Neural basis of novel and well-learned recognition memory in schizophrenia: a positron emission tomography study

Convergent lines of evidence supporting involvement of NFKB1 in schizophrenia

OBJECTIVES

NFKB1 was associated with treatment-refractory schizophrenia (SZ) and response to antipsychotics; however, the underlying mechanisms through which NFKB1 confers its risk for SZ are largely unknown. We aimed to investigate the potential role of NFKB1 in SZ.

METHODS

In the present study, we investigated the association of the risk SNP rs230529 of NFKB1 with gray matter density and with NFKB1 mRNA levels in various human brain regions. The spatiotemporal expression pattern of NFKB1 in human brains was explored. We constructed a miRNA-NFKB1-target gene regulatory network and analyzed its druggability through targeting NFKB1 for SZ treatment.

RESULTS

NFKB1 showed the highest expression levels in the cerebellum, in which these levels were stratified by genotypes of rs230529. Interestingly, the allelic state of rs230529 was significantly associated with regional gray matter density in multiple brain regions (including the cerebellum), which also differed between patients with schizophrenia and controls. Furthermore, regulatory targets of NFKB1 were enriched among SZ susceptibility genes. A substantial proportion of NFKB1 target genes were subject to combinatorial regulation by NFKB1 and miRNAs, constituting a hybrid NFKB1-miRNA-gene regulatory network. Some components of this network showed expression changes relevant to both the disease and the treatment. Finally, we detected the dynamic changes of NFKB1-miR-155-5p-GSK3B and NFKB1-miR-155-5p/let-7a-5p-IL6 networks in course of the treatment of SZ.

CONCLUSION

Taken together, our findings support the involvement of NFKB1-mediated dysregulation in the development of SZ.

Interactions between knockout of schizophrenia risk factor Dysbindin-1 and copper metabolism in mice

BACKGROUND AND PURPOSE

DTNBP1 gene variation and lower dysbindin-1 protein are associated with schizophrenia. Previous evidence suggests that downregulated dysbindin-1 expression results in lower expression of copper transporters ATP7A (intracellular copper transporter) and SLC31A1 (CTR1; extracellular copper transporter), which are required for copper transport across the blood brain barrier. However, whether antipsychotic medications used for schizophrenia treatment may modulate these systems is unclear.

EXPERIMENTAL APPROACH

The current study measured behavioral indices of neurological function in dysbindin-1 functional knockout (KO) mice and their wild-type (WT) littermates with or without quetiapine treatment. We assessed serum and brain copper levels, ATP7A and CTR1 mRNA, and copper transporter-expressing cellular population transcripts: TTR (transthyretin; choroid plexus epithelial cells), MBP (myelin basic protein; oligodendrocytes), and GJA1 (gap-junction protein alpha-1; astrocytes) in cortex and hippocampus.

KEY RESULTS

Regardless of genotype, quetiapine significantly reduced TTR, MBP, CTR1 mRNA, and serum copper levels. Neurological function of untreated KO mice was abnormal, and ledge instability was rescued with quetiapine. KO mice were hyperactive after 10 min in the open-field assay, which was not affected by treatment.

CONCLUSIONS AND IMPLICATIONS

Dysbindin-1 KO results in hyperactivity, altered serum copper, and neurological impairment, the last of which is selectively rescued with quetiapine. Antipsychotic treatment modulates specific cellular populations, affecting myelin, the choroid plexus, and copper transport across the blood brain barrier. Together these results indicate the widespread impact of antipsychotic treatment, and that alteration of dysbindin-1 may be sufficient, but not necessary, for specific schizophrenia pathology.

Resting regional brain activity correlates of verbal learning deficit in major depressive disorder

Memory deficits are reported in major depressive disorder (MDD). Prefrontal cortical and mesiotemporal cortical (MTC)/subcortical regions are involved in the Buschke Selective Reminding Task (SRT), a verbal list-learning task. To determine whether depression-related changes in resting brain metabolism explain (in part) the deficits in SRT performance found in MDD, statistical correlation maps were calculated between SRT total recall score (TR) and relative regional cerebral metabolic rate for glucose (rCMRglu), measured by [¹⁸F]-flourodeoxyglucose (FDG) positron emission tomography (PET), in unmedicated, depressed MDD patients (N = 29). Subsequently, to explore hypothesized loss of top-down control in MDD, we compared the correlations between rCMRglu of SRT-relevant regions of the dorsolateral prefrontal cortex (dlPFC) and amygdala in a larger cohort of MDD (N = 60; 29 inclusive) versus healthy controls (HC) (N = 43). SRT performance of patients is on average 0.5 standard deviation below published normative mean. TR and rCMRglu positively correlate in bilateral dorsomedial PFC, dlPFC, dorsal anterior cingulate; negatively correlate in bilateral MTC/subcortical regions, and cerebellum. rCMRglu in dlPFC correlates negatively with that in amygdala in HC but not in MDD. Depression-related changes present in FDG-PET measured resting brain activity may be in part responsible for memory deficit found in MDD.

Gray matter differences between affective and non-affective first episode psychosis: A review of Magnetic Resonance Imaging studies: Special Section on "Translational and Neuroscience Studies in Affective Disorders" Section Editor, Maria Nobile MD, PhD. This Section of JAD focuses on the relevance of translational and neuroscience studies in providing a better understanding of the neural basis of affective disorders. The main aim is to briefly summaries relevant research findings in clinical neuroscience with particular regards to specific innovative topics in mood and anxiety disorders

BACKGROUND

Non-affective and affective psychoses are very common mental disorders. However, their neurobiological underpinnings are still poorly understood. Therefore, the goal of the present review was to evaluate structural Magnetic Resonance Imaging (MRI) studies exploring brain deficits in both non-affective (NA-FEP) and affective first episode psychosis (A-FEP).

METHODS

A bibliographic search on PUBMED of all MRI studies exploring gray matter (GM) differences between NA-FEP and A-FEP was conducted.

RESULTS

Overall, the results from the available evidence showed that the two diagnostic groups share common GM alterations in fronto-temporal regions and anterior cingulate cortex. In contrast, unique GM deficits have also been observed, with reductions in amygdala for A-FEP and in hippocampus and insula for NA-FEP.

LIMITATIONS

Few small MRI studies with heterogeneous methodology.

CONCLUSIONS

Although the evidences are far to be conclusive, they suggest the presence of common and distinct pattern of GM alterations in NA-FEP and A-FEP. Future larger longitudinal studies are needed to further characterize specific neural biomarkers in homogenous NA-FEP and A-FEP samples.

Chronic Adolescent Δ9-Tetrahydrocannabinol Treatment of Male Mice Leads to Long-Term Cognitive and Behavioral Dysfunction, Which Are Prevented by Concurrent Cannabidiol Treatment

Introduction: The high prevalence of adolescent cannabis use, the association between this use and later psychiatric disease, and increased access to high-potency cannabis highlight the need for a better understanding of the long-term effects of adolescent cannabis use on cognitive and behavioral outcomes. Furthermore, increasing Δ9-tetrahydrocannabinol (THC) in high-potency cannabis is accompanied by a decrease in cannabidiol (CBD), thus an understanding of the interactions between CBD and THC in the neurodevelopmental effects of THC is also important. The current study examined the immediate and long-term behavioral consequences of THC, CBD, and their combination in a mouse model of adolescent cannabis use. Materials and Methods: Male CD1 mice received daily injections of THC (3 mg/kg), CBD (3 mg/kg), CBD+THC (3 mg/kg each), vehicle, or remained undisturbed in their home cage (no handling/injections), either during adolescence (postnatal day [PND] 28-48) or during early adulthood (PND 69-89). Animals were then evaluated with a battery of behavioral tests 1 day after drug treatment, and again after 42 drug-free days. The tests included the following: open field (day 1), novel object recognition (NOR; day 2), marble burying (day 3), elevated plus maze (EPM; day 4), and Nestlet shredding (day 5). Results: Chronic administration of THC during adolescence led to immediate and long-term impairments in object recognition/working memory, as measured by the NOR task. In contrast, adult administration of THC caused immediate, but not long term, impairment of object/working memory. Adolescent chronic exposure to THC increased repetitive and compulsive-like behaviors, as measured by the Nestlet shredding task. Chronic administration of THC, either during adolescence or during adulthood, led to a delayed increase in anxiety as measured by the EPM. All THC-induced behavioral abnormalities were prevented by the coadministration of CBD+THC, whereas CBD alone did not influence behavioral outcomes. Conclusion: These data suggest that chronic exposure to THC during adolescence leads to some of the behavioral abnormalities common in schizophrenia. Interestingly, CBD appeared to antagonize all THC-induced behavioral abnormalities. These findings support the hypothesis that adolescent THC use can impart long-term behavioral deficits; however, cotreatment with CBD prevents these deficits.

