Making sense of sentences in schizophrenia: Electrophysiological evidence for abnormal interactions between semantic and syntactic processing

The influence of social knowledge structures on hostile attribution bias in aggressive and nonaggressive individuals: An ERP study

According to several social-cognitive models, social knowledge structures described as hostile scripts or schemas may explain why aggressive individuals are prone to attribute hostile intention to others' ambiguous behaviors, a cognitive bias called hostile attribution bias (HAB). The aggression-related concepts in aggressive individuals' semantic memory would be highly accessible, notably through the activation of hostile concepts in nonhostile social contexts, and such an activation would result in HAB. The aim of the study was to test this hypothesis using the N400 component with EEG measurements to assess objectively, in real time, the violation of hostile expectations following a nonhostile situation. To this end, scenarios with a clear nonhostile context (mismatch condition) vs. without nonhostile context (match condition) followed by a character's ambiguous provocative behavior were presented to readers, and ERPs to critical words that specified the hostile intent behind the behavior were analysed. Twelve aggressive and twelve nonaggressive individuals participated in the study. The presentation of a critical word (hostile intent) that violated nonhostile expectation caused an N400 response among nonaggressive whereas such an N400 effect was absent in aggressive individuals. The results suggest that, in nonaggressive individuals, a nonhostile social context activates nonhostile concepts, whereas in the same context, aggressive individuals activate nonhostile as well as hostile concepts. Numerous research applications of the Hostile Expectancy Violation paradigm in the field of HAB are discussed.

Processing of complex morphosyntactic structures in French: ERP evidence from native speakers

This event-related brain potentials (ERP) study investigated the neurocognitive mechanisms underlying the auditory processing of verbal complexity in French illustrated by the prescriptive present subjunctive mode. Using a violation paradigm, ERPs of 32 French native speakers were continuously recorded while they listened to 200 ecological French sentences selected from the INTEFRA oral corpus (2006). Participants performed an offline acceptability judgement task on each sentence, half of which contained a correct present subjunctive verbal agreement (reçoive) and the other half an incorrect present indicative one (peut). Critically, the present subjunctive mode was triggered either by verbs (Ma mère desire que j'apprenneMy mother wants me to learn) or by subordinating conjunctions (Pour qu'elle reçoiveSo that she receives). We found a delayed anterior negativity (AN) due to the length of the verbal forms and a P600 that were larger for incongruent than for congruent verbal agreement in the same time window. While the two effects were left lateralized for subordinating conjunctions, they were right lateralized for both structures with a larger effect for subordinating conjunctions than for verbs. Moreover, our data revealed that the AN/P600 pattern was larger in late position than in early ones. Taken together, these results suggest that morphosyntactic complexity conveyed by the French subjunctive involves at least two neurocognitive processes thought to support an initial morphosyntactic analysis (AN) and a syntactic revision and repair (posterior P600). These two processes may be modulated as a function of both the element (i.e., subordinating conjunction vs verb) that triggers the subjunctive mode and the moment at which this element is used while sentence processing.

Finding normal-to-better neurocognitive indexes in individuals with schizotypal traits using a social role task

Schizophrenia patients make more errors and have longer reaction times (RTs) than healthy controls in most cognitive tasks. Deficits are also observed in subclinical participants having high scores on the schizotypal personality questionnaire (SPQ). They are accompanied by smaller amplitudes of the event-related brain potentials (ERPs) that index attention and semantic- and working-memory. These functions are thus thought to be impaired in individuals having various schizophrenia attributes (SzAs). Nevertheless, normal RTs were recently found in SzAs during a particular self-referential task where half of the stimuli were names of extraordinary social roles (e.g., genius). Each name (ordinary or extraordinary) was presented individually, and participants were asked to decide whether or not they would consider themselves performing the role at any moment of their lives. To further test an absence of cognitive deficits in this task, the ERPs elicited by names of social roles were also examined in 175 healthy participants. The absence of longer RTs in high- than in low-SPQs was replicated. Moreover, the ERPs of high SPQs had larger occipital N1s, larger P2s and larger occipital N400s than those of low SPQs while late positive potentials (LPPs) were of similar amplitudes. Such results are consistent with clinical observations of greater attention and faster processing of stimuli related to extraordinary/delusional beliefs. Further studies should test whether the cognitive deficits found in SzAs are due to the use of tasks and stimuli that are less within their focus of interest than within that of healthy controls.

Agency of Subjects and Eye Movements in Schizophrenia Spectrum Disorders

People with schizophrenia spectrum disorders (SSD) show anomalies in language processing with respect to "who is doing what" in an action. This linguistic behavior is suggestive of an atypical representation of the formal concepts of "Agent" in the lexical representation of a verb, i.e., its thematic grid. To test this hypothesis, we administered a silent-reading task with sentences including a semantic violation of the animacy trait of the grammatical subject to 30 people with SSD and 30 healthy control participants (HCs). When the anomalous grammatical subject was the Agent of the event, a significant increase of Gaze Duration was observed in HCs, but not in SSDs. Conversely, when the anomalous subject was a Theme, SSDs displayed an increased probability of go-back movements, unlike HCs. These results are suggestive of a higher tolerability for anomalous Agents in SSD compared to the normal population. The fact that SSD participants did not show a similar tolerability for anomalous Themes rules out the issue of an attention deficit. We suggest that general communication abilities in SSD might benefit from explicit training on deep linguistic structures.

Processing Argument Structure and Syntactic Complexity in People with Schizophrenia Spectrum Disorders

INTRODUCTION

Deficits in language comprehension and production have been repeatedly observed in Schizophrenia Spectrum Disorders (SSD). However, the characterization of the language profile of this population is far from complete, and the relationship between language deficits, impaired thinking and cognitive functions is widely debated.

