Identifying canonical and replicable multi-scale intrinsic connectivity networks in 100k+ resting-state fMRI datasets

Despite the known benefits of data-driven approaches, the lack of approaches for identifying functional neuroimaging patterns that capture both individual variations and inter-subject correspondence limits the clinical utility of rsfMRI and its application to single-subject analyses. Here, using rsfMRI data from over 100k individuals across private and public datasets, we identify replicable multi-spatial-scale canonical intrinsic connectivity network (ICN) templates via the use of multi-model-order independent component analysis (ICA). We also study the feasibility of estimating subject-specific ICNs via spatially constrained ICA. The results show that the subject-level ICN estimations vary as a function of the ICN itself, the data length, and the spatial resolution. In general, large-scale ICNs require less data to achieve specific levels of (within- and between-subject) spatial similarity with their templates. Importantly, increasing data length can reduce an ICN's subject-level specificity, suggesting longer scans may not always be desirable. We also find a positive linear relationship between data length and spatial smoothness (possibly due to averaging over intrinsic dynamics), suggesting studies examining optimized data length should consider spatial smoothness. Finally, consistency in spatial similarity between ICNs estimated using the full data and subsets across different data lengths suggests lower within-subject spatial similarity in shorter data is not wholly defined by lower reliability in ICN estimates, but may be an indication of meaningful brain dynamics which average out as data length increases.

A method for estimating and characterizing explicitly nonlinear dynamic functional network connectivity in resting-state fMRI data

The past 10 years have seen an explosion of approaches that focus on the study of time-resolved change in functional connectivity (FC). FC characterization among networks at a whole-brain level is frequently termed functional network connectivity (FNC). Time-resolved or dynamic functional network connectivity (dFNC) focuses on the estimation of transient, recurring, whole-brain patterns of FNC. While most approaches in this area have attempted to capture dynamic linear correlation, we are particularly interested in whether explicitly nonlinear relationships, above and beyond linear, are present and contain unique information. This study thus proposes an approach to assess explicitly nonlinear dynamic functional network connectivity (EN dFNC) derived from the relationship among independent component analysis time courses. Linear relationships were removed at each time point to evaluate, typically ignored, explicitly nonlinear dFNC using normalized mutual information (NMI). Simulations showed the proposed method estimated explicitly nonlinearity over time, even within relatively short windows of data. We then, applied our approach on 151 schizophrenia patients, and 163 healthy controls fMRI data and found three unique, highly structured, mostly long-range, functional states that also showed significant group differences. In particular, explicitly nonlinear relationships tend to be more widespread than linear ones. Results also highlighted a state with long range connections to the visual domain, which were significantly reduced in schizophrenia. Overall, this work suggests that quantifying EN dFNC may provide a complementary and potentially valuable tool for studying brain function by exposing relevant variation that is typically ignored.

Moving beyond the 'CAP' of the Iceberg: Intrinsic connectivity networks in fMRI are continuously engaging and overlapping

Resting-state functional magnetic resonance imaging is currently the mainstay of functional neuroimaging and has allowed researchers to identify intrinsic connectivity networks (aka functional networks) at different spatial scales. However, little is known about the temporal profiles of these networks and whether it is best to model them as continuous phenomena in both space and time or, rather, as a set of temporally discrete events. Both categories have been supported by series of studies with promising findings. However, a critical question is whether focusing only on time points presumed to contain isolated neural events and disregarding the rest of the data is missing important information, potentially leading to misleading conclusions. In this work, we argue that brain networks identified within the spontaneous blood oxygenation level-dependent (BOLD) signal are not limited to temporally sparse burst moments and that these event present time points (EPTs) contain valuable but incomplete information about the underlying functional patterns. We focus on the default mode and show evidence that is consistent with its continuous presence in the BOLD signal, including during the event absent time points (EATs), i.e., time points that exhibit minimum activity and are the least likely to contain an event. Moreover, our findings suggest that EPTs may not contain all the available information about their corresponding networks. We observe distinct default mode connectivity patterns obtained from all time points (AllTPs), EPTs, and EATs. We show evidence of robust relationships with schizophrenia symptoms that are both common and unique to each of the sets of time points (AllTPs, EPTs, EATs), likely related to transient patterns of connectivity. Together, these findings indicate the importance of leveraging the full temporal data in functional studies, including those using event-detection approaches.

Resting-state thalamic dysconnectivity in schizophrenia and relationships with symptoms

BACKGROUND

Schizophrenia (SZ) is a severe neuropsychiatric disorder associated with disrupted connectivity within the thalamic-cortico-cerebellar network. Resting-state functional connectivity studies have reported thalamic hypoconnectivity with the cerebellum and prefrontal cortex as well as thalamic hyperconnectivity with sensory cortical regions in SZ patients compared with healthy comparison participants (HCs). However, fundamental questions remain regarding the clinical significance of these connectivity abnormalities.

METHOD

Resting state seed-based functional connectivity was used to investigate thalamus to whole brain connectivity using multi-site data including 183 SZ patients and 178 matched HCs. Statistical significance was based on a voxel-level FWE-corrected height threshold of p < 0.001. The relationships between positive and negative symptoms of SZ and regions of the brain demonstrating group differences in thalamic connectivity were examined.

RESULTS

HC and SZ participants both demonstrated widespread positive connectivity between the thalamus and cortical regions. Compared with HCs, SZ patients had reduced thalamic connectivity with bilateral cerebellum and anterior cingulate cortex. In contrast, SZ patients had greater thalamic connectivity with multiple sensory-motor regions, including bilateral pre- and post-central gyrus, middle/inferior occipital gyrus, and middle/superior temporal gyrus. Thalamus to middle temporal gyrus connectivity was positively correlated with hallucinations and delusions, while thalamus to cerebellar connectivity was negatively correlated with delusions and bizarre behavior.

CONCLUSIONS

Thalamic hyperconnectivity with sensory regions and hypoconnectivity with cerebellar regions in combination with their relationship to clinical features of SZ suggest that thalamic dysconnectivity may be a core neurobiological feature of SZ that underpins positive symptoms.

Decreased hemispheric connectivity and decreased intra- and inter- hemisphere asymmetry of resting state functional network connectivity in schizophrenia

Many studies have shown that schizophrenia patients have aberrant functional network connectivity (FNC) among brain regions, suggesting schizophrenia manifests with significantly diminished (in majority of the cases) connectivity. Schizophrenia is also associated with a lack of hemispheric lateralization. Hoptman et al. (2012) reported lower inter-hemispheric connectivity in schizophrenia patients compared to controls using voxel-mirrored homotopic connectivity. In this study, we merge these two points of views together using a group independent component analysis (gICA)-based approach to generate hemisphere-specific timecourses and calculate intra-hemisphere and inter-hemisphere FNC on a resting state fMRI dataset consisting of age- and gender-balanced 151 schizophrenia patients and 163 healthy controls. We analyzed the group differences between patients and healthy controls in each type of FNC measures along with age and gender effects. The results reveal that FNC in schizophrenia patients shows less hemispheric asymmetry compared to that of the healthy controls. We also found a decrease in connectivity in all FNC types such as intra-left (L_FNC), intra-right (R_FNC) and inter-hemisphere (Inter_FNC) in the schizophrenia patients relative to healthy controls, but general patterns of connectivity were preserved in patients. Analyses of age and gender effects yielded results similar to those reported in whole brain FNC studies.