Cognitive performance is associated with gray matter decline in first-episode psychosis

Progressive loss of gray matter has been demonstrated over the early course of schizophrenia. Identification of an association between cognition and gray matter may lead to development of early interventions directed at preserving gray matter volume and cognitive ability. The present study evaluated the association between gray matter using voxel-based morphometry (VBM) and cognitive testing in a sample of 16 patients with first-episode psychosis. A simple regression was applied to investigate the association between gray matter at baseline and 80 months and cognitive tests at baseline. Performance on the Wisconsin Card Sorting Task (WCST) at baseline was positively associated with gray matter volume in several brain regions. There was an association between decreased gray matter at baseline in the nucleus accumbens and Trails B errors. Performing worse on Trails B and making more WCST perseverative errors at baseline was associated with gray matter decline over 80 months in the right globus pallidus, left inferior parietal lobe, Brodmann's area (BA) 40, and left superior parietal lobule and BA 7 respectively. All significant findings were cluster corrected. The results support a relationship between aspects of cognitive impairment and gray matter abnormalities in first-episode psychosis.

The Role of the Pediatric Cerebellum in Motor Functions, Cognition, and Behavior: A Clinical Perspective

This article discusses the contribution of the pediatric cerebellum to locomotion, ocular motor control, speech articulation, cognitive function, and behavior modulation. Hypotheses on cerebellar function are discussed. Clinical features in patients with cerebellar disorders are outlined. Cerebellar abnormalities in cognitive and behavioral disorders are detailed.

Delayed match-to-sample in working memory: A BrainMap meta-analysis

Working memory (WM), or the ability to temporarily store and manipulate information, is one of the most widely studied constructs in cognitive psychology. Since its inception, it has become one of the leading explanations for how humans are able to operate on a cognitive level. The current study probed the neural networks underlying one of the most commonly used tasks, delayed match-to-sample (DMTS), to study WM. An activation likelihood estimation (ALE) analysis of 42 functional neuroimaging studies (626 participants) was conducted to demonstrate neural network engagement during DMTS. Results demonstrated strong convergence in brain regions commonly associated with the working memory construct (i.e., dorsolateral prefrontal cortex, fusiform gyrus, and posterior parietal cortex). However, neural activation in two regions frequently attributed to WM were absent from this meta-analysis: the anterior cingulate and the rostral prefrontal cortex, suggesting that these regions may be more sensitive to task or stimuli characteristics. In a post-hoc analysis, we deconstructed the DMTS meta-analysis to examine nonverbal versus verbal stimuli, and found notable neurofunctional differences such that DMTS using nonverbal stimuli consistently engaged the right middle frontal gyrus (BA 6/46) and precuneus (BA 7) more so than verbal stimuli based DMTS. These results provide a foundation for future models of functional connectivity that may elucidate subtle differences in working memory attributable to pathological processes.

Neural substrate of quality of life in patients with schizophrenia: a magnetisation transfer imaging study

The aim of this study was to investigate the neural substrate underlying quality of life (QoL) and to demonstrate the microstructural abnormalities associated with impaired QoL in a large sample of patients with schizophrenia, using magnetisation transfer imaging. A total of 81 right-handed men with a diagnosis of schizophrenia and 25 age- and sex-similar healthy controls were included and underwent a 3T MRI with magnetization transfer ratio (MTR) to detect microstructural abnormalities. Compared with healthy controls, patients with schizophrenia had grey matter (GM) decreased MTR values in the temporal lobe (BA21, BA37 and BA38), the bilateral insula, the occipital lobe (BA17, BA18 and BA19) and the cerebellum. Patients with impaired QoL had lower GM MTR values relative to patients with preserved QoL in the bilateral temporal pole (BA38), the bilateral insula, the secondary visual cortex (BA18), the vermis and the cerebellum. Significant correlations between MTR values and QoL scores (p < 0.005) were observed in the GM of patients in the right temporal pole (BA38), the bilateral insula, the vermis and the right cerebellum. Our study shows that QoL impairment in patients with schizophrenia is related to the microstructural changes in an extensive network, suggesting that QoL is a bio-psychosocial marker.

The therapeutic potential of the cerebellum in schizophrenia

The cognitive role of the cerebellum is critically tied to its distributed connections throughout the brain. Accumulating evidence from anatomical, structural and functional imaging, and lesion studies advocate a cognitive network involving indirect connections between the cerebellum and non-motor areas in the prefrontal cortex. Cerebellar stimulation dynamically influences activity in several regions of the frontal cortex and effectively improves cognition in schizophrenia. In this manuscript, we summarize current literature on the cingulocerebellar circuit and we introduce a method to interrogate this circuit combining opotogenetics, neuropharmacology, and electrophysiology in awake-behaving animals while minimizing incidental stimulation of neighboring cerebellar nuclei. We propose the novel hypothesis that optogenetic cerebellar stimulation can restore aberrant frontal activity and rescue impaired cognition in schizophrenia. We focus on how a known cognitive region in the frontal cortex, the anterior cingulate, is influenced by the cerebellum. This circuit is of particular interest because it has been confirmed using tracing studies, neuroimaging reveals its role in cognitive tasks, it is conserved from rodents to humans, and diseases such as schizophrenia and autism appear in its aberrancy. Novel tract tracing results presented here provide support for how these two areas communicate. The primary pathway involves a disynaptic connection between the cerebellar dentate nuclei (DN) and the anterior cingulate cortex. Secondarily, the pathway from cerebellar fastigial nuclei (FN) to the ventral tegmental area, which supplies dopamine to the prefrontal cortex, may play a role as schizophrenia characteristically involves dopamine deficiencies. We hope that the hypothesis described here will inspire new therapeutic strategies targeting currently untreatable cognitive impairments in schizophrenia.

Consensus paper: the cerebellum's role in movement and cognition

While the cerebellum's role in motor function is well recognized, the nature of its concurrent role in cognitive function remains considerably less clear. The current consensus paper gathers diverse views on a variety of important roles played by the cerebellum across a range of cognitive and emotional functions. This paper considers the cerebellum in relation to neurocognitive development, language function, working memory, executive function, and the development of cerebellar internal control models and reflects upon some of the ways in which better understanding the cerebellum's status as a "supervised learning machine" can enrich our ability to understand human function and adaptation. As all contributors agree that the cerebellum plays a role in cognition, there is also an agreement that this conclusion remains highly inferential. Many conclusions about the role of the cerebellum in cognition originate from applying known information about cerebellar contributions to the coordination and quality of movement. These inferences are based on the uniformity of the cerebellum's compositional infrastructure and its apparent modular organization. There is considerable support for this view, based upon observations of patients with pathology within the cerebellum.

