Thought Disorder in Schizophrenia: A Reappraisal of Older Formulations and an Overview of Some Recent Studies

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.

The Imbalanced Plasticity Hypothesis of Schizophrenia-Related Psychosis: A Predictive Perspective

A considerable number of studies have attempted to account for the psychotic aspects of schizophrenia in terms of the influential predictive coding (PC) hypothesis. We argue that the prediction-oriented perspective on schizophrenia-related psychosis may benefit from a mechanistic model that: 1) gives due weight to the extent to which alterations in short- and long-term synaptic plasticity determine the degree and the direction of the functional disruption that occurs in psychosis; and 2) addresses the distinction between the two central syndromes of psychosis in schizophrenia: disorganization and reality-distortion. To accomplish these goals, we propose the Imbalanced Plasticity Hypothesis - IPH, and demonstrate that it: 1) accounts for commonalities and differences between disorganization and reality distortion in terms of excessive (hyper) or insufficient (hypo) neuroplasticity, respectively; 2) provides distinct predictions in the cognitive and electrophysiological domains; and 3) is able to reconcile conflicting PC-oriented accounts of psychosis.

Structure in the stream of consciousness: Evidence from a verbalized thought protocol and automated text analytic methods

A key question about the spontaneous stream of thought (SST), often called the stream of consciousness, concerns its serial structure: How are thoughts in an extended sequence related to each other? In this study, we used a verbalized thought protocol to investigate "clump-and-jump" structure in SST-clusters of related thoughts about a topic followed by a jump to a new topic, in a repeating pattern. Several lines of evidence convergently supported the presence of clump-and-jump structure: high interrater agreement in identifying jumps, corroboration of rater-assigned jumps by automated text analytic methods, identification of clumps and jumps by a data-driven algorithm, and the inferred presence of clumps and jumps in unverbalized SST. We also found evidence that jumps involve a discontinuous shift in which a new clump is only modestly related to the previous one. These results illuminate serial structure in SST and invite research into the processes that generate the clump-and-jump pattern.

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.

Metaphor Comprehension in Schizophrenic Patients

People with schizophrenia often exhibit difficulties to comprehend figurative expressions, such as irony, proverbs, metaphors and idioms, with a general proneness to neglect the figurative meaning and to accept the more literal one. This inability is usually referred to as concretism and it constitutes a clinical manifestation of the broader language dysfunction called Formal Thought Disorder. The current review focuses on the neuropsychological and neuroanatomical underpinnings of schizophrenics’ misinterpretation of a subgroup of figurative expressions, i.e., metaphors. Metaphors are heterogeneous in nature, classifiable according to various criteria; for instance, metaphors can be conventional and familiar, or conversely, novel and unusual. These linguistic distinctions are substantial because the comprehension of the different types of metaphor entails partially different cognitive strategies and neural substrates. This review gathers studies that have directly investigated which neurocognitive deficits explain the inefficient comprehension of metaphor in schizophrenia. Several impairments have been put forward, such as general intelligence, executive functions and theory of mind deficits. Moreover, the neural correlates of metaphor comprehension in schizophrenia, like the left inferior/medial frontal gyrus and the temporal lobe, match those cortices affected by the neuropathology of schizophrenia. Even though the causal defective mechanism is still a matter of investigation, we provide an attempt to integrate existing findings.

Formal thought disorder in schizophrenia and bipolar disorder: A systematic review and meta-analysis

Historically, formal thought disorder has been considered as one of the distinctive symptoms of schizophrenia. However, research in last few decades suggested that there is a considerable clinical and neurobiological overlap between schizophrenia and bipolar disorder (BP). We conducted a meta-analysis of studies comparing positive (PTD) and negative formal thought disorder (NTD) in schizophrenia and BP. We included 19 studies comparing 715 schizophrenia and 474 BP patients. In the acute inpatient samples, there was no significant difference in the severity of PTD (d=-0.07, CI=-0.22-0.09) between schizophrenia and BP. In stable patients, schizophrenia was associated with increased PTD compared to BP (d=1.02, CI=0.35-1.70). NTD was significantly more severe (d=0.80, CI=0.52-0.1.08) in schizophrenia compared to BP. Our findings suggest that PTD is a shared feature of both schizophrenia and BP but persistent PTD or NTD can distinguish subgroups of schizophrenia from BP and schizophrenia patients with better clinical outcomes.

