Double dissociation of N1 and P3 abnormalities in deficit and nondeficit schizophrenia

Features of attention network impairment in patients with temporal lobe epilepsy: Evidence from eye-tracking and electroencephalogram

AIM

To explore multiple features of attention impairments in patients with temporal lobe epilepsy (TLE).

METHODS

A total of 93 patients diagnosed with TLE at Xiangya Hospital during May 2022 and December 2022 and 85 healthy controls were included in this study. Participants were asked to complete neuropsychological scales and attention network test (ANT) with recording of eye-tracking and electroencephalogram.

RESULTS

All means of evaluation showed impaired attention functions in TLE patients. ANT results showed impaired orienting (p < 0.001) and executive control (p = 0.041) networks. Longer mean first saccade time (p = 0.046) and more total saccadic counts (p = 0.035) were found in eye-tracking results, indicating abnormal alerting and orienting networks. Both alerting, orienting and executive control networks were abnormal, manifesting as decreased amplitudes (N1 & P3, p < 0.001) and extended latency (P3, p = 0.002). The energy of theta, alpha and beta were all sensitive to the changes of alerting and executive control network with time, but only beta power was sensitive to the changes of orienting network.

CONCLUSION

Our findings are helpful for early identification of patients with TLE combined with attention impairments, which have strong clinical guiding significance for long-term monitoring and intervention.

Topological Perturbations in the Functional Connectome Support the Deficit/Non-deficit Distinction in Antipsychotic Medication-Naïve First Episode Psychosis Patients

BACKGROUND

Heterogeneity in the etiology, pathophysiology, and clinical features of schizophrenia challenges clinicians and researchers. A helpful approach could be stratifying patients according to the presence or absence of clinical features of the deficit syndrome (DS). DS is characterized by enduring and primary negative symptoms, a clinically less heterogeneous subtype of the illness, and patients with features of DS are thought to present abnormal brain network characteristics, however, this idea has received limited attention. We investigated functional brain network topology in patients displaying deficit features and those who do not.

DESIGN

We applied graph theory analytics to resting-state functional magnetic resonance imaging data of 61 antipsychotic medication-naïve first episode psychosis patients, 18 DS and 43 non-deficit schizophrenia (NDS), and 72 healthy controls (HC). We quantified small-worldness, global and nodal efficiency measures, shortest path length, nodal local efficiency, and synchronization and contrasted them among the 3 groups.

RESULTS

DS presented decreased network integration and segregation compared to HC and NDS. DS showed lower global efficiency, longer global path lengths, and lower global local efficiency. Nodal efficiency was lower and the shortest path length was longer in DS in default mode, ventral attention, dorsal attention, frontoparietal, limbic, somatomotor, and visual networks compared to HC. Compared to NDS, DS showed lower efficiency and longer shortest path length in default mode, limbic, somatomotor, and visual networks.

CONCLUSIONS

Our data supports increasing evidence, based on topological perturbations of the functional connectome, that deficit syndrome may be a distinct form of the illness.

Electrophysiological Correlates of Reward Anticipation in Subjects with Schizophrenia: An ERP Microstate Study

The current study aimed to investigate alterations of event-related potentials (ERPs) microstate during reward anticipation in subjects with schizophrenia (SCZ), and their association with hedonic experience and negative symptoms. EEG data were recorded in thirty SCZ and twenty-three healthy controls (HC) during the monetary incentive delay task in which reward, loss and neutral cues were presented. Microstate analysis and standardized low-resolution electromagnetic tomography (sLORETA) were applied to EEG data. Furthermore, analyses correlating a topographic index (the ERPs score), calculated to quantify brain activation in relationship to the microstate maps, and scales assessing hedonic experience and negative symptoms were performed. Alterations in the first (125.0-187.5 ms) and second (261.7-414.1 ms) anticipatory cue-related microstate classes were observed. In SCZ, reward cues were associated to shorter duration and earlier offset of the first microstate class as compared to the neutral condition. In the second microstate class, the area under the curve was smaller for both reward and loss anticipation cues in SCZ as compared to HC. Furthermore, significant correlations between ERPs scores and the anticipation of pleasure scores were detected, while no significant association was found with negative symptoms. sLORETA analysis showed that hypo-activation of the cingulate cortex, insula, orbitofrontal and parietal cortex was detected in SCZ as compared to HC. Abnormalities in ERPs could be traced already during the early stages of reward processing and were associated with the anticipation of pleasure, suggesting that these dysfunctions might impair effective evaluation of incoming pleasant experiences. Negative symptoms and anhedonia are partially independent results.

Negative symptoms of schizophrenia: Trying to answer unanswered research questions

My research has focused on unmet needs in caring for people with schizophrenia. In particular, I focused on negative symptoms, a complex psychopathological dimension of the disorder, with a significant impact on the disease outcome, and not effectively addressed by existing treatments. In the present commentary, I summarize the trajectory of my research activity. I start with the description of my initial attempts to define the role of the dorsolateral prefrontal cortex in the pathogenesis of broadly defined negative symptoms. Then, I report on the evidence that led me to realize that no progress in research on schizophrenia negative symptoms could occur without considering the heterogeneity and complexity of the construct. Finally, I illustrate my attempts to succeed in this direction and the most pressing unsolved issues in this research field.

Tracing Links Between Early Auditory Information Processing and Negative Symptoms in Schizophrenia: An ERP Study

Background: Negative symptoms represent a heterogeneous dimension with a strong impact on functioning of subjects with schizophrenia (SCZ). Five constructs are included in this dimension: anhedonia, asociality, avolition, blunted affect, and alogia. Factor analyses revealed that these symptoms cluster in two domains: experiential domain (avolition, asociality, and anhedonia) and the expressive deficit (alogia and blunted affect), that might be linked to different neurobiological alterations. Few studies investigated associations between N100, an electrophysiological index of early sensory processing, and negative symptoms, reporting controversial results. However, none of these studies investigated electrophysiological correlates of the two negative symptom domains. Objectives: The aim of our study was to evaluate, within the multicenter study of the Italian Network for Research on Psychoses, the relationships between N100 and negative symptom domains in SCZ. Methods: Auditory N100 was analyzed in 114 chronic stabilized SCZ and 63 healthy controls (HCs). Negative symptoms were assessed with the Brief Negative Symptom Scale (BNSS). Repeated measures ANOVA and correlation analyses were performed to evaluate differences between SCZ and HCs and association of N100 features with negative symptoms. Results: Our findings demonstrated a significant N100 amplitude reduction in SCZ compared with HCs. In SCZ, N100 amplitude for standard stimuli was associated with negative symptoms, in particular with the expressive deficit domain. Within the expressive deficit, blunted affect and alogia had the same pattern of correlation with N100. Conclusion: Our findings revealed an association between expressive deficit and N100, suggesting that these negative symptoms might be related to deficits in early auditory processing in SCZ.