OBJECTIVE

The aims of the present study were to assess production and comprehension of verbs with different argument structures, as well as production and comprehension of sentences with canonical and non-canonical word order in people with SSD. In addition, the study investigated the relationship between language deficits and cognitive functions.

METHODS

Thirty-four participants with a diagnosis of SSD and a group of healthy control participants (HC) were recruited and evaluated using the Italian version of the Northwestern Assessment of Verbs and Sentences (NAVS, Cho-Reyes & Thompson, 2012; Barbieri et al., 2019).

RESULTS

Results showed that participants with SSD were impaired - compared to HC - on both verb and sentence production, as well as on comprehension of syntactically complex (but not simple) sentences. While verb production was equally affected by verb-argument structure complexity in both SSD and HC, sentence comprehension was disproportionately more affected by syntactic complexity in SSD than in HC. In addition, in the SSD group, verb production deficits were predicted by performance on a measure of visual attention, while sentence production and comprehension deficits were explained by performance on measures of executive functions and working memory, respectively.

DISCUSSION

Our findings support the hypothesis that language deficits in SSD may be one aspect of a more generalized, multi-domain, cognitive impairment, and are consistent with previous findings pointing to reduced inter- and intra-hemispheric connectivity as a possible substrate for such deficits. The study provides a systematic characterization of lexical and syntactic deficits in SSD and demonstrates that psycholinguistically-based assessment tools may be able to capture language deficits in this population.

Semantic priming and neurobiology in schizophrenia: A theoretical review

In this theoretical review we bridge the cognitive and neurobiological sciences to shed light on the neurocognitive foundations of the semantic priming effect in schizophrenia. We review and theoretically evaluate the neurotransmitter systems (dopaminergic, GABAergic and glutamatergic) and neurobiological underpinnings of behavioural and electrophysiological (N400) semantic priming in the pathology, and the main hypotheses on their geneses: a disinhibition of the semantic spread of activation, a disorganised semantic storage or noisy lexical-semantic associations, a psychomotor artefact, an artefact of relatedness proportions, or an inability to mobilise contextual information. We further assess the literature on the endophenotype of Formal Thought Disorder from multiple standpoints, ranging from neurophysiology to cognition: considerations are weaved on neuronal (PV basket cell, SST, VIP) and receptor deficits (DRD1, NMDA), neurotransmitter imbalances (dopamine), cortical and dopaminergic lateralisation, inter alia. In conclusion, we put forth novel postulates on the underlying causes of controlled hypopriming, automatic hyperpriming, N400 reversals (larger amplitudes for close associations), indirect versus direct hyperpriming, and the endophenotype of lexical-semantic disturbances in schizophrenia.

The effects of the activation of hostile and non-hostile schemas on intent attribution processes in non-aggressive individuals: An ERP study

We investigated the influences of hostile and non-hostile schemas activations in non-aggressive individuals on their intent attribution processes in various social contexts. 38 non-aggressive participants were randomly assigned to one of two groups, one primed with negative words, to be conditioned as temporarily hostile (TH), and the other with positive words, be conditioned as temporarily non-hostile (TNH). They were asked to read social scenarios composed of positive or negative behaviors of others whose intentions are ambiguous followed by a disambiguation of others' real intentions (hostile vs non-hostile) behind their behaviors. Neural activity related to spontaneous intent attribution processes was measured using electroencephalography (EEG). The results showed that when non-hostile intentions were revealed following ambiguous-negative behaviors of others, the N400 effect was observed only in the TH group. Similarly, when hostile intentions were revealed following ambiguous-positive behaviors of others, the N400 effect was observed only in the TNH group. In other words, non-aggressive individuals were led to attribute either hostile or non-hostile intentions to the same ambiguous behaviors of others depending on which concepts or thoughts (hostile vs non hostile) were activated and accessible in memory by priming at the time of social interactions.

Language Dysfunction in Schizophrenia: Assessing Neural Tracking to Characterize the Underlying Disorder(s)?

Deficits in language production and comprehension are characteristic of schizophrenia. To date, it remains unclear whether these deficits arise from dysfunctional linguistic knowledge, or dysfunctional predictions derived from the linguistic context. Alternatively, the deficits could be a result of dysfunctional neural tracking of auditory information resulting in decreased auditory information fidelity and even distorted information. Here, we discuss possible ways for clinical neuroscientists to employ neural tracking methodology to independently characterize deficiencies on the auditory-sensory and abstract linguistic levels. This might lead to a mechanistic understanding of the deficits underlying language related disorder(s) in schizophrenia. We propose to combine naturalistic stimulation, measures of speech-brain synchronization, and computational modeling of abstract linguistic knowledge and predictions. These independent but likely interacting assessments may be exploited for an objective and differential diagnosis of schizophrenia, as well as a better understanding of the disorder on the functional level-illustrating the potential of neural tracking methodology as translational tool in a range of psychotic populations.

Spared bottom-up but impaired top-down interactive effects during naturalistic language processing in schizophrenia: evidence from the visual-world paradigm

BACKGROUND

People with schizophrenia process language in unusual ways, but the causes of these abnormalities are unclear. In particular, it has proven difficult to empirically disentangle explanations based on impairments in the top-down processing of higher level information from those based on the bottom-up processing of lower level information.

METHODS

To distinguish these accounts, we used visual-world eye tracking, a paradigm that measures spoken language processing during real-world interactions. Participants listened to and then acted out syntactically ambiguous spoken instructions (e.g. 'tickle the frog with the feather', which could either specify how to tickle a frog, or which frog to tickle). We contrasted how 24 people with schizophrenia and 24 demographically matched controls used two types of lower level information (prosody and lexical representations) and two types of higher level information (pragmatic and discourse-level representations) to resolve the ambiguous meanings of these instructions. Eye tracking allowed us to assess how participants arrived at their interpretation in real time, while recordings of participants' actions measured how they ultimately interpreted the instructions.

