Differential activation of temporal cortex during sentence completion in schizophrenic patients with and without formal thought disorder

Illness-related variables and abnormalities of resting-state brain activity in schizophrenia

Background

The development of neuroimaging biomarkers in patients with schizophrenia (SCZ) requires a refined clinical characterization. A limitation of the neuroimaging literature is the partial uptake of progress in characterizing disease-related features, particularly negative symptoms (NS) and cognitive impairment (CI). In the present study, we assessed NS and CI using up-to-date instruments and investigated the associations of abnormalities in brain resting-state (rs)-activity with disease-related features.

Methods

Sixty-two community-dwelling SCZ subjects participated in the study. Multiple regression analyses were performed with the rs-activity of nine regions of interest as dependent variables and disease-related features as explanatory variables.

Results

Attention/vigilance deficits were negatively associated with dorsal anterior cingulate rs-activity and, together with depression, were positively associated with right dorsolateral prefrontal cortex rs-activity. These deficits and impairment of Reasoning/problem-solving, together with conceptual disorganization, were associated with right inferior parietal lobule and temporal parietal junction rs-activity. Independent of other features, the NS Expressive Deficit domain was associated with the left ventral caudate, while the Motivational Deficit was associated with the dorsal caudate rs-activity.

Conclusion

Neurocognitive deficits and the two negative symptom domains are associated with different neural markers. Replications of these findings could foster the identification of clinically actionable biomarkers of poor functional outcomes.

Brain Structural Network Connectivity of Formal Thought Disorder Dimensions in Affective and Psychotic Disorders

BACKGROUND

The psychopathological syndrome of formal thought disorder (FTD) is not only present in schizophrenia (SZ), but also highly prevalent in major depressive disorder and bipolar disorder. It remains unknown how alterations in the structural white matter connectome of the brain correlate with psychopathological FTD dimensions across affective and psychotic disorders.

METHODS

Using FTD items of the Scale for the Assessment of Positive Symptoms and Scale for the Assessment of Negative Symptoms, we performed exploratory and confirmatory factor analyses in 864 patients with major depressive disorder (n= 689), bipolar disorder (n = 108), or SZ (n = 67) to identify psychopathological FTD dimensions. We used T1- and diffusion-weighted magnetic resonance imaging to reconstruct the structural connectome of the brain. To investigate the association of FTD subdimensions and global structural connectome measures, we employed linear regression models. We used network-based statistic to identify subnetworks of white matter fiber tracts associated with FTD symptomatology.

RESULTS

Three psychopathological FTD dimensions were delineated, i.e., disorganization, emptiness, and incoherence. Disorganization and incoherence were associated with global dysconnectivity. Network-based statistics identified subnetworks associated with the FTD dimensions disorganization and emptiness but not with the FTD dimension incoherence. Post hoc analyses on subnetworks did not reveal diagnosis × FTD dimension interaction effects. Results remained stable after correcting for medication and disease severity. Confirmatory analyses showed a substantial overlap of nodes from both subnetworks with cortical brain regions previously associated with FTD in SZ.

CONCLUSIONS

We demonstrated white matter subnetwork dysconnectivity in major depressive disorder, bipolar disorder, and SZ associated with FTD dimensions that predominantly comprise brain regions implicated in speech. Results open an avenue for transdiagnostic, psychopathology-informed, dimensional studies in pathogenetic research.

Losing the chain of thought: A meta-analysis of functional neuroimaging studies using verbal tasks in schizophrenia

BACKGROUND

Disorganization symptoms are a main feature of schizophrenia, which include illogical and incoherent thinking, circumstantiality, tangentiality and loose associations. As these symptoms entail language deficits, several functional neuroimaging studies have been performed in schizophrenia using verbal tasks, producing somewhat heterogenous results. Hence, we performed a meta-analysis seeking to identify the most reliable neural alterations observed in schizophrenia patients during such tasks.

METHODS

Web of Sciences, PubMed, and EMBASE were searched for functional neuroimaging studies during verbal tasks (e.g. verbal fluency and semantic processing) in schizophrenia. Out of 795 screened articles, 33 were eligible for this meta-analysis. A coordinated-based meta-analysis was performed with the activation likelihood estimation (ALE) approach, using the cluster-level family-wise error (FWE) correction set at p < 0.05.

RESULTS

In schizophrenia, hyperactivations were observed in the left inferior frontal gyrus (IFG) and middle frontal gyrus (MFG) and hypoactivations were observed in the right IFG, the precentral gyrus and the left caudate nucleus. Another analysis pooling hyper- and hypoactivations revealed altered activations, firstly, in the left IFG and MFG, secondly, in the left precentral gyrus, IFG and insula, and, thirdly, in the left angular gyrus and precuneus. In the light of these results, not only classic language-related regions are abnormally activated during verbal tasks in schizophrenia, but also brain regions involved in executive functions, autobiographical memory and, unexpectedly, in motor functions. Further functional neuroimaging studies are needed to investigate the role of the striatum in linguistic sequencing in schizophrenia.

The Neurobiology of Formal Thought Disorder

The concept of Formal Thought Disorder (FTD) is an ambiguous and disputed one, even though it has endured as a core psychopathological construct in clinical Psychiatry. FTD can be summarized as a multidimensional construct, reflecting difficulties or idiosyncrasies in thinking, language, and communication in general and is usually subdivided into positive versus negative. In this article, we aim to explore the putative neurobiology of FTD, ranging from changes in neurotransmitter systems to alterations in the functional anatomy of the brain. We also discuss recent critiques of the operationalist view of FTD and how they might fit in its biological underpinnings. We conclude that FTD might be the observable phenotype of many distinct underlying alterations in different proportions.

Structural and Functional Brain Patterns Predict Formal Thought Disorder's Severity and Its Persistence in Recent-Onset Psychosis: Results From the PRONIA Study

BACKGROUND

Formal thought disorder (FThD) is a core feature of psychosis, and its severity and long-term persistence relates to poor clinical outcomes. However, advances in developing early recognition and management tools for FThD are hindered by a lack of insight into the brain-level predictors of FThD states and progression at the individual level.

METHODS

Two hundred thirty-three individuals with recent-onset psychosis were drawn from the multisite European Prognostic Tools for Early Psychosis Management study. Support vector machine classifiers were trained within a cross-validation framework to separate two FThD symptom-based subgroups (high vs. low FThD severity), using cross-sectional whole-brain multiband fractional amplitude of low frequency fluctuations, gray matter volume and white matter volume data. Moreover, we trained machine learning models on these neuroimaging readouts to predict the persistence of high FThD subgroup membership from baseline to 1-year follow-up.

RESULTS

Cross-sectionally, multivariate patterns of gray matter volume within the salience, dorsal attention, visual, and ventral attention networks separated the FThD severity subgroups (balanced accuracy [BAC] = 60.8%). Longitudinally, distributed activations/deactivations within all fractional amplitude of low frequency fluctuation sub-bands (BACslow-5 = 73.2%, BACslow-4 = 72.9%, BACslow-3 = 68.0%), gray matter volume patterns overlapping with the cross-sectional ones (BAC = 62.7%), and smaller frontal white matter volume (BAC = 73.1%) predicted the persistence of high FThD severity from baseline to follow-up, with a combined multimodal balanced accuracy of BAC = 77%.

CONCLUSIONS

We report the first evidence of brain structural and functional patterns predictive of FThD severity and persistence in early psychosis. These findings open up avenues for the development of neuroimaging-based diagnostic, prognostic, and treatment options for the early recognition and management of FThD and associated poor outcomes.