Inner Speech and Clarity of Self-Concept in Thought Disorder and Auditory-Verbal Hallucinations

Eighty patients and thirty controls were interviewed using one interview that promoted personal disclosure and another about everyday topics. Speech was scored using the Thought, Language and Communication scale (TLC). All participants completed the Self-Concept Clarity Scale (SCCS) and the Varieties of Inner Speech Questionnaire (VISQ). Patients scored lower than comparisons on the SCCS. Low scores were associated the disorganized dimension of TD. Patients also scored significantly higher on condensed and other people in inner speech, but not on dialogical or evaluative inner speech. The poverty of speech dimension of TD was associated with less dialogical inner speech, other people in inner speech, and less evaluative inner speech. Hallucinations were significantly associated with more other people in inner speech and evaluative inner speech. Clarity of self-concept and qualities of inner speech are differentially associated with dimensions of TD. The findings also support inner speech models of hallucinations.

Characterising receptive language processing in schizophrenia using word and sentence tasks

INTRODUCTION

Language dysfunction is proposed to relate to the speech disturbances in schizophrenia, which are more commonly referred to as formal thought disorder (FTD). Presently, language production deficits in schizophrenia are better characterised than language comprehension difficulties. This study thus aimed to examine three aspects of language comprehension in schizophrenia: (1) the role of lexical processing, (2) meaning attribution for words and sentences, and (3) the relationship between comprehension and production.

METHODS

Fifty-seven schizophrenia/schizoaffective disorder patients and 48 healthy controls completed a clinical assessment and three language tasks assessing word recognition, synonym identification, and sentence comprehension. Poorer patient performance was expected on the latter two tasks.

RESULTS

Recognition of word form was not impaired in schizophrenia, indicating intact lexical processing. Whereas single-word synonym identification was not significantly impaired, there was a tendency to attribute word meanings based on phonological similarity with increasing FTD severity. Importantly, there was a significant sentence comprehension deficit for processing deep structure, which correlated with FTD severity.

CONCLUSIONS

These findings established a receptive language deficit in schizophrenia at the syntactic level. There was also evidence for a relationship between some aspects of language comprehension and speech production/FTD. Apart from indicating language as another mechanism in FTD aetiology, the data also suggest that remediating language comprehension problems may be an avenue to pursue in alleviating FTD symptomatology.

Building a neurocognitive profile of thought disorder in schizophrenia using a standardized test battery

A core symptom of schizophrenia is thought disorder (TD). The cognitive abilities of semantic processing and executive function are argued to be etiologically linked to TD. However, there has been no comprehensive investigation of neurocognition in TD to date. The neurocognitive profile of 58 schizophrenia patients and 48 healthy controls was examined using the MATRICS Consensus Cognitive Battery and the D-KEFS Color-Word Interference Test. TD patients performed more poorly than non-TD patients on the cognitive domains of Verbal Learning and Inhibition, reflective of semantic and executive function respectively, confirming their critical roles over and above other cognitive deficits in schizophrenia.

Metaphor interpretation and use: a window into semantics in schizophrenia

The nature of putative semantic anomalies in schizophrenia is controversial. Metaphor interpretation and use provide a useful methodology with which to probe semantics since metaphors are critical in reasoning processes and in how conceptual knowledge is organized. The first study examined free speech for figurative language. The second study explored whether emotional versus non-emotional metaphorical language interpretation elicits differences in the tendencies to produce idiosyncratic (bizarre) or literal interpretations or use of other metaphors to describe the meaning of a metaphor. The third study examined the interpretation of time metaphors. We expected the time perspective in ambiguous sentences to be differentially influenced by previously presented unambiguous sentences of a specific perspective, either events moving relative to a stationary observer (moving-time) or an observer moving relative to a stationary event (moving-ego). First, we found that patients used a similar amount of figurative language as control participants. Second, we did not find any difference between the groups in terms of idiosyncratic interpretations, although patients did interpret more metaphors literally and controls utilized more figurative language. Third, we did not find evidence of a difference between the groups in terms of time perspectives influencing ambiguous target sentences differentially. As operationalized here, the interpretation and use of metaphors is similar in patients with schizophrenia to that of healthy control participants. To the extent that metaphors recruit semantic processes this area of cognition is generally intact in schizophrenia.

