distribution of phenotypic variance is both wide and under heritable influences. Here, we use this approach to show a dissociation between the effects of two dopamine genes that are differentially expressed in the brain. We show that the DAT1 gene, a gene expressed predominantly in the basal ganglia, preferentially influences caudate volume, whereas the DRD4 gene, a gene expressed predominantly in the prefrontal cortex, preferentially influences prefrontal gray matter volume in a sample of subjects including subjects with ADHD, their unaffected siblings, and healthy controls. This demonstrates that, by constraining our investigations by prior knowledge of gene expression, including samples in which the distribution of phenotypic variance is wide and under heritable influences, and by using intermediate phenotypes, such as neuroimaging, we may begin to map out the pathways by which genes influence behavior.

Accurate determination of microsatellite allele frequencies in pooled DNA samples

Pooling of DNA samples instead of individual genotyping can speed up genetic association studies. However, for microsatellite markers, the electrophoretic pattern of DNA pools can be complex, and procedures for deriving allele frequencies are often confounded by PCR-induced stutter artefacts. We have developed a mathematical procedure to remove stutter noise and accurately determine allele frequencies in pools. A stutter correction model can be reliably derived from one standard 'training set' of the same 10 individual DNA samples for each marker, which can also include heterozygous patterns with partially overlapping peaks. Compared with earlier methods, this reduces the number of genotypes needed in the training set considerably, and allows standardization of analyses for different markers. Moreover, the use of a procedure that fits all data simultaneously makes the method less sensitive to aberrant data. The model was tested with 34 markers, 18 of which were newly defined from human sequence data. Allele frequencies derived from stutter-corrected DNA pool patterns were compared with the summed individual genotyping results of all the individuals in the pools (n = 109 and n = 64). We show that the model is robust and accurately extracts allele frequencies from pooled DNA samples for 32 of the 34 microsatellite markers tested. Finally, we performed a case-control study in celiac disease and found that weakly associated disease alleles, identified by individual genotyping, were only detectable in pools after stutter correction. This efficient method for correcting stutter artefacts in microsatellite markers enables large-scale genetic association studies using DNA pools to be performed.

Migration, family dysfunction and psychotic symptoms in children and adolescents

A cross-sectional study of 3426 referred children and adolescents showed that the presence of both migration history and family dysfunction was associated with a fourfold (95% CI 2-9) higher risk of psychotic symptoms compared with the absence of these factors. The relative risk was 2 (95% CI 1-4) for migration history only. Interaction between migration history and family dysfunction accounted for 58% (95% CI 5-91%) of those with psychotic symptoms. These results suggest a relationship between family dysfunction and migration in the development of psychosis.

Antipsychotic drug effects on brain morphology in first-episode psychosis

BACKGROUND

Pathomorphologic brain changes occurring as early as first-episode schizophrenia have been extensively described. Longitudinal studies have demonstrated that these changes may be progressive and associated with clinical outcome. This raises the possibility that antipsychotics might alter such pathomorphologic progression in early-stage schizophrenia.

OBJECTIVE

To test a priori hypotheses that olanzapine-treated patients have less change over time in whole brain gray matter volumes and lateral ventricle volumes than haloperidol-treated patients and that gray matter and lateral ventricle volume changes are associated with changes in psychopathology and neurocognition.

DESIGN

Longitudinal, randomized, controlled, multisite, double-blind study. Patients treated and followed up for up to 104 weeks. Neurocognitive and magnetic resonance imaging (MRI) assessments performed at weeks 0 (baseline), 12, 24, 52, and 104. Mixed-models analyses with time-dependent covariates evaluated treatment effects on MRI end points and explored relationships between MRI, psychopathologic, and neurocognitive outcomes.

SETTING

Fourteen academic medical centers (United States, 11; Canada, 1; Netherlands, 1; England, 1).

PARTICIPANTS

Patients with first-episode psychosis (DSM-IV) and healthy volunteers.

INTERVENTIONS

Random allocation to a conventional antipsychotic, haloperidol (2-20 mg/d), or an atypical antipsychotic, olanzapine (5-20 mg/d).

MAIN OUTCOME MEASURES

Brain volume changes assessed by MRI.

RESULTS

Of 263 randomized patients, 161 had baseline and at least 1 postbaseline MRI evaluation. Haloperidol-treated patients exhibited significant decreases in gray matter volume, whereas olanzapine-treated patients did not. A matched sample of healthy volunteers (n = 58) examined contemporaneously showed no change in gray matter volume.