From communication dysfunction to treatment options in serious mental illness

The Commentary covers research focused on language dysfunction in schizophrenia, and more broadly in communication dysfunction in this disorder, which I have examined with a variety of both behavioral and imaging methodologies. It briefly outlines how further progress can be achieved in pursuing the goal of a comprehensive understanding of its underlying causes. Possible therapeutic approaches are also briefly discussed.

The role of white matter abnormality in the left anterior corona radiata: In relation to formal thought disorder in patients with schizophrenia

White matter abnormality has been widely reported in patients with schizophrenia (Sz). However, few studies have focused on the relationship between the white matter deficit and formal thought disorder (FTD). Moreover, the role of genetic high risk in FTD-related white matter deficit remains unclear. The present study recruited 46 Sz patients, 18 unaffected first-degree relatives of Sz patients, and 29 healthy controls. There was a widespread fractional anisotropy (FA) reduction in Sz. In addition, reduced FA in the left anterior corona radiata was related to more severe FTD symptoms in Sz. However, the genetic high-risk group only showed lower mean FA in the left anterior limb of the internal capsule than healthy controls. Our findings suggest that abnormality in the left anterior corona radiata may only occur in Sz but not in the genetic high-risk group. Such an abnormality might be associated with the severity of FTD symptoms. Meanwhile, genetic vulnerability may contribute to the abnormality in the left anterior limb of the internal capsule. Better analytical methods are needed to validate our results.

Neurobiological substrates of the positive formal thought disorder in schizophrenia revealed by seed connectome-based predictive modeling

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Formal thought disorder (FTD) is a core symptom of schizophrenia, but its neurobiological substrates remain elusive.

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Resting-state functional connectivity (rsFC) of three meta-analytically defined seeds were correlated to positive and negative symptom dimensions of FTD.

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RsFC patterns allowed individual prediction of positive FTD symptom severity.

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These findings generalized to an independent data set.

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Our study has identified robust neurobiological correlates of positive FTD in schizophrenia.

Formal thought disorder (FTD) is a core symptom cluster of schizophrenia, but its neurobiological substrates remain poorly understood. Here we collected resting-state fMRI data from 276 subjects at seven sites and employed machine-learning to investigate the neurobiological correlates of FTD along positive and negative symptom dimensions in schizophrenia. Three a priori, meta-analytically defined FTD-related brain regions were used as seeds to generate whole-brain resting-state functional connectivity (rsFC) maps, which were then compared between schizophrenia patients and controls. A repeated cross-validation procedure was realized within the patient group to identify clusters whose rsFC patterns to the seeds were repeatedly observed as significantly associated with specific FTD dimensions. These repeatedly identified clusters (i.e., robust clusters) were functionally characterized and the rsFC patterns were used for predictive modeling to investigate predictive capacities for individual FTD dimensional-scores. Compared with controls, differential rsFC was found in patients in fronto-temporo-thalamic regions. Our cross-validation procedure revealed significant clusters only when assessing the seed-to-whole-brain rsFC patterns associated with positive-FTD. RsFC patterns of three fronto-temporal clusters, associated with higher-order cognitive processes (e.g., executive functions), specifically predicted individual positive-FTD scores (p = 0.005), but not other positive symptoms, and the PANSS general psychopathology subscale (p > 0.05). The prediction of positive-FTD was moreover generalized to an independent dataset (p = 0.013). Our study has identified neurobiological correlates of positive FTD in schizophrenia in a network associated with higher-order cognitive functions, suggesting a dysexecutive contribution to FTD in schizophrenia. We regard our findings as robust, as they allow a prediction of individual-level symptom severity.

Understanding Language Abnormalities and Associated Clinical Markers in Psychosis: The Promise of Computational Methods

The language and speech of individuals with psychosis reflect their impairments in cognition and motor processes. These language disturbances can be used to identify individuals with and at high risk for psychosis, as well as help track and predict symptom progression, allowing for early intervention and improved outcomes. However, current methods of language assessment-manual annotations and/or clinical rating scales-are time intensive, expensive, subject to bias, and difficult to administer on a wide scale, limiting this area from reaching its full potential. Computational methods that can automatically perform linguistic analysis have started to be applied to this problem and could drastically improve our ability to use linguistic information clinically. In this article, we first review how these automated, computational methods work and how they have been applied to the field of psychosis. We show that across domains, these methods have captured differences between individuals with psychosis and healthy controls and can classify individuals with high accuracies, demonstrating the promise of these methods. We then consider the obstacles that need to be overcome before these methods can play a significant role in the clinical process and provide suggestions for how the field should address them. In particular, while much of the work thus far has focused on demonstrating the successes of these methods, we argue that a better understanding of when and why these models fail will be crucial toward ensuring these methods reach their potential in the field of psychosis.

Linking language features to clinical symptoms and multimodal imaging in individuals at clinical high risk for psychosis

BACKGROUND

Abnormalities in the semantic and syntactic organization of speech have been reported in individuals at clinical high-risk (CHR) for psychosis. The current study seeks to examine whether such abnormalities are associated with changes in brain structure and functional connectivity in CHR individuals.

METHODS

Automated natural language processing analysis was applied to speech samples obtained from 46 CHR and 22 healthy individuals. Brain structural and resting-state functional imaging data were also acquired from all participants. Sparse canonical correlation analysis (sCCA) was used to ascertain patterns of covariation between linguistic features, clinical symptoms, and measures of brain morphometry and functional connectivity related to the language network.

RESULTS

In CHR individuals, we found a significant mode of covariation between linguistic and clinical features (r = 0.73; p = 0.003), with negative symptoms and bizarre thinking covarying mostly with measures of syntactic complexity. In the entire sample, separate sCCAs identified a single mode of covariation linking linguistic features with brain morphometry (r = 0.65; p = 0.05) and resting-state network connectivity (r = 0.63; p = 0.01). In both models, semantic and syntactic features covaried with brain structural and functional connectivity measures of the language network. However, the contribution of diagnosis to both models was negligible.

CONCLUSIONS

Syntactic complexity appeared sensitive to prodromal symptoms in CHR individuals while the patterns of brain-language covariation seemed preserved. Further studies in larger samples are required to establish the reproducibility of these findings.

Sentence contexts and cloze probabilities for Brazilian Portuguese children and adolescents

PURPOSE

In this study we investigated a set of 100 sentence contexts and their cloze probabilities to develop a database of linguistic stimuli for Brazilian Portuguese children and adolescents. The study also examined age-related changes on cloze probabilities, and specified the predictor effects of age and cloze probabilities on idiosyncratic responses and errors (semantic, syntactic, and other errors). Finally, the study also aimed to shed light on cultural effects on word generation by comparing Brazilian and Portuguese sentence databases.

METHOD

361 typically developing monolingual Brazilian speakers, with ages ranging from 7 to 18 years, participated in the study. The cloze task was composed by 100 sentence contexts, grounded on the European Portuguese database. Responses were classified as valid (correct) or invalid (semantic, syntactic, and other-type errors). Statistical analyses were based on mixed-effects logistic models.

RESULTS

Sixty-three sentences met criteria for high cloze probabilities, 30 for medium cloze, and 7 for low cloze. Age was a significant predictor of idiosyncratic responses, semantic and syntactic errors: older participants were less likely to produce idiosyncratic responses, as well as semantic and syntactic errors. Cloze probability values were concordant in the Brazilian and Portuguese databases for 31 out of 49 (83.7%) high-cloze sentences and for 7 low-cloze sentences.