Schizophrenia, dissociation, and consciousness

Current thinking suggests that dissociation could be a significant comorbid diagnosis in a proportion of schizophrenic patients with a history of trauma. This potentially may explain the term "schizophrenia" in its original definition by Bleuler, as influenced by his clinical experience and personal view. Additionally, recent findings suggest a partial overlap between dissociative symptoms and the positive symptoms of schizophrenia, which could be explained by inhibitory deficits. In this context, the process of dissociation could serve as an important conceptual framework for understanding schizophrenia, which is supported by current neuroimaging studies and research of corollary discharges. These data indicate that the original conception of "split mind" may be relevant in an updated context. Finally, recent data suggest that the phenomenal aspects of dissociation and conscious disintegration could be related to underlying disruptions of connectivity patterns and neural integration.

Reinforcement ambiguity and novelty do not account for transitive inference deficits in schizophrenia

The capacity for transitive inference (TI), a form of relational memory organization, is impaired in schizophrenia patients. In order to disambiguate deficits in TI from the effects of ambiguous reinforcement history and novelty, 28 schizophrenia and 20 nonpsychiatric control subjects were tested on newly developed TI and non-TI tasks that were matched on these 2 variables. Schizophrenia patients performed significantly worse than controls on the TI task but were able to make equivalently difficult nontransitive judgments as well as controls. Neither novelty nor reinforcement ambiguity accounted for the selective deficit of the patients on the TI task. These findings implicate a disturbance in relational memory organization, likely subserved by hippocampal dysfunction, in the pathophysiology of schizophrenia.

Genetic variation in the schizophrenia-risk gene neuregulin 1 correlates with brain activation and impaired speech production in a verbal fluency task in healthy individuals

Impaired performance in verbal fluency tasks is an often replicated finding in schizophrenia. In functional neuroimaging studies, this dysfunction has been linked to signal changes in prefrontal and temporal areas. Since schizophrenia has a high heritability, it is of interest whether susceptibility genes for the disorder, such as NRG1, modulate verbal fluency performance and its neural correlates. Four hundred twenty-nine healthy individuals performed a semantic and a lexical verbal fluency task. A subsample of 85 subjects performed an overt semantic verbal fluency task while brain activation was measured with functional magnetic resonance imaging (MRI). NRG1 (SNP8NRG221533; rs35753505) status was determined and correlated with verbal fluency performance and brain activation. For the behavioral measure, there was a linear effect of NRG1 status on semantic but not on lexical verbal fluency. Performance decreased with number of risk-alleles. In the fMRI experiment, decreased activation in the left inferior frontal and the right middle temporal gyri as well as the anterior cingulate gyrus was correlated with the number of risk-alleles in the semantic verbal fluency task. NRG1 genotype does influence language production on a semantic level in conjunction with the underlying neural systems. These findings are in line with results of studies in schizophrenia and may explain some of the cognitive and brain activation variation found in the disorder. More generally, NRG1 might be one of several genes that influence semantic language capacities.

Clinical differences between late-onset and early-onset chronically hospitalized elderly schizophrenic patients in Taiwan

OBJECTIVES

To examine the clinical differences between late-onset schizophrenia (LOS) and early-onset schizophrenia (EOS) in Taiwanese elderly chronic hospitalized schizophrenic patients.

METHODS

By using a cross-sectional study method, we investigated all the hospitalized elderly schizophrenic patients in a general hospital's psychiatric ward during July-September 2007. All the subjects matched DSM-IV-TR diagnostic criteria and were aged 60 years or above. A total of 52 subjects were enrolled (LOS = 23, EOS = 29). Demographic data, illness history, and antipsychotic treatment record were documented; the positive and negative syndrome scale (PANSS), Center for Epidemiological Studies Depression scale (CES-D), mini-mental status examination (MMSE), activities of daily living rating scale for psychiatric patients (ADLRS), community self-sufficiency test (CST), clinical global impression (CGI), and general assessment of functioning scale (GAF) were administered.