Widespread white matter microstructural differences in schizophrenia across 4322 individuals: results from the ENIGMA Schizophrenia DTI Working Group

The regional distribution of white matter (WM) abnormalities in schizophrenia remains poorly understood, and reported disease effects on the brain vary widely between studies. In an effort to identify commonalities across studies, we perform what we believe is the first ever large-scale coordinated study of WM microstructural differences in schizophrenia. Our analysis consisted of 2359 healthy controls and 1963 schizophrenia patients from 29 independent international studies; we harmonized the processing and statistical analyses of diffusion tensor imaging (DTI) data across sites and meta-analyzed effects across studies. Significant reductions in fractional anisotropy (FA) in schizophrenia patients were widespread, and detected in 20 of 25 regions of interest within a WM skeleton representing all major WM fasciculi. Effect sizes varied by region, peaking at (d=0.42) for the entire WM skeleton, driven more by peripheral areas as opposed to the core WM where regions of interest were defined. The anterior corona radiata (d=0.40) and corpus callosum (d=0.39), specifically its body (d=0.39) and genu (d=0.37), showed greatest effects. Significant decreases, to lesser degrees, were observed in almost all regions analyzed. Larger effect sizes were observed for FA than diffusivity measures; significantly higher mean and radial diffusivity was observed for schizophrenia patients compared with controls. No significant effects of age at onset of schizophrenia or medication dosage were detected. As the largest coordinated analysis of WM differences in a psychiatric disorder to date, the present study provides a robust profile of widespread WM abnormalities in schizophrenia patients worldwide. Interactive three-dimensional visualization of the results is available at www.enigma-viewer.org.

The role of the ITIH3 rs2535629 variant in antipsychotic response

INTRODUCTION

There is mounting evidence that schizophrenia risk variants influence response to antipsychotic medication. Common single nucleotide polymorphisms (SNPs) in or near the inter-alpha-trypsin inhibitor heavy chain H3 (ITIH3) gene have been repeatedly associated with schizophrenia and related psychiatric disorders in genome-wide association studies. Here, we provide the first study to assess the relevance of the ITIH3 rs2535629 SNP in response to antipsychotic medication.

METHODS

The rs2535629 SNP was genotyped in N=256 patients receiving various antipsychotics for up to 26weeks. Treatment response was assessed using the Brief Psychiatric Rating Scale (BPRS) including its positive and negative subscales. Follow-up analyses were performed after stratifying for ethnicity and medication.

RESULTS

We found significant association of rs2535629 with improvement of negative symptoms in patients of European ancestry after six months of clozapine treatment (F1,87=8.8, pcorr=0.032). Patients homozygous for the minor A-allele showed the best improvement of negative BPRS scores. However, we observed no association between rs2535629 and changes in total BPRS score in the entire sample or the clozapine-treated subgroup.

DISCUSSION

Although there was no association of genotype with overall changes in BPRS scores, the greater improvement of negative symptoms in minor allele carriers indicates that rs2535629 may help to identify a subset of schizophrenia patients with better treatment response to clozapine. Therefore, our findings provide the first suggestive evidence that rs2535629 is relevant in antipsychotic response.

Subcortical brain volume abnormalities in 2028 individuals with schizophrenia and 2540 healthy controls via the ENIGMA consortium

The profile of brain structural abnormalities in schizophrenia is still not fully understood, despite decades of research using brain scans. To validate a prospective meta-analysis approach to analyzing multicenter neuroimaging data, we analyzed brain MRI scans from 2028 schizophrenia patients and 2540 healthy controls, assessed with standardized methods at 15 centers worldwide. We identified subcortical brain volumes that differentiated patients from controls, and ranked them according to their effect sizes. Compared with healthy controls, patients with schizophrenia had smaller hippocampus (Cohen's d=-0.46), amygdala (d=-0.31), thalamus (d=-0.31), accumbens (d=-0.25) and intracranial volumes (d=-0.12), as well as larger pallidum (d=0.21) and lateral ventricle volumes (d=0.37). Putamen and pallidum volume augmentations were positively associated with duration of illness and hippocampal deficits scaled with the proportion of unmedicated patients. Worldwide cooperative analyses of brain imaging data support a profile of subcortical abnormalities in schizophrenia, which is consistent with that based on traditional meta-analytic approaches. This first ENIGMA Schizophrenia Working Group study validates that collaborative data analyses can readily be used across brain phenotypes and disorders and encourages analysis and data sharing efforts to further our understanding of severe mental illness.

Dynamic functional connectivity analysis reveals transient states of dysconnectivity in schizophrenia

Schizophrenia is a psychotic disorder characterized by functional dysconnectivity or abnormal integration between distant brain regions. Recent functional imaging studies have implicated large-scale thalamo-cortical connectivity as being disrupted in patients. However, observed connectivity differences in schizophrenia have been inconsistent between studies, with reports of hyperconnectivity and hypoconnectivity between the same brain regions. Using resting state eyes-closed functional imaging and independent component analysis on a multi-site data that included 151 schizophrenia patients and 163 age- and gender matched healthy controls, we decomposed the functional brain data into 100 components and identified 47 as functionally relevant intrinsic connectivity networks. We subsequently evaluated group differences in functional network connectivity, both in a static sense, computed as the pairwise Pearson correlations between the full network time courses (5.4 minutes in length), and a dynamic sense, computed using sliding windows (44 s in length) and k-means clustering to characterize five discrete functional connectivity states. Static connectivity analysis revealed that compared to healthy controls, patients show significantly stronger connectivity, i.e., hyperconnectivity, between the thalamus and sensory networks (auditory, motor and visual), as well as reduced connectivity (hypoconnectivity) between sensory networks from all modalities. Dynamic analysis suggests that (1), on average, schizophrenia patients spend much less time than healthy controls in states typified by strong, large-scale connectivity, and (2), that abnormal connectivity patterns are more pronounced during these connectivity states. In particular, states exhibiting cortical–subcortical antagonism (anti-correlations) and strong positive connectivity between sensory networks are those that show the group differences of thalamic hyperconnectivity and sensory hypoconnectivity. Group differences are weak or absent during other connectivity states. Dynamic analysis also revealed hypoconnectivity between the putamen and sensory networks during the same states of thalamic hyperconnectivity; notably, this finding cannot be observed in the static connectivity analysis. Finally, in post-hoc analyses we observed that the relationships between sub-cortical low frequency power and connectivity with sensory networks is altered in patients, suggesting different functional interactions between sub-cortical nuclei and sensorimotor cortex during specific connectivity states. While important differences between patients with schizophrenia and healthy controls have been identified, one should interpret the results with caution given the history of medication in patients. Taken together, our results support and expand current knowledge regarding dysconnectivity in schizophrenia, and strongly advocate the use of dynamic analyses to better account for and understand functional connectivity differences.

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Studied both static and dynamic connectivity changes in schizophrenia during rest

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Small but significant connectivity differences might be obscured in static analysis.

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Patients show significant differences in dwell times in multiple states.

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Disrupted thalamo-cortical connectivity in schizophrenia in a state-specific manner

Genome-wide association study of CSF biomarkers Abeta1-42, t-tau, and p-tau181p in the ADNI cohort

OBJECTIVES

CSF levels of Aβ1-42, t-tau, and p-tau181p are potential early diagnostic markers for probable Alzheimer disease (AD). The influence of genetic variation on these markers has been investigated for candidate genes but not on a genome-wide basis. We report a genome-wide association study (GWAS) of CSF biomarkers (Aβ1-42, t-tau, p-tau181p, p-tau181p/Aβ1-42, and t-tau/Aβ1-42).

METHODS

A total of 374 non-Hispanic Caucasian participants in the Alzheimer's Disease Neuroimaging Initiative cohort with quality-controlled CSF and genotype data were included in this analysis. The main effect of single nucleotide polymorphisms (SNPs) under an additive genetic model was assessed on each of 5 CSF biomarkers. The p values of all SNPs for each CSF biomarker were adjusted for multiple comparisons by the Bonferroni method. We focused on SNPs with corrected p<0.01 (uncorrected p<3.10×10(-8)) and secondarily examined SNPs with uncorrected p values less than 10(-5) to identify potential candidates.