CONCLUSION

In this study we have provided a database with cloze probability values for a set of 100 sentence-final word contexts for Brazilian Portuguese children and adolescents. Results showed that both age and sentence contextual level predicted sentence final word completion. Older participants were more likely to choose more consistently the same final word, with the contextual level of a given sentence also contributing to the final word selection. Age should be controlled for in future studies probing semantic processing with this set of sentences.

Element-centric clustering comparison unifies overlaps and hierarchy

Clustering is one of the most universal approaches for understanding complex data. A pivotal aspect of clustering analysis is quantitatively comparing clusterings; clustering comparison is the basis for many tasks such as clustering evaluation, consensus clustering, and tracking the temporal evolution of clusters. In particular, the extrinsic evaluation of clustering methods requires comparing the uncovered clusterings to planted clusterings or known metadata. Yet, as we demonstrate, existing clustering comparison measures have critical biases which undermine their usefulness, and no measure accommodates both overlapping and hierarchical clusterings. Here we unify the comparison of disjoint, overlapping, and hierarchically structured clusterings by proposing a new element-centric framework: elements are compared based on the relationships induced by the cluster structure, as opposed to the traditional cluster-centric philosophy. We demonstrate that, in contrast to standard clustering similarity measures, our framework does not suffer from critical biases and naturally provides unique insights into how the clusterings differ. We illustrate the strengths of our framework by revealing new insights into the organization of clusters in two applications: the improved classification of schizophrenia based on the overlapping and hierarchical community structure of fMRI brain networks, and the disentanglement of various social homophily factors in Facebook social networks. The universality of clustering suggests far-reaching impact of our framework throughout all areas of science.

Formal thought disorder is related to aberrations in language-related white matter tracts in patients with schizophrenia

This study examined the hypothesis that a fronto-temporal disconnection in the language network underpins formal thought disorder (FTD) in schizophrenia. Forty-nine patients with a schizophrenia spectrum disorder (27 with mild FTD, 22 with severe FTD) and 26 healthy controls (HC) were included. Overall psychopathology and FTD were assessed by the Positive and Negative Syndrome Scale and the Thought, Language, and Communication scale, respectively. White matter (WM) microstructure was analysed using Tract-Based Spatial Statistics. In patients, severity of overall FTD (TLC Sum Score) was predicted by decreased fractional anisotropy (FA) in the right superior longitudinal fasciculus (SLF), and severity of negative FTD (TLC Emptiness subscale) was predicted by increased FA in the left SLF and arcuate fasciculus (AF). Notably, these results were no longer significant after correction for multiple comparisons. Compared with HC, patients showed lower FA in all the investigated language-related WM tracts as well as across the whole WM skeleton. No difference in FA was found between patients with severe and patients with mild FTD. Our results are compatible with earlier studies reporting impairments in widely spread WM tracts including those related to language processing in patients with schizophrenia.

Is formal thought disorder in schizophrenia related to structural and functional aberrations in the language network? A systematic review of neuroimaging findings

Formal thought disorder (FTD) is a core feature of schizophrenia, a marker of illness severity and a predictor of outcome. The underlying neural mechanisms are still a matter of debate. This study aimed at 1) reviewing the literature on the neural correlates of FTD in schizophrenia, and 2) testing the hypothesis that FTD correlates with structural and functional aberrations in the language network. Medline, PsychInfo, and Embase were searched for neuroimaging studies, which applied a clinical measure to assess FTD in adults with schizophrenia and were published in English or German in peer-reviewed journals until December 2016. Of 412 articles identified, 61 studies were included in the review. Volumetric studies reported bilateral grey matter deficits (L > R) to be associated with FTD in the inferior frontal gyrus, the superior temporal gyrus and the inferior parietal lobe. The same regions showed hyperactivity in resting state functional magnetic resonance imaging (fMRI) studies and both hyper- and hypoactivity in fMRI studies that employed semantic processing or free speech production tasks. Diffusion tensor imaging studies demonstrated white matter aberrations in fibre tracts that connect the frontal and temporo-parietal regions. FTD in schizophrenia was found to be associated with structural and functional aberrations in the language network. However, there are studies that did not find an association between FTD and neural aberrations of the language network and regions not included in the language network have been associated with FTD. Thus, future research is needed to clarify the specificity of the language network for FTD in schizophrenia.

A systematic review of task-based functional neuroimaging studies investigating language, semantic and executive processes in thought disorder

The aim of the current systematic review was to synthesise the research that has investigated thought disorder (TD) using task-based functional neuroimaging techniques to target executive, language, or semantic functions. Thirty-five pertinent studies were identified from January 1990 to August 2016. Functional correlates of TD included the superior and middle temporal, fusiform, and inferior frontal gyri bilaterally, as well as the left and right cingulate cortex, the right caudate nucleus, and the cerebellum. TD-related increases and decreases in activation were both evident in most of these regions. However, the specificity of these correlates from general clinical and cognitive influences is unknown. The cortical regions implicated overlap with those thought to contribute to language and semantic systems. Cortico-striatal circuitry may also play a role in some aspects of TD through aberrant salience representation and inappropriate attentional prioritisation. To advance the field further, greater integration across structural, functional, and behavioural measures is required, in addition to non-unitary considerations of TD.

Formal thought disorders: from phenomenology to neurobiology

Formal thought disorder (FTD) is present in most psychiatric disorders and in some healthy individuals. In this Review, we present a comprehensive, integrative, and multilevel account of what is known about FTD, covering genetic, cellular, and neurotransmitter effects, environmental influences, experimental psychology and neuropsychology, brain imaging, phenomenology, linguistics, and treatment. FTD is a dimensional, phenomenologically defined construct, which can be clinically subdivided into positive versus negative and objective versus subjective symptom clusters. Because FTDs have been traditionally linked to schizophrenia, studies in other diagnoses are scarce. Aetiologically, FTD is the only symptom under genetic influence in schizophrenia as shown in linkage studies, but familial communication patterns (allusive thinking) have also been associated with the condition. Positive FTDs are related to synaptic rarefication in the glutamate system of the superior and middle lateral temporal cortices. Cortical volume of the left superior temporal gyrus is decreased in patients with schizophrenia who have positive FTD in structural MRI studies and shows reversed hemispheric (right more than left) activation in functional MRI experiments during speech production. Semantic network dysfunction in positive FTD has been demonstrated in experiments of indirect semantic hyperpriming (reaction time). In acute positive FTD, antipsychotics are effective, but a subgroup of patients have treatment-resistant, chronic, positive or negative FTD. Specific psychotherapy as treatment for FTD has not yet been developed. With this solid data on the pathogenesis of FTD, we can now implement clinical studies to treat this condition.