RESULTS

In our samples, a lower educational level was found to be more common in late-onset patients. In LOS, there was no significant increase in the severity of PANSS psychopathology except for greater thought disorder symptoms. Both LOS and EOS patients had similar cognitive and functioning impairment with poor global outcomes. There was a trend of low antipsychotic drug use in LOS.

CONCLUSIONS

In Taiwan, elderly chronic inpatients LOS had greater thought disorders compared to findings in Western studies. Further large-scale longitudinal studies are needed to understand the factors related to these findings.

Chaos in schizophrenia associations, reality or metaphor?

There is evidence that schizophrenic associations display "chaotic", random-like behavior and decreased predictability. The evidence suggests a hypothesis that the "chaotic" mental disorganization could be explained within the concept of nonlinear dynamics and complexity in the brain that may cause chaotic neural organization. Testing of the hypothesis in the present study was performed using nonlinear analysis of bilateral electrodermal activity (EDA) during resting state and an association test in 56 schizophrenic patients and 44 healthy participants. EDA is a suitable measure of brain and autonomic activity reflecting neurobiological changes in schizophrenia that may indicate changes in nonlinear neural dynamics related to associative process. The results show that quantitative indices of chaotic dynamics (the largest Lyapunov exponents) calculated from EDA signals recorded during rest and the association test are significantly higher in schizophrenia patients than in the control group and increase during the test in comparison to the resting state. The difference was confirmed by statistical methods and using surrogate data testing that rejected an explanation within the linear statistical framework. The results provide supportive evidence that pseudo-randomness of schizophrenic associations and less predictability could be linked to increased complexity of nonlinear neural dynamics, although certain limitations in data interpretation must be taken into account.

ERP correlates of superordinate category activation

The human semantic network is hierarchically organized, containing superordinate, basic and subordinate levels. Various impairments are thought to be connected with abnormal access to superordinate concepts. We devised an ERP paradigm to examine the activation of superordinate versus otherwise related concepts in 20 healthy participants. Following the presentation of a typical category member an arrow indicated whether the appropriate superordinate category had to be generated (categorization task) or an otherwise related word (relation task). To control task execution, a second word was presented for which a match-mismatch-judgment was required. Reaction times, accuracy rates and ERPs after the second word showed that participants successfully accessed the superordinate category name and that verification in the categorization task was faster and easier than in the relation task. Comparison of ERPs after the arrow revealed topographical, Global Field Power (GFP), and onset latency differences between the two tasks and thus indicated the involvement of at least partially different neural generators. Source localization analysis confirmed that brain regions were activated that were also identified in previous experiments with semantic task. The paradigm seems to be suitable for further examination of superordinate activation processes and evaluation of impairments such as thought disorders in schizophrenic patients.

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.

Confabulation in schizophrenia and its relationship to clinical and neuropsychological features of the disorder

BACKGROUND

A form of confabulation has been documented in schizophrenia and appears to be related to the symptom of thought disorder. It is unclear whether it is associated with the same pattern of neuropsychological deficits as confabulation in neurological patients.

METHOD

Thirty-four patients with chronic schizophrenia, including those with and without thought disorder, and 17 healthy controls were given a fable recall task to elicit confabulation. They were also examined on a range of executive, episodic and semantic memory tests.

RESULTS

Confabulation was seen at a significantly higher rate in the schizophrenic patients than the controls, and predominated in those with thought disorder. Neuropsychologically, it was not a function of general intellectual impairment, and was not clearly related to episodic memory or executive impairment. However, there were indications of an association with semantic memory impairment.

CONCLUSIONS

The findings support the existence of a form of confabulation in schizophrenia that is related to thought disorder and has a different neuropsychological signature to the neurological form of the symptom.