Expression of GABAA α2-, β1- and ε-receptors are altered significantly in the lateral cerebellum of subjects with schizophrenia, major depression and bipolar disorder

There is abundant evidence that dysfunction of the γ-aminobutyric acid (GABA)ergic signaling system is implicated in the pathology of schizophrenia and mood disorders. Less is known about the alterations in protein expression of GABA receptor subunits in brains of subjects with schizophrenia and mood disorders. We have previously demonstrated reduced expression of GABA(B) receptor subunits 1 and 2 (GABBR1 and GABBR2) in the lateral cerebella of subjects with schizophrenia, bipolar disorder and major depressive disorder. In the current study, we have expanded these studies to examine the mRNA and protein expression of 12 GABA(A) subunit proteins (α1, α2, α3, α5, α6, β1, β2, β3, δ, ε, γ2 and γ3) in the lateral cerebella from the same set of subjects with schizophrenia (N=9-15), bipolar disorder (N=10-15) and major depression (N=12-15) versus healthy controls (N=10-15). We found significant group effects for protein levels of the α2-, β1- and ε-subunits across treatment groups. We also found a significant group effect for mRNA levels of the α1-subunit across treatment groups. New avenues for treatment, such as the use of neurosteroids to promote GABA modulation, could potentially ameliorate GABAergic dysfunction in these disorders.

The incidence and nature of cerebellar findings in schizophrenia: a quantitative review of fMRI literature

Clinical evidence and structural neuroimaging studies linked cerebellar deficits to cognitive-related symptoms in schizophrenia. Yet, in functional neuroimaging literature to date, the role of the cerebellum in schizophrenia was not explored in a systematic fashion. Here, we reviewed 234 functional magnetic resonance imaging studies indexed by PubMed and published in 1997-2010 that had at least one group of schizophrenia patients, used blood oxygenation level dependent contrast and the general linear model to assess neuronal activity. We quantified presence/absence of cerebellar findings and the frequency of hypo- and hyperactivations (ie, less or more activity in patients relative to healthy controls). We used peaks of activations reported in these studies to build a topographical representation of group differences on a cerebellar map. Cerebellar activity was reported in patients in 41.02% of the articles, with more than 80% of these dedicated to cognitive, emotional, and executive processes in schizophrenia. Almost two-thirds of group comparisons resulted in cerebellar hypoactivation, with a frequency that presented an inverted U shape across different age categories. The majority of the hypoactivation foci were located in the medial portion of the anterior lobe and the lateral hemispheres (lobules IV-V) of the cerebellum. Even though most experimental manipulations did not target explicitly the cerebellum's functions in schizophrenia, the cerebellar findings are frequent and cerebellar hypoactivations predominant. Therefore, although the cerebellum seems to play an important functional role in schizophrenia, the lack of reporting and interpretation of these data may hamper the full understanding of the disorder.

Meta-analytic evidence for a superordinate cognitive control network subserving diverse executive functions

Classic cognitive theory conceptualizes executive functions as involving multiple specific domains, including initiation, inhibition, working memory, flexibility, planning, and vigilance. Lesion and neuroimaging experiments over the past two decades have suggested that both common and unique processes contribute to executive functions during higher cognition. It has been suggested that a superordinate fronto-cingulo-parietal network supporting cognitive control may also underlie a range of distinct executive functions. To test this hypothesis in the largest sample to date, we used quantitative meta-analytic methods to analyze 193 functional neuroimaging studies of 2,832 healthy individuals, ages 18-60, in which performance on executive function measures was contrasted with an active control condition. A common pattern of activation was observed in the prefrontal, dorsal anterior cingulate, and parietal cortices across executive function domains, supporting the idea that executive functions are supported by a superordinate cognitive control network. However, domain-specific analyses showed some variation in the recruitment of anterior prefrontal cortex, anterior and midcingulate regions, and unique subcortical regions such as the basal ganglia and cerebellum. These results are consistent with the existence of a superordinate cognitive control network in the brain, involving dorsolateral prefrontal, anterior cingulate, and parietal cortices, that supports a broad range of executive functions.

Neural correlates of emotional recognition memory in schizophrenia: effects of valence and arousal

Schizophrenia patients are often impaired in their memory for emotional events compared with healthy subjects. Investigations of the neural correlates of emotional memory in schizophrenia patients are scarce in the literature. The present study aimed to compare cerebral activations in schizophrenia patients and healthy controls during memory retrieval of emotional images that varied in both valence and arousal. In a study with functional magnetic resonance imaging, 37 schizophrenia patients were compared with 37 healthy participants while performing a yes/no recognition paradigm with positive, negative (differing in arousal intensity) and neutral images. Schizophrenia patients performed worse than healthy controls in all experimental conditions. They showed less cerebral activation in limbic and prefrontal regions than controls during retrieval of negatively valenced stimuli, but had a similar pattern of brain activation compared with controls during retrieval of positively valenced stimuli (particularly in the high arousal condition) in the cerebellum, temporal lobe and prefrontal cortex. Both groups demonstrated increased brain activations in the high relative to low arousing conditions. Our results suggest atypical brain function during retrieval of negative pictures, but intact functional circuitry of positive affect during episodic memory retrieval in schizophrenia patients. The arousal data revealed that schizophrenia patients closely resemble the control group at both the behavioral and neurofunctional level.

Acquired self-control of insula cortex modulates emotion recognition and brain network connectivity in schizophrenia

Real-time functional magnetic resonance imaging (rtfMRI) is a novel technique that has allowed subjects to achieve self-regulation of circumscribed brain regions. Despite its anticipated therapeutic benefits, there is no report on successful application of this technique in psychiatric populations. The objectives of the present study were to train schizophrenia patients to achieve volitional control of bilateral anterior insula cortex on multiple days, and to explore the effect of learned self-regulation on face emotion recognition (an extensively studied deficit in schizophrenia) and on brain network connectivity. Nine patients with schizophrenia were trained to regulate the hemodynamic response in bilateral anterior insula with contingent rtfMRI neurofeedback, through a 2-weeks training. At the end of the training stage, patients performed a face emotion recognition task to explore behavioral effects of learned self-regulation. A learning effect in self-regulation was found for bilateral anterior insula, which persisted through the training. Following successful self-regulation, patients recognized disgust faces more accurately and happy faces less accurately. Improvements in disgust recognition were correlated with levels of self-activation of right insula. RtfMRI training led to an increase in the number of the incoming and outgoing effective connections of the anterior insula. This study shows for the first time that patients with schizophrenia can learn volitional brain regulation by rtfMRI feedback training leading to changes in the perception of emotions and modulations of the brain network connectivity. These findings open the door for further studies of rtfMRI in severely ill psychiatric populations, and possible therapeutic applications.

Altered prefrontal and hippocampal function during verbal encoding and recognition in people with prodromal symptoms of psychosis

Despite robust evidence of hippocampal abnormalities in schizophrenia, it is unclear whether hippocampal dysfunction predates the onset of psychosis. We used functional magnetic resonance imaging to investigate hippocampal function in subjects with an at-risk mental state (ARMS). Eighteen subjects meeting criteria for an ARMS and 22 healthy controls, matched for age, gender, and premorbid IQ, were scanned while performing a version of the Deese-Roediger-McDermott false memory task. During an encoding phase, subjects read lists of words aloud. Following a delay, they were presented with 24 target words, 24 semantically related lure words, and 24 novel words and required to indicate if each had been presented before. Behaviorally, the ARMS group made more false alarm responses for novel words than controls (P = .04) and had a lower discrimination accuracy for target words (P = .02). During encoding, ARMS subjects showed less activation than healthy controls in the left middle frontal gyrus, the bilateral medial frontal gyri, and the left parahippocampal gyrus. Correct recognition relative to false alarms was associated with differential engagement of the hippocampus bilaterally in healthy controls, but this difference was absent in the ARMS group. The ARMS was associated with altered function in the medial temporal cortex, as well as in the prefrontal regions, during both verbal encoding and recognition. These neurofunctional differences were associated with diminished recognition performance and may reflect the greatly increased risk of psychosis associated with the ARMS.

Deficits in GABA(B) receptor system in schizophrenia and mood disorders: a postmortem study

Postmortem and genetic studies have clearly demonstrated changes in GABA(B) receptors in neuropsychiatric disorders such as autism, bipolar disorder, major depression, and schizophrenia. Moreover, a number of recent studies have stressed the importance of cerebellar dysfunction in these same disorders. In the current study, we examined protein levels of the two GABA(B) receptor subunits GABBR1 and GABBR2 in lateral cerebella from a well-characterized cohort of subjects with schizophrenia (n=15), bipolar disorder (n=14), major depression (n=13) and healthy controls (n=12). We found significant reductions in protein for both GABBR1 and GABBR2 in lateral cerebella from subjects with schizophrenia, bipolar disorder and major depression when compared with controls. These results provide further evidence of GABAergic dysfunction in these three disorders as well as identify potential targets for therapeutic intervention.