Investigating the Relationships of P3b with Negative Symptoms and Neurocognition in Subjects with Chronic Schizophrenia

Neurocognitive deficits and negative symptoms (NS) have a pivotal role in subjects with schizophrenia (SCZ) due to their impact on patients' functioning in everyday life and their influence on goal-directed behavior and decision-making. P3b is considered an optimal electrophysiological candidate biomarker of neurocognitive impairment for its association with the allocation of attentional resources to task-relevant stimuli, an important factor for efficient decision-making, as well as for motivation-related processes. Furthermore, associations between P3b deficits and NS have been reported. The current research aims to fill the lack of studies investigating, in the same subjects, the associations of P3b with multiple cognitive domains and the expressive and motivation-related domains of NS, evaluated with state-of-the-art instruments. One hundred and fourteen SCZ and 63 healthy controls (HCs) were included in the study. P3b amplitude was significantly reduced and P3b latency prolonged in SCZ as compared to HCs. In SCZ, a positive correlation was found between P3b latency and age and between P3b amplitude and the Attention-vigilance domain, while no significant correlations were found between P3b and the two NS domains. Our results indicate that the effortful allocation of attention to task-relevant stimuli, an important component of decision-making, is compromised in SCZ, independently of motivation deficits or other NS.

EEG-Based Measures in At-Risk Mental State and Early Stages of Schizophrenia: A Systematic Review

Introduction: Electrophysiological (EEG) abnormalities in subjects with schizophrenia have been largely reported. In the last decades, research has shifted to the identification of electrophysiological alterations in the prodromal and early phases of the disorder, focusing on the prediction of clinical and functional outcome. The identification of neuronal aberrations in subjects with a first episode of psychosis (FEP) and in those at ultra high-risk (UHR) or clinical high-risk (CHR) to develop a psychosis is crucial to implement adequate interventions, reduce the rate of transition to psychosis, as well as the risk of irreversible functioning impairment. The aim of the review is to provide an up-to-date synthesis of the electrophysiological findings in the at-risk mental state and early stages of schizophrenia. Methods: A systematic review of English articles using Pubmed, Scopus, and PsychINFO was undertaken in July 2020. Additional studies were identified by hand-search. Electrophysiological studies that included at least one group of FEP or subjects at risk to develop psychosis, compared to healthy controls (HCs), were considered. The heterogeneity of the studies prevented a quantitative synthesis. Results: Out of 319 records screened, 133 studies were included in a final qualitative synthesis. Included studies were mainly carried out using frequency analysis, microstates and event-related potentials. The most common findings included an increase in delta and gamma power, an impairment in sensory gating assessed through P50 and N100 and a reduction of Mismatch Negativity and P300 amplitude in at-risk mental state and early stages of schizophrenia. Progressive changes in some of these electrophysiological measures were associated with transition to psychosis and disease course. Heterogeneous data have been reported for indices evaluating synchrony, connectivity, and evoked-responses in different frequency bands. Conclusions: Multiple EEG-indices were altered during at-risk mental state and early stages of schizophrenia, supporting the hypothesis that cerebral network dysfunctions appear already before the onset of the disorder. Some of these alterations demonstrated association with transition to psychosis or poor functional outcome. However, heterogeneity in subjects' inclusion criteria, clinical measures and electrophysiological methods prevents drawing solid conclusions. Large prospective studies are needed to consolidate findings concerning electrophysiological markers of clinical and functional outcome.

Independent vector analysis for common subspace analysis: Application to multi-subject fMRI data yields meaningful subgroups of schizophrenia

The extraction of common and distinct biomedical signatures among different populations allows for a more detailed study of the group-specific as well as distinct information of different populations. A number of subspace analysis algorithms have been developed and successfully applied to data fusion, however they are limited to joint analysis of only a couple of datasets. Since subspace analysis is very promising for analysis of multi-subject medical imaging data as well, we focus on this problem and propose a new method based on independent vector analysis (IVA) for common subspace extraction (IVA-CS) for multi-subject data analysis. IVA-CS leverages the strength of IVA in identification of a complete subspace structure across multiple datasets along with an efficient solution that uses only second-order statistics. We propose a subset analysis approach within IVA-CS to mitigate issues in estimation in IVA due to high dimensionality, both in terms of components estimated and the number of datasets. We introduce a scheme to determine a desirable size for the subset that is high enough to exploit the dependence across datasets and is not affected by the high dimensionality issue. We demonstrate the success of IVA-CS in extracting complex subset structures and apply the method to analysis of functional magnetic resonance imaging data from 179 subjects and show that it successfully identifies shared and complementary brain patterns from patients with schizophrenia (SZ) and healthy controls group. Two components with linked resting-state networks are identified to be unique to the SZ group providing evidence of functional dysconnectivity. IVA-CS also identifies subgroups of SZs that show significant differences in terms of their brain networks and clinical symptoms.

Topography of activation deficits in schizophrenia during P300 task related to cognition and structural connectivity

BACKGROUND

The study of cerebral underpinnings of schizophrenia may benefit from the high temporal resolution of electromagnetic techniques, but its spatial resolution is low. However, source imaging approaches such as low-resolution brain electromagnetic tomography (LORETA) allow for an acceptable compromise between spatial and temporal resolutions.

METHODS

We combined LORETA with 32 channels and 3-Tesla diffusion magnetic resonance (Dmr) to study cerebral dysfunction in 38 schizophrenia patients (17 first episodes, FE), compared to 53 healthy controls. The EEG was acquired with subjects performing an odd-ball task. Analyses included an adaptive window of interest to take into account the interindividual variability of P300 latency. We compared source activation patters to distractor (P3a) and target (P3b) tones within- and between-groups.