RESULTS

Four SNPs in the regions of the APOE, LOC100129500, TOMM40, and EPC2 genes reached genome-wide significance for associations with one or more CSF biomarkers. SNPs in CCDC134, ABCG2, SREBF2, and NFATC4, although not reaching genome-wide significance, were identified as potential candidates.

CONCLUSIONS

In addition to known candidate genes, APOE, TOMM40, and one hypothetical gene LOC100129500 partially overlapping APOE; one novel gene, EPC2, and several other interesting genes were associated with CSF biomarkers that are related to AD. These findings, especially the new EPC2 results, require replication in independent cohorts.

Effect of dopamine D3 receptor gene polymorphisms and clozapine treatment response: exploratory analysis of nine polymorphisms and meta-analysis of the Ser9Gly variant

D2 blockade has been implicated in having a central role in antipsychotic response. However, treatment refractoriness, in spite of complete D2 blockade, as well as the efficacy of clozapine (CLZ) in a portion of this patient population, indicates the involvement of other factors as well. Several lines of evidence suggest a role for D3. Furthermore, an earlier meta-analysis by Jönsson et al. (2003) (n=233) suggested a role for genetic variation in the D3 gene. Relevant to this study, Jönsson et al. found the Ser allele of the D3 serine-to-glycine substitution at amino acid position 9 (Ser9Gly) polymorphism to be associated with worse CLZ response compared with the Gly allele. In this study, we attempt to validate these findings by performing a meta-analysis in a much larger sample (n=758). Eight other variants were also tested in our own sample to explore the possible effect of other regions of the gene. We report a negative but consistent trend across individual studies in our meta-analysis for the DRD3 Ser allele and poor CLZ response. A possible minor role for this single-nucleotide polymorphism cannot be disregarded, as our sample size may have been insufficient. Other DRD3 variants and haplotypes of possible interest were also identified for replication in future studies.

Working memory and DLPFC inefficiency in schizophrenia: the FBIRN study

BACKGROUND

The Functional Imaging Biomedical Informatics Network is a consortium developing methods for multisite functional imaging studies. Both prefrontal hyper- or hypoactivity in chronic schizophrenia have been found in previous studies of working memory.

METHODS

In this functional magnetic resonance imaging (fMRI) study of working memory, 128 subjects with chronic schizophrenia and 128 age- and gender-matched controls were recruited from 10 universities around the United States. Subjects performed the Sternberg Item Recognition Paradigm1,2 with memory loads of 1, 3, or 5 items. A region of interest analysis examined the mean BOLD signal change in an atlas-based demarcation of the dorsolateral prefrontal cortex (DLPFC), in both groups, during both the encoding and retrieval phases of the experiment over the various memory loads.

RESULTS

Subjects with schizophrenia performed slightly but significantly worse than the healthy volunteers and showed a greater decrease in accuracy and increase in reaction time with increasing memory load. The mean BOLD signal in the DLPFC was significantly greater in the schizophrenic group than the healthy group, particularly in the intermediate load condition. A secondary analysis matched subjects for mean accuracy and found the same BOLD signal hyperresponse in schizophrenics.

CONCLUSIONS

The increase in BOLD signal change from minimal to moderate memory loads was greater in the schizophrenic subjects than in controls. This effect remained when age, gender, run, hemisphere, and performance were considered, consistent with inefficient DLPFC function during working memory. These findings from a large multisite sample support the concept not of hyper- or hypofrontality in schizophrenia, but rather DLPFC inefficiency that may be manifested in either direction depending on task demands. This redirects the focus of research from direction of difference to neural mechanisms of inefficiency.

Effects of rivastigmine on cognitive function in patients with traumatic brain injury

OBJECTIVE

To compare the efficacy and safety of rivastigmine (3 to 6 mg/day) vs placebo over 12 weeks in patients with traumatic brain injury and persistent cognitive impairment.

METHODS

This prospective, randomized, double-blind, placebo-controlled study was conducted in 157 patients at least 12 months after injury. The primary efficacy measures were the Cambridge Neuropsychological Test Automated Battery (CANTAB) Rapid Visual Information Processing (RVIP) A' subtest and the Hopkins Verbal Learning Test (HVLT). The primary efficacy outcome was the proportion of patients who demonstrated 1.0 SD or greater improvement from baseline at week 12 on CANTAB RVIP A' or HVLT.

RESULTS

The percentage of responders at week 12 on either the CANTAB RVIP A' or HVLT was 48.7% for rivastigmine and 49.3% for placebo (p = 0.940). Furthermore, for the overall study population, there were no significant differences for any of the secondary efficacy variables. In a subgroup of patients with moderate to severe memory impairment (n = 81), defined as 25% impairment or greater on HVLT at baseline, rivastigmine was significantly better than placebo for a number of measures, including the proportion of HVLT responders and CANTAB RVIP mean latency.

CONCLUSIONS

Rivastigmine was safe and well tolerated in patients with traumatic brain injury with cognitive deficits. Rivastigmine shows promising results in the subgroup of patients with traumatic brain injury with moderate to severe memory deficits.

Three-month change in cerebral glucose metabolism in patients with nonarteritic ischemic optic neuropathy

BACKGROUND

No specific therapy is available for non-arteritic ischemic optic neuropathy (NAION), a blinding disease, which is related to microvascular insufficiency of the optic disc and white matter lesions in brain MRI representing ischemia. We hypothesize that pentoxifylline, traditionally used for treatment of peripheral vascular disease due to its ability to decrease viscosity and increase erythrocyte flexibility, may be useful to improve blood flow in patients with NAION. Positron emission tomography (PET) to determine the change in glucose metabolic rate in the visual cortex of patients with NAION versus age-matched controls was performed after 3 months' administration of pentoxifylline.

METHODS

Eight patients clinically diagnosed with NAION underwent clinical and laboratory evaluation, brain MRI and PET with fluoride-18 fluorodeoxyglucose (FDG). All patients were treated with oral pentoxifylline 400 mg three times a day for a period of at least 3 months. Three patients were included in the final PET data analysis.

RESULTS

At baseline, PET revealed bilateral metabolic decreases especially in the ventral visual stream in all patients compared with 56 age- and gender-normalized controls. Metabolic changes were seen in the dorsal stream areas 17, 18, and 19, cerebellar region, dorsolateral prefrontal cortex, medial temporal lobe, and frontal eye fields 8 and 6. At 3 months following pentoxifylline, all three patients included in the final PET data analysis showed partial normalization from the baseline metabolism.

CONCLUSIONS

Metabolic imaging with FDG-PET in NAION provides functional information not attainable with conventional brain MRI. The exact relevance of these results, and the role of pentoxifylline in these metabolic changes, should be determined by means of a larger randomized and controlled trial.

D1 receptor alleles predict PET metabolic correlates of clinical response to clozapine

A goal of pharmacogenetics is to clarify associations between allelic variation and risk factors in psychiatric illness. We report changes in regional brain metabolism based on dopamine alleles. Treatment-resistant schizophrenic subjects were positron emission tomography scanned with 18F-fluorodeoxyglucose after 5 weeks each of placebo and clozapine treatment. Significant regional brain metabolic effects were found for the D1 receptor genotypes (P < 0.05), adjusted for multiple comparisons. Metabolic decreases for the 2,2 genotype but not the 1,2 genotype were observed in all major sectors of the brain, with the exception of the ventral parts of the caudate and putamen. Frontal, temporal, parietal, and occipital neocortices showed decreased metabolism as did the cingulate juxta-allocortex and the parahippocampal allocortex. Decreases were also observed in the thalamus, amygdala, and cerebellum bilaterally. No significant metabolic differences by genotype were observed for D3, 5HT(2A), and 5HT(2C) polymorphisms. In terms of clinical response, the DRD1 2,2 genotype significantly improved with clozapine treatment, demonstrating a 30% decrease in the Brief Psychiatric Rating Scale positive symptoms in contrast to a 7% worsening for the 1,2 genotype (P < 0.05). In this preliminary study, brain metabolic and clinical response to clozapine are related to the D1 receptor genotype.