RESULTS

We found a striking dissociation in participants' eye movements: the two groups were similarly adept at using lower level information to immediately constrain their interpretations of the instructions, but only controls showed evidence of fast top-down use of higher level information. People with schizophrenia, nonetheless, did eventually reach the same interpretations as controls.

CONCLUSIONS

These data suggest that language abnormalities in schizophrenia partially result from a failure to use higher level information in a top-down fashion, to constrain the interpretation of language as it unfolds in real time.

Language comprehension and neurocognition independently and concurrently contribute to formal thought disorder severity in schizophrenia

Formal thought disorder (FTD) in schizophrenia is a prevalent symptom that has a significant impact on patients but low remediation options. This is largely due to a still unclear aetiology, where both neurocognitive and language dysfunction have been shown to contribute. Given established relationships between neurocognition and language themselves, this study aimed to examine if language comprehension impairments have a significant effect on FTD severity independent of neurocognition. 54 schizophrenia/schizoaffective disorder patients (M = 43.35, SD = 10.74) completed three measures of language comprehension along with the MATRICS Consensus Cognitive Battery and the D-KEFS Colour Word Interference Test. Symptomatology was assessed using the Positive and Negative Symptom Scale and the Scale for the Assessment of Thought, Language and Communication. Hierarchical linear regression analyses revealed syntactic sentence processing had a significant, and independent, contribution to positive FTD severity above neurocognition, while semantic sentence processing and single word semantic processing did not. The findings support the existence of a specific relationship between language comprehension dysfunction and FTD; however the question of generalisation to all aspects of language processing or FTD types needs further investigation. The establishment of a specific language-related impairment in schizophrenia which contributes independently to FTD severity supports the benefit of language-based remediation approaches for alleviating FTD symptoms and their effects. Clinical, aetiological and nosological implications of the results are discussed.

Multimodal neuroimaging evidence for looser lexico-semantic networks in schizophrenia:Evidence from masked indirect semantic priming

It has been hypothesized that schizophrenia is characterized by overly broad automatic activity within lexico-semantic networks. We used two complementary neuroimaging techniques, Magnetoencephalography (MEG) and functional Magnetic Resonance Imaging (fMRI), in combination with a highly automatic indirect semantic priming paradigm, to spatiotemporally localize this abnormality in the brain. Eighteen people with schizophrenia and 20 demographically-matched control participants viewed target words ("bell") preceded by directly related ("church"), indirectly related ("priest"), or unrelated ("hammer") prime words in MEG and fMRI sessions. To minimize top-down processing, the prime was masked, the target appeared only 140 ms after prime onset, and participants simply monitored for words within a particular semantic category that appeared in filler trials. Both techniques revealed a significantly larger automatic indirect priming effect in people with schizophrenia than in control participants. MEG temporally localized this enhanced effect to the N400 time window (300-500 ms) - the critical stage of accessing meaning from words. fMRI spatially localized the effect to the left temporal fusiform cortex, which plays a role in mapping of orthographic word-form on to meaning. There was no evidence of an enhanced automatic direct semantic priming effect in the schizophrenia group. These findings provide converging neural evidence for abnormally broad highly automatic lexico-semantic activity in schizophrenia. We argue that, rather than arising from an unconstrained spread of automatic activation across semantic memory, this broader automatic lexico-semantic activity stems from looser mappings between the form and meaning of words.

The Effect of Emotional State on the Processing of Morphosyntactic and Semantic Reversal Anomalies in Japanese: Evidence from Event-Related Brain Potentials

The present study examined the locus responsible for the effect of emotional state on sentence processing in healthy native speakers of Japanese, using event-related brain potentials. The participants were induced into a happy, neutral, or sad mood and then subjected to electroencephalogram recording during which emotionally neutral sentences, including grammatical sentences (e.g. window-NOM close vi, 'The window closes.'), morphosyntactically-violated sentences (e.g. window-ACC close vi, Lit. 'Close the window.'), and semantically-reversed sentences (e.g. window-NOM close vt, 'The window closes pro.') were presented. The results of the ERP experiment demonstrated that while the P600 effect elicited by morphosyntactic violation was not modulated by mood, the P600 effect elicited by semantic reversal anomaly was observed only in participants previously induced into a happy mood. The LAN and N400 were not sensitive to the participants' transient emotional state. These results suggest intact memory access and impaired integration of syntactic and semantic information in individuals in a sad mood.

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.

P600 alteration of syntactic language processing in patients with bipolar mania: Comparison to schizophrenic patients and healthy subjects

BACKGROUND

Disturbances in thought, speech, and linguistic processing are frequently observed in bipolar manic patients, but the underlying neurophysiological mechanisms are not well understood. P600 is a distinct, positive event-related potential component elicited by syntactic violations. Using the P600 ERP, we examined neural processing of syntactic language comprehension in patients with bipolar mania compared to patients with schizophrenia and healthy people.

METHOD

P600s were recorded from 21 manic patients with bipolar disorder, 26 patients with schizophrenia, and 29 healthy subjects during the presentation of 120 auditory sentences with syntactic violations or non-violations. Subjects were asked to judge whether each sentence was correct or incorrect.

RESULTS

Patients with mania and schizophrenia had significantly smaller P600 amplitudes associated with syntactic violations compared with healthy subjects. There was no difference in P600 amplitude between patient groups. For behavioral performance, patients with schizophrenia had significantly less accurate rates and longer reaction times compared with healthy subjects, whereas manic patients exhibited no significant differences in accuracy and only showed increased reaction times in comparison with healthy subjects.

LIMITATIONS

Psychotropic drug usage and small sample size.

CONCLUSION

Patients with bipolar mania have reduced P600 amplitude, comparable to patients with schizophrenia. Our findings may represent the first neurophysiological evidence of abnormal syntactic linguistic processing in bipolar mania.