A neural plasticity perspective on the schizophrenic condition

Imbalanced plasticity of neural networks in the brain is proposed to underlie deficits in the integration of efferent and afferent processes in schizophrenia. These deficits affect the priming of the behavior implementing systems by prior knowledge, and thus impair both controlled regulation and automatic activation of mental and motor processes. The sense of self as a distinct entity can consequently be undermined. In predominantly reality-distorting patients, hypo-plasticity of neural connectivity may cause the emergence of highly focused but inflexible patterns of activation in their representation and response systems. This may lead to dominance of prepotent patterns of activity in these systems and a relative inability of higher control systems to bias lower level activity towards congruence with the ongoing cognitive and motor context. By contrast, predominantly disorganized patients are characterized by hyper-plastic connectivity. This leads to a weakening of prepotent response tendencies but also, as in reality-distorting patients, to less effective top-down contextual constraining.

Formal thought disorder is characterised by impaired lexical access

Recent studies have proposed that difficulty with accessing the lexical-semantic memory store may underpin some of the specific linguistic problems associated with formal thought disorder (FTD). We examined the consistency of name retrieval as an indicator of the ability to access lexical-semantic knowledge in patients with and without marked FTD to see if problems are specific to the former or common to schizophrenic patients in general. A graded naming test was administered on two separate occasions 8-16 weeks apart to 48 participants in three groups: 16 schizophrenic patients with high ratings of FTD, 16 schizophrenic patients with low ratings of FTD and 16 healthy controls. We compared the groups for naming consistency across time and the relationship between naming consistency and specific symptoms of FTD. Both patient groups had impaired naming and this was significantly greater in high than low FTD patients. The high FTD patients showed a profile that differed from both low FTD patients and healthy controls insofar as their naming was inconsistent across time, characteristic of an access disorder. Specifically, the FTD symptoms of derailment, tangentality and incoherence were related to the ability to access the lexical-semantic store. In conclusion, most patients with schizophrenia show an impaired semantic memory store. Nevertheless, FTD is associated with additional lexical-semantic difficulties that are quantitatively different to those seen in patients without FTD, and which may reflect disorganized semantic access.

Madness explained: Why we must reject the Kraepelinian paradigm and replace it with a ‘complaint-orientated’ approach to understanding mental illness

This article is a synopsis of the argument outlined in my book Madness explained: Psychosis and human nature, in which I describe a new paradigm (which might be called a 'complaint-orientated' approach) for understanding the psychotic disorders, the most disabling forms of psychiatric illness. Despite extensive efforts to study the genetics, pathophysiology and neuropsychology of the psychoses, replicable findings have been rare. I argue that this is because the phenomena concerned have been poorly defined. Since the end of the 19th century, research into the psychoses has been dominated by the system of classification first proposed by the German psychiatrist Emil Kraepelin, which assumes that the severe mental illnesses fall into discrete types such as 'schizophrenia' and 'manic depression', and that there is a clear dividing line between madness and normal functioning. However, Kraepelinian diagnoses fail all empirical tests of their validity. For example, they do not identify patients with common symptoms, with common aetiologies, who respond to specific treatments. I suggest that we therefore need to abandon psychiatric diagnoses altogether and must instead attempt to explain the specific complaints ('symptoms') that patients bring to our attention. These include hallucinations, delusional beliefs, thought and communication disorders, which are much more widely experienced than was previously thought (for example, about 10% of the population have experienced hallucinations). I show that recent psychological research has revealed much about the mechanisms underlying each of these complaints. For example, auditory hallucinations occur when the individual mistakes inner speech for an external stimulus, and delusions appear to be the product of abnormal inferential processes. The new approach has implications for aetiology. For example, researchers working within the Kraepelinian paradigm have often assumed that the psychoses are endogenous. However, there is compelling evidence that the risk of experiencing psychotic complaints is influenced by adverse environmental factors such as insecure attachment relations and exposure to sexual and other kinds of trauma. These associations are relatively easy to understand once the psychological mechanisms leading to specific complaints are known. When all of the psychotic complaints have been explained, there will be no 'schizophrenia' or 'manic depression' left behind awaiting explanation. The approach that I advocate is not only more scientific than the Kraepelinian approach, but also more humane. In contrast to the Kraepelinian approach, which has encouraged disrespect for patients' experiences, it encourages us to treat patients as rational agents and to take what they say seriously.