Social appraisal in chronic psychosis: role of medial frontal and occipital networks

Persons with schizophrenia often appraise other individuals as threatening or persecutory. To evaluate social appraisal in schizophrenia, we probed brain networks with a task in which subjects judged whether or not they liked face stimuli with emotional expressions. We predicted that appraising negative expressions would engage patients, more than controls, and negative faces would be related to higher levels of negative affect and produce increased activity in the medial frontal cortex, an area involved in social appraisal. Twenty-one stable outpatients with chronic non-affective psychosis (16 schizophrenic, 5 schizoaffective) and 21 healthy subjects underwent functional magnetic resonance imaging. Compared with the control subjects, patients were slower to respond, but particularly slow when they judged negatively-valenced faces, a slowness correlated with negative affect in the psychosis patients. Appraisal activated the medial prefrontal cortex (mPFC) across all face valences. For negative expressions, patients exhibited greater activation of the dorsal anterior cingulate cortex (dACC). A psychophysiological interaction analysis of the dACC revealed co-modulation of the mPFC in controls, significantly less in patients, and a trend for co-modulation of occipital cortex in the patients. Activity in occipital cortex correlated with poor social adjustment and impaired social cognition, and co-modulation of the occipital gyrus by the dACC was correlated with poorer social cognition. The findings link appraisal of negative affect with aberrant activation of the medial frontal cortex, while early sensory processing of this social cognitive task was linked with poor social function, reflecting either top-down or bottom-up influences.

Insular cortex morphometry in first-episode schizophrenia-spectrum patients: Diagnostic specificity and clinical correlations

Evidence so far indicates that the consistent association between insular cortex abnormalities and schizophrenia is already present at early phases of the illness. In the present investigation we aimed to study the specificity of insular structural abnormalities in schizophrenia by using region-of-interest morphometry to assess insular cortex morphological characteristics in the same heterogeneous sample of schizophrenia-spectrum patients. The 225 subjects, comprising 82 schizophrenia patients, 36 schizophreniform disorder patients and 24 patients with nonschizophrenic non-affective psychoses, and 83 healthy individuals were investigated. Magnetic resonance imaging brain scans (1.5T) were obtained and images analysed to evaluate insular cortex morphometric variables. The main resulting measurements were for insular gray matter volume and cortical surface area. The contribution of sociodemographic and clinical characteristics was controlled. Patients with schizophrenia-spectrum disorders did not significantly differ from controls in the insular cortex morphometric variables evaluated (all P's>0.11). Clinical variables were not significantly related with insular morphological changes. Noteworthy is the fact that none of the group morphological measurements varied significantly by gender or hemisphere. Neither did we find significant differences when patients with schizophrenia and with other non-affective psychoses were compared. Contrary to our initial hypotheses, we were unable to demonstrate significant morphometric anomalies in a large and heterogeneous sample of patients with a first-episode of schizophrenia-spectrum disorders.

Functional brain imaging in schizophrenia: selected results and methods

Functional brain imaging studies of patients with schizophrenia may be grouped into those that assume that the signs and symptoms of schizophrenia are due to disordered circuitry within a critical brain region and studies that assume that the signs and symptoms are due to disordered connections among brain regions. Studies have investigated the disordered functional brain anatomy of both the positive and negative symptoms of schizophrenia. Studies of spontaneous hallucinations find that although hallucinations are associated with abnormal brain activity in primary and secondary sensory areas, disordered brain activation associated with hallucinations is not limited to sensory systems. Disordered activation in non-sensory regions appear to contribute to the emotional strength and valence of hallucinations, to be a factor underlying an inability to distinguish ongoing mental processing from memories, and to reflect the brain's attempt to modulate the intensity of hallucinations and resolve conflicts with other processing demands. Brain activation studies support the view that auditory/verbal hallucinations are associated with an impaired ability of internal speech plans to modulate neural activation in sensory language areas. In early studies, negative symptoms of schizophrenia were hypothesized to be associated with impaired function in frontal brain areas. In support of this hypothesis meta-analytical studies have found that resting blood flow or metabolism in frontal cortex is reduced in schizophrenia, though the magnitude of the effect is only small to moderate. Brain activation studies of working memory (WM) functioning are typically associated with large effect sizes in the frontal cortex, whereas studies of functions other than WM generally reveal smaller effects. Findings from some functional connectivity studies have supported the hypothesis that schizophrenia patients experience impaired functional connections between frontal and temporal cortex, although the nature of the disordered connectivity is complex. More recent studies have used functional brain imaging to study neural compensation in schizophrenia, to serve as endophenotypes in genetic studies and to provide biomarkers in drug development studies. These emerging trends in functional brain imaging research are likely to help stimulate the development of a general neurobiological theory of the complex symptoms of schizophrenia.

Meta-analysis of 41 functional neuroimaging studies of executive function in schizophrenia

CONTEXT

Prefrontal cortical dysfunction is frequently reported in schizophrenia. It remains unclear whether this represents the coincidence of several prefrontal region- and process-specific impairments or a more unitary dysfunction in a superordinate cognitive control network. Whether these impairments are properly considered reflective of hypofrontality vs hyperfrontality remains unresolved.

OBJECTIVES

To test whether common nodes of the cognitive control network exhibit altered activity across functional neuroimaging studies of executive cognition in schizophrenia and to evaluate the direction of these effects.

DATA SOURCES

PubMed database.

STUDY SELECTION

Forty-one English-language, peer-reviewed articles published prior to February 2007 were included. All reports used functional neuroimaging during executive function performance by adult patients with schizophrenia and reported whole-brain analyses in standard stereotactic space. Tasks primarily included the delayed match-to-sample, N-back, AX-CPT, and Stroop tasks.

DATA EXTRACTION

Activation likelihood estimation modeling reported activation maxima as the center of a 3-dimensional gaussian function in the meta-analysis, with statistical thresholding and correction for multiple comparisons.

DATA SYNTHESIS

In within-group analyses, healthy controls and patients activated a similarly distributed cortical-subcortical network, prominently including the dorsolateral prefrontal cortex (PFC), ventrolateral PFC, anterior cingulate cortex (ACC), and thalamus. In between-group analyses, patients showed reduced activation in the left dorsolateral PFC, rostral/dorsal ACC, left thalamus (with significant co-occurrence of these areas), and inferior/posterior cortical areas. Increased activation was observed in several midline cortical areas. Activation within groups varied modestly by task.

CONCLUSIONS

Healthy adults and schizophrenic patients activate a qualitatively similar neural network during executive task performance, consistent with the engagement of a general-purpose cognitive control network, with critical nodes in the dorsolateral PFC and ACC. Nevertheless, patients with schizophrenia show altered activity with deficits in the dorsolateral PFC, ACC, and mediodorsal nucleus of the thalamus. Increases in activity are evident in other PFC areas, which could be compensatory in nature.

Prefrontal activation deficits during episodic memory in schizophrenia

OBJECTIVE

Episodic memory impairments represent a core deficit in schizophrenia that severely limits patients' functional outcome. This quantitative meta-analysis of functional imaging studies of episodic encoding and retrieval tests the prediction that these deficits are most consistently associated with dysfunction in the prefrontal cortex.

METHOD

Activation likelihood estimation (ALE) was used to perform a quantitative meta-analysis of functional imaging studies that contrasted patients with schizophrenia and healthy volunteers during episodic encoding and retrieval. From a pool of 36 potential studies, 18 whole-brain studies in standard space that included a healthy comparison sample and low-level baseline contrast were selected.