Stability of exploratory eye movements as a marker of schizophrenia--a WHO multi-center study. World Health Organization

The exploratory eye movements of patients with schizophrenia reportedly differ from those of patients without schizophrenia and healthy controls. In an attempt to determine whether exploratory eye movements provide valid markers for schizophrenia, the present collaborative study was conducted in six countries to analyze the stability of and variation in the following parameters of exploratory eye movements: the number of eye fixations (NEFs) and mean eye scanning length (MESL) in a retention task; the cognitive search score (CSS) that indicates how frequently the eye focused on each important area of a figure in order to recognize it in a comparison task; and the responsive search score (RSS), which reflects the frequency of eye fixations on each section of a figure in response to questioning in a comparison task. In addition, we investigated the validity of the currently employed discriminant function to extract a common feature of schizophrenia by applying it to the findings of the present study. The exploratory eye movements of 145 patients with schizophrenia, 116 depressed patients and 124 healthy controls at seven WHO collaborative centers in six countries were measured using eye mark recorders during viewing of stationary S-shaped figures in two sequential tasks. The RSSs of patients with schizophrenia were found to be significantly lower than those of depressed patients or healthy controls irrespective of geographical location, with no significant difference existing between the RSSs for depressed patients and those for healthy controls. By inserting the RSS and NEF data for each subject into the formula used to calculate discriminant function, patients with schizophrenia could be discriminated from depressed patients and healthy controls with a sensitivity of 89.0% and a specificity of 86.7%. The RSS is an exploratory eye movement parameter that detected schizophrenia irrespective of culture, race and various other subject variables. Furthermore, it is indicative of the stable, significant difference that exists between subjects with and without schizophrenia. The results of discriminant analysis confirm the previously reported validity of discriminant function.

Clozapine enhances neurocognition and clinical symptomatology more than standard neuroleptics

Neurocognition and clinical symptomatology were evaluated in 27 patients with schizophrenia during a double-blind, placebo-controlled, cross-over study involving clozapine, an atypical antipsychotic agent, and haloperidol, a conventional neuroleptic. Patients were assessed 5 to 6 weeks after initiation of each phase. Clinical symptomatology, based on Brief Psychiatric Rating Scale and Scale for the Assessment of Negative Symptoms ratings, markedly improved after treatment with both haloperidol and clozapine. The beneficial effects of clozapine were statistically significantly greater than the effects from the haloperidol treatment. Regarding neurocognition, both agents proved efficacious in improving performance on nearly all measures compared with placebo. In addition, as compared with haloperidol, clozapine significantly improved performance on Trails B, Verbal Fluency, and measures of delayed verbal memory, and it tended to increase performance on most measures. Additional analyses indicated that the improvement on neurocognitive measures was not because of symptom amelioration; rather, neurocognitive deficits seem to be an intrinsic enduring feature of schizophrenia. The superiority of clozapine over haloperidol may be related to clozapine's unique psychopharmacologic profile.

Brain metabolic and clinical effects of rivastigmine in Alzheimer's disease

In-vivo metabolic measures with positron emission tomography using (18)F-fluorodeoxyglucose (FDG-PET) have demonstrated hypometabolism in temporal, frontal, and hippocampal areas during the early stages of Alzheimer's disease (AD). Progression of the dementia in AD involves compromised cholinergic functioning. Cholinesterase inhibitors have demonstrated efficacy in improving cognition and behaviour in AD. In this study, we demonstrate the usefulness of FDG-PET in measuring the progression of untreated AD and its modification by treatment with rivastigmine (Exelon, Novartis Pharmaceuticals, East Hanover, New Jersey, USA), a centrally selective cholinesterase inhibitor of the carbamate type. Patients with mild to moderate probable AD (Mini-Mental Status Exam scores of 10-26, inclusive) were enrolled in a double-blind, placebo controlled comparison of three fixed daily doses of rivastigmine (3, 6, or 9 mg/d) or placebo for 26 wk. FDG-PET scans were obtained on 27 patients at baseline and following 26 wk of treatment using the Snodgrass Picture Naming activation task. A total of 71.4% of the patients treated with placebo deteriorated clinically compared to only 25.0% of the patients treated with rivastigmine (chi2 = 4.8; p & 0.03). Rivastigmine-responders (i.e. those who clinically improved or remained clinically stable as measured by the Clinicianaposs Interview-Based Impression of Change-plus) showed a marked increase in brain metabolism (p <0.01) involving, but not limited to, structures comprising the memory-related cortices and the prefrontal system. These metabolic changes were not observed in the placebo-treated patients or the rivastigmine non-responders. Of note is that responders increased hippocampal metabolism by 32.5% (p < 0.03) compared to a non-significant decrease in the non-responders (6.4%) and placebo-treated patients (4.1%). These results are consistent with the literature suggesting that FDG-PET can sensitively measure the progression of AD and its improvement with cholinesterase inhibitors. Rivastigmine prevented the expected deterioration in clinical status and dramatically increased brain metabolic activity in a majority of patients.

Fluvoxamine in the treatment of panic disorder: a multi-center, double-blind, placebo-controlled study in outpatients

Serotonergic mechanisms have been implicated in panic disorder, and several preliminary studies suggest that fluvoxamine, a selective serotonin reuptake inhibitor (SSRI), is helpful in its treatment. This 8-week double-blind parallel-group study compared fluvoxamine with a placebo in 188 patients with DSM-III-R defined panic disorder with or without agoraphobia. Efficacy assessments included a Daily Panic Attack Inventory, the Sheehan Disability Scale, the Clinical Anxiety Scale and the Clinical Global Impression Scale. When compared with the placebo, fluvoxamine produced highly significant improvements in most measures of the frequency and severity of panic disorder and in the more global aspects of disability and distress. Significant improvement was evident as early as week 1 for some panic variables. Fluvoxamine is a potent anti-panic agent with a relatively rapid onset of action.

Intramuscular (IM) ziprasidone 20 mg is effective in reducing acute agitation associated with psychosis: a double-blind, randomized trial

RATIONALE

Intramuscular (IM) conventional antipsychotics and/or benzodiazepines are effective in the short-term treatment of acutely agitated psychotic patients but may be associated with adverse effects. A short-acting IM formulation of the novel antipsychotic, ziprasidone, which may offer advantages over conventional agents, has been developed.

OBJECTIVE

To compare ziprasidone IM 2 mg (n=38) and 20 mg (n=41) in the acute control and short-term management of agitated psychotic patients.

METHODS

A prospective, randomized, double-blind, 24-h study assessed efficacy using the Behavioral Activity Rating Scale (BARS) and the PANSS. The BARS is a validated rating scale for the assessment of treatment response in acute agitation associated with psychosis. Following the initial dose, three more doses could be given 4 h apart if needed during the 24-h period.