RESULTS

Patients showed a reduced activation in anterior cingulate and lateral and medial prefrontal cortices, as well as inferior/orbital frontal regions. This was also found in the FE patients alone. The activation was directly related to IQ in the patients and controls and to working memory performance in controls. Symptoms were unrelated to source activation. Fractional anisotropy in the tracts connecting lateral prefrontal and anterior cingulate regions predicted source activation in these regions in the patients.

CONCLUSIONS

These results replicate the source activation deficit found in a previous study with smaller sample size and a lower number of sensors and suggest an association between structural connectivity deficits and functional alterations.

Evoked Potentials Investigations of Deficit Versus Nondeficit Schizophrenia: EEG-MEG Preliminary Data

Heterogeneity of schizophrenia is a major obstacle toward understanding the disorder. One likely subtype is the deficit syndrome (DS) where patients suffer from predominantly negative symptoms. This study investigated the evoked responses and the evoked magnetic fields to identify the neurophysiological deviations associated with the DS. Ten subjects were recruited for each group (Control, DS, and Nondeficit schizophrenia [NDS]). Subjects underwent magnetoencephalography (MEG) and electroencephalography (EEG) testing while listening to an oddball paradigm to generate the P300 as well as a paired click paradigm to generate the mid-latency auditory-evoked responses (MLAER) in a sensory gating paradigm. MEG-coherence source imaging (CSI) during P300 task revealed a significantly higher average coherence value in DS than NDS subjects in the gamma band (30-80 Hz), when listening to standard stimuli but only NDS subjects had a higher average coherence level in the gamma band than controls when listening to the novel sounds. P50, N100, and P3a ERP amplitudes (EEG analysis) were significantly decreased in NDS compared with DS subjects. The data suggest that the deviations in the 2 patient groups are qualitatively different. Deviances in NDS patients suggest difficulty in both early (as in the gating paradigm), as well as later top-down processes (P300 paradigm). The main deviation in the DS group was an exaggerated responsiveness to ongoing irrelevant stimuli detected by EEG whereas NDS subjects had an exaggerated response to novelty.

TNF-α and IL-6 are associated with the deficit syndrome and negative symptoms in patients with chronic schizophrenia

INTRODUCTION

Increased inflammatory markers have been found in patients with chronic schizophrenia, and have been associated with negative symptoms. The deficit syndrome is a distinct subtype of schizophrenia, characterized by primary and enduring negative symptoms.

METHOD

We measured inflammatory markers in patients with and without deficit schizophrenia and controls.

RESULTS

Using multivariate analyses, tumor necrosis factor (TNF)-α and interleukin-6 were associated with the deficit syndrome, and TNF-α predicted blunted affect, alogia, and total negative symptoms.

CONCLUSIONS

Findings suggest that deficit schizophrenia subtype is associated with increased inflammation and immunotherapies may be a novel target for negative symptoms.

Dynamic Facial Expressions Prime the Processing of Emotional Prosody

Evidence suggests that emotion is represented supramodally in the human brain. Emotional facial expressions, which often precede vocally expressed emotion in real life, can modulate event-related potentials (N100 and P200) during emotional prosody processing. To investigate these cross-modal emotional interactions, two lines of research have been put forward: cross-modal integration and cross-modal priming. In cross-modal integration studies, visual and auditory channels are temporally aligned, while in priming studies they are presented consecutively. Here we used cross-modal emotional priming to study the interaction of dynamic visual and auditory emotional information. Specifically, we presented dynamic facial expressions (angry, happy, neutral) as primes and emotionally-intoned pseudo-speech sentences (angry, happy) as targets. We were interested in how prime-target congruency would affect early auditory event-related potentials, i.e., N100 and P200, in order to shed more light on how dynamic facial information is used in cross-modal emotional prediction. Results showed enhanced N100 amplitudes for incongruently primed compared to congruently and neutrally primed emotional prosody, while the latter two conditions did not significantly differ. However, N100 peak latency was significantly delayed in the neutral condition compared to the other two conditions. Source reconstruction revealed that the right parahippocampal gyrus was activated in incongruent compared to congruent trials in the N100 time window. No significant ERP effects were observed in the P200 range. Our results indicate that dynamic facial expressions influence vocal emotion processing at an early point in time, and that an emotional mismatch between a facial expression and its ensuing vocal emotional signal induces additional processing costs in the brain, potentially because the cross-modal emotional prediction mechanism is violated in case of emotional prime-target incongruency.

Is the Prevalence of the Deficit Syndrome in Schizophrenia Higher than Estimated? Results of a Meta-Analysis

The primary and enduring presence of negative symptoms observed in a relatively homogeneous subgroup of patients with schizophrenia led to the concept of deficit syndrome (DS). Until date, it is considered that 20-25% of schizophrenia cohorts have DS. The aim of this meta-analysis was to determine the current prevalence of DS, including international and most recent studies. Thirteen observational studies met the inclusion criteria, comprising 2092 patients from eight countries. Pooled proportion of the DS subgroup was 32.64%, higher than previously reported. Based on our outcomes, up to one-third of patients with schizophrenia might have idiopathic and stable negative symptoms. This significant proportion of patients should be well represented in clinical trial's samples.

Comparing EEG Nonlinearity in Deficit and Nondeficit Schizophrenia Patients: Preliminary Data

Electroencephalogram (EEG) contains valuable information obtained noninvasively that can be used for assessment of brain's processing capacity of patients with psychiatric disorders. The purpose of the present work was to evaluate possible differences in EEG complexity between deficit (DS) and nondeficit (NDS) subtypes of schizophrenia as a reflection of the cognitive processing capacities in these groups. A particular nonlinear metric known as Lempel-Ziv complexity (LZC) was used as a computational tool in order to determine the randomness in EEG alpha band time series from 3 groups (deficit schizophrenia [n = 9], nondeficit schizophrenia [n = 10], and healthy controls [n = 10]) according to time series randomness. There was a significant difference in frontal EEG complexity between the DS and NDS subgroups ( p = .013), with DS group showing less complexity. A significant positive correlation was found between LZC values and Positive and Negative Syndrome Scale (PANSS) general psychopathology scores (ie, larger frontal EEG complexity correlated with more severe psychopathology), explained partially by the emotional component subscore of the PANSS. These findings suggest that cognitive processing occurring in the frontal networks in DS is less complex compared to NDS patients as reflected by EEG complexity measures. The data also suggest that there may be a relationship between the degree of emotionality and the complexity of the frontal EEG signal.