Schizophrenia: the quest for a minimum sense of identity to ward off delusional disorder

OBJECTIVE

This study was designed to analyze the language of patients with schizophrenia exhibiting negative symptoms during a 3-month period.

METHOD

The computer-assisted ALCESTE method was used to simultaneously analyze the subjects' oral behaviour and speech patterns at various levels.

RESULTS

The tested subjects had very specific speech patterns. Most significantly, analysis of the underlying syntactic processes showed that the patients exhibited a sense of identity, however minimum, based on their own pathologies and on the surrounding world. In our previous study, no such characteristics were observed in the discourse of schizophrenia patients with delusions (exhibiting positive symptoms). This suggests that the minimum sense of identity that develops in patients with schizophrenia allows them to avoid positive symptoms.

CONCLUSION

In studies of language production by subjects suffering from schizophrenia, it is necessary to distinguish between patients with positive symptoms and those with negative symptoms. The speech patterns of these 2 groups have to be analyzed separately, which has not been done previously, since the groups differ in too many respects.

Recognition of metaphor and irony in young adults: the impact of schizotypal personality traits

Patients with schizophrenia demonstrate two dissociable impairments of pragmatic language comprehension: (1) an insensitivity to irony, which is associated with poor theory-of-mind (i.e. a difficulty with inferring other people's thoughts); and (2) poor recognition of metaphors, which may reflect degraded semantics. This study investigated whether non-clinical high-schizotypal adults show similar impairments of pragmatic language. Thirty-six university students completed the Raine Schizotypal Personality Questionnaire, the Wechsler Memory Scale Logical-Memories subtest, Raven's Progressive Matrices and a story comprehension task that tested the ability to discriminate between incongruous statements and appropriate uses of ironical, metaphorical or literal speech. Counter to the pattern found for patients, high-schizotypal adults were just as capable as low-schizotypal adults of identifying appropriate metaphors, suggesting a discontinuity between schizophrenia and schizotypy for the metaphor-recognition problem. This study's finding of intact metaphor recognition in high-schizotypal adults contrasts with previous findings of poor proverb comprehension in these individuals and is interpreted in terms of different semantic processes required for recognizing and interpreting metaphors. Consistent with the pattern found for patients, high-schizotypal adults were significantly impaired in their ability to appreciate when a literally contradictory utterance could be interpreted as ironical, suggesting continuity between schizophrenia and schizotypy for the irony-appreciation problem.

Thought disorder in schizophrenia: working memory and impaired context

This research was designed to provide data on whether thought disorder in schizophrenia patients is due to difficulty in holding external stimuli or the external context online in working memory. We assessed 231 early phase acute inpatients, including 68 schizophrenic patients and 38 bipolar manic patients. Patients were administered a thought disorder test that requires holding stimuli online in working memory as they respond and another in which the stimuli is in direct view of the patients throughout the test procedure. The results indicated that patients who were thought disordered on the test requiring holding the external stimuli online in memory also were more thought disordered on the test that provides full vision of the stimuli throughout the testing (p < 0.001). Thus, schizophrenia patients vulnerable to thought disorder show thought disorder regardless of whether or not they are required to hold the stimuli online in memory. Overall, the data did not support the formulation that thought disorder is primarily a consequence of failure to hold external stimuli or contextual material online in working memory. An alternate view of thought disorder is presented.

Scaling and clustering in the study of semantic disruptions in patients with schizophrenia: a re-evaluation

Some recent studies of semantics in schizophrenia have employed multidimensional scaling and clustering techniques to analyse verbal fluency and triadic comparison data. The conclusions have been: (i) patients generate fewer words in fluency tasks and display more variable similarity groupings of words in triadic tasks, and (ii) this is due to deficits in semantics. We analysed data from both tasks. On the verbal fluency task, patients produced significantly fewer responses than controls. The results also showed little patient-specific inter-individual consistency. Similarly, for triadic comparison data, we did not find much patient-specific inter-individual consistency. When correlating patients' results at different measurement times with means of controls, the data of individual patients (at either of the two measurement times) were not predicted better from their data at the other measurement time than from controls. This latter finding suggests little patient-specific intra-individual consistency and, thus, pleads against idiosyncratic semantic deficits. Our findings do not refute the hypothesis that schizophrenia is associated with semantic disruptions. However, our results demonstrate that because of severe statistical restrictions and requirements associated with some scaling and clustering techniques, these methods may not be as useful in this enterprise as previously thought.