RESULTS

The mean BARS score had decreased 15 min after the first 20 mg IM dose and was statistically significantly lower than the 2 mg group at 30 min post-dose. The improvement with the 20 mg dose increased until 2 h, and was maintained until at least 4 h post-dose (P<0.001). Two hours after the first injection, almost all of the patients receiving ziprasidone 20 mg were BARS responders compared with just one-third of those receiving 2 mg ziprasidone (P<0.001). The calming effect of ziprasidone was also evident by the significant reduction in PANSS agitation items (P<0.05) and CGI-severity at 4 h (P=0.008). Both ziprasidone doses were very well tolerated. Ziprasidone IM 20 mg was not associated with EPS, dystonia, akathisia, respiratory depression or with excessive sedation.

CONCLUSIONS

Ziprasidone IM 20 mg substantially and significantly reduced the symptoms of acute agitation in patients with psychotic disorders. Ziprasidone 20 mg IM was very well tolerated and produced no dystonia or akathisia.

Structured Interview for Assessing Perceptual Anomalies (SIAPA)

Clinical descriptions of perceptual and attentional anomalies in schizophrenia emphasize phenomena such as flooding, or inundation, by sensory stimuli. A failure of sensory "gating" mechanisms in the brain is hypothesized to account for these symptoms, and this hypothesis has led to a marked interest in their putative psychophysiological substrates. However, there are no systematic analyses of the phenomenology of these perceptual experiences, nor has the hypothesized connection between the clinical phenomena and their reported psychophysiological substrates been tested. In this investigation, a structured interview instrument was developed to measure perceptual anomalies as distinct from hallucinations and to determine their prevalence across sensory modalities in schizophrenia in 67 schizophrenia subjects and 98 normal controls. The instrument includes Likert ratings of hypersensitivity, inundation, and selective attention to external sensory stimuli. Good interrater agreement, determined from interviews, was obtained. Schizophrenia subjects had significantly higher auditory, visual, and combined scores (i.e., across all modalities) than normal controls did, indicating significantly more perceptual anomalies. For the schizophrenia group, the prevalence of auditory and visual anomalies was significantly greater than the other sensory modalities. The data indicate that the putative phenomenological correlates of sensory gating may be reliably measured and tested with the Structured Interview for Assessing Perceptual Anomalies.

Lack of association between serotonin-2A receptor gene (HTR2A) polymorphisms and tardive dyskinesia in schizophrenia

Tardive dyskinesia (TD) is a disabling neurological side effect associated with long-term treatment with typical antipsychotics. Family studies and animal models lend evidence for hereditary predisposition to TD. The newer atypical antipsychotics pose a minimal risk for TD which is in part attributed to their ability to block the serotonin-2A (5-HT(2A)) receptor. 5-HT(2A) receptors were also identified in the basal ganglia; a brain region that plays a critical role in antipsychotic-induced movement disorders. We tested the significance of variation in the 5-HT(2A) receptor gene (HTR2A) in relation to the TD phenotype. Three polymorphisms in HTR2A, one silent (C102T), one that alters the amino acid sequence (his452tyr) and one in the promoter region (A-1437G) were investigated in 136 patients refractory or intolerant to treatment with typical antipsychotics and with a DSM-IIIR diagnosis of schizophrenia. We did not find any significant difference in allele, genotype or haplotype frequencies of polymorphisms in HTR2A among patients with or without TD (P > 0.05). Further analysis using the ANCOVA statistic with a continuous measure of the TD phenotype (Abnormal Involuntary Movement Scale (AIMS) score) found that the AIMS scores were not significantly influenced by HTR2A polymorphisms, despite controlling for potential confounders such as age, gender and ethnicity (P > 0.05). Theoretically, central serotonergic function can be subject to genetic control at various other mechanistic levels including the rate of serotonin synthesis (tryptophane hydroxylase gene), release, reuptake (serotonin transporter gene) and degradation (monoamine oxidase gene). Analyses of these other serotonergic genes are indicated. In summary, polymorphisms in HTR2A do not appear to influence the risk for TD. Further studies evaluating in tandem multiple candidate genes relevant for the serotonergic system are warranted to dissect the genetic basis of the complex TD phenotype.

Sex-related difference in amygdala activity during emotionally influenced memory storage

We tested the possibility suggested by previous imaging studies that amygdala participation in the storage of emotionally influenced memory is differentially lateralized in men and women. Male and female subjects received two PET scans for regional cerebral glucose-one while viewing a series of emotionally provocative (negative) films, and a second while viewing a series of matched, but emotionally more neutral, films. Consistent with suggestions from several previously published studies, enhanced activity of the right, but not the left, amygdala in men was related to enhanced memory for the emotional films. Conversely, enhanced activity of the left, but not the right, amygdala in women was related to enhanced memory for the emotional films. These results demonstrate a clear gender-related lateralization of amygdala involvement in emotionally influenced memory, and indicate that theories of the neurobiology of emotionally influenced memory must begin to account for the influence of gender.

EEG resonant responses in schizophrenia: a photic driving study with improved harmonic resolution

Twenty seven drug-free schizophrenic patients and 25 normal controls were studied in an EEG photic driving paradigm with an improved harmonic resolution. Consistent with previous results, the present data show that schizophrenics have lower EEG responses to photic stimulation in alpha frequency. The differences between normal and schizophrenic subjects were distributed across major brain areas except centro-temporal regions. It also demonstrated that 1-Hz narrow-pulsed stimulation was feasible in EEG photic driving studies. The enhanced harmonic resolution produced significantly more information in the frequency domain about EEG oscillatory responses to visual stimulus. Using this new technique, the authors showed for the first time that alpha photic driving was a well defined resonant system and that the group differences in harmonic responses were primarily confined in the high frequency portion of alpha band, suggesting a peak frequency shift of EEG resonance in schizophrenia.

Subnucleus-specific loss of neurons in medial thalamus of schizophrenics

The hypoactivity of dorsolateral prefrontal cortex in schizophrenics is well known. One cause of this hypoactivity may be defective corticocortical or thalamocortical connections. Recent imaging studies of the thalamus suggest reductions in volume of the whole thalamus and reduced activity in the medial group of thalamic nuclei, which may indicate loss of functional input to the cortex. Using stereological techniques in six pairs of individually matched brains from schizophrenics and controls, we measured the volumes and obtained estimates of the number of neurons in the three subnuclei (parvocellular, pc; densocellular, dc; magnocellular, mc) of the mediodorsal nucleus (MD) and from the ventral posterior medial nucleus. There was a significant reduction in total neuron number in MD as a whole but this neuron loss was largely restricted to MDpc and MDdc [-30.9 and -24.5%, respectively (P </= 0.01)]. MDmc and the control ventral posterior medial nucleus showed no significant changes in cell number. Because the subnuclei of MD have different connections and project to different areas of the frontal cortex, the specific loss of neurons in MDpc and MDdc has implications for the functional defects observed in schizophrenia.

A functional polymorphism of the cytochrome P450 1A2 (CYP1A2) gene: association with tardive dyskinesia in schizophrenia

Tardive dyskinesia (TD) is a common and potentially irreversible side effect associated with long-term treatment with typical antipsychotics. Approximately, 80% or more of patients with schizophrenia are smokers. Smoking is a potent inducer of the CYP1A2 enzyme, and is known to cause a significant decrease in plasma concentrations of some antipsychotics. Therefore, person-to-person differences in the extent of CYP1A2 induction by smoking may contribute to risk for the development of TD. Recently, a (C-->A) genetic polymorphism in the first intron of the CYP1A2 gene was found to be associated with variation in CYP1A2 inducibility in healthy volunteer smokers. The aim of this study was to test the clinical importance of the (C-->A) polymorphism in CYP1A2 in relation to TD severity. A total of 85 patients with schizophrenia were assessed for TD severity using the Abnormal Involuntary Movement Scale (AIMS), and were subsequently genotyped for the (C-->A) polymorphism in CYP1A2. The mean AIMS score in patients with the (C/C) genotype (associated with reduced CYP1A2 inducibility) was 2.7- and 3.4-fold greater than in those with the (A/C) or (A/A) genotype, respectively (F[2,82] = 7.4, P = 0.0007). Further, a subanalysis in the 44 known smokers in our sample, revealed a more pronounced effect. The means AIMS score in smokers was 5.4- and 4. 7-fold greater in (C/C) homozygotes when compared to heterozygotes and (A/A) homozygotes, respectively (F[2,41] = 3.7, P = 0.008). These data suggest that the (C-->A) genetic polymorphism in the CYP1A2 gene may serve as a genetic risk factor for the development of TD in patients with schizophrenia. Further studies in independent samples are warranted to evaluate the applicability of our findings to the general patient population receiving antipsychotic medications.