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.

Is the comprehension of idiomatic sentences indeed impaired in paranoid Schizophrenia? A window into semantic processing deficits

Schizophrenia patients have been reported to be more impaired in comprehending non-literal than literal language since early studies on proverbs. Preference for literal rather than figurative interpretations continues to be documented. The main aim of this study was to establish whether patients are indeed able to use combinatorial semantic processing to comprehend literal sentences and both combinatorial analysis, and retrieval of pre-stored meanings to comprehend idiomatic sentences. The study employed a sentence continuation task in which subjects were asked to decide whether a target word was a sensible continuation of a previous sentence fragment to investigate idiomatic and literal sentence comprehension in patients with paranoid schizophrenia. Patients and healthy controls were faster in accepting sensible continuations than in rejecting non-sensible ones in both literal and idiomatic sentences. Patients were as accurate as controls in comprehending literal and idiomatic sentences, but they were overall slower than controls in all conditions. Once the contribution of cognitive covariates was partialled out, the response times (RTs) to sensible idiomatic continuations of patients did not significantly differ from those of controls. This suggests that the state of residual schizophrenia did not contribute to slower processing of sensible idioms above and beyond the cognitive deficits that are typically associated with schizophrenia.

Verbatim recall in formal thought disorder in schizophrenia: a study of contextual influences

INTRODUCTION

We have previously reported that people with schizophrenia and formal thought disorder (FTD) were disproportionately impaired in recalling sentences verbatim and in judging their plausibility. We proposed that these deficits were due to impairment in integrating higher-order semantic information to construct a global whole. However, it is also possible that a lower-level linguistic problem affecting lexical activation could account for this pattern.

METHODS

The present study analysed and compared the sentence repetition errors produced by people with FTD, people with schizophrenia who were non-FTD and healthy controls. Errors due to failure of activation of the target lexical items were differentiated from those due to erroneous integration of information.

RESULTS

People with FTD produced significantly more unrelated lexical substitutions and omissions in their corpora than the other two groups, indicating an impairment of activation. In addition, they made significantly more erroneous contextual inferences and unrelated references, suggesting they were impaired in reconstructing the global whole from successfully activated items.

CONCLUSION

These findings are consistent with a dual process account of impairments in FTD. Difficulties in repeating and judging sentence acceptability arises due to a combination of difficulty with activation and deficits in using linguistic context to process and produce speech. It is suggested that processing difficulties in FTD result from an impairment in using semantic context to drive lexical access and construction of a global whole.

Abnormal dynamics of language in schizophrenia

Language could be conceptualized as a dynamic system that includes multiple interactive levels (sub-lexical, lexical, sentence, and discourse) and components (phonology, semantics, and syntax). In schizophrenia, abnormalities are observed at all language elements (levels and components) but the dynamic between these elements remains unclear. We hypothesize that the dynamics between language elements in schizophrenia is abnormal and explore how this dynamic is altered. We, first, investigated language elements with comparable procedures in patients and healthy controls. Second, using measures of reaction time, we performed multiple linear regression analyses to evaluate the inter-relationships among language elements and the effect of group on these relationships. Patients significantly differed from controls with respect to sub-lexical/lexical, lexical/sentence, and sentence/discourse regression coefficients. The intercepts of the regression slopes increased in the same order above (from lower to higher levels) in patients but not in controls. Regression coefficients between syntax and both sentence level and discourse level semantics did not differentiate patients from controls. This study indicates that the dynamics between language elements is abnormal in schizophrenia. In patients, top-down flow of linguistic information might be reduced, and the relationship between phonology and semantics but not between syntax and semantics appears to be altered.

Higher-order semantic processing in formal thought disorder in schizophrenia

Higher-order semantic impairments and lack of sensitivity to linguistic context have both been implicated in formal thought disorder (FTD) in schizophrenia. Most investigations have focused on comprehension. We investigated the processing of higher-order semantic relations and the role of emotional arousal in FTD patients' linguistic comprehension and production. We compared FTD schizophrenia patients (n=14) with non-FTD schizophrenia patients (n=18) and healthy controls (n=15) on sense-judgment and repetition tasks, in emotionally negative and neutral conditions. We predicted that the FTD group would display poor sensitivity compared to the other two groups in comprehension and production, and that this would be exacerbated by sentence complexity and negative emotional arousal. The emotional manipulation was not robustly successful, and did not affect task performance in the patient groups. FTD patients made significantly more errors on sense-judgments and repetition than the other two groups. Complexity affected all groups to a similar extent in sense-judgments, but affected FTD patients disproportionately in the repetition task. These results support the view that a lack of sensitivity to context underlies FTD in comprehension and production stages of processing. Patients fail to utilise linguistic context to integrate lexical forms into a global whole and guide their access to lexical targets.

Event-related potentials in substance use disorders: a narrative review based on articles from 1984 to 2012

Mechanisms that mediate the transition from occasional, controlled, drug use to the impaired control that characterizes severe dependence are still a matter of investigation. The etiology of substance use disorders (SUDs) is complex, and in this context of complexity, the concept of "endophenotype," has gained extensive popularity in recent years. The main aim of endophenotypes is to provide a simpler, more proximal target to discover the biological underpinnings of a psychiatric syndrome. In this view, neurocognitive and neurophysiological impairments that suggest functional impairments associated with SUDs have been proposed as possible endophenotypes. Because of its large amplitude and relatively easy elicitation, the most studied of the cognitive brain event-related potentials (ERPs), the P300 component, has been proposed as one possible candidate. However, if a P300 amplitude alteration is a common finding in SUDs, it is also observable in other psychiatric afflictions, suggesting that the associations found may just reflect a common measure of brain dysfunction. On this basis, it has been proposed that a multivariate endophenotype, based on a weighted combination of electrophysiological features, may provide greater diagnostic classification power than any single endophenotype. The rationale for investigating multiple features is to show that combining them provides extra useful information that is not available in the individual features, leading ultimately to a multivariate phenotype.The aim of the present article is to outline the potential usefulness of this kind of "combined electrophysiological procedure" applied to SUDs. We present a review of ERP studies, combining data from people with SUD, family members, and normal control subjects, to verify whether the combination of 4ERPs (P50, MMN, P300, and N400) may produce profiles of cortical anomalies induced by different types of SUD (alcohol vs cocaine vs cannabis vs heroin).