S-Ketamine-Induced NMDA Receptor Blockade during Natural Speech Production and Its Implications for Formal Thought Disorder in Schizophrenia: A Pharmaco-fMRI Study

Structural and functional changes in the lateral temporal language areas have been related to formal thought disorder (FTD) in schizophrenia. Continuous, natural speech production activates the right lateral temporal lobe in schizophrenia, as opposed to the left in healthy subjects. Positive and negative FTD can be elicited in healthy subjects by glutamatergic NMDA blockade with ketamine. It is unclear whether the glutamate system is related to the reversed hemispheric lateralization during speaking in patients. In a double-blind, crossover, placebo-controlled study, 15 healthy, male, right-handed volunteers overtly described 7 pictures for 3 min each while BOLD signal changes were acquired with fMRI. As a measure of linguistic demand, the number of words within 20 s epochs was correlated with BOLD responses. Participants developed S-ketamine-induced psychotic symptoms, particularly positive FTD. Ketamine vs placebo was associated with enhanced neural responses in the right middle and inferior temporal gyri. Similar to a previous fMRI study in schizophrenia patients vs healthy controls applying the same design, S-ketamine reversed functional lateralization during speech production in healthy subjects. Results demonstrate an association between glutamatergic imbalance, dysactivations in lateral temporal brain areas, and FTD symptom formation.

The Comprehension of Familiar and Novel Metaphoric Meanings in Schizophrenia: A Pilot Study

Miscomprehension of nonliteral (“figurative”) language like metaphors, proverbs, idioms, and ironic expressions by patients with schizophrenia is a phenomenon mentioned already in historical psychiatric descriptions. However, it was only recently that studies did differentiate between novel and conventional metaphors, a factor that is known to influence the difficulty of comprehension in healthy subjects. Further, familiarity with stimuli is an important factor for comprehension, which was not recommended in utmost previous studies. In this study, 23 patients with DSM IV schizophrenia and 19 healthy control subjects performed a newly-developed German metaphor comprehension test with three types of stimuli: novel metaphors, conventional German metaphors, and meaningless statements. During the test procedure, participants indicated familiarity with the stimulus and then matched the meaning with one out of four given alternatives. Familiarity rankings did not significantly differ between patients and control subjects. However, on descriptive level, there was a tendency for healthy controls to be more familiar with conventional metaphors than schizophrenic patients. Further, comprehension of conventional and novel metaphors differed significantly between the groups, with higher performance in healthy controls. Considering only those metaphors that had been ranked as familiar, patients only revealed significant lower performance opposed to controls regarding novel metaphors, while they did not differ in conventional metaphors. Taken together, the results indicate that patients with schizophrenia might show an altered way of comprehension in novel metaphors, leading to more misunderstandings. However, their previously reported impairments in conventional metaphors might rather be due to a lack of familiarity with the stimuli—making conventional metaphors to novel metaphors in the individual case.

Neural correlates of formal thought disorder: An activation likelihood estimation meta-analysis

Formal thought disorder (FTD) refers to a psychopathological dimension characterized by disorganized and incoherent speech. Whether symptoms of FTD arise from aberrant processing in language-related regions or more general cognitive networks, however, remains debated. Here, we addressed this question by a quantitative meta-analysis of published functional neuroimaging studies on FTD. The revised Activation Likelihood Estimation (ALE) algorithm was used to test for convergent aberrant activation changes in 18 studies (30 experiments) investigating FTD, of which 17 studies comprised schizophrenia patients and one study healthy subjects administered to S-ketamine. Additionally, we analyzed task-dependent and task-independent (resting-state) functional connectivity (FC) of brain regions showing convergence in activation changes. Subsequent functional characterization was performed for the initial clusters and the delineated connectivity networks by reference to the BrainMap database. Consistent activation changes were found in the left superior temporal gyrus (STG) and two regions within the left posterior middle temporal gyrus (p-MTG), ventrally (vp-MTG) and dorsally (dp-MTG). Functional characterization revealed a prominent functional association of ensuing clusters from our ALE meta-analysis with language and speech processing, as well as auditory perception in STG and with social cognition in dp-MTG. FC analysis identified task-dependent and task-independent networks for all three seed regions, which were mainly related to language and speech processing, but showed additional involvement in higher order cognitive functions. Our findings suggest that FTD is mainly characterized by abnormal activation in brain regions of the left hemisphere that are associated with language and speech processing, but also extend to higher order cognitive functions. Hum Brain Mapp 38:4946-4965, 2017. © 2017 Wiley Periodicals, Inc.

A Hierarchical Generative Framework of Language Processing: Linking Language Perception, Interpretation, and Production Abnormalities in Schizophrenia

Language and thought dysfunction are central to the schizophrenia syndrome. They are evident in the major symptoms of psychosis itself, particularly as disorganized language output (positive thought disorder) and auditory verbal hallucinations (AVHs), and they also manifest as abnormalities in both high-level semantic and contextual processing and low-level perception. However, the literatures characterizing these abnormalities have largely been separate and have sometimes provided mutually exclusive accounts of aberrant language in schizophrenia. In this review, we propose that recent generative probabilistic frameworks of language processing can provide crucial insights that link these four lines of research. We first outline neural and cognitive evidence that real-time language comprehension and production normally involve internal generative circuits that propagate probabilistic predictions to perceptual cortices - predictions that are incrementally updated based on prediction error signals as new inputs are encountered. We then explain how disruptions to these circuits may compromise communicative abilities in schizophrenia by reducing the efficiency and robustness of both high-level language processing and low-level speech perception. We also argue that such disruptions may contribute to the phenomenology of thought-disordered speech and false perceptual inferences in the language system (i.e., AVHs). This perspective suggests a number of productive avenues for future research that may elucidate not only the mechanisms of language abnormalities in schizophrenia, but also promising directions for cognitive rehabilitation.

Haemodynamic and electrophysiological markers of pragmatic language comprehension in schizophrenia

OBJECTIVES

The present study aimed at investigating neurophysiological markers of language perception in schizophrenia using simultaneous near-infrared spectroscopy (NIRS) and event-related potentials (ERPs), which have been proven to be useful for studying language processing abilities in psychiatric patients. The study shall help to integrate previous findings from ERP and fMRI studies on figurative language comprehension in schizophrenia and elucidate how electrophysiological and haemodynamic markers of language processing are related.

METHODS

Twenty-two healthy subjects and 22 schizophrenia patients judged 120 sentences regarding their meaningfulness. Phrases were literal, metaphoric, or meaningless. EEG-fNIRS signals were recorded throughout the entire experiment.

RESULTS

Schizophrenia patients showed deficient and delayed sentence comprehension. Both the early N400 and left-hemispheric activation during language comprehension were altered in patients. Correlation analyses showed that metaphor-related ERPs were strongly linked to haemodynamic cortical activity in healthy subjects, but not in patients.

CONCLUSIONS

Our results indicate group differences in cortical electrophysiological and haemodynamic activation that represent rather general impairments in the processing of complex language. Simultaneous EEG/NIRS applications are useful to depict these neural markers and to investigate their relationship. Future studies are needed to clarify the nature of respective anomalies and their potential as putative neural markers in schizophrenia research.

Functional MRI of sentence-level language comprehension in schizophrenia: a coordinate-based analysis

Numerous authors have hypothesised that abnormal pathways for language play a key role in the pathophysiology of schizophrenia, a notion that is supported by structural imaging and post-mortem findings especially in patients with thought disorder and auditory verbal hallucinations. Recently, an increasing number of functional magnetic resonance imaging (fMRI) investigations addressed language comprehension schizophrenia. We present a systematic review of the fMRI-studies on sentence- and text-level language comprehension in schizophrenia. 13 studies met the inclusion criteria. Additional studies specifically addressed language lateralization. Coordinates for differential contrasts for healthy controls>patients reported in these studies indicate that the left fronto-temporal language network is altered in schizophrenia. 33 out of the 51 reported coordinates are located in the left hemisphere. Overactivation in schizophrenia extends into premotor areas and is about equally divided among the left and right hemispheres. Several negative studies indicate heterogeneity within schizophrenia, which could possibly be related to the severity of thought disorder or auditory verbal hallucinations of patients. Activation changes related to thought disorder within schizophrenia (n=4 studies) include the inferior frontal and superior temporal gyri and are moderately lateralized to the left hemisphere. Although current fMRI literature is still insufficient to draw decisive conclusions, results point towards functionally altered pathways for language in schizophrenia. This notion is also plausible from the viewpoint of psychopathology especially since hallmark symptoms of the disease, thought disorder, auditory verbal hallucinations and alogia, are expressed in terms of language or represent abnormalities of language function.