Relative sparing of emotionally influenced memory in Alzheimer's disease

Studies suggest that emotionally influenced events enhance long-term memory. This study aimed to uncover whether this phenomenon exists in Alzheimer's Disease (AD) by comparing patients' performance with that of controls on a memory task. Overall, controls performed better than AD subjects on a delayed recognition task of a story containing emotional elements (95.8+/-2.4% vs 66.6+/-28.5%; mean +/- s.d.), respectively. Among AD subjects, there was relative sparing of emotionally influenced memory, which was not seen in controls because of a ceiling effect. Retention of the emotional phase of the story differed significantly from that of the neutral phases. These findings suggest that the influence of emotion on memory is spared, at least to some degree, in AD.

An unstable trinucleotide-repeat region on chromosome 13 implicated in spinocerebellar ataxia: a common expansion locus

Larger CAG/CTG trinucleotide-repeat tracts in individuals affected with schizophrenia (SCZ) and bipolar affective disorder (BPAD) in comparison with control individuals have previously been reported, implying a possible etiological role for trinucleotide repeats in these diseases. Two unstable CAG/CTG repeats, SEF2-1B and ERDA1, have recently been cloned, and studies indicate that the majority of individuals with large repeats as detected by repeat-expansion detection (RED) have large repeat alleles at these loci. These repeats do not show association of large alleles with either BPAD or SCZ. Using RED, we have identified a BPAD individual with a very large CAG/CTG repeat that is not due to expansion at SEF2-1B or ERDA1. From this individual's DNA, we have cloned a highly polymorphic trinucleotide repeat consisting of (CTA)n (CTG)n, which is very long ( approximately 1,800 bp) in this patient. The repeat region localizes to chromosome 13q21, within 1.2 cM of fragile site FRA13C. Repeat alleles in our sample were unstable in 13 (5.6%) of 231 meioses. Large alleles (>100 repeats) were observed in 14 (1. 25%) of 1,120 patients with psychosis, borderline personality disorder, or juvenile-onset depression and in 5 (.7%) of 710 healthy controls. Very large alleles were also detected for Centre d'Etude Polymorphisme Humaine (CEPH) reference family 1334. This triplet expansion has recently been reported to be the cause of spinocerebellar ataxia type 8 (SCA8); however, none of our large alleles above the disease threshold occurred in individuals either affected by SCA or with known family history of SCA. The high frequency of large alleles at this locus is inconsistent with the much rarer occurrence of SCA8. Thus, it seems unlikely that expansion alone causes SCA8; other genetic mechanisms may be necessary to explain SCA8 etiology.

Association of the MscI polymorphism of the dopamine D3 receptor gene with tardive dyskinesia in schizophrenia

In 112 schizophrenic patients previously treated with typical neuroleptics, we investigated the putative role of the dopamine D3 receptor gene (DRD3) in tardive dyskinesia (TD). Patients were assessed for TD severity using the Abnormal Involuntary Movement Scale (AIMS) and were subsequently genotyped for the MscI polymorphism that identifies a serine to glycine substitution in DRD3. A modified analysis of covariance model, which incorporated several clinical risk factors for TD, was utilized to detect differences in TD severity among the various genotypic groups. The glycine allele of DRD3 was found to be associated with typical neuroleptic-induced TD (F[2,95] = 8.25, p < .0005). Higher mean AIMS scores were found in patients homozygous for the glycine variant of the DRD3 gene, as compared to both heterozygous and serine homozygous patients. Although replication is necessary, this finding supports a role for the dopamine D3 receptor in the pathogenesis of TD.

Ziprasidone 80 mg/day and 160 mg/day in the acute exacerbation of schizophrenia and schizoaffective disorder: a 6-week placebo-controlled trial. Ziprasidone Study Group

In this double-blind study, patients with an acute exacerbation of schizophrenia or schizoaffective disorder were randomized to receive either ziprasidone 80 mg/day (n = 106) or 160 mg/day (n = 104) or placebo (n = 92), for 6 weeks. Both doses of ziprasidone were statistically significantly more effective than placebo in improving the PANSS total, BPRS total, BPRS core items, CGI-S, and PANSS negative subscale scores (p < .05). Ziprasidone 160 mg/day significantly improved depressive symptoms in patients with clinically significant depression at baseline (MADRS > or = 14, over-all mean 23.5) (p < .05) as compared with placebo. The percentage of patients experiencing adverse events was similar in each treatment group, and resultant discontinuation was rare. The most frequent adverse events associated with ziprasidone were generally mild dyspepsia, nausea, dizziness, and transient somnolence. Ziprasidone was shown to have a very low liability for inducing movement disorders and weight gain. The results indicate that ziprasidone is effective and well tolerated in the treatment of the positive, negative, and depressive symptoms of an acute exacerbation of schizophrenia or schizoaffective disorder.

Effect of clozapine and adjunctive high-dose glycine in treatment-resistant schizophrenia

OBJECTIVE

The focus of this study was the systematic evaluation of the clinical effects of glycine as an adjunct to the atypical antipsychotic clozapine in the treatment of schizophrenia.

METHOD

In a double-blind, placebo-controlled study, 19 patients with chronic, treatment-resistant schizophrenia who were maintained on optimal doses of clozapine (400-1200 mg/day) were administered either 30 g/day of glycine (N=9) or placebo (N=10) for 12 weeks. Clinical evaluations with the Brief Psychiatric Rating Scale, the Scale for the Assessment of Negative Symptoms, and the Simpson-Angus movement scale were completed biweekly.

RESULTS

The use of glycine as an adjunct to clozapine was not effective in decreasing positive or negative symptoms. In contrast, the patients treated with clozapine without glycine had a 35% reduction in positive symptoms.

CONCLUSIONS

These preliminary data suggest that glycine may interfere with the antipsychotic efficacy of atypical neuroleptics such as clozapine.

Altered ratios of alternatively spliced long and short gamma2 subunit mRNAs of the gamma-amino butyrate type A receptor in prefrontal cortex of schizophrenics

The relative abundance of alternatively spliced long (gamma2L) and short (gamma2S) mRNAs of the gamma2 subunit of the gamma-amino butyrate type A (GABAA) receptor was examined in dorsolateral prefrontal cortex of schizophrenics and matched controls by using in situ hybridization histochemistry and semiquantitative reverse transcription-PCR (RT-PCR) amplification. A cRNA probe identifying both mRNAs showed that the transcripts are normally expressed at moderately high levels in the prefrontal cortex. Consistent with previous studies, overall levels of gamma2 transcripts in prefrontal cortex of brains from schizophrenics were reduced by 28.0%, although this reduction did not reach statistical significance. RT-PCR, performed under nonsaturating conditions on total RNA from the same blocks of tissue used for in situ hybridization histochemistry, revealed a marked reduction in the relative proportion of gamma2S transcripts in schizophrenic brains compared with controls. In schizophrenics, gamma2S transcripts had fallen to 51.7% (+/-7.9% SE; P < 0.0001) relative to control levels. Levels of gamma2L transcripts showed only a small and nonsignificant reduction of 16. 9% (+/-12.0% SE, P > 0.05). These findings indicate differential transcriptional regulation of two functionally distinct isoforms of one of the major GABAA receptor subunits in the prefrontal cortex of schizophrenics. The specific reduction in relative abundance of gamma2S mRNAs and the associated relative increase in gamma2L mRNAs should result in functionally less active GABAA receptors and have severe consequences for cortical integrative function.