RESULTS

As predicted, patients showed less prefrontal activation than comparison subjects in the frontal pole, dorsolateral and ventrolateral prefrontal cortex during encoding, and the dorsolateral prefrontal cortex and ventrolateral prefrontal cortex during retrieval. The ventrolateral prefrontal cortex encoding deficits were not present in studies that provided patients with encoding strategies, but dorsolateral prefrontal cortex deficits remained and were not secondary to group performance differences. The only medial temporal lobe finding was relatively greater patient versus comparison subject activation in the parahippocampal gyrus during encoding and retrieval.

CONCLUSIONS

The finding of prominent prefrontal dysfunction suggests that cognitive control deficits strongly contribute to episodic memory impairment in schizophrenia. Memory rehabilitation approaches developed for patients with frontal lobe lesions and pharmacotherapy approaches designed to improve prefrontal cortex function may therefore hold special promise for remediating memory deficits in patients with schizophrenia.

Diagnostic specificity of the insular cortex abnormalities in first-episode psychotic disorders

Volume reductions of the insular cortex have been described in schizophrenia, but it remains unclear whether other psychotic disorders such as affective psychosis also exhibit insular cortex abnormalities. In this study, we used magnetic resonance imaging to investigate the gray matter volume of the anterior (short) and posterior (long) insular cortices in 162 first-episode patients with various psychotic disorders (46 schizophrenia, 57 schizophreniform disorder, 34 affective psychosis, and 25 other psychoses) and 62 age- and gender-matched healthy comparison subjects. Patients with schizophrenia showed bilateral volume reduction of the anterior and posterior insular cortices compared with controls, but the remaining first-episode psychosis subgroups had normal insular volumes. The volumes of these insular subregions were significantly smaller in schizophrenia patients than in patients with schizophreniform disorder or affective psychoses. There was no association between the insular cortex volume and daily dosage or type of antipsychotic medication in any patient group. These findings suggest that the widespread volume reduction of the insular cortex is specific to established schizophrenia, implicating its role in the neurobiology of clinical characteristics associated with schizophrenia.

Insular cortex gray matter changes in individuals at ultra-high-risk of developing psychosis

Morphologic abnormalities of the insular cortex have been described in psychotic disorders such as schizophrenia, but it remains unclear whether these changes predate the onset of psychosis or develop progressively over the course of illness. In this study, we used magnetic resonance imaging to investigate the gray matter volume of the long and short insular cortices in 97 neuroleptic-naïve individuals at ultra-high-risk (UHR) for developing psychosis [of whom 31 (32%) later developed psychosis (UHR-P) and 66 (68%) did not (UHR-NP)] and 55 age- and gender-matched healthy comparisons. We also conducted a longitudinal comparison of the insular cortex gray matter changes in 31 UHR individuals (20 UHR-NP and 11 UHR-P) and 20 controls for whom follow-up MRI data between 1 and 4 years later were available. In the cross-sectional comparison, the UHR-P subjects had a significantly smaller insular cortex compared with the UHR-NP subjects bilaterally and with the controls on the right hemisphere, especially for the short insular region. More severe negative symptoms in UHR-P subjects at baseline were associated with smaller volumes of the right long insular cortex. In the longitudinal comparison, the UHR-P subjects showed greater gray matter reduction of insular cortex bilaterally (-5.0%/year) compared with controls (-0.4%/year) or UHR-NP subjects (-0.6%/year). Our findings suggest that insular cortex gray matter abnormalities in psychotic disorders may reflect pre-existing vulnerability, but that there are also active progressive changes of the insular cortex during the transition period into psychosis. Whether these longitudinal changes are features of the disorder or related to treatment with antipsychotic medication remains to be determined.

Follow-up MRI study of the insular cortex in first-episode psychosis and chronic schizophrenia

Morphologic abnormalities of the insular cortex have been described in psychotic disorders such as schizophrenia, but it remains unknown whether these abnormalities develop progressively over the course of the illness. In the current study, longitudinal magnetic resonance imaging data were obtained from 23 patients with first-episode psychosis (FEP), 11 patients with chronic schizophrenia, and 26 healthy controls. The volumes of the short (anterior) and long (posterior) insular cortices were measured on baseline and follow-up (between 1 and 4 years later) scans and were compared across groups. In cross-sectional comparison at baseline, the FEP and chronic schizophrenia patients had significantly smaller short insular cortex than did controls. In longitudinal comparison, the FEP patients showed significant gray matter reduction of the insular cortex over time (-4.3%/2.0 years) compared with controls (0.3%/2.2 years) without significant subregional effects, but there was no difference between chronic schizophrenia patients (-1.7%/2.4 years) and controls. The gray matter loss of the left insular cortex over time in FEP patients was correlated with the severity of positive and negative symptoms at follow-up. These findings indicate that patients with psychotic disorders have smaller gray matter volume of the insular cortex especially for its anterior portion (short insula) at first expression of overt psychosis, but also exhibit a regional progressive pathological process of the insular cortex during the early phase after the onset, which seems to reflect the subsequent symptomatology.

Predicting the brain response to treatment using a Bayesian hierarchical model with application to a study of schizophrenia

In vivo functional neuroimaging, including functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), is becoming increasingly important in defining the pathophysiology of psychiatric disorders such as schizophrenia, major depression, and Alzheimer's disease. Furthermore, recent studies have begun to investigate the possibility of using functional neuroimaging to guide treatment selection for individual patients. By studying the changes between a patient's pre- and post-treatment brain activity, investigators are gaining insights into the impact of treatment on behavior-related neural processing traits associated with particular psychiatric disorders. Furthermore, these studies may shed light on the neural basis of response and nonresponse to specific treatments. The practical limitation of such studies is that the post-treatment scans offer little guidance to treatment selection in clinical settings, since treatment decisions precede the availability of post-treatment brain scans. This shortcoming represents the impetus for developing statistical methodology that would provide clinicians with predictive information concerning the effect of treatment on brain activity and, ultimately, symptom-related behaviors. We present a prediction algorithm that uses a patient's pretreatment scans, coupled with relevant patient characteristics, to forecast the patient's brain activity following a specified treatment regimen. We derive our predictive method from a Bayesian hierarchical model constructed on the pre- and post-treatment scans of designated training data. We perform estimation using the expectation-maximization algorithm. We evaluate the accuracy of our proposed prediction method using K-fold cross-validation, quantifying the error using two new measures that we propose for neuroimaging data. The proposed method is applicable to both PET and fMRI studies. We illustrate its use with a PET study of working memory in patients with schizophrenia and an fMRI data example is also provided.

Cerebellum and psychiatric disorders

OBJECTIVE: The objective of this update article is to report structural and functional neuroimaging studies exploring the potential role of cerebellum in the pathophysiology of psychiatric disorders. METHOD: A non-systematic literature review was conducted by means of Medline using the following terms as a parameter: "cerebellum", "cerebellar vermis", "schizophrenia", "bipolar disorder", "depression", "anxiety disorders", "dementia" and "attention deficit hyperactivity disorder". The electronic search was done up to April 2008. DISCUSSION: Structural and functional cerebellar abnormalities have been reported in many psychiatric disorders, namely schizophrenia, bipolar disorder, major depressive disorder, anxiety disorders, dementia and attention deficit hyperactivity disorder. Structural magnetic resonance imaging studies have reported smaller total cerebellar and vermal volumes in schizophrenia, mood disorders and attention deficit hyperactivity disorder. Functional magnetic resonance imaging studies using cognitive paradigms have shown alterations in cerebellar activity in schizophrenia, anxiety disorders and attention deficit hyperactivity disorder. In dementia, the cerebellum is affected in later stages of the disease. CONCLUSION: Contrasting with early theories, cerebellum appears to play a major role in different brain functions other than balance and motor control, including emotional regulation and cognition. Future studies are clearly needed to further elucidate the role of cerebellum in both normal and pathological behavior, mood regulation, and cognitive functioning.

The role of the cerebellum in schizophrenia

For many years the cerebellum has been considered to serve as a coordinator of motor function. Likewise, for many years schizophrenia has been considered to be a disease that primarily affects the cerebrum. This review summarizes recent evidence that both these views must be revised in the light of emerging evidence about cerebellar function and the mechanisms of schizophrenia. Evidence indicating that the cerebellum plays a role in higher cortical functions is summarized. Evidence indicating that cerebellar abnormalities occur in schizophrenia is also reviewed. These suggest interesting directions for future research.