Negative symptoms: History of the concept and their position in diagnosis of schizophrenia

Current conceptualizations of schizophrenia have been introduced over centuries and continue to progress in recent decades. Symptoms have been divided into several domains, contrasting negative and positive symptoms which are different in their nature, onset, progression and response to treatment. An account of the different historical changes of the concept – essentially nosographic – has led to models attempting to integrate findings for each dimension of the disorder. This paper reviews the history of negative symptoms in diagnosis and how different approaches have been utilised to consider negative symptoms in the concept of schizophrenia. The paper also bridges various international classifications which have evolved and modified the role of negative symptoms in their diagnostic criteria for schizophrenia, which highlights the challenge of defining this disease.

Primary and persistent negative symptoms: Concepts, assessments and neurobiological bases

Primary and persistent negative symptoms (PPNS) represent an unmet need in the care of people with schizophrenia. They have an unfavourable impact on real-life functioning and do not respond to available treatments. Underlying etiopathogenetic mechanisms of PPNS are still unknown. The presence of primary and enduring negative symptoms characterizes deficit schizophrenia (DS), proposed as a separate disease entity with respect to non-deficit schizophrenia (NDS). More recently, to reduce the heterogeneity of negative symptoms by using criteria easily applicable in the context of clinical trials, the concept of persistent negative symptoms (PNS) was developed. Both PNS and DS constructs include enduring negative symptoms (at least 6months for PNS and 12months for DS) that do not respond to available treatments. PNS exclude secondary negative symptoms based on a cross-sectional evaluation of severity thresholds on commonly used rating scales for positive symptoms, depression and extrapyramidal side effects; the DS diagnosis, instead, excludes all potential sources of secondary negative symptoms based on a clinical longitudinal assessment. In this paper we review the evolution of concepts and assessment modalities relevant to PPNS, data on prevalence of DS and PNS, as well as studies on clinical, neuropsychological, brain imaging electrophysiological and psychosocial functioning aspects of DS and PNS.

Emotional self-other voice processing in schizophrenia and its relationship with hallucinations: ERP evidence

Abnormalities in self-other voice processing have been observed in schizophrenia, and may underlie the experience of hallucinations. More recent studies demonstrated that these impairments are enhanced for speech stimuli with negative content. Nonetheless, few studies probed the temporal dynamics of self versus nonself speech processing in schizophrenia and, particularly, the impact of semantic valence on self-other voice discrimination. In the current study, we examined these questions, and additionally probed whether impairments in these processes are associated with the experience of hallucinations. Fifteen schizophrenia patients and 16 healthy controls listened to 420 prerecorded adjectives differing in voice identity (self-generated [SGS] versus nonself speech [NSS]) and semantic valence (neutral, positive, and negative), while EEG data were recorded. The N1, P2, and late positive potential (LPP) ERP components were analyzed. ERP results revealed group differences in the interaction between voice identity and valence in the P2 and LPP components. Specifically, LPP amplitude was reduced in patients compared with healthy subjects for SGS and NSS with negative content. Further, auditory hallucinations severity was significantly predicted by LPP amplitude: the higher the SAPS "voices conversing" score, the larger the difference in LPP amplitude between negative and positive NSS. The absence of group differences in the N1 suggests that self-other voice processing abnormalities in schizophrenia are not primarily driven by disrupted sensory processing of voice acoustic information. The association between LPP amplitude and hallucination severity suggests that auditory hallucinations are associated with enhanced sustained attention to negative cues conveyed by a nonself voice.

The current conceptualization of negative symptoms in schizophrenia

Negative symptoms have long been conceptualized as a core aspect of schizophrenia. They play a key role in the functional outcome of the disorder, and their management represents a significant unmet need. Improvements in definition, characterization, assessment instruments and experimental models are needed in order to foster research aimed at developing effective interventions. A consensus has recently been reached on the following aspects: a) five constructs should be considered as negative symptoms, i.e. blunted affect, alogia, anhedonia, asociality and avolition; b) for each construct, symptoms due to identifiable factors, such as medication effects, psychotic symptoms or depression, should be distinguished from those regarded as primary; c) the five constructs cluster in two factors, one including blunted affect and alogia and the other consisting of anhedonia, avolition and asociality. In this paper, for each construct, we report the current definition; highlight differences among the main assessment instruments; illustrate quantitative measures, if available, and their relationship with the evaluations based on rating scales; and describe correlates as well as experimental models. We conclude that: a) the assessment of the negative symptom dimension has recently improved, but even current expert consensus-based instruments diverge on several aspects; b) the use of objective measures might contribute to overcome uncertainties about the reliability of rating scales, but these measures require further investigation and validation; c) the boundaries with other illness components, in particular neurocognition and social cognition, are not well defined; and d) without further reducing the heterogeneity within the negative symptom dimension, attempts to develop successful interventions are likely to lead to great efforts paid back by small rewards.

The current conceptualization of negative symptoms in schizophrenia

Negative symptoms have long been conceptualized as a core aspect of schizophrenia. They play a key role in the functional outcome of the disorder, and their management represents a significant unmet need. Improvements in definition, characterization, assessment instruments and experimental models are needed in order to foster research aimed at developing effective interventions. A consensus has recently been reached on the following aspects: a) five constructs should be considered as negative symptoms, i.e. blunted affect, alogia, anhedonia, asociality and avolition; b) for each construct, symptoms due to identifiable factors, such as medication effects, psychotic symptoms or depression, should be distinguished from those regarded as primary; c) the five constructs cluster in two factors, one including blunted affect and alogia and the other consisting of anhedonia, avolition and asociality. In this paper, for each construct, we report the current definition; highlight differences among the main assessment instruments; illustrate quantitative measures, if available, and their relationship with the evaluations based on rating scales; and describe correlates as well as experimental models. We conclude that: a) the assessment of the negative symptom dimension has recently improved, but even current expert consensus-based instruments diverge on several aspects; b) the use of objective measures might contribute to overcome uncertainties about the reliability of rating scales, but these measures require further investigation and validation; c) the boundaries with other illness components, in particular neurocognition and social cognition, are not well defined; and d) without further reducing the heterogeneity within the negative symptom dimension, attempts to develop successful interventions are likely to lead to great efforts paid back by small rewards.