Is P50 suppression a measure of sensory gating in schizophrenia?

BACKGROUND

Abnormal P50 response has been hypothesized to reflect the sensory gating deficit in schizophrenia. Despite the extensive literature concerning the sensory filtering or gating deficit in schizophrenia, no evidence has been provided to test the relationship of the P50 phenomenon with patients' experiences of perceptual anomalies.

METHODS

Sixteen drug-free DSM-IV diagnosed schizophrenic patients who reported moderate to severe perceptual anomalies in the auditory or visual modality were examined as compared to 16 schizophrenic patients who did not report perceptual anomalies, and 16 normal subjects. Both control groups were age- and gender-matched with the study group.

RESULTS

Patients reporting perceptual anomalies exhibited P50 patterns that did not differ from normal subjects. In contrast, patients who did not report perceptual anomalies showed the abnormal P50 ratios previously found to be associated with schizophrenia.

CONCLUSIONS

These paradoxical findings do not support the hypothetical relationship between the P50 and behavioral measures of sensory gating, suggesting that additional studies are needed to further explore the clinical correlates of the P50.

Topographic analysis of EEG photic driving in patients with schizophrenia following clozapine treatment

Reduced EEG photic driving has been found to be diagnostically sensitive and specific for schizophrenia. Thirty-one patients with schizophrenia were tested in this study to identify the typical and atypical neuroleptic effects on the photic driving. Compared with the placebo, clozapine significantly enhanced the photically driven EEG in theta and low alpha frequency band, while haloperidol did not have the same effect. These changes with clozapine appeared to be symmetrical and located primarily in the frontal, central and mid-parietal areas but not in the lateral parietal, temporal and occipital regions. Results were consistent with previous findings and suggested that the atypical EEG profile of clozapine might be associated with 5-HT2 antagonistic property.

Bipolar affective disorder partially cosegregates with a balanced t(9;11)(p24;q23.1) chromosomal translocation in a small pedigree

Analysis of an extended pedigree in which a balanced t(9;11)(p24;q23.1) translocation was found to cosegregate with bipolar affective disorder revealed that five of 11 translocation carriers had bipolar affective disorder and one carrier had unipolar depression. There were no affected individuals in the pedigree without the balanced translocation. We hypothesized that gene(s) or gene regulatory regions disrupted by the translocation might be contributing to the bipolar affective disorder in a dominant fashion. To test this hypothesis, we isolated the derivative chromosome 9 and derivative chromosome 11 in somatic cell hybrids and identified the nearest flanking markers on chromosome 9 (D9S230 and D9S2011E/HRFX3) and chromosome 11 (EST00652 and CRYA2). YAC contigs were constructed in the region of flanking markers for both chromosomes 9 and 11. Chromosome 11 breakpoint was localized within an 8-kb region in a small insert (100 kb) YAC. Chromosome 9 breakpoint was localized within approximately 2 Mb region. Several genes and ESTs including EST00652, CRYA2, DRD2, 5HTR3 on chromosome 11 and VLDLR and SLC1A1 on chromosome 9 were mapped within the vicinity of the breakpoint but were shown not to be disrupted by the translocation breakpoint. Although several possibilities exist regarding the role of the balanced translocation in developing bipolar affective disorder in this pedigree, including a chance cosegregation, identification of a disrupted gene or gene regulatory region with the help of physical mapping resources described in this study may help to identify the presence of a susceptibility gene for this disorder.

Lateralized attentional deficits in drug-free and medicated schizophrenic patients

Performance on a cued reaction time (RT) task, theoretically linked to posterior and anterior neuroanatomical systems in the brain (Posner, M. I. et al., Science, 1988, 210, 1627-1631; Archives of General Psychiatry, 1988, 15, 811-821), was used to assess sensory orienting and maintenance of attention. In schizophrenic patients, Posner et al. found a lateralized abnormality in RT (longer RTs to uncued targets in the right visual field than in the left visual field), as did Maruff et al. (Neuropsychologia, 1995, 33, 1205-1223), but Strauss et al. (Journal of Psychiatric Research, 1991, 37, 139-146), among others, did not replicate this effect. However, the subjects in these studies differed in the percentage of schizophrenic patients taking neuroleptic medication at the time of testing and in the chronicity of the illness. In the present study, we used two groups of schizophrenic subjects to control for the use of neuroleptic medication. The lateralized abnormality in RT was observed in the drug-free group of schizophrenic subjects, but not in the group of drug-treated schizophrenic subjects.

Effects of P50 temporal variability on sensory gating in schizophrenia

The conditioning-testing (S1-S2) P50 auditory evoked potential (EP) has been well-documented and accepted as an important tool for measuring sensory gating in schizophrenia research. However, the physiological mechanism of the phenomenon is not known. In this study a single-trial analysis was used to determine the influence of the latency variability of the responses in the formation of the averaged P50. Ten schizophrenic patients and 10 normal controls were tested in the dual-click EP paradigm. Using ensemble averaging analysis, we replicated the previous finding of a lower S1 P50 amplitude and higher S2/S1 ratio in schizophrenics compared with normal controls. The single-trial analysis revealed that patients had significantly higher trial-to-trial latency variability in S1 responses than normal subjects, while the S2 showed the same variability as in controls. Measured by the single-trial procedure, the arithmetic mean amplitudes of P50 responses to S1 and S2 were similar between normal and schizophrenic subjects. The same measure also eliminated the difference in averaged P50 amplitude between S1 and S2 for both groups. Temporal variability appears to be an important factor in the assessment of averaged EPs and thus contribute to the change of P50 amplitude observed in schizophrenia.

REM sleep eye movement counts correlate with visual imagery in dreaming: a pilot study

Based on the findings of our previously published positron emission tomography study, we proposed that recorded eye movements during REM sleep are visually targeted saccades. In the present study, we examined the correlation between the number of eye movements in REM sleep (EM) and visual imagery in dreaming (V) and provided further support for our proposal. All the observations (N = 11) were made with one individual to eliminate interindividual variation and were made during the second REM sleep period to control for a time-of-night effect. V, with or without dream report length partialled out, was strongly associated with EM only in the 1-min interval immediately preceding awakening. The time course of the association suggests that the strong EM-V association reflects a phasic, localized activation of the eye-movement-control system in association with REM sleep eye movements.

Neuropathological studies of brain tissue in schizophrenia

Postmortem neuropathological investigations in the last half decade provide increasing evidence compatible with a neurodevelopmental defect in schizophrenia. Basic and clinical data support hypotheses suggesting that disturbances in neurodevelopment in schizophrenia may involve the cortical subplate and a theorized second trimester "window of vulnerability". The focus of this paper is on (1) selected methodological issues involved in the collection, analyses and preservation of human postmortem brain tissue; (2) a review of evidence showing morphological defects particularly in prefrontal cortical regions of the schizophrenic brain; and (3) potential future research directions.