Isn't it ironic? Neural correlates of irony comprehension in schizophrenia

Ironic remarks are frequent in everyday language and represent an important form of social cognition. Increasing evidence indicates a deficit in comprehension in schizophrenia. Several models for defective comprehension have been proposed, including possible roles of the medial prefrontal lobe, default mode network, inferior frontal gyri, mirror neurons, right cerebral hemisphere and a possible mediating role of schizotypal personality traits. We investigated the neural correlates of irony comprehension in schizophrenia by using event-related functional magnetic resonance imaging (fMRI). In a prosody-free reading paradigm, 15 female patients with schizophrenia and 15 healthy female controls silently read ironic and literal text vignettes during fMRI. Each text vignette ended in either an ironic (n = 22) or literal (n = 22) statement. Ironic and literal text vignettes were matched for word frequency, length, grammatical complexity, and syntax. After fMRI, the subjects performed an off-line test to detect error rate. In this test, the subjects indicated by button press whether the target sentence has ironic, literal, or meaningless content. Schizotypal personality traits were assessed using the German version of the schizotypal personality questionnaire (SPQ). Patients with schizophrenia made significantly more errors than did the controls (correct answers, 85.3% vs. 96.3%) on a behavioural level. Patients showed attenuated blood oxygen level-dependent (BOLD) response during irony comprehension mainly in right hemisphere temporal regions (ironic>literal contrast) and in posterior medial prefrontal and left anterior insula regions (for ironic>visual baseline, but not for literal>visual baseline). In patients with schizophrenia, the parahippocampal gyrus showed increased activation. Across all subjects, BOLD response in the medial prefrontal area was negatively correlated with the SPQ score. These results highlight the role of the posterior medial prefrontal and right temporal regions in defective irony comprehension in schizophrenia and the mediating role of schizotypal personality traits.

Resting-state fMRI mapping of cerebellar functional dysconnections involving multiple large-scale networks in patients with schizophrenia

BACKGROUND

Recent findings have indicated that patients with schizophrenia have altered cortico-cerebellar connectivity, but the nature of these network dysconnections remains unclear.

AIMS

We applied a network-based approach to investigate the functional connectivity (FC) of the cerebellum in patients with schizophrenia.

METHODS

Thirty-six patients with schizophrenia and 36 healthy controls underwent resting functional magnetic resonance imaging. We derived the following 6 major networks by applying group independent component analysis: (1) the cingulo-opercular network (CON); (2) the dorsal default-mode networks (dDMN); (3) the ventral default-mode network (vDMN); (4) the left frontoparietal networks (lFPN); (5) the right frontoparietal network (rFPN); and (6) the motor network (MOT). We defined 12 regions of interest (ROIs) by selecting the first 2 peaks of each network in the cerebellum. The FC map of all ROIs was calculated for each participant and compared between groups.

RESULTS

The schizophrenic patients showed a decrease in FC between the cerebellar ROIs and the thalamus in all networks except the MOT. The FC decreased between cerebellar ROIs and the frontal cortex in the CON, rFPN, and MOT. However, the FC increased with the precentral gyrus and postcentral gyrus for the CON, lFPN, and dDMN. An increased FC with the occipital fusiform gyrus and the temporal occipital fusiform gyrus was also noted in the dDMN, vDMN, and MOT.

CONCLUSIONS

The dysconnection of the cerebellum in the examined patients with schizophrenia was network-specific. The cerebellar-thalamic dysconnections were the most prominent findings and were common to all cognitive-related networks, whereas the cortico-cerebellar connectivity involved both an increase and decrease in FC, and depended more on the nature of the specific network.

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.

Unique topology of language processing brain network: a systems-level biomarker of schizophrenia

OBJECTIVE

Schizophrenia is a severe and heritable brain disorder. Language impairment has been hypothesized to spur its onset and underlie the characteristic symptoms. In this study, we investigate whether altered topological pattern of the language processing brain network exists and could be a potential biomarker of schizophrenia. We hypothesized that both patients with schizophrenia and the genetic high risk population would show significantly weakened efficiencies of the network hubs for normal language processing, especially at left inferior frontal and bilateral temporal lobes.

METHOD

Language task-based fMRI data from 21 patients with schizophrenia, 22 genetic high risk subjects and 36 controls were analyzed. Graph theoretic and post hoc analyses of the fMRI data, and correlations between the functional network features and scores of language tests were carried out.

RESULTS

Compared to controls, patients with schizophrenia and the high risk subjects showed significantly weakened network hubs in left inferior frontal and right fusiform gyri. A unique topology of super active and intercommunicating network hubs at left fusiform gyrus and right inferior/middle frontal gyri, which were associated with the behavioral language impairment was found in the patient group, compared to the high risk and control groups.

CONCLUSIONS

Aberrant systems-level topology of language processing network, especially significantly weakened network hubs in left inferior frontal and right fusiform gyri, may serve as a candidate biomarker of schizophrenia. Supported by existing findings, the hyperactive left fusiform gyrus communicating with right frontal lobe might be the key neurophysiological component causing hallucinations in schizophrenia. These findings provided a new systems-level diagnostic target for the disorder.

Effects of ketamine-induced psychopathological symptoms on continuous overt rhyme fluency

The N-methyl-D-aspartate receptor (NMDAR) has been implicated in the pathophysiology of schizophrenia. Administered to healthy individuals, a subanesthetic dose of the noncompetitive NMDAR antagonist ketamine reproduces several psychopathological symptoms commonly observed in patients with schizophrenia. In a counterbalanced, placebo-controlled, double-blind, within-participants study, fifteen healthy subjects were administered a continuous subanesthetic S-ketamine infusion while cortical activation was measured using functional magnetic resonance imaging. While being scanned, subjects performed an overt word generation task. Ketamine-induced psychopathological symptoms were assessed with the Positive and Negative Syndrome Scale (PANSS). Ketamine administration elicited effects on psychopathology, including difficulties in abstract thinking, lack of spontaneity and flow of conversation as well as formal thought disorder. On a behavioral level, verbal fluency performance was unaffected. The PANSS score for formal thought disorder positively correlated with activation measures encompassing the left superior temporal gyrus, the right middle and inferior frontal gyrus and the precuneus. Difficulty in abstract thinking was correlated with pronounced activations in prefrontal as well as in anterior cingulate regions, whereas hyperactivations in the left superior temporal gyrus were found in association with a lack of spontaneity and flow of conversation. In the absence of behavioral impairments during verbal fluency, NMDAR blocking evoked psychopathological symptoms and cortical activations in regions previously reported in schizophrenia patients. The results provide further support for the hypothesis of an NMDAR dysfunction in the pathophysiology of schizophrenia.