The role of the cerebellum in schizophrenia: an update of clinical, cognitive, and functional evidences

The role of the cerebellum in schizophrenia has been highlighted by Andreasen's hypothesis of "cognitive dysmetria," which suggests a general dyscoordination of sensorimotor and mental processes. Studies in schizophrenic patients have brought observations supporting a cerebellar impairment: high prevalence of neurological soft signs, dyscoordination, abnormal posture and propioception, impaired eyeblink conditioning, impaired adaptation of the vestibular-ocular reflex or procedural learning tests, and lastly functional neuroimaging studies correlating poor cognitive performances with abnormal cerebellar activations. Despite those compelling evidences, there has been, to our knowledge, no recent review on the clinical, cognitive, and functional literature supporting the role of the cerebellum in schizophrenia. We conducted a Medline research focusing on cerebellar dysfunctions in schizophrenia. Emphasis was given to recent literature (after 1998). The picture arising from this review is heterogeneous. While in some domains, the role of the cerebellum seems clearly defined (ie, neurological soft signs, posture, or equilibrium), in other domains, the cerebellar contribution to schizophrenia seems limited or indirect (ie, cognition) if present at all (ie, affectivity). Functional models of the cerebellum are proposed as a background for interpreting these results.

Frontal and parietal ERPs associated with duration discriminations with or without task interference

The main objective of this study was to examine fronto-parietal networks underlying visual duration discriminations. Two types of interference tasks were used to augment cognitive load: line orientation associated with the right hemisphere and multiplication with the left. Both subtasks deteriorated duration discriminations, more severely for line orientation. Relative to the condition without interference, the dual task paradigm decreased amplitudes of the contingent negative variation (CNV) wave, predominant at frontal sites, and the P300 wave, predominant at parietal sites. Inversely, amplitudes of a later appearing positive component (LPC) and its parietal counterpart of opposite polarity (LNC) increased with spatial or numeric task interference. These results are concordant with the view that fronto-parietal networks underlying duration discriminations act in a concerted fashion, with the LPC/LNC waves acting as a warning signal to mitigate errors during high cognitive load.

Insular cortex and neuropsychiatric disorders: A review of recent literature

The insular cortex is located in the centre of the cerebral hemisphere, having connections with the primary and secondary somatosensory areas, anterior cingulate cortex, amygdaloid body, prefrontal cortex, superior temporal gyrus, temporal pole, orbitofrontal cortex, frontal and parietal opercula, primary and association auditory cortices, visual association cortex, olfactory bulb, hippocampus, entorhinal cortex, and motor cortex. Accordingly, dense connections exist among insular cortex neurons. The insular cortex is involved in the processing of visceral sensory, visceral motor, vestibular, attention, pain, emotion, verbal, motor information, inputs related to music and eating, in addition to gustatory, olfactory, visual, auditory, and tactile data. In this article, the literature on the relationship between the insular cortex and neuropsychiatric disorders was summarized following a computer search of the Pub-Med database. Recent neuroimaging data, including voxel based morphometry, PET and fMRI, revealed that the insular cortex was involved in various neuropsychiatric diseases such as mood disorders, panic disorders, PTSD, obsessive-compulsive disorders, eating disorders, and schizophrenia. Investigations of functions and connections of the insular cortex suggest that sensory information including gustatory, olfactory, visual, auditory, and tactile inputs converge on the insular cortex, and that these multimodal sensory information may be integrated there.

Patterns of anterior cingulate activation in schizophrenia: a selective review

BACKGROUND

Anterior cingulate cortex (ACC) dysfunction is implicated in schizophrenia by numerous strands of scientific investigation. Functional neuroimaging studies of the ACC in schizophrenia have shown task-related hypo-activation, hyper-activation, and normal activation relative to comparison subjects. Interpreting these results and explaining their inconsistencies has been hindered by our ignorance of the healthy ACC's function. This review aims to clarify the site and magnitude of ACC activations in schizophrenia, and sources of their variation.

METHOD

48 studies of mnemonic and executive task-related activations in schizophrenia using both positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) were analyzed.

RESULTS

Abnormal activations in schizophrenia were not restricted to the "cognitive" part of the ACC. Hypoactivations were most common, and were found in all types of tasks. Hyperac-tivations when found, were largely in n-back tasks.

CONCLUSIONS

Hypoactivations cannot be explained by poor performance, more demanding control conditions or chronicity of illness alone. Patients on anti-psychotic medication tended to show both greater ACC activation and better performance, although whether this is directly due to their medication or the resultant reduction in symptoms is unclear. The relationship between ACC rCBF and task performance is not straightforward. Future research should better control confounding factors and incorporate different levels of difficulty.

Alterations of muscarinic and GABA receptor binding in the posterior cingulate cortex in schizophrenia

The posterior cingulate cortex (PCC), a key component of the limbic system, has been implicated in the pathology of schizophrenia because of its sensitivity to NMDA receptor antagonists. Recent studies have shown that the PCC is dysfunctional in schizophrenia, and it is now suspected to be critically involved in the pathogenesis of schizophrenia. Studies also suggest that there are abnormalities in muscarinic and GABAergic neurotransmission in schizophrenia. Therefore, in the present study we used quantitative autoradiography to investigate the binding of [(3)H]pirenzepine, [(3)H]AF-DX 384 and [(3)H]muscimol, which respectively label M1/4 and M2/4 muscarinic and GABA(A) receptors, in the PCC of schizophrenia and control subjects matched for age and post-mortem interval. The present study found that [(3)H]pirenzepine binding was significantly decreased in the superficial (-24%, p=0.002) and deep (-35%, p<0.001) layers of the PCC in the schizophrenia group as compared with the control group. In contrast, a dramatic increase in [(3)H]muscimol binding was observed in the superficial (+112%, p=0.001) and deep layers (+100%, p=0.017) of the PCC in the schizophrenia group. No difference was observed for [(3)H]AF-DX 384 binding between the schizophrenia and control groups. The authors found a significant inverse correlation between [(3)H]pirenzepine binding in the deep cortical layers and [(3)H]muscimol binding in the superficial layers (rho=-0.732, p=0.003). In addition, negative correlations were also found between age and [(3)H]pirenzepine binding in both superficial and deep cortical layers (rho=-0.669 p=0.049 and rho=-0.778, p=0.014), and between age of schizophrenia onset and [(3)H]AF-DX 384 binding (rho=-0.798, p=0.018). These results for the first time demonstrated the status of M1/M4, M2/M4 and GABA(A) receptors in the PCC in schizophrenia. Whilst the exact mechanism causing these alterations is not yet known, a possible increased acetylcholine and down regulated GABA stimulation in the PCC of schizophrenia is suggested.

Object-location memory in schizophrenia: interference of symbolic threatening content

INTRODUCTION

Monitoring environmental stimuli for their emotional relevance is inherently associated with spatial processing. In schizophrenia, deficits in spatial working memory on one hand, and abnormal emotion processing on the other, have been documented, but these have not been related to each other. In the present study, we investigated whether a specific aspect of spatial memory (i.e., object-location memory), is impaired in patients with schizophrenia. Moreover, we hypothesised that symbolic threatening content of objects would interfere with spatial processing in patients with schizophrenia but not in healthy controls.

METHODS

Spatial memory for symbolic pictorial stimuli was assessed in 40 patients with schizophrenia compared to 41 healthy matched control participants using an object-relocation task.

RESULTS

Patients with schizophrenia performed worse in relocating objects, independent of overall intellectual ability. More specifically, patients were particularly worse in the relocation of objects with a symbolic threatening content.

CONCLUSIONS

These results suggest that a threatening semantic emotional content of schematic stimuli can interfere with spatial processing in schizophrenia. We hypothesise that a disproportional influence of the amygdala on other brain areas, such as the hippocampus, might underlie this specific emotional interference.