CONCLUSIONS

Patients with first-episode psychosis exhibited a significant between-treatment difference in MRI volume changes. Haloperidol was associated with significant reductions in gray matter volume, whereas olanzapine was not. Post hoc analyses suggested that treatment effects on brain volume and psychopathology of schizophrenia may be associated. The differential treatment effects on brain morphology could be due to haloperidol-associated toxicity or greater therapeutic effects of olanzapine.

Catatonia: disappeared or under-diagnosed?

BACKGROUND

Over the last century, especially during the latter half, the prevalence of the diagnosis of catatonic schizophrenia decreased considerably. Several explanations for this phenomenon have been put forward.

SAMPLING AND METHODS

The present study investigated the frequency of the diagnosis of catatonic schizophrenia in a large sample of admitted psychiatric patients (n = 19,309). In addition, the presence of catatonic symptoms was studied in a sample of patients with schizophrenia (n = 701) and in a group of consecutively admitted psychotic patients (n = 139). In these two groups the effect of the diagnostic procedures on the recognition of catatonia was examined.

RESULTS

The diagnosis of catatonic schizophrenia dropped from 7.8% in 1980-1989 to 1.3% in 1990-2001 (p < 0.001). In addition, a possible under-diagnosis of catatonic schizophrenia was found in an independent sample of patients with schizophrenia. Application of a systematic catatonia rating scale in patients admitted with acute psychosis identified a bimodally distributed catatonic dimension. At least 18% of these patients fulfilled the criteria for catatonia. Interestingly, the catatonic subgroup used atypical antipsychotic compounds more frequently (p < 0.05).

CONCLUSIONS

The results suggest that changes in diagnostic criteria and the diagnostic procedure itself are responsible for the under-recognition of catatonia.

Hippocampal changes and white matter lesions in early-onset depression

BACKGROUND

Hippocampal volume reduction and increased prevalence of subcortical white matter lesions have been reported in late-life depression. We aimed to examine whether total number of subcortical white matter lesions were associated with reduced hippocampal volume in aged female subjects with early-onset depression (< 45 years) and healthy comparison subjects.

METHODS

The study included 28 middle-aged and elderly subjects with major depression and 41 age-matched control subjects. Hippocampal, parahippocampal gyrus, and orbitofrontal cortex volumes were determined using manual tracing methods. White matter lesions were rated from T2-weighted MRI scans using a semiquantitative classification scale.

RESULTS

After controlling for total brain volume and age, patients had reduced hippocampal volume due to right hippocampal volume decrease (2.84 mL vs. 3.12 mL, F = 16.6, p < .001). Parahippocampal and orbitofrontal volumes did not differ significantly between groups. Multiple linear regression analysis indicated that reduced hippocampal volume did not significantly correlate with total number of subcortical white matter lesions (t = .673, p = .518).

CONCLUSIONS

Right hippocampal volume was reduced in aged female early-onset subjects with depression. Total number of subcortical white matter lesions was not associated with the decrease in right hippocampal volume. Our data suggest hippocampal involvement, independent of subcortical white matter lesions, in the neuropathology of early-onset depression.

Amino acids in schizophrenia: evidence for lower tryptophan availability during treatment with atypical antipsychotics?

Amino acids play a role in neurotransmitter availability in the central nervous system, in that e.g. the synthesis of brain serotonin depends on the concentration of its precursor tryptophan. Disturbances in amino acid metabolism have been implicated in the pathophysiology of schizophrenia.In the present study the effect of a 14 week treatment with atypical antipsychotics on the plasma levels of amino acids was investigated in patients with schizophrenia and compared to normal controls.Non-responders (< or =20% decrease in BPRS at endpoint) demonstrated lower baseline values of methionine as compared to good responders (> or =50% decrease in BPRS at endpoint; p<.05) and controls (p<.01). The ratio between tryptophan and the other large neutral amino acids (Trp/LNAA ratio) in poor-responders (<40%) decreased during treatment as compared to responders (> or =40%; p<.05). It is concluded that poor or non-response to atypical antipsychotics may be associated with an impaired synthesis of serotonin in the central nervous system.