Faulty suppression of irrelevant material in patients with thought disorder linked to attenuated frontotemporal activation

Formal thought disorder is a feature schizophrenia that manifests as disorganized, incoherent speech, and is associated with a poor clinical outcome. The neurocognitive basis of this symptom is unclear but it is thought to involve an impairment in semantic processing classically described as a loosening of meaningful associations. Using a paradigm derived from the n400 event-related, potential, we examined the extent to which regional activation during semantic processing is altered in schizophrenic patients with formal thought disorder. Ten healthy control and 18 schizophrenic participants (9 with and 9 without formal thought disorder) performed a semantic decision sentence task during an event-related functional magnetic resonance imaging experiment. We employed analysis of variance to estimate the main effects of semantic congruency and groups on activation and specific effects of formal thought disorder were addressed using post-hoc comparisons. We found that the frontotemporal network, normally engaged by a semantic decision task, was underactivated in schizophrenia, particularly in patients with FTD. This network is implicated in the inhibition of automatically primed stimuli and impairment of its function interferes with language processing and contributes to the production of incoherent speech.

Left but not right hemisphere semantic processing abnormalities in language comprehension in subjects with schizotypy traits

Thought and language disorders in schizophrenia and schizotypy are thought to result from hemispheric dysfunction during semantic processing. Left hemisphere (LH) abnormalities are well established, but little is known about right hemisphere (RH) semantic processes. We explored hemispheric processing in 50 healthy volunteers assigned to high (h-SZT) or low schizotypy (l-SZT) group using the Schizotypal Personality Questionnaire (SPQ). Subjects were asked to make semantic judgments on sentence pair ending with a target that was either expected word (EW) or an unexpected word from the same (related violation, RV) or a different category (unrelated violation, URV). Targets were presented in a dichotic manner to the left or right ear. Analyses of reaction times in the l-SZT group showed semantic compatibility effect (URV-EW) in the LH and semantic memory activation effect (RV-URV) as well as semantic compatibility effect in the RH. The h-SZT group showed semantic memory activation but no semantic compatibility effect in the LH, the RH pattern resembling that of the l-SZT group. The magnitude of the LH semantic compatibility effect was inversely correlated with SPQ total scores and SPQ Cognitive-perceptual factor. Thus, RH semantic processes are effective and there is a deficit in LH focused activation in schizotypy.

Genetic variation in G72 correlates with brain activation in the right middle temporal gyrus in a verbal fluency task in healthy individuals

The D-amino acid oxidase activator gene (G72) has been found associated with several psychiatric disorders such as schizophrenia, major depression, and bipolar disorder. Impaired performance in verbal fluency tasks is an often replicated finding in the mentioned disorders. In functional neuroimaging studies, this dysfunction has been linked to signal changes in prefrontal and lateral temporal areas and could possibly constitute an endophenotype. Therefore, it is of interest whether genes associated with the disorders, such as G72, modulate verbal fluency performance and its neural correlates. Ninety-six healthy individuals performed a semantic verbal fluency task while brain activation was measured with functional MRI. All subjects were genotyped for two single nucleotide polymorphisms (SNP) in the G72 gene, M23 (rs3918342) and M24 (rs1421292), that have previously shown association with the above-mentioned disorders. The effect of genotype on brain activation was assessed with fMRI during a semantic verbal fluency task. Although there were no differences in performance, brain activation in the right middle temporal gyrus (BA 39) and the right precuneus (BA 7) was positively correlated with the number of M24 risk alleles in the G72 gene. G72 genotype does modulate brain activation during language production on a semantic level in key language areas. These findings are in line with structural and functional imaging studies in schizophrenia, which showed alterations in the right middle temporal gyrus.

Language in schizophrenia Part 1: an Introduction

This is the first of two articles that discuss higher-order language and semantic processing in schizophrenia. This article reviews clinical characterizations of language output and the phenomenon of positive thought disorder, as well as more principled characterizations of language output in schizophrenia. It also gives an overview of evidence for the predominant theory of language dysfunction in schizophrenia: that it arises from abnormalities in (a) semantic memory and/or (b) working memory and executive function. The companion article (Part 2) focuses on the study of language in schizophrenia using online psycholinguistic methods and considers how the study of schizophrenia may inform our understanding of normal language processing.

Building coherence: A framework for exploring the breakdown of links across clause boundaries in schizophrenia

Clinically, patients with schizophrenia show prominent abnormalities at the discourse level, with production characterized by tangential and illogical relationships between ideas and unclear references. Despite these clinical manifestations, most studies of language in schizophrenia have focused on semantic relationships between single words and the build-up of meaning within single-clause sentences. The present paper discusses the few studies that have gone beyond clause boundaries to fully understand language impairments in schizophrenia. We also give an overview of a relevant literature that considers the neurocognitive mechanisms by which coherence links are established across clauses in healthy adults, providing a framework that may guide future research in this area.

Semantic Processing and Thought Disorder in Childhood-Onset Schizophrenia: Insights from fMRI

Impairments in language processing and thought disorder are core symptoms of schizophrenia. Here we used fMRI to investigate functional abnormalities in the neural networks subserving sentence-level language processing in childhood-onset schizophrenia (COS). Fourteen children with COS (mean age: 13.34; IQ: 95) and 14 healthy controls (HC; mean age: 12.37; IQ: 104) underwent fMRI while performing a semantic judgment task previously shown to differentially engage semantic and syntactic processes. We report four main results. First, different patterns of functional specialization for semantic and syntactic processing were observed within each group, despite similar level of task performance. Second, after regressing out IQ, significant between-group differences were observed in the neural correlates of semantic and, to a lesser extent, syntactic processing, with HC children showing overall greater activity than COS children. Third, while these group differences were not related to effects of medications, a significant negative correlation was observed in the COS group between neuroleptic dosage and activity in the left inferior frontal gyrus for the semantic condition. Finally, COS children's level of thought disorder was significantly correlated with task-related activity in language-relevant networks. Taken together, these findings suggest that children with COS exhibit aberrant patterns of neural activity during semantic, and to a lesser extent syntactic, processing and that these functional abnormalities in language-relevant networks are significantly related to severity of thought disorder.

Catechol-o-methyltransferase valine(158)methionine genotype and resting regional cerebral blood flow in medication-free patients with schizophrenia

BACKGROUND

A valine(158)methionine (val(158)met) polymorphism in catechol-O-methyltransferase (COMT) modulates cortical dopaminergic catabolism and has been associated with schizophrenia. Consistent with schizophrenia itself, during cognitive tasks, the risk (val) allele predicts less efficient prefrontal cortex (PFC) physiology and worse performance, while during aversive stimuli viewing, this allele predicts less limbic activation. Task-independent effects of this polymorphism in schizophrenia have not yet been characterized.

METHODS

Twenty-five medication-free patients (28 +/- 6 years; 19 male patients) and 47 healthy individuals (29 +/- 8 years; 33 male individuals) were genotyped for the COMT val(158)met polymorphism and underwent two 60-second radiolabeled water ([(15)O]H(2)O) regional cerebral blood flow (rCBF) positron emission tomography scans (10 mCi/scan) during rest. Data were analyzed with a random-effects general linear model using COMT genotype as a covariate.

RESULTS

In patients, but not healthy individuals, val (risk) allele load predicted less regional cerebral blood flow in the right dorsolateral PFC, right superior temporal gyrus, and left precuneus, but greater rCBF in the amygdala and parahippocampal gyrus.

CONCLUSIONS

In schizophrenia, brain structures important for executive and affective processing show activity that is differentially predicted by COMT allelic variation in an opposing manner even at rest, providing evidence for the salience of prefrontal dopaminergic tone in task-independent, basal-level neural activity.