The neurochemical hypothesis of 'theory of mind'

This paper aims to explore the neurochemical basis of the ability to represent one's own or other's mental states such as intentions, beliefs, wants and knowledge, an ability often referred to as 'theory of mind'. Based on neurochemical and psychopharmacological investigations in autism and schizophrenia, pathologies in which this ability is impaired, it is hypothesized that 'theory of mind' abilities are contingent on the integrity of the serotonergic and dopaminergic system. This hypothesis is discussed in light of the system's neurochemical properties and role in cognition. It is suggested that specific abnormalities to this system can account for differences in the profile of 'theory of mind' impairments that may exist among patients belonging to different pathologies.

Cerebral correlates of selective attention in schizophrenic patients with formal thought disorder: a controlled H2 15O-PET study

There is a widespread belief that formal thought disorders may be associated with disturbed selective attention in schizophrenia. Two hypotheses are derived: (1) patients with slightly pronounced formal thought disorders should differ from those with severely expressed formal thought disorders in terms of selective attention; and (2) the cerebral correlates of selective attention should be organised differently in mildly versus severely thought-disordered patients. We compared 20 female schizophrenic patients, one-half with mild, one-half with obvious formal thought disorders, and 10 control subjects on a neuropsychological battery and a cognitive activation task for selective attention (Go/NoGo) for the assessment of rCBF using H2 15O-PET. While the first hypothesis has not been confirmed, we found that the cerebral regions activated by selective attention in the two patient groups showed completely differing organisations. Low degrees of formal thought disorders were associated with significant activations in frontal superior gyrus and ventral anterior thalamic nucleus whereas high degrees of formal thought disorders were accompanied by significant activations in fusiform gyrus and precuneus. We suggest that differing task-solving strategies are applied by both clinical subgroups to achieve comparable results on the selective attention paradigm.

Cognitive neuropsychiatry: towards a scientific psychopathology

Cognitive neuropsychiatry represents a systematic and theoretically driven approach to explain clinical psychopathologies in terms of deficits to normal cognitive mechanisms. A concern with the neural substrates of impaired cognitive mechanisms links cognitive neuropsychiatry to the basic neurosciences. The emergence of cognitive neuropsychiatry in the 1990s illustrates the growing rapprochement between cognitive neuropsychology, clinical medicine and the neurosciences in addressing common questions about disorders of the mind/brain. In reviewing recent applications, we highlight how this hybrid discipline will make a distinctive contribution to the science of psychopathology.

The effects of psychoactive drugs and neuroleptics on language in normal subjects and schizophrenic patients: a review

The aim of this survey is to present an overview of research into psychopharmacology as regards the effects of different psychoactive drugs and neuroleptics (NL) on language in normal subjects and schizophrenic patients. Eighteen studies that have investigated the effects of different drugs (alcohol, amphetamines, secobarbital, L-dopa, psilocybin, ketamine, fenfluramine) and neuroleptics (conventional and atypical) on language are reviewed. There are no studies concerning the effects of neuroleptics on language in healthy subjects. The results of the effects of other molecules indicate that language production can be increased (alcohol, amphetamine, secobarbital), rendered more complex (d-amphetamine), more focused (L-dopa) or more unfocused (psilocybin) and clearly impaired (ketamine). For schizophrenic patients, most studies show that conventional neuroleptic treatments, at a therapeutic dosage and in acute or chronic mode, reduce language disorders at all levels (clinic, linguistic, psycholinguistic). In conjunction with other molecules, the classical NL, when administered at a moderate dosage and in chronic mode, modify language in schizophrenia, either by improving the verbal flow and reducing pauses and positive thought disorder (NL + amphetamine) or by inducing an impairment in the language measurements (NL + fenfluramine). Clinical, methodological and theoretical considerations of results are debated in the framework of schizophrenic language disorders.