Increasing dopaminergic activity: effects of L-dopa and bromocriptine on human sensory gating

Schizophrenic patients show a loss of sensory gating, which is reflected in a reduced P50 suppression. Because most of the symptoms in schizophrenia can be reduced by antagonists of the dopaminergic (D2) system, the loss in sensory gating might be related to an increased dopaminergic activity. Therefore, in the present study, the effects of increased dopaminergic neurotransmisson on sensory gating in healthy volunteers were investigated. In a double-blind, balanced, placebo-controlled design, healthy male volunteers were challenged in two separate studies with either 300 mg L-dopa (precursor of dopamine) or placebo (n=16) and 1.25 mg bromocriptine (D2 agonist) or placebo (n=17). Subsequently, they were tested for their sensory gating (P50 suppression). P50 suppression values in the placebo condition were comparable to those found in literature. Although both L-dopa and bromocriptine reduced P50 amplitude, they did so in an equal ratio for both the response to the conditioning (C) and the testing (T) stimuli, therefore not resulting in a reduction of the P50 suppression ratio (T/C). In the present study, neither L-dopa nor bromocriptine reduced sensory gating in healthy volunteers. This suggests that an increased dopaminergic activity in humans is not responsible for the reduction in sensory gating as seen, for example, in schizophrenia.

Nonschizophrenic psychotic disorders: the case of cycloid psychoses

BACKGROUND

Cycloid psychosis is a psychiatric disorder known for about 100 years. This disorder is at present partly and simplified represented in the ICD-10.

SAMPLING AND METHODS

Over a period of 15 months, 139 consecutively acutely admitted psychotic patients were assessed, by means of different diagnostic instruments, in order to investigate the prevalence and the symptom profile of cycloid psychoses. In addition, the concordance between the diagnoses cycloid psychosis, brief psychotic disorder, and acute polymorphic psychotic disorder with or without symptoms of schizophrenia was calculated.

RESULTS

Cycloid psychoses were present in 13% of the patients. There was a significant but small overlap with the DSM brief psychotic disorder and the ICD acute polymorphic psychotic disorder.

CONCLUSIONS

This study demonstrates that cycloid psychoses can be identified with the proper diagnostic instruments in a proportion that is also found in other studies. Since this type of psychosis entails a distinct prognosis and may require a specific treatment, its identification is of clinical importance. Limitations are the nature of the psychiatric facility with an inherent bias in the selection of patients and the lack of a long-term evaluation.

Working memory capacity in schizophrenia: a parametric fMRI study

Impaired working memory (WM) function in schizophrenia has been associated with abnormal activation of the dorsolateral prefrontal cortex (DLPFC). It is, however, not clear whether abnormal activation is a sign of DLPFC pathology, or a correlate of poor performance. We address this question by examining activity in the WM brain system at different levels of task difficulty. A parametric fMRI paradigm is used to examine how the WM system responds to increasing load. A parametric fMRI design with four levels of a spatial N-back task was used to examine the relationships between working memory load, functional output (performance) and brain activity in 10 schizophrenic patients on atypical antipsychotic medication and to compare these to 10 healthy controls. In spite of increasingly poor performance in schizophrenic patients, activity increased normally in DLPFC and inferior parietal cortex bilaterally and in anterior cingulate, with increasing load. At 3-back, activity dropped in DLPFC in comparison with controls, but not in the other regions. The results indicate that peak activation of the WM-system is reached at a lower processing load in schizophrenic patients than in healthy controls. As a decline of DLPFC activity at high processing loads in itself is not abnormal, WM dysfunction in schizophrenia appears to be the result of an impaired functional output of the whole WM system, causing elevation of the effective burden imposed by WM tasks.

Atypical antipsychotics and the relevance of glutamate and serotonin

In the present study, including 66 schizophrenic patients and 73 healthy controls, the effect of atypical antipsychotic treatment over a period of 14 weeks on psychotic symptoms and plasma levels of glutamate and monoaminergic metabolites was investigated. Treatment induced a modest reduction of psychotic symptoms in 42% of the patients (response criterion: Brief Psychiatric Rating Scale [BPRS] decrease >/=40%). Poor response was associated with severity of psychopathology, age and duration of disease. Glutamate at baseline was significantly higher in patients as compared to controls (p<0.01). During treatment, a significant further increase of glutamate, not related to response, was observed. Glutamate levels correlated significantly with negative symptom scores at baseline and weeks 3, 6 and 14 (p<0.05). At baseline, serotonin (5-HT) in plasma and 5-HT in platelets were significantly lower in the poor responders as compared to controls (p<0.05) and increased significantly during treatment (p<0.05). In the responders, treatment coincided with a decrease of 5-HT parameters. No differences in plasma levels of HVA, 5-HIAA and their ratio were observed between controls and response groups. The results of this study suggest an effect of atypical antipsychotics on glutamatergic neurotransmission and an association between lower pretreatment peripheral 5-HT parameters and response.