Language pathway abnormalities in schizophrenia: a review of fMRI and other imaging studies

PURPOSE OF REVIEW

Schizophrenia is a severe mental disorder with substantial genetic vulnerability. This review discusses recent neuroimaging studies reporting on impairment in brain functioning relevant to language processing in individuals with schizophrenia and those who are at a genetic risk for its development.

RECENT FINDINGS

Studies have shown that schizophrenia is associated with deficits in language function, as well as structural and functional abnormalities in brain regions that are involved with language perception and processing. Individuals who are at genetic high risk for schizophrenia also have structural and functional deficits in brain pathways for language processing. These studies consistently suggest that the normal pattern of left hemisphere dominance of language processing is significantly disturbed.

SUMMARY

This review suggests that future studies should examine the underlying mechanism for producing this disturbance in language processing and that prospective studies should be carried out that aim to follow individuals over time to determine whether these anomalies eventually lead to clinical symptoms of schizophrenia.

The neural correlates of ego-disturbances (passivity phenomena) and formal thought disorder in schizophrenia

Ego-disturbances (passivity phenomena) and formal thought disorder are two hallmark symptoms of schizophrenia. Formal thought disorder has been highlighted already very early by Eugen Bleuler in his concept of basic symptoms (Grundsymptome). In contrast ego-disturbances (Ich-Störungen) or passivity phenomena have been declared as core symptoms of schizophrenia by Kurt Schneider in his concept of first-rank symptoms (Erstrangsymptome) that influenced the whole concept of schizophrenia until today (ICD10; DSM IV). We present new neuroimaging and cognitive neuropsychological results that help to explain what brain and cognitive functions may be involved in the emergence of these symptoms. Questions on cognitive and neural correlates of notions such as self-awareness, self-consciousness, introspective perspective or subjective experiences have re-emerged as topics of great interest in the scientific community. Employing new neuroscientific methods such as functional brain imaging, advances into thus far unexplored territory of mind-brain relationships have been made. These findings give new impulses for the search on the neural basis of psychopathological symptoms. We will review neuroscientific data and models on the pathogenesis of two of the core symptoms of schizophrenia, i.e. passivity phenomena and formal thought disorder.

Functional magnetic resonance imaging reveals neuroanatomical dissociations during semantic integration in schizophrenia

BACKGROUND

Schizophrenia symptoms can be conceptualized in terms of a breakdown of a balance between 1) activating, retrieving, and matching stored representations to incoming information (semantic memory-based processing) and 2) fully integrating activated semantic representations with one another and with other types of representations to form a gestalt representation of meaning (semantic integration). Semantic memory-based processes are relatively more dependent on inferior frontal and temporal cortices, whereas particularly demanding integrative processes additionally recruit the dorsolateral prefrontal cortex (DLPFC) and sometimes parietal cortices. We used functional magnetic resonance imaging (fMRI) to determine whether the modulation of temporal/inferior frontal cortices and the DLPFC can be neuroanatomically dissociated in schizophrenia, as semantic integration demands increase. Integration demands were manipulated by varying the nature (concrete vs. abstract) and the congruity (incongruous vs. congruous) of words within sentences.

METHODS

Sixteen right-handed schizophrenia patients and 16 healthy volunteers, matched on age and parental socioeconomic status, underwent event-related fMRI scanning while they read sentences. Blood oxygen level dependent (BOLD) effects were contrasted to words within sentences that were 1) concrete versus abstract and 2) semantically incongruous versus congruous with their preceding contexts.

RESULTS

In both contrasts, large networks mediating the activation and retrieval of verbal and imagistic representations were normally modulated in patients. However, unlike control subjects, patients failed to recruit the DLPFC, medial frontal and parietal cortices to incongruous (relative to congruous) sentences, and failed to recruit the DLPFC to concrete (relative to abstract) sentences.

CONCLUSIONS

As meaning is built from language, schizophrenia patients demonstrate a neuroanatomical dissociation in the modulation of temporal/inferior frontal cortices and the DLPFC.

Individual differences in psychotic effects of ketamine are predicted by brain function measured under placebo

The symptoms of major psychotic illness are diverse and vary widely across individuals. Furthermore, the prepsychotic phase is indistinct, providing little indication of the precise pattern of symptoms that may subsequently emerge. Likewise, although in some individuals who have affected family members the occurrence of disease may be predicted, the specific symptom profile may not. An important question, therefore, is whether predictive physiological markers of symptom expression can be identified. We conducted a placebo-controlled, within-subjects study in healthy individuals to investigate whether individual variability in baseline physiology, as assessed using functional magnetic resonance imaging, predicted psychosis elicited by the psychotomimetic drug ketamine and whether physiological change under drug reproduced those reported in patients. Here we show that brain responses to cognitive task demands under placebo predict the expression of psychotic phenomena after drug administration. Frontothalamic responses to a working memory task were associated with the tendency of subjects to experience negative symptoms under ketamine. Bilateral frontal responses to an attention task were also predictive of negative symptoms. Frontotemporal activations during language processing tasks were predictive of thought disorder and auditory illusory experiences. A subpsychotic dose of ketamine administered during a second scanning session resulted in increased basal ganglia and thalamic activation during the working memory task, paralleling previous reports in patients with schizophrenia. These results demonstrate precise and predictive brain markers for individual profiles of vulnerability to drug-induced psychosis.

Hippocampal dysfunction during free word association in male patients with schizophrenia

In schizophrenia, speech production deficits in patients with positive formal thought disorder (FTD e.g. loosening of associations and derailment) have been attributed to impairments in the semantic network. The brain area implicated in the retrieval of associated (i.e. relational) concepts is the hippocampus, a key region in the psychopathology of schizophrenia. However, its role in schizophrenic speech production and FTD in particular is yet little understood. To investigate the neural correlates of associative verbal retrieval, twelve patients with schizophrenia with varying degrees of FTD and twelve matched healthy control subjects underwent a free verbal association (FVA), a semantic (SVF) and a phonological verbal fluency (PVF) task while brain activity was measured with fMRI. The tasks varied in the relational binding operations needed for linking the stimulus to the respective response. Compared to control subjects, patients revealed attenuated left hippocampal activity during both semantic word generation tasks (FVA, SVF). Contrasting verbal fluency with FVA, a failure in recruiting the anterior cingulate gyrus emerged in the patient group. A negative correlation was found between right middle temporal activity and the severity of FTD during FVA. The hippocampus seems to play a major role in word generation. In schizophrenia, attenuated hippocampal activity during semantic tasks strengthens the hypothesis of impaired relational memory processes, affecting thought and language.

Future directions for examining semantic memory in schizophrenia spectrum disorders

Language abnormalities in schizophrenia are regarded as a hallmark of the disease. Clinical investigations provided accurate descriptions of the different manifestations of abnormal language use, and behavioral studies suggested several mechanisms that might contribute to these abnormalities. This review focuses on semantic memory dysfunction and, primarily, on functional methodologies such as ERP and fMRI that provide more direct measures of abnormal neural mechanisms related to language use in schizophrenia. In addition, the review points to future directions of study of the areas that received little attention thus far and whose investigation might contribute to a more detailed understanding of semantic memory dysfunction in schizophrenia.