Natural speech comprehension in bipolar disorders: an event-related brain potential study among manic patients

BACKGROUND

Thought and language disturbances are crucial clinical features in Bipolar Disorders (BD), and constitute a fundamental basis for social cognition. In BD, clinical manifestations such as disorganization and formal thought disorders may play a role in communication disturbances. However, only few studies have explored language disturbances in BD at a neurophysiological level. Two main Event-Related brain Potentials (ERPs) have been used in language comprehension research: the N400 component, elicited by incongruous word with the preceding semantic context, and the Late Positive Component (LPC), associated with non-specifically semantic and more general cognitive processes. Previous studies provided contradictory results regarding N400 in mood disorders, showing either preserved N400 in depression or dysthymia, or altered N400 in BD during semantic priming paradigm. The aim of our study was to explore N400 and LPC among patients with BD in natural speech conditions.

METHODS

ERPs from 19 bipolar type I patients with manic or hypomanic symptomatology and 19 healthy controls were recorded. Participants were asked to listen to congruous and incongruous complete sentences and to judge the match between the final word and the sentence context. Behavioral results and ERPs data were analyzed.

RESULTS

At the behavioral level, patients with BD show worst performances than healthy participants. At the electrophysiological level, our results show preserved N400 component in BD. LPC elicited under natural speech conditions shows preserved amplitude but delayed latency in difference waves.

LIMITATIONS

Small size of samples, absence of schizophrenic group and medication status.

CONCLUSIONS

In contrast with the only previous N400 study in BD that uses written semantic priming, our results show a preserved N400 component in ecological and natural speech conditions among patients with BD. Possible implications in terms of clinical specificity are discussed.

Jung's views on causes and treatments of schizophrenia in light of current trends in cognitive neuroscience and psychotherapy research II: psychological research and treatment

Jung was the first to emphasize the importance of psychological factors in the aetiology and treatment of schizophrenia. Despite this, and other seminal contributions, his work on schizophrenia is almost completely ignored or forgotten today. This paper, a follow-up to one on Jung's theories of aetiology and symptom formation in schizophrenia (Journal of Analytical Psychology, 59, 1) reviews Jung's views on psychological approaches to research on, and treatment of, the disorder. Five themes are covered: 1) experimental psychopathology; 2) attentional disturbance; 3) psychological treatment; 4) the relationship between the environment (including the psychiatric hospital) and symptom expression; and 5) heterogeneity and the schizophrenia spectrum. Review of these areas reveal that Jung's ideas about the kind of research that can elucidate psychological mechanisms in schizophrenia, and the importance of psychotherapy for people with this condition, are very much in line with contemporary paradigms. Moreover, further exploration of several points of convergence could lead to advances in both of these fields, as well as within analytical psychology.

Schizotypal people stick longer to their first choices

Many studies have reported that schizophrenic patients show a Bias Against Disconfirmatory Evidence (BADE). This cognitive bias has been related to the formation and maintenance of delusion. The aim of this paper was to study whether BADE was present in healthy people displaying psychometric schizotypy, and to compare a closure task, which has been used for schizophrenia, with a new chronometric paradigm. Results with the new paradigm showed that the high-schizotypy group maintained their initial hypotheses longer than the low-schizotypy group. This finding corroborated the similarities between schizophrenic disorder and schizotypal traits, in this case with respect to the BADE. Research of this kind could facilitate the study of cognition in the schizophrenic spectrum without the difficulties of working with schizophrenic patients for some tasks and the assessment and early intervention in at-risk populations.

Cognitive control and discourse comprehension in schizophrenia

Cognitive deficits across a wide range of domains have been consistently observed in schizophrenia and are linked to poor functional outcome (Green, 1996; Carter, 2006). Language abnormalities are among the most salient and include disorganized speech as well as deficits in comprehension. In this review, we aim to evaluate impairments of language processing in schizophrenia in relation to a domain-general control deficit. We first provide an overview of language comprehension in the healthy human brain, stressing the role of cognitive control processes, especially during discourse comprehension. We then discuss cognitive control deficits in schizophrenia, before turning to evidence suggesting that schizophrenia patients are particularly impaired at processing meaningful discourse as a result of deficits in control functions. We conclude that domain-general control mechanisms are impaired in schizophrenia and that during language comprehension this is most likely to result in difficulties during the processing of discourse-level context, which involves integrating and maintaining multiple levels of meaning. Finally, we predict that language comprehension in schizophrenia patients will be most impaired during discourse processing. We further suggest that discourse comprehension problems in schizophrenia might be mitigated when conflicting information is absent and strong relations amongst individual words are present in the discourse context."There is no "centre of Speech" in the brain any more than there is a faculty of Speech in the mind.The entire brain, more or less, is at work in a man who uses language"William JamesFrom The Principles of Psychology, 1890"The mind in dementia praecox is like an orchestra without a conductor"Kraepelin, 1919.