Decrease in sigma but no increase in striatal dopamine D4 sites in schizophrenic brains

[3H]Nemonapride differentially defines sigma and dopamine receptor sites depending upon assay conditions. In post-mortem schizophrenic brain tissues, [3H]nemonapride-labeled sigma receptor binding is decreased compared to match normal controls. No striatal dopamine D4/D4-like receptor differential was observed between the schizophrenic or control tissues, using the [3H]nemonapride minus [3H]raclopride subtraction method.

P50 changes with visual interference in normal subjects: a sensory distraction model for schizophrenia

Twenty-five normal subjects were tested in a Conditioning-Testing (S1-S2) auditory P50 study. Each subject was tested twice under two experimental conditions: distraction condition (with light interference) and control condition (without interference). Results showed that S1 P50 amplitude was significantly decreased with visual interference compared with that in the control condition, while the S2 response remained unchanged. Consequently, the S2/S1 gating ratio was also increased remarkably in the distraction condition. The auditory EP changes with the visual distraction in normals closely resembled the abnormal findings in schizophrenic subjects. These data may provide an alternative model to elucidate the psychophysiological mechanism that possibly rules the changes of attention in schizophrenia.

Maldistribution of interstitial neurons in prefrontal white matter of the brains of schizophrenic patients

BACKGROUND

The cortical subplate is a transitory structure involved in the formation of connections in developing cerebral cortex. Interstitial neurons, normally present in subcortical white matter (WM) of the adult brain, have escaped the programmed cell death that eliminates most subplate neurons. Previous investigations indicated a maldistribution of one population of interstitial neurons in the WM of brains of schizophrenic patients, suggesting a defect of the subplate during brain development.

METHODS

Three histochemically or immunocytochemically defined neuronal populations were studied in WM beneath the middle frontal gyrus of 20 schizophrenic patients and 20 matched control subjects.

RESULTS

Brains of schizophrenic patients showed significant changes in the distribution of the three neuronal populations: microtubule-associated protein 2 and nonphosphorylated neurofilament-immunoreactive neurons showed a decreased density in superficial WM and an increased density in deeper WM. Nicotinamide adenine dinucleotide phosphate-diaphorase neurons were reduced in superficial WM and showed variable densities in deeper WM. Thirty-five percent of the brains of schizophrenic patients but no brains of the control subjects showed a maldistribution of neurons toward deeper WM with at least two of the three markers. Changes in neuronal distribution were not linked to age, gender, autolysis time, or subtype of schizophrenia.

CONCLUSIONS

Selective displacement of interstitial WM neurons in the frontal lobe of brains of schizophrenic patients may indicate alteration in the migration of subplate neurons or in the pattern of programmed cell death. Both could lead to defective cortical circuitry in the brains of schizophrenic patients.

Language in dreaming and regional EEG alpha power

In an intensive single-subject design, electroencephalographic (EEG) alpha power and receptive and expressive language in dreaming were studied in 12 dreams during rapid eye movement (REM) sleep on 12 separate nights. Bilateral EEG was recorded continuously from 21 sites and digitized. We used the Fast Fourier transformation (FFT) for power spectral analysis to measure EEG power in the alpha frequency range (8-12 Hz) at each of the EEG sites. The subject was awakened after about 14 minutes into the second REM period, and dream reports were collected. We scored the dream reports for expressive and receptive language. The lower the alpha power on the left sides of those homologous pairs that roughly correspond to Broca's (C3) or Wernicke's area (P3), the more expressive or receptive language in dream reports. The largest difference between the correlation of the left and that of the right homologous pair of regions was found in the central (C3, C4) area for expressive language and in the parietal (P3, P4) area for receptive language. Our finding suggests lateralized and localized cortical activation in relation to language in dreaming.

Cerebral metabolic activity correlates of subsyndromes in chronic schizophrenia

Seventy-nine patients with schizophrenia and 47 healthy controls received positron-emission tomography (PET) with 18F-2-deoxyglucose uptake while executing the Continuous Performance Test (CPT). Patients had been off all psychoactive medication for at least four weeks. Patients' symptoms were assessed with the Brief Psychiatric Rating Scale and factor scale scores were obtained. These scores were used in cluster analysis to identify patients with predominantly delusional, negative, disorganized, and remitted symptoms. To address the interconnective nature of cerebral functioning, regions of interest were defined on the basis of the results of a factor analysis of metabolic rate in selected brain regions. This procedure identified six cortical and eight subcortical region of interest factors. Metabolic rate factor scale scores were compared between the patients' clusters and the healthy controls. The delusional cluster showed a significantly reduced hippocampal activity, while the negative symptoms cluster presented with a prominent hypofrontality and significantly increased left temporal cortex values. Concurrently, both clusters were associated with a decreased activity on the factor 'anterior cingulum and medial frontal gyrus'. The disorganized cluster was characterized by a significant overactivity in the parietal cortex and motor strip and a decreased activity in the corpus callosum. The subsyndromes of chronic schizophrenia are therefore characterized by deviant patterns of cerebral activity rather than deficits in a single location.

Gender differences in gating of the auditory evoked potential in normal subjects

Central nervous system (CNS) inhibitory mechanisms hypothesized to "gate" repetitive sensory inputs have been implicated in the pathology of schizophrenia. The present study investigated gender differences in inhibitory gating of evoked brain responses to repeated stimuli in normal subjects (30 women and 30 men) using an auditory conditioning-testing paradigm. Pairs of click stimuli (S1 and S2) were presented with a 0.5 s intrapair and a 10 s interpair interval. The amplitudes and latencies of the P50, N100, P180 components of the auditory evoked response to the conditioning (S1) and test response (S2) were measured, and the gating ratios were computed (T/C ratio = S2/S1 * 100). The amplitudes to S1 were not significantly different between men and women at P50, N100, or P180. However, women had significantly higher amplitudes to S2 at P50 (p = 0.03) and N100 (p = 0.04). The T/C ratios for women were higher (i.e., less suppression of response to S2) for P50 (p = 0.08) and N100 (p = 0.04) compared to men. The results suggested that differences in auditory gating between men and women were not due to biological differences in the P50 and N100 generators but possibly to differential influence of inhibitory mechanisms acting on the generator substrates of these evoked responses.

Selective alterations in gene expression for NMDA receptor subunits in prefrontal cortex of schizophrenics

NMDA receptor antagonists can induce a schizophrenia-like psychosis, but the role of NMDA receptors in the pathophysiology of schizophrenia remains unclear. Expression patterns of mRNAs for five NMDA receptor subunits (NR1/NR2A-D) were determined by in situ hybridization in prefrontal, parieto-temporal, and cerebellar cortex of brains from schizophrenics and from neuroleptic-treated and nonmedicated controls. In the cerebral cortex of both schizophrenics and controls, mRNAs for NR1, NR2A, NR2B, and NR2D subunits were preferentially expressed in layers II/III, Va, and VIa, with much higher levels in the prefrontal than in the parieto-temporal cortex. Levels of mRNA for the NR2C subunit were very low overall. By contrast, the cerebellar cortex of both schizophrenics and controls contained very high levels of NR2C subunit mRNA, whereas levels for the other subunit mRNAs were very low, except NR1, for which levels were moderate. Significant alterations in the schizophrenic cohort were confined to the prefrontal cortex. Here there was a shift in the relative proportions of mRNAs for the NR2 subunit family, with a 53% relative increase in expression of the NR2D subunit mRNA. No comparable changes were found in neuroleptic-treated or untreated controls. These findings indicate regional heterogeneity of NMDA receptor subunit expression in human cerebral and cerebellar cortex. In schizophrenics, the alterations in expression of NR2 subunit mRNA in prefrontal cortex are potential indicators of deficits in NMDA receptor-mediated neurotransmission accompanying functional hypoactivity of the frontal lobes.