Auditory P3a and P3b neural generators in schizophrenia: An adaptive sLORETA P300 localization approach

The present study investigates the neural substrates underlying cognitive processing in schizophrenia (Sz) patients. To this end, an auditory 3-stimulus oddball paradigm was used to identify P3a and P3b components, elicited by rare-distractor and rare-target tones, respectively. Event-related potentials (ERP) were recorded from 31 Sz patients and 38 healthy controls. The P3a and P3b brain-source generators were identified by time-averaging of low-resolution brain electromagnetic tomography (LORETA) current density images. In contrast with the commonly used fixed window of interest (WOI), we proposed to apply an adaptive WOI, which takes into account subjects' P300 latency variability. Our results showed different P3a and P3b source activation patterns in both groups. P3b sources included frontal, parietal and limbic lobes, whereas P3a response generators were localized over bilateral frontal and superior temporal regions. These areas have been related to the discrimination of auditory stimulus and to the inhibition (P3a) or the initiation (P3b) of motor response in a cognitive task. In addition, differences in source localization between Sz and control groups were observed. Sz patients showed lower P3b source activity in bilateral frontal structures and the cingulate. P3a generators were less widespread for Sz patients than for controls in right superior, medial and middle frontal gyrus. Our findings suggest that target and distractor processing involves distinct attentional subsystems, both being altered in Sz. Hence, the study of neuroelectric brain information can provide further insights to understand cognitive processes and underlying mechanisms in Sz.

Are Negative Symptoms Dimensional or Categorical? Detection and Validation of Deficit Schizophrenia With Taxometric and Latent Variable Mixture Models

Studies have supported the validity of the deficit form of schizophrenia (ie, people with primary and enduring negative symptoms). A test of whether that group is a true taxon-that is, a distinct, discontinuous group-has yet to be conducted and the underlying structure of negative symptoms as categorical or dimensional remains undetermined. The present study examined the latent structure of negative and deficit symptoms to determine if a nonarbitrary boundary distinguishes deficit from nondeficit forms of schizophrenia (ie, whether these symptoms reflect a continuous or categorical variable). Schedule for the Deficit Syndrome ratings of 789 individuals with a psychotic disorder were submitted to taxometric and latent variable mixture analyses to test categorical vs dimensional hypotheses of negative symptoms and deficit schizophrenia. Analytic models favored a taxonic structure of negative symptoms and the validity of the deficit/nondeficit classification scheme. Taxometric classification outperformed clinician-based deficit/nondeficit classification in its association with summer birth, male sex, premorbid adjustment, neurocognition, and psychosocial functioning. Within taxon and complement classes, severity scores remained significant predictors of premorbid adjustment, neurocognition, and psychosocial functioning. Thus, although a categorical approach is validated, a hybrid categorical-dimensional conceptualization of negative symptoms also has validity for the prediction of external variables.

Contingent negative variation in patients with deficit schizophrenia or bipolar I disorder with psychotic features: measurement and correlation with clinical characteristics

BACKGROUND

Schizophrenia is a highly heterogeneous disease. Event-related potentials have been regarded to establish intermediate phenotypes of schizophrenia. Our previous study found that patients with deficit schizophrenia (DS) are relatively homogeneous and show a significantly longer onset latency of contingent negative variation (CNV) expectancy wave.

AIMS

To further examine CNV in patients with first-episode and drug-naïve DS or bipolar I disorder (BP I) with psychotic features, and also investigate correlations between CNV and clinical characteristics in DS and BP I.

METHOD

We elicited a CNV using an alarm (S1)-imperative (S2) paradigm in 30 DS patients or 33 BP I with psychotic features as well as 40 healthy controls.

RESULTS

CNV amplitude was significantly smaller and reaction time significantly longer in the DS and BP I groups than in healthy controls. Post-imperative negative variation (PINV) interval was significantly shorter in the DS group than in healthy controls. The onset latency of CNV expectancy wave was significantly longer and PINV area significantly smaller in the DS group than in the other groups. In the DS group, CNV amplitude and PINV interval correlated negatively with the subscale of negative symptoms on the Positive and Negative Syndrome Scale (PANSS); CNV amplitude also correlated negatively with disease duration. In the BP I group, CNV amplitude and reaction time showed no correlation with clinical features.

CONCLUSIONS

CNV amplitude is a common trait marker for psychosis. The onset latency of CNV expectancy wave appears to be a specific trait marker and may be used to identify candidate genes for DS.

Impairments of event-related magnetic fields in schizophrenia patients with predominant negative symptoms

Recently there is a growing understanding that patients suffering from negative symptoms of schizophrenia represent a distinct patient population. However, despite the abundance of EEG studies characterizing schizophrenia patients in general, only a handful of studies have focused on the electrophysiological correlates of negative symptoms. The current study examined whether the impairments in event-related magnetic fields (ERFs) commonly reported in heterogeneous groups of patients with mixed positive and negative symptoms also occur in patients with predominantly negative symptoms, and investigated their correlation to clinical symptoms and cognitive deficits. Twenty schizophrenia patients suffering from predominant negative symptoms and 25 healthy subjects underwent neuropsychological and electromagnetic assessments. ERFs were recorded during a three-stimuli novelty oddball and a sensory gating paradigm, and M50, P300m and Novelty-P3m components were investigated. Patients displayed impaired M50 ratios, reduced left P300m and frontal Novelty-P3m amplitudes. These electromagnetic measures correlated significantly with the severity of negative symptoms (SANS scale). The electrophysiological abnormalities which have been proposed as candidate biomarkers for schizophrenia are also manifested in patients with predominantly negative symptoms.

Brain white matter microstructure in deficit and non-deficit subtypes of schizophrenia

Dividing schizophrenia into its deficit (SZD) and nondeficit (SZND) subtypes may help to identify specific and more homogeneous pathophysiological characteristics. Our aim was to define a whole brain voxelwise map specifically characterizing white matter tracts of schizophrenia patients with and without the deficit syndrome. We compared microstructural diffusion-related parameters as measured by diffusion tensor imaging in 21 SZD patients, 21 SZND patients, and 21 healthy controls, age- and gender-matched. Results showed that fractional anisotropy was reduced in the right precentral area in SZND patients, and in the left corona radiata of the schizophrenia group as a whole. Axial diffusivity was reduced in the left postcentral area of SZD patients and in the left cerebellum of the whole schizophrenia group. Radial diffusivity was increased in the left forceps minor of SZD patients, in the left internal capsule of SZND patients, and in the right inferior fronto-occipital fasciculus in the whole schizophrenia group. Mean diffusivity was increased from healthy controls to SZD patients to SZND patients in the right occipital lobe. In conclusion, SZD patients are not simply at the extreme end of a severity continuum of white matter disruption. Rather, the SZD and SZND subtypes are associated with distinct and specific brain microstructural anomalies that are consistent with their peculiar psychopathological dimensions.