Effect of retrieval effort and switching demand on fMRI activation during semantic word generation in schizophrenia

Verbal fluency deficits in schizophrenia are difficult to interpret because the tasks are multi-factorial and groups differ in total words generated. We manipulated retrieval and switching demands by requiring alternation between over-learned sequences in which retrieval is relatively automatic (OS) and semantic categories requiring increased retrieval effort (SC). Controlled processing was also manipulated by including switching and non-switching conditions, and formal thought disorder (FTD) was assessed with the communication disorders index (CDI). The OS/SC semantic fluency paradigm was administered during fMRI to 13 patients with schizophrenia and 14 matched controls. Images were acquired on a 3 Tesla Siemens scanner using compressed image acquisition to allow for cued overt word production. Subjects alternated between OS, SC, OS-switch, SC-switch, and baseline blocks. Images were pre-processed in SPM-2, and a two-stage random effects analysis tested within and between group contrasts. There were no group performance differences. fMRI analysis did not reveal any group differences during the OS non-switching condition. Both groups produced expected activation in bilateral prefrontal and inferior parietal regions. However, during the SC condition patients had greater activation than controls in left prefrontal, right anterior cingulate, right superior temporal, bilateral thalamus, and left parietal regions. There was also evidence of patient over-activation in prefrontal, superior temporal, superior parietal, and visual association areas when a switching component was added. FTD was negatively correlated with BOLD response in the right anterior cingulate, cuneus and superior frontal gyrus during increased retrieval demand, and positively correlated with fMRI activation in the left lingual gyrus, right fusiform gyrus and left superior parietal lobule during increased switching demand. These results indicate that patients are able to successfully perform effortful semantic fluency tasks during non-speeded conditions. When retrieval is relatively automatic there does not appear to be an effect of schizophrenia on fMRI response. However, when retrieval and controlled processing demands increase, patients have greater activation than controls despite unimpaired task performance. This inefficient BOLD response may explain why patients are slower and less accurate on standard self-paced fluency tasks.

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.

Brain activation mediates the association between structural abnormality and symptom severity in schizophrenia

Thought disorder is a symptom of schizophrenia expressed as disorganized or incoherent speech. Severity of thought disorder correlates with decreased left superior temporal gyrus grey matter volume and cortical activation in posterior temporal regions during the performance of language tasks. The goal of this study was to determine whether language-related activation mediates the association between thought disorder and left superior temporal lobe grey matter volume. 12 patients with schizophrenia were assessed for thought disorder. FMRI images were acquired for each subject while they listened to English speech, along with a high resolution structural image. Thought disorder was used as a covariate in the functional analysis to identify brain regions within which activation correlated with symptom severity. Voxel based morphometry was used to calculate grey matter volume of the planum temporale. A mediation model waste-tested using a four-step multiple regression approach incorporating cortical volume, functional activation and symptom severity. Thought disorder correlated with activation in a single cluster within the left posterior middle temporal gyrus during listening to speech. Grey matter volume within the planum temporale correlated significantly with severity of thought disorder and activation within the functional cluster. Regressing thought disorder on grey matter volume and BOLD response simultaneously led to a significant reduction in the correlation between grey matter volume and thought disorder. These results support the hypothesis that the association between decreased grey matter volume in the left planum temporale and severity of thought disorder is mediated by activation in the posterior temporal lobe during language processing.

An fMRI study of language processing in people at high genetic risk for schizophrenia

BACKGROUND

Abnormalities in language processing and the related brain structures have been reported in people with schizophrenia. It has been proposed that the brain pathways for language processing are anomalous in these individuals and form the underlying basis for the positive symptoms of the illness. If language pathway abnormalities can be detected early in people at high-risk for schizophrenia prior to the onset of symptoms, early treatment can ensue.

METHODS

Fifteen young adults at high genetic risk for developing schizophrenia were compared with 15 of their siblings with schizophrenia or schizoaffective disorder and 15 age and sex matched individuals at low risk for schizophrenia using a visual lexical decision task during fMRI. The data were analyzed by contrasting activation obtained during a real word-pseudoword discrimination task to activation obtained during a nonlinguistic discrimination task, and the differential activations were examined.

RESULTS

Patterns of brain activation while reading and discriminating between real and pseudowords differed across groups, with more bilateral activation in schizophrenia patients and their high-risk siblings than controls. In control subjects discrimination of words from psuedowords significantly activated Brodmann's area 44 more strongly than when non-linguistic symbols were discriminated. However, high-risk subjects and their siblings with schizophrenia activated this region similarly for both language and non-language tasks.

CONCLUSIONS

Normal individuals can be distinguished from subjects at high genetic risk for schizophrenia and patients with schizophrenia by their more lateralized and stronger activation of Brodmann's area 44 to word compared with symbol discrimination tasks. Thus, evaluation of language processing by fMRI may be a valuable tool for use in the prediction of individual risk for developing schizophrenia.

Elaborative verbal encoding and altered anterior parahippocampal activation in adolescents and young adults at genetic risk for schizophrenia using FMRI

BACKGROUND

First-degree relatives of persons with schizophrenia are at elevated risk for the illness, demonstrate deficits in verbal memory, and exhibit structural abnormalities in the medial temporal lobe (MTL). We used functional magnetic resonance imaging (fMRI) to assess brain activity in the MTL during novel and repeated word-pair encoding.

METHODS

Participants were 21 non-psychotic, first-degree relatives of persons with schizophrenia and 26 matched healthy controls (ages 13-28). fMRI signal change was measured using a Siemens 1.5T MR scanner, and data were analyzed using SPM-2. Verbal memory was assessed using the Miller Selfridge (MS) Context Memory test prior to scanning.

RESULTS

The groups were comparable on demographics, intelligence and post-scan word recognition. Relatives at genetic risk (GR) had significantly more psychopathology than controls and worse performance on the MS test (p < .05). GR participants exhibited greater repetition suppression of activation in the left and right anterior parahippocampus (PHA, in the region of the entorhinal cortex region), after controlling for possible confounders. Controls and GR participants with above-median MS performance showed significantly greater repetition suppression of activation in left inferior frontal gyrus than those scoring below the median.

CONCLUSIONS

This is the first study to demonstrate an alteration of brain activity in the PHA in persons at GR for schizophrenia.

Neural correlates of metaphor processing in schizophrenia

OBJECTIVE

A main feature of schizophrenic thought and language disturbance is concretism, the inability to understand the figurative meaning of proverbs and metaphors. Although this is routinely tested during clinical interview, its neural basis is unknown.

METHOD

We investigated processing of metaphoric sentences with functional magnetic resonance imaging (fMRI) in 12 patients with schizophrenia and 12 control subjects. Stimuli consisted of 60 novel short sentences with either metaphoric or literal meaning presented visually, intersparsed by a low level baseline (grey background). Subjects read these sentences silently and judged by button press whether they had a positive or negative connotation.

RESULTS

Reading metaphors in contrast to literal sentences revealed signal changes in the left inferior frontal gyrus in the control subjects (BA 45/47) and an area 3 cm dorsal to that in the patients (BA 45). Only activation in this area was negatively correlated with the severity of concretism rated with the PANSS. Comparison between groups for the contrast metaphors vs. low level baseline revealed stronger signal changes in the control group in the right superior/middle temporal gyrus (BA 39) and the left inferior frontal gyrus (BA 45) in the patients.

CONCLUSIONS

The results in the control subjects are in line with studies showing an involvement of the left inferior frontal and right lateral temporal cortex during context processing. Failure to recruit these areas in the patients may underlie schizophrenic concretism.