Methodological and Conceptual Issues in Functional Magnetic Resonance Imaging: Applications to Schizophrenia Research

Functional magnetic resonance imaging (MRI) is a noninvasive, highly repeatable, and increasingly available method to study disordered brain activity among patients with psychological or neurological disorders. In this chapter the biophysical principles underlying functional MRI are presented, and methodological limitations of the method are discussed. Artifacts related to the biophysical basis of the functional MRI signal or associated with image acquisition methods are presented, as are artifacts related to baseline effects-especially those associated with medication, caffeine, and nicotine use. The difficulties associated with the comparison of groups of subjects differing in performance receive special attention. The limitations of cognitive subtraction designs for functional MRI are also discussed. Functional MRI studies of schizophrenia patients are used to illustrate these points.

Episodic memory-related activation in schizophrenia: meta-analysis

BACKGROUND

Numerous studies have examined the neural correlates of episodic memory deficits in schizophrenia, yielding both consistencies and discrepancies in the reported patterns of results.

AIMS

To identify in schizophrenia the brain regions in which activity is consistently abnormal across imaging studies of memory.

METHOD

Data from 18 studies meeting the inclusion criteria were combined using a recently developed quantitative meta-analytic approach.

RESULTS

Regions of consistent differential activation between groups were observed in the left inferior prefrontal cortex, medial temporal cortex bilaterally, left cerebellum, and in other prefrontal and temporal lobe regions. Subsequent analyses explored memory encoding and retrieval separately and identified between-group differences in specific prefrontal and medial temporal lobe regions.

CONCLUSIONS

Beneath the apparent heterogeneity of published findings on schizophrenia and memory, a consistent and robust pattern of group differences is observed as a function of memory processes.

Ionotropic glutamate receptor binding in the posterior cingulate cortex in schizophrenia patients

Using quantitative autoradiography, the present study examined ionotropic glutamatergic receptor binding sites using [3H]dizocilpine, [3H]alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate, and [3H]kainate in the posterior cingulate cortex of schizophrenia patients and matched controls. We found a significant increase in [3H]dizocilpine binding in the superficial layers (41%, p<0.001) and deep layers (30%, p=0.004) of the posterior cingulate cortex in the schizophrenia group compared with controls. No significant differences were observed in [3H]alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate and [3H]kainate binding. In summary, the present study has for the first time demonstrated that the glutamatergic system is affected in the posterior cingulate cortex in schizophrenia patients. The fact that only the N-methyl-D-aspartate receptor densities are significantly altered suggests that this is unlikely to be caused by a simple decrease in glutamatergic transmission.

Cognitive and clinical moderators of recognition memory in schizophrenia: a meta-analysis

Recognition memory performance in schizophrenia has been shown to vary greatly across studies. To identify the conditions under which recognition memory is significantly impaired, we used a meta-analytic strategy to quantify the moderating effects of several cognitive and clinical variables. Eighty-four studies (from 1965 to July 2003) provided recognition memory data for both a schizophrenia and control group. The overall group comparison for recognition memory yielded a significant mean weighted effect size of d=0.76. Material specificity was the most significant cognitive variable found, with patients exhibiting greater impairment for figural than verbal recognition. A yes-no recognition format and auditory encoding also led to significantly greater effect sizes for recognition memory relative to forced-choice recognition tests and visual encoding, respectively. Furthermore, the effect size for recognition memory as measured by false alarm was smaller than the effect size as measured by hit rate or by d-prime and its related measures. Among clinical variables that were associated with higher effect sizes, chronicity was the most significant, but different trends linking poor performance to negative symptoms and general symptomatology were also observed. Thus, a recognition memory deficit moderated by both cognitive and clinical variables is clearly present in schizophrenia.

Volumetric MRI study of the short and long insular cortices in schizophrenia spectrum disorders

We have previously reported volume reductions of the insular cortex in schizophrenia, but it is still not clear whether insular cortex volume loss preferentially involves the anterior (short insular cortex) or posterior (long insular cortex) portion. On the other hand, no volumetric studies of the brain have examined changes in insular cortex volume in subjects with schizotypal features. In this study, we separately investigated the volumes of the short and long insular cortex portions using magnetic resonance imaging in 37 schizotypal disorder patients (24 males, 13 females), 62 schizophrenia patients (32 males, 30 females), and 69 healthy controls (35 males, 34 females). While the volumes of the short and long insular cortex were significantly reduced in schizophrenia patients compared with schizotypal disorder patients and control subjects, there was no difference between schizotypal disorder patients and control subjects. These results suggest that the volume reduction of the insular cortex may be specific to overt schizophrenia without topographically specific localization.

Evidence for a dysfunctional retrosplenial cortex in patients with schizophrenia: a functional magnetic resonance imaging study with a semantic-perceptual contrast

We investigated whether the retrosplenial and the posterior cingulate cortex (RS-PCC) is functionally impaired in schizophrenia patients. Therefore, we measured functional magnetic resonance imaging (fMRI) signal changes associated with a synonym-judgment task known to activate, among other areas, the RS-PCC. Compared to 12 matched control subjects, 12 schizophrenia patients exhibited reliably weaker activations in the RS-PCC, the dorsolateral prefrontal cortex and the left orbitofrontal cortex (P < 0.05, corrected). Differences in frontal activations are in line with previous studies showing a structurally and functionally affected prefrontal cortex in schizophrenia. The impaired RS-PCC functionality in a semantic task may relate to verbal memory deficits frequently observed in schizophrenia patients, because this region is pivotal for gating information into the medial temporal lobe memory system.

Bilateral volume reduction of the insular cortex in patients with schizophrenia: a volumetric MRI Study

The morphologic changes of the insular cortex have been described in schizophrenia, but with inconsistencies between reports. We investigated the insular cortex volume by magnetic resonance imaging in 59 schizophrenia patients (31 males, 28 females) and 62 age- and gender-matched healthy controls (31 males, 31 females). The insular cortex volume was measured on consecutive coronal 1-mm slices. Volumes of the left and right insular cortex were significantly reduced in schizophrenia patients compared with control subjects. There were no effects of gender on the insular cortex volume in the patient group or control subjects. Bilateral insular cortex volumes were correlated negatively with illness duration in the patient group. The findings of this study suggest that there is a possible progressive loss of the gray matter volume of the bilateral insular cortices subsequent to the onset of schizophrenia.

Progressive ratio performance following challenge with antipsychotics, amphetamine, or NMDA antagonists in adult rats treated perinatally with phencyclidine

RATIONALE

Previous research has shown that rats exposed perinatally to phencyclidine (PCP) exhibited neuroanatomical abnormalities and altered cognition. In addition to cognitive deficits, schizophrenic patients may also exhibit negative symptoms such as lack of motivation.

OBJECTIVES

In this study, we used a progressive ratio (PR) schedule of food reinforcement to assess motivation following early exposure to PCP.

METHODS

Male rat pups were injected SC with 10 mg/kg PCP on postnatal days (PN) 7, 9, and 11. On PN 120, they began training in a PR 5 schedule of food reinforcement.

RESULTS

Significant PCP effects on acquisition and baseline performance were not noted. After acquisition of the task, challenges with PCP, dizocilpine, amphetamine, haloperidol, and clozapine resulted in dose-dependent decreases in response rates of similar magnitudes in both groups. In rats that continued to respond at higher doses, PCP, dizocilpine, and clozapine failed to alter breakpoints. In contrast, a 5.6 mg/kg dose of amphetamine selectively increased breakpoints in PCP-treated rats, although very few rats responded at this dose. Haloperidol decreased breakpoints in most rats at non-sedating doses.

CONCLUSIONS

These results suggest that a regimen of perinatal PCP administration sufficient to disrupt cognition did not alter motivation for food reinforcement, regardless of whether rats also received challenges with NMDA antagonists or antipsychotics. Interpretation of amphetamine's high dose effects on breakpoints was complicated by the failure of many rats to respond at this dose. Further research is needed to determine whether negative symptoms such as social withdrawal may be modeled within this neurodevelopmental approach to schizophrenia.