Slow and steady: sustained effects of lexico-semantic associations can mediate referential impairments in schizophrenia

The present study investigated the contribution of lexico-semantic associations to impairments in establishing reference in schizophrenia. We examined event-related potentials as schizophrenia patients and healthy, demographically matched controls read five-sentence scenarios. Sentence 4 introduced a noun that referred back to three possible referents introduced in Sentences 1-3. These referents were contextually appropriate, contextually inappropriate but lexico-semantically associated, and contextually inappropriate and lexico-semantically nonassociated. In order to determine whether participants had correctly linked the anaphor to its referent, the final sentence reintroduced each referent, and participants indicated whether the last two sentences referred to the same entity. Results indicated that between 300 and 400 ms, patients, like healthy controls, used discourse context to link the noun with its preceding referent. However, between 400 and 500 ms, neural activity in patients was modulated only by lexico-semantic associations, rather than by discourse context. Moreover, patients were also more likely than controls to incorrectly link the noun with contextually inappropriate but lexico-semantically associated referents. These results suggest that at least some types of referential impairments may be driven by sustained activation of contextually inappropriate lexico-semantic associations.

Schizotypal traits and N400 in healthy subjects

We examined whether correlations previously found between symptoms of schizophrenia patients and the amplitude of an event-related potential (ERP), the N400, could be also found between schizotypal experiences of healthy subjects and the N400. We chose a semantic categorization task previously used with patients. Schizotypal experiences were measured with the schizotypal personality questionnaire (SPQ). The effects of the other factors were controlled for when assessing the correlations between each SPQ factor and N400s. These correlations were assessed at each electrode site to see whether their distribution on the scalp follows that of the N400 effect. Disorganization and interpersonal scores were found to correlate with ERPs in the N400 time window, as previously reported for the comparable symptoms of patients. However, the scalp distribution of these correlations differed from that of the N400 effect.

Lexico-semantic processing in children with specific language impairment: the overactivation hypothesis

The hypothesis indicating an overactivation of the lexico-semantic network in children with specific language impairment (SLI) was tested using an auditory pair-primed paradigm (PPP), where participants made a lexical-decision on the second word of a noun pair that could be semantically related, or not, to the first one. Though children with SLI were proven to be as accurate as children matched for receptive vocabulary age, they presented a larger priming effect in the PPP in terms of both reaction time and accuracy. These results preliminarily support the hypothesis of an overactivation of the lexico-semantic network.

LEARNING OUTCOMES

As a result of reading this paper the reader will be able to (1) understand how the pair-primed paradigm can contribute to investigate the online spreading of the activation within the lexico-semantic network; (2) be aware of the fact that during development it is unlikely that some cognitive domain are completely typical (residual normality), while others develop atypically; (3) the reader will be aware that children with SLI present some subtle abnormalities in the lexico-semantic network, which appears to be overactive.

Selective emotional processing deficits to social vignettes in schizophrenia: an ERP study

Schizophrenia is associated with abnormalities in emotional processing and social cognition. However, it remains unclear whether patients show abnormal neurophysiological responses during fast, online appraisals of the emotional meaning of social information. To examine this question, event-related potentials (ERPs) were collected while 18 schizophrenia patients and 18 demographically matched controls evaluated 2-sentence vignettes describing negative, positive, or neutral social situations. ERPs were time locked to a critical word (CW) in the second sentence that conferred emotional valence. A late positivity effect to emotional (vs neutral) CWs was seen in both groups (in controls, to negative and positive CWs; in patients, to negative CWs only). However, the controls showed a greater late positivity effect to the negative and positive (vs neutral) CWs than the schizophrenia patients at mid-posterior (negative vs neutral) and at right posterior peripheral (positive vs neutral) sites. These between-group differences arose from reduced amplitudes of the late positivity to the negative and positive CWs in the patients relative to the controls; there was no difference between the 2 groups in the amplitude of the late positivity to the neutral CWs. These findings suggest that schizophrenia is associated with a specific neural deficit during the online evaluation of emotionally valent, socially relevant information.

Language in schizophrenia Part 2: What can psycholinguistics bring to the study of schizophrenia...and vice versa?

This is the second of two articles that discuss higher-order language and semantic processing in schizophrenia. The companion article (Part 1) gives an introduction to language dysfunction in schizophrenia patients. This article reviews a selection of psycholinguistic studies which suggest that sentence-level abnormalities in schizophrenia may stem from a relative overdependence on semantic associative relationships at the expense of building higher-order meaning. Language disturbances in schizophrenia may be best conceptualized as arising from an imbalance of activity across two streams of processing, one drawing upon semantic relationships within semantic memory and the other involving the use of combinatorial mechanisms to build propositional meaning. I will also discuss some of the ways in which the study of schizophrenia may offer new insights into the cognitive and neural architecture of the normal language system.

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.

Brain/behavior Asymmetry in Schizophrenia: A MEG Study of Cross-modal Semantic Priming

Semantic priming has long been used to investigate how concepts and ideas are related at the level of language, and has become a convenient tool for assessing conceptual and semantic dysfunction in cognitive disorders, including schizophrenia. The study of semantic priming in schizophrenia has led to diverse results: enhanced priming, reduced priming, and priming equivalent to that found in nonpsychiatric comparison groups. A number of hypotheses have been proposed to explain some of the observed deficits in schizophrenia patients. For example, difficulties in word recognition may be due to hyperactivation of too many lexical representations or to a failure to inhibit lexical competitors. One way to distinguish between these possible explanations is to move beyond reliance on behavior alone and to examine the neural processes involved in lexical recognition. Here we present a magnetoencephalographic study of semantic priming in schizophrenia. Importantly, schizophrenia patients and healthy controls did not differ in performance on a priming task. We show that normal behavioral performance can occur in a context of aberrant neural responses. These findings suggest that normal behavioral responses in schizophrenia can be achieved through neural mechanisms that differ from those seen in the psychiatrically well brain.