Impulsiveness in patients with bulimia nervosa: electrophysiological evidence of reduced inhibitory control

OBJECTIVES

Bulimia nervosa (BN) is associated with a deficit of self-regulatory control and impulsivity. The present study aimed to clarify whether an impaired inhibitory control due to hyperarousal underlies impulsivity in BN subjects.

METHODS

Event-related potentials (ERPs) were recorded in 17 female patients with BN and 17 healthy controls during a three-tone oddball task. ERP components related to inhibition of irrelevant distractor stimuli, as well as effortful processing, were analyzed. Standardized low-resolution electromagnetic tomography (sLORETA) was used to assess ERP source activity.

RESULTS

Compared to healthy controls, BN patients showed reduced amplitude and shorter latency of the N200 (N2), increased amplitude and shorter latency of the target slow wave (SW), and higher amplitude of the P300 for distractor stimuli (P3a) and for targets (P3b). sLORETA showed the following: (1) higher activity of the P3a generators in the left parietal cortex, bilateral precuneus and right frontal and anterior cingulate for distractor stimuli and (2) lower activity of the SW generators in the left medial frontal gyrus, bilateral superior frontal, anterior cingulate and cuneus for target stimuli. The reduction of the N2 latency was associated with the Barratt scores for impulsiveness.

CONCLUSIONS

The observed electrophysiological abnormalities suggest a condition of hyperarousal, with impaired suppression of irrelevant stimuli due to abnormal cortical activation and reduced signal-to-noise ratio. Our findings point to functional abnormalities within a neural system that subserves attention and self-regulatory control, which may contribute to impulsive behaviors in BN.

Progress in the study of negative symptoms

A selective review of the negative symptoms of schizophrenia is an appropriate article to result from the festschrift honoring William T. Carpenter Jr, as he has made substantial contributions in this area. This review assesses progress in 3 areas in which he has been an important investigator: the distinction between primary vs secondary negative symptoms; the appropriate design for treatment trials; and the nosology of negative symptoms.

Cytomegalovirus seropositivity and serointensity are associated with hippocampal volume and verbal memory in schizophrenia and bipolar disorder

INTRODUCTION

Cytomegalovirus (CMV) is a member of the herpesviridae family that has a limbic and temporal gray matter tropism. It is usually latent in humans but has been associated with schizophrenia, bipolar disorder and cognitive deficits in some populations. Hippocampal decreased volume and dysfunction play a critical role in these cognitive deficits. We hypothesized that CMV seropositivity and serointensity would be associated with hippocampal volume and cognitive functioning in patients with schizophrenia or bipolar disorder.

METHODS

102 healthy controls, 118 patients with bipolar disorder and 69 patients with schizophrenia performed the California Verbal Learning Test (CVLT) and had blood samples drawn to assess CMV IgG levels. A subgroup of 52 healthy controls, 31 patients with bipolar disorder and 27 patients with schizophrenia underwent T1 MRI for hippocampal volumetry. We analyzed the association between CMV serointensity and seropositivity with hippocampal volume. We also explored the correlation between CMV serointensity and seropositivity and CVLT scores.

RESULTS

In both patient groups but not in controls, higher CMV serointensity was significantly associated with smaller right hippocampal volume. Further, in the group of patients with schizophrenia but not bipolar disorder, CMV serointensity was negatively correlated with CVLT scores.

CONCLUSION

CMV IgG titers are associated with decreased hippocampal volume and poorer episodic verbal memory in patients with schizophrenia or bipolar disorder. The mechanism of this association warrants further exploration.

Electrophysiological aberrations associated with negative symptoms in schizophrenia

Clinical heterogeneity is a confound common to all of schizophrenia research. Deficit schizophrenia has been proposed as a homogeneous disease entity within the schizophrenia syndrome. The use of the Schedule for the Deficit Syndrome (SDS) has allowed the definition of a subgroup dominated by persistent and primary negative symptoms. While a number of studies have appeared over the years examining the electrophysiological correlates of the cluster of negative symptoms in schizophrenia, only a few studies have actually focused on the Deficit Syndrome (DS). In this chapter, electrophysiological investigations utilizing EEG, Evoked Potentials (EPs), polysomnography (PSG), or magnetoencephalography (MEG) to probe "negative symptoms," or "Deficit Syndrome" are reviewed. While this line of research is evidently in its infancy, two significant trends emerge. First, spectral EEG studies link increased slow wave activity during wakefulness to the prevalence of negative symptoms. Second, sleep studies point to an association between decrease in slow wave sleep and prevalence of negative symptoms. Several studies also indicate a relationship of negative symptoms with reduced alpha activity. A host of other abnormalities including sensory gating and P300 attenuation are less consistently reported. Three studies specifically addressed electrophysiology of the DS. Two of the three studies provided evidence suggesting that the DS may be a separate disease entity and not simply a severe form of schizophrenia.

Multi-components of evoked-brain potentials in deficit and nondeficit schizophrenia

INTRODUCTION

The present study aims to detect the specific and common impairment index relative to evoked brain potentials (EBPS ) in deficit schizophrenia (DS) and nondeficit schizophrenia (NDS), and investigates the relationship between EBPs and clinical variables.

METHODS

The study used EBPs in 21 patients with DS, 38 patients with NDS, and 50 healthy controls (HCs) to investigate P300 waves, mismatch negative (MMN), sensory gating (SG) P50 and contingent negative variation (CNV). A comparison of three groups and the relationship between EBPs and clinical variables were performed using general linear model analyses and partial correlation, respectively.

RESULTS

Compared with HCs, both groups of patients showed delayed N1 , N2 , and P3a latency, and reduced N1 and N2 amplitude. The MMN showed delayed latency. The P50 ratios and the inhibited ratios were impaired, whereas SG loss ratios increased. CNV amplitude was reduced. Compared with HCs, NDS showed delayed latency of S2'-C in CNV, whereas DS showed shortened latency. Only NDS, when compared with HCs, showed delayed latency of P3b , Also, only DS, when compared with HCs, showed delayed latency of point A in CNV. Latency of point A in CNV of DS, correlated with a poorer Global Assessment of Functioning Scale (6 weeks) and was independent of clinical characteristics.