Bilateral volume reduction of the insular cortex in patients with schizophrenia: a volumetric MRI study

The morphologic changes of the insular cortex have been described in schizophrenia, but with inconsistencies between reports. We investigated the insular cortex volume by magnetic resonance imaging in 59 schizophrenia patients (31 males, 28 females) and 62 age- and gender-matched healthy controls (31 males, 31 females). The insular cortex volume was measured on consecutive coronal 1-mm slices. Volumes of the left and right insular cortex were significantly reduced in schizophrenia patients compared with control subjects. There were no effects of gender on the insular cortex volume in the patient group or control subjects. Bilateral insular cortex volumes were correlated negatively with illness duration in the patient group. The findings of this study suggest that there is a possible progressive loss of the gray matter volume of the bilateral insular cortices subsequent to the onset of schizophrenia.

Chronic pubertal, but not adult chronic cannabinoid treatment impairs sensorimotor gating, recognition memory, and the performance in a progressive ratio task in adult rats

There is evidence from studies in humans and animals that a vulnerable period for chronic cannabinoid administration exists during certain phases of development. The present study tested the hypothesis that long-lasting interference of cannabinoids with the developing endogenous cannabinoid system during puberty causes persistent behavioral alterations in adult rats. Chronic treatment with the synthetic cannabinoid agonist WIN 55,212-2 (WIN) (1.2 mg/kg) or vehicle was extended over 25 days either throughout the rats' puberty or for a similar time period in adult rats. The rats received 20 injections intraperitoneally (i.p.), which were not delivered regularly. Adult rats were tested for object recognition memory, performance in a progressive ratio (PR) operant behavior task, locomotor activity, and prepulse inhibition (PPI) of the acoustic startle response (ASR). PPI was significantly disrupted only by chronic peripubertal cannabinoid treatment. This long-lasting PPI deficit was reversed by the acute administration of the dopamine antagonist haloperidol. Furthermore, we found deficits in recognition memory of pubertal-treated rats and these animals showed lower break points in a PR schedule, whereas food preference and locomotion were not affected. Adult chronic cannabinoid treatment had no effect on the behaviors tested. Therefore, we conclude that puberty in rats is a vulnerable period with respect to the adverse effects of cannabinoid treatment. Since PPI deficits, object recognition memory impairments, and anhedonia/avolition are among the endophenotypes of schizophrenia, we propose chronic cannabinoid administration during pubertal development as an animal model for some aspects of the etiology of schizophrenia.

Pharmacological challenge reveals long-term effects of perinatal phencyclidine on delayed spatial alternation in rats

Administration of the N-methyl-D-aspartate (NMDA) antagonist phencyclidine (PCP) may produce alterations in behavior that resemble those that have been observed in animal models of schizophrenia. This study was designed to examine the effects of early postnatal injection of PCP on later acquisition and performance of a delayed spatial alternation task, a procedure that is sensitive to manipulations of the prefrontal cortex. At the beginning of the study, we injected cross-fostered female rat pups subcutaneously with either saline or 10 mg/kg PCP on postnatal (PN) days 7, 9, and 11. On PN34, the rats began training in a delayed spatial alternation task consisting of 10 daily trials with a 10-s intertrial interval. Although accuracy improved significantly faster in the saline-treated group than in the PCP-treated group, by PN70, both groups had acquired the task with approximately equal accuracies. Pharmacological challenges with the NMDA antagonists, PCP and ketamine, and with the dopamine modulator, amphetamine, decreased accuracy to a similar extent in both groups of rats when intertrial delays were held constant at 10 s; however, nicotine did not decrease accuracy in either group. In contrast, dizocilpine (a high-affinity NMDA open-channel blocker) produced a more pronounced decrease in accuracy in the PCP-treated rats than in the saline-treated rats. When delays were lengthened to 30 s, PCP also decreased accuracy in the PCP-treated rats to a greater extent than in saline-treated rats. These results suggest that perinatal administration of PCP may produce long-term alterations in cognition that are revealed by pharmacological challenge and manipulation of task difficulty.

More "mapping" in brain mapping: statistical comparison of effects

The term "mapping" in the context of brain imaging conveys to most the concept of localization; that is, a brain map is meant to reveal a relationship between some condition or parameter and specific sites within the brain. However, in reality, conventional voxel-based maps of brain function, or for that matter of brain structure, are generally constructed using analyses that yield no basis for inferences regarding the spatial nonuniformity of the effects. In the normal analysis path for functional images, for example, there is nowhere a statistical comparison of the observed effect in any voxel relative to that in any other voxel. Under these circumstances, strictly speaking, the presence of significant activation serves as a legitimate basis only for inferences about the brain as a unit. In their discussion of results, investigators rarely are content to confirm the brain's role, and instead generally prefer to interpret the spatial patterns they have observed. Since "pattern" implies nonuniform effects over the map, this is equivalent to interpreting results without bothering to test their significance, a practice most of the experimentally-trained would eschew in other contexts. In this review, we appeal to investigators to adopt a new standard of data presentation that facilitates comparison of effects across the map. Evidence for sufficient effect size difference between the effects in structures of interest should be a prerequisite to the interpretation of spatial patterns of activation.

Effects of repetitive transcranial magnetic stimulation on memory subtypes: a controlled study

Repetitive transcranial magnetic stimulation (rTMS) of human cortex may disrupt or facilitate cortical activity. The aim of the present study was to investigate the consequences of rTMS applied over different cortical areas during various memory tasks, measuring immediate, working and episodic verbal memory. The study was performed in 16 right-handed healthy men. A double-blind, cross-over, within-subject repeated measures design was used. There were five rTMS conditions: baseline without stimulation, high frequency (HF) rTMS over right and left dorsolateral prefrontal cortex (DLPFC) and over right cerebellum, and low frequency (LF) parameters over left DLPFC. Digits forwards and backwards and letter-number sequencing of the Wechsler Adults Intelligence Scale (WAIS) were used to assess immediate and working verbal memory, and logical memory of the Rivermead Behavioural Memory Test was used to assess episodic memory encoding. An analysis of variance (ANOVA) for repeated measures in the scores of each memory task according to rTMS conditions was used. Significantly lower scores in the number of memory units of the episodic memory task were observed when rTMS high frequency parameters were applied over left DLPFC (P=0.009). No significant differences were found in the other memory subtype tasks analysed during the different rTMS conditions. These findings provide evidence for the significant role of the left DLPFC in episodic verbal memory processes.

Prefrontal-posterior parietal networks in schizophrenia: primary dysfunctions and secondary compensations

BACKGROUND

Working memory (WM) deficits are well known in schizophrenia and have been associated with abnormal activation patterns of the prefrontal cortex (PFC) during cognitive performance. The magnitude and particularly the direction of the PFC activation -- i.e., increased (hyperfrontality) or decreased (hypofrontality) -- in schizophrenia, as well as its pathophysiological implications, remain controversial. Working memory is supported by a distributed neural network, whose main components are the PFC and the posterior parietal (PPC) cortices. Monkey studies indicate that, during WM performance, PFC functional lesions may be compensated by the PPC if task demands center mainly on anticipating responses, but not if they center on remembering cues. We hypothesized that a primarily dysfunctional PFC in schizophrenia might show hypofrontality or hyperfrontality as a result, respectively, of efficient or inefficient PPC compensation, as dictated by task demands. To test our proposition, we biased the demands of WM tasks toward anticipating responses or remembering cues and measured its impact on the PFC-PPC functional balance in a group of schizophrenic patients and one of normal control subjects.

METHODS

We used functional magnetic resonance imaging to measure correlates of neuronal activity in the PFC and PPC of schizophrenic patients and control subjects performing WM tasks that either demanded information retention or allowed for response anticipation.

RESULTS

When compared to control subjects, schizophrenic patients exhibited decreased PFC activation and increased PPC activation during anticipatory WM performance, and increased PFC activation during mnemonic WM performance.

CONCLUSIONS

In schizophrenia, a PFC dysfunction results in hypo- or hyperfrontality as a function of whether other alternate areas of a PFC-PPC network for WM are available and efficacious in supporting specific task demands.