Electrophysiological insights into the processing of nominal metaphors

We used event-related potentials (ERPs) to examine the time-course of processing metaphorical and literal sentences in the brain. ERPs were measured to sentence-final (Experiment 1) and mid-sentence (Experiment 2) critical words (CWs) as participants read and made plausibility judgments about familiar nominal metaphors ("A is a B") as well as literal and semantically anomalous sentences of the same form. Unlike the anomalous words, which evoked a robust N400 effect (on the CW in experiments 1 and 2 as well as on the sentence-final word in experiment 2), CWs in the metaphorical, relative to the literal, sentences only evoked an early, localized N400 effect that was over by 400ms after CW onset, suggesting that, by this time, their metaphorical meaning had been accessed. CWs in the metaphorical sentences also evoked a significantly larger LPC (Late Positive Component) than in the literal sentences. We suggest that this LPC reflected additional analysis that resolved a conflict between the implausibility of the literal sentence interpretation and the match between the metaphorical meaning of the CW, the context and stored information within semantic memory, resulting from early access to both literal and figurative meanings of the CWs.

What can Event-related Potentials tell us about language, and perhaps even thought, in schizophrenia?

Disturbances of thought and language are fundamental to schizophrenia. Cognitive behavioral and electrophysiological research has implicated problems in two different neurocognitive mechanisms: abnormalities in the structure and function of semantic memory, and abnormalities in combining and integrating words together to build up sentence and discourse context. This review discusses recent electrophysiological evidence suggesting that these two deficits are not completely distinct, but rather that language impairment in schizophrenia results from a dysfunctional interaction between these systems in an effort to build up higher-order meaning. Moreover, although language abnormalities are more pronounced in patients with positive thought disorder, they manifest themselves in all patients when increased demands are placed on the comprehension system. Further investigation of language dysfunction may also provide insights into other aspects of psychotic thought.

Neurocognitive mechanisms of conceptual processing in healthy adults and patients with schizophrenia

This overview outlines findings of cognitive and neurocognitive studies on comprehension of verbal, pictorial, and video stimuli in healthy participants and patients with schizophrenia. We present evidence for a distinction between two complementary neurocognitive streams of conceptual analysis during comprehension. In familiar situations, adequate understanding of events may be achieved by mapping the perceived information on the associative and similarity-based connections between concepts in semantic memory - a process reflected by an N400 waveform of event-related electrophysiological potentials (ERPs). However, in less conventional contexts, a more flexible mechanism may be needed. We suggest that this alternative processing stream, reflected by a P600 ERP waveform, may use discrete, rule-like goal-related requirements of real-world actions to comprehend relationships between perceived people, objects, and actions. This neurocognitive model of comprehension is used as a basis in discussing studies in schizophrenia. These studies suggest an imbalanced engagement of the two conceptual streams in schizophrenia, whereby patients may rely on the associative and similarity-based networks in semantic memory even when it would be more adaptive to recruit mechanisms that draw upon goal-related requirements. Finally, we consider the roles that these conceptual mechanisms may play in real-life behavior, and the consequences that their dysfunction may have for disorganized behavior and inability to plan actions to achieve behavioral goals in schizophrenia.

Event-related potentials in clinical research: guidelines for eliciting, recording, and quantifying mismatch negativity, P300, and N400

This paper describes recommended methods for the use of event-related brain potentials (ERPs) in clinical research and reviews applications to a variety of psychiatric and neurological disorders. Techniques are presented for eliciting, recording, and quantifying three major cognitive components with confirmed clinical utility: mismatch negativity (MMN), P300, and N400. Also highlighted are applications of each of the components as methods of investigating central nervous system pathology. The guidelines are intended to assist investigators who use ERPs in clinical research, in an effort to provide clear and concise recommendations and thereby to standardize methodology and facilitate comparability of data across laboratories.

N400 deficits from semantic matching of pictures in probands and first-degree relatives from multiplex schizophrenia families

Endophenotypes is one emerging strategy in schizophrenia research that is being used to identify the functional importance of genetically transmitted, brain-based deficits present in this disease. Currently, event-related potentials (ERPs) are timely used in this search. Several ERPs, including N400, present deficits in relation to schizophrenia. In order to assess the genetic liability of N400 as a possible endophenotype, a picture semantic matching task (congruent and incongruent pairs of pictures) was performed by 21 unaffected first-degree relatives of patients with schizophrenia, 21 DSM-IV diagnosed schizophrenia probands, and 21 control subjects, matched by age, gender and educational level. Probands and relatives were selected form Multiplex schizophrenia families. Significantly reduced N400 amplitude for congruent categories in N400 was found in probands and relatives in relation to controls. The latency onset and the maximum peak latency of N400 were delayed in both, relatives and probands groups compared to control. The voltage maps of incongruous-minus-congruous difference indicate a more reduced right restricted negativity in probands and relatives, when compared to a widely extended bilateral negativity in controls. No general differences were found between patients and relatives. These results demonstrate an electrophysiological deficit in semantic match processing in clinically unaffected first-degree relatives of patients with schizophrenia, suggesting a possible use of this marker as endophenotype.

Why all the confusion? Experimental task explains discrepant semantic priming effects in schizophrenia under "automatic" conditions: evidence from Event-Related Potentials

The schizophrenia research literature contains many differing accounts of semantic memory function in schizophrenia as assessed through the semantic priming paradigm. Most recently, Event-Related Potentials (ERPs) have been used to demonstrate both increased and decreased semantic priming at a neural level in schizophrenia patients, relative to healthy controls. The present study used ERPs to investigate the role of behavioral task in determining neural semantic priming effects in schizophrenia. The same schizophrenia patients and healthy controls completed two experiments in which word stimuli were identical, and the time between the onset of prime and target remained constant at 350 ms: in the first, participants monitored for words within a particular semantic category that appeared only in filler items (implicit task); in the second, participants explicitly rated the relatedness of word-pairs (explicit task). In the explicit task, schizophrenia patients showed reduced direct and indirect semantic priming in comparison with healthy controls. In contrast, in the implicit task, schizophrenia patients showed normal or, in positively thought-disordered patients, increased direct and indirect N400 priming effects compared with healthy controls. These data confirm that, although schizophrenia patients with positive thought disorder may show an abnormally increased automatic spreading activation, the introduction of semantic decision-making can result in abnormally reduced semantic priming in schizophrenia, even when other experimental conditions bias toward automatic processing.