DISCUSSION

Schizophrenia represents a clinical syndrome with shared impairments in brain function, whereas DS is a relatively homogeneous subgroup of schizophrenia with unique pathophysiological changes.

Dysfunctional attitudes and expectancies in deficit syndrome schizophrenia

The deficit syndrome was proposed over 20 years ago as a separate negative symptom syndrome within schizophrenia with a distinct neurobiological pathophysiology and etiology. Recent research, however, has indicated that psychological factors such as negative attitudes and expectancies are significantly associated with the broad spectrum of negative symptoms. Specifically, defeatist beliefs regarding performance mediate between neurocognitive impairment and both negative symptoms and functional outcome. Additionally, asocial beliefs predict asocial behavior and negative expectancies regarding future pleasure are associated with negative symptoms. The present study explored whether these dysfunctional beliefs and negative expectancies might also be a feature of the deficit syndrome. Based on a validated proxy method, 22 deficit and 72 nondeficit patients (from a pool of 139 negative symptom patients) were identified and received a battery of symptom, neurocognitive, and psychological measures. The deficit group scored significantly worse on measures of negative symptoms, insight, emotion recognition, defeatist attitudes, and asocial beliefs but better on measures of depression, anxiety, and distress than the nondeficit group. Moreover, the deficit group showed a trend for higher scores on self-esteem. Based on these findings, we propose a more comprehensive formulation of deficit schizophrenia, characterized by neurobiological factors and a cluster of psychological attributes that lead to withdrawal and protect the self-esteem. Although the patients have apparently opted-out of participation in normal activities, we suggest that a psychological intervention that targets these negative attitudes might improve their functioning and quality of life.

Inflammatory markers in antipsychotic-naïve patients with nonaffective psychosis and deficit vs. nondeficit features

Newly diagnosed, antipsychotic-naïve patients with nonaffective psychosis appear to have increases in pro-inflammatory cytokines. Patients characterized by primary, enduring negative symptoms (deficit symptoms) differ from patients without such features with regard to course of illness, treatment response, risk factors and metabolic disturbances. We hypothesized that they would also differ on concentrations of the inflammatory markers interleukin-6 (IL6) and C-reactive protein (CRP). Newly diagnosed, antipsychotic-naïve patients with nonaffective psychosis were categorized into deficit (N=20) and nondeficit (N=42) groups, and were matched on age, gender, body mass index, smoking, cortisol level, socioeconomic status, and the severity of psychotic symptoms. Fasting concentrations of IL6 were significantly higher in deficit (mean [S.D.]) (8.0 pg/ml [12.7]) than nondeficit patients (0.3 pg/ml [1.3]). CRP levels were also significantly higher in the deficit patients (0.3 mg/dl [0.4]) vs. (0.2 mg/dl [0.4]), respectively. In contrast, 2-h glucose concentrations (2HG) in a glucose tolerance test were lower in the deficit than the nondeficit group. Our results show a double dissociation with regard to glucose intolerance and inflammation: the deficit group has greater inflammation, but less severe glucose intolerance. These results provide further evidence for the validity of the deficit/nondeficit categorization.

P50 gating in deficit and nondeficit schizophrenia

Dysfunctional auditory sensory processing has generally been found in schizophrenia and it has been suggested that these deficits might be related to clinical and psychosocial variables. The present study included P50 recordings using a simple-paired click auditory evoked potential paradigm in sixty patients with deficit schizophrenia (DS), sixty patients with nondeficit schizophrenia (NDS), and sixty comparison subjects. The Schedule for the Deficit Syndrome was used to categorize patients as DS or NDS. The two patient groups did not differ in clinical variables, except for higher negative dimension and lower community outcome scores in DS than in NDS patients. There were no differences in P50 ratios between deficit and nondeficit subgroups; compared with normal subjects both groups of schizophrenia patients showed impaired P50 ratios (p<0.0001). This ratio appears to be independent of positive and negative symptoms. However, impairment in P50 gating correlated with poorer community outcome. The data document the existence of early auditory sensory processing abnormalities in DS and NDS, and might suggest that common neuronal network abnormalities underlie both forms of schizophrenia. Deficient P50 gating may be associated with impaired functional outcome in schizophrenia.

Deficit schizophrenia: an overview of clinical, biological and treatment aspects

The concept of deficit schizophrenia is regarded as one of the most promising attempts to reduce heterogeneity within schizophrenia. This paper summarizes the clinical, neurocognitive, brain imaging and electrophysiological correlates of this subtype of schizophrenia. Attempts to identify genetic and non-genetic risk factors are reviewed. Methodological limitations of studies supporting the efficacy of atypical antipsychotics in the treatment of the syndrome are highlighted. Two decades of research on deficit schizophrenia have failed to prove that it represents the extreme end of a severity continuum in schizophrenia, while some findings support the claim that it may be a separate disease entity.

Psychological investigation of the "feeling of being seen through" in a non-clinical sample using an ERP paradigm

This study aimed to explore the validity of an experiment-based paradigm for assessing the suspicious thoughts in healthy volunteers and its corresponding neural process. Twenty-four pairs of healthy college students participated in this study and were randomly assigned to two experimental conditions: the informed (12 pairs) and the naive (12 pairs) conditions. EEG of one subject in each pair was recorded when the 'feeling of being seen through' was evoked. The findings showed a prominent positive deflection of the difference wave within the time window 200 ms-400 ms after stimuli presentation (0 ms) in the naive group. The ERP amplitude of frontal and central scalp sites was significantly different between high and low paranoia rating scores. These findings provide preliminary evidence on the use of an ERP paradigm to detect paranoid ideation or suspicious thoughts in non-clinical sample.