Neurocognitive abnormalities during comprehension of real-world goal-directed behaviors in schizophrenia

Origins of impaired adaptive functioning in schizophrenia remain poorly understood. Behavioral disorganization may arise from an abnormal reliance on common combinations between concepts stored in semantic memory. Avolition-apathy may be related to deficits in using goal-related requirements to flexibly plan behavior. The authors recorded event-related potentials (ERPs) in 16 patients with medicated schizophrenia and 16 healthy controls in a novel video paradigm presenting congruous or incongruous objects in real-world activities. All incongruous objects were contextually inappropriate, but the incongruous scenes varied in comprehensibility. Psychopathology was assessed with the Scales for the Assessment of Positive and Negative Symptoms (SAPS/SANS) and the Brief Psychiatric Rating Scale. In patients, an N400 ERP, thought to index activity in semantic memory, was abnormally enhanced to less comprehensible incongruous scenes, and larger N400 priming was associated with disorganization severity. A P600 ERP, which may index flexible object-action integration based on goal-related requirements, was abnormally attenuated in patients, and its smaller magnitude was associated with the SANS rating of impersistence at work or school (goal-directed behavior). Thus, distinct neurocognitive abnormalities may underlie disorganization and goal-directed behavior deficits in schizophrenia.

Semantic memory in schizophrenia: association with cell membrane essential fatty acids

INTRODUCTION

Semantic memory and language deficits are associated with schizophrenia. Understanding how these systems operate in this disorder will likely require a multi-factorial model that explains their linkages with cognition and modulation by dopamine. A biological factor that may provide causal convergence for these connections is cell membrane composition and dynamics.

METHODS

N400 is an electrophysiological measure of semantic memory and language that is sensitive to deficits in schizophrenia. Relationships among N400, cognition, dopamine, and cell membrane polyunsaturated fatty acids (PUFAs) were examined for patients tested under medicated (haloperidol only) and unmedicated (placebo) conditions. Relationships between these factors and clinical symptoms were also evaluated. The sample included 37 male schizophrenia inpatients and 34 male normal controls. The N400 priming effect was measured from visual event-related potentials recorded during a semantic priming-lexical decision task, in which semantic association (related versus unrelated words) and presentation rate (Stimulus Onset Asynchrony/SOAs: 350 and 950 ms) were varied.

RESULTS

N400 was associated with cognition (speed, visuoperception, attention) in patients and controls. These relationships were influenced by SOA in both groups, and by pharmacological condition in patients. Levels of total PUFAs and arachidonic acid were associated with N400 in unmedicated patients. Clinical symptoms (paranoia, thought disturbance) were associated with N400, but not with cognition or PUFAs.

CONCLUSIONS

Results suggest cell membrane fatty acids are associated with semantic memory and language in schizophrenia. Findings also suggest a series of linkages that are modulated by dopamine: cell membrane fatty acids are associated with N400 semantic priming; N400 semantic priming is associated with clinical symptoms.

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.

Neural evidence for faster and further automatic spreading activation in schizophrenic thought disorder

It has been proposed that the loose associations characteristic of thought disorder in schizophrenia result from an abnormal increase in the automatic spread of activation through semantic memory. We tested this hypothesis by examining the time course of neural semantic priming using event-related potentials (ERPs). ERPs were recorded to target words that were directly related, indirectly related, and unrelated to their preceding primes, while thought-disordered (TD) and non-TD schizophrenia patients and healthy controls performed an implicit semantic categorization task under experimental conditions that encouraged automatic processing. By 300-400 milliseconds after target word onset, TD patients showed increased indirect semantic priming relative to non-TD patients and healthy controls, while the degree of direct semantic priming was increased in only the most severely TD patients. By 400-500 milliseconds after target word onset, both direct and indirect semantic priming were generally equivalent across the 3 groups. These findings demonstrate for the first time at a neural level that, under automatic conditions, activation across the semantic network spreads further within a shorter period of time in specific association with positive thought disorder in schizophrenia.

Building meaning in schizophrenia

The schizophrenia syndrome is clinically characterized by abnormal constructions of meaning during comprehension (delusions), perception (hallucinations), action (disorganized and non-goal-directed behavior) and language production (thought disorder). This article provides an overview of recent studies from our laboratory that have used event-related potentials and functional magnetic resonance imaging to elucidate abnormalities in temporal and spatial patterns of neural activity as meaning is built from language and real-world visual events in schizophrenia. Our findings support the hypothesis that automatic activity across semantic memory spreads further within a shorter period of time in thought-disordered patients, relative to non-thought-disordered patients and healthy controls. Neuroanatomically, increased activity to semantic associates is reflected by inappropriate recruitment of temporal cortices. In building meaning within sentences, the fine balance between semantic memory-based mechanisms and semantic-syntactic integration (dictating "who does what to whom") is disrupted, such that comprehension is driven primarily by semantic memory-based processes. Neuroanatomically, this imbalance is reflected by preserved (and sometimes increased) activity within temporal and inferior prefrontal cortices, but abnormal modulation of dorsolateral prefrontal and parietal cortices. In building meaning across sentences (discourse), patients fail to immediately construct coherence links, but may show inappropriate recruitment of temporal and inferior prefrontal cortices to incoherent discourse, again reflecting inappropriate semantic memory-based processing (abnormal inferencing). Finally, these abnormalities may generalize to real-world visual event comprehension, where patients show reduced neural activity in determining relationships around goal-directed actions, and comprehension is again dominated by semantic memory-based mechanisms.