Differences in glucose tolerance between deficit and nondeficit schizophrenia

Some studies suggest that schizophrenia is associated with an increased risk of diabetes independently of antipsychotic use. People with deficit schizophrenia, which is characterized by primary (or idiopathic), enduring negative symptoms, differ from those with nondeficit schizophrenia on course of illness, treatment response, risk factors, and biological correlates. We hypothesized that deficit and nondeficit subjects would also differ with regard to glucose tolerance. Newly diagnosed, antipsychotic-naïve subjects with nonaffective psychosis and matched control subjects were administered a 75 g oral glucose tolerance test (GTT). Two-hour glucose concentrations were significantly higher in the nondeficit patients (N=23; mean [SD] of 121.6 [42.0]) than in deficit (N=23; 100.2 [23.1]) and control subjects (N=59; 83.8 [21.9]); the deficit subjects also had significantly higher two-hour glucose concentrations than did the control subjects. These results provide further support that the deficit group has a distinctive etiopathophysiology.

Reduced auditory evoked potential component N100 in schizophrenia--a critical review

The role of a reduced N100 (or N1) component of the auditory event related potential as a potential trait marker of schizophrenia is critically discussed in this review. We suggest that the extent of the N100 amplitude reduction in schizophrenia depends on experimental and subject factors, as well as on clinical variables: N100 is more consistently reduced in studies using interstimulus intervals (ISIs) >1 s than in studies using shorter ISIs. An increase of the N100 amplitude by allocation of attention is often lacking in schizophrenia patients. A reduction of the N100 amplitude is nevertheless also observed when such an allocation is not required, proposing that both endogenous and exogenous constituents of the N100 are affected by schizophrenia. N100 is more consistently reduced in medicated than unmedicated patients, but a reduction of the N100 amplitude as a consequence of antipsychotic medication was shown in only two of seven studies. In line with that, the association between the N100 reduction and degree of psychopathology of patients appears to be weak overall. A reduced N100 amplitude is found in first degree relatives of schizophrenia patients, but the risk of developing schizophrenia is not reflected in the N100 amplitude reduction.

Deficit schizophrenia: an update

The criteria for deficit schizophrenia were designed to define a group of patients with enduring, primary (or idiopathic) negative symptoms. In 2001, a review of the literature suggested that deficit schizophrenia constitutes a disease separate from nondeficit forms of schizophrenia. Here we provide a review of new studies, not included in that paper, in which patients with deficit schizophrenia and those with nondeficit schizophrenia were compared on dimensions typically used to distinguish diseases: signs and symptoms, course of illness, pathophysiological correlates, risk and etiological factors, and treatment response. Replicated findings and new evidence of double dissociation supporting the separate disease hypothesis are highlighted. Weaknesses in research and treatment options for these patients are also emphasized.

Schizoid-like features and season of birth in a nonpatient sample

OBJECTIVES

People with the deficit subtype of schizophrenia differs from others with schizophrenia with regard to risk factors, signs and symptoms, biological correlates, treatment response, and course of illness. The deficit group, which is characterized by decreased social interests and a lack of depression, has a well-replicated association with June/July birth, which contrasts with the association of schizophrenia as a whole with winter birth. As some of the correlates of schizophrenia are found in subclinical form in the schizophrenia spectrum, we hypothesized that June/July birth would be associated with the combination of decreased sociality in the absence of depression in a nonpatient group as well.

METHODS

The Beck Depression Inventory and Chapman's Perceptual Aberration, Magical Ideation, and Social Anhedonia scales were administered to university students. The Perceptual Aberration and Magical Ideation scale scores were combined into a single psychotic-like symptom score (PerMag). Blind to month of birth, each subject (N=425) was given a score that quantified the combination of social anhedonia and an absence of depression. Analyses were then performed in subjects in the upper 50% of PerMag scores who had complete data (N=171, 27.5% male).

RESULTS

June/July birth (p=.037) and male gender (p=.002) were both found to be associated with higher scores on the combination of social anhedonia and a low depression score; the interaction of these factors was not significant.

CONCLUSIONS

These results suggest that the same seasonal factor that contributes to the risk of deficit schizophrenia may affect brain development and personality characteristics in the general population.

Patterns of structural MRI abnormalities in deficit and nondeficit schizophrenia

Negative symptoms of schizophrenia have generally been found in association with ventricular enlargement and prefrontal abnormalities. These relationships, however, have not been observed consistently, most probably because negative symptoms are heterogeneous and result from different pathophysiological mechanisms. The concept of deficit schizophrenia (DS) was introduced by Carpenter et al to identify a clinically homogeneous subgroup of patients characterized by the presence of primary and enduring negative symptoms. Findings of brain structural abnormalities reported by magnetic resonance imaging (MRI) studies focusing on DS have been mixed. The present study included 34 patients with DS, 32 with nondeficit schizophrenia (NDS), and 31 healthy comparison subjects, providing the largest set of MRI findings in DS published so far. The Schedule for the Deficit Syndrome was used to categorize patients as DS or NDS patients. The 2 patient groups were matched on age and gender and did not differ on clinical variables, except for higher scores on the negative dimension and more impaired interpersonal relationships in DS than in NDS subjects. Lateral ventricles were larger in NDS than in control subjects but were not enlarged in patients with DS. The cingulate gyri volume was smaller in NDS but not in DS patients as compared with healthy subjects. Both groups had smaller dorsolateral prefrontal cortex and temporal lobes than healthy subjects, but DS patients had significantly less right temporal lobe volume as compared with NDS patients. These findings do not support the hypothesis that DS is the extreme end of a severity continuum within schizophrenia.

Negative symptoms in schizophrenia: a review

Negative symptoms refer to the weakening or lack of normal thoughts, emotions or behaviour in schizophrenia patients. Their prevalence in first-episode psychosis is high, 50-90%, and 20-40% of schizophrenia patients have persisting negative symptoms. Severe negative symptoms during the early stages of treatment predict poor prognosis. The aim of the study was to review the current literature on the negative symptoms of schizophrenia. In June 2007, the following databases were searched: Web of Science, PubMed, PsycINFO, Medline (Ovid) and Scopus. The search included articles written in English and no time limit was determined. The studies were manually screened by one of the authors according to the title and abstract. About one in three schizophrenia patients suffer from significant negative symptoms. In these patients, negative symptoms constitute a key element of overall symptoms, weakening their ability to cope with everyday activities, affecting their quality of life and their ability to manage without significant outside help. About one in three schizophrenia patients suffer from significant negative symptoms. Attention should be focused on negative symptoms during the early phase of treatment, because they cause significant impairment to patients' quality of life. So far, no treatment appears to substantially improve negative symptoms narrowly defined. However, according to clinical experience, when treating negative symptoms, the best effect is achieved by optimizing the dose of medication and by complementing it with psychosocial therapies.