Positive symptoms and duration of illness predict functional laterality and attention modulation in schizophrenia

The relationship between obsessive-compulsive symptoms and real-life functioning in schizophrenia: New insights from the multicenter study of the Italian Network for Research on Psychoses

BACKGROUND

Although obsessive-compulsive disorder (OCD) is highly prevalent in schizophrenia, its relationship with patients' real-life functioning is still controversial.

METHODS

The present study aims at investigating the prevalence of OCD in a large cohort of non-preselected schizophrenia patients living in the community and verifying the relationship of OCD, as well as of other psychopathological symptoms, with real-life functioning along a continuum of OCD severity and after controlling for demographic variables.

RESULTS

A sample of 327 outpatients with schizophrenia was enrolled in the study and collapsed into three subgroups according to OCD severity (subclinical, mild-moderate, severe). A series of structural equation modeling (SEM) was performed to analyze in each subgroup the association of obsessive-compulsive symptoms with real-life functioning, assessed through the Specific Levels of Functioning Scale and the UCSD Performance-Based Skills Assessment. Moreover, latent profile analysis (LPA) was performed to infer latent subpopulations. In the subclinical OCD group, obsessive-compulsive symptoms (OCS) were not associated with functioning, whereas in the mild-moderate OCD group, they showed a positive relationship, particularly in the domains of work and everyday life skills. The paucity of patients with severe OCD did not allow performing SEM analysis in this group. Finally, LPA confirmed a subgroup with mild-moderate OCS and more preserved levels of functioning.

CONCLUSIONS

These findings hint at a positive association between mild-moderate OCD and real-life functioning in individuals with schizophrenia and encourage a careful assessment of OCD in personalized programs to sustain daily life activities.

The impact of preoperative nutritional screening, ERAS protocol, and mini-invasive surgery in surgical oncology: A multi-institutional SEM analysis of patients with digestive cancer

Background

Mini-invasive surgery (MIS), ERAS, and preoperative nutritional screening are currently used to reduce complications and the length of hospital stay (LOS); however, inter-variable correlations have seldom been explored. This research aimed to define inter-variable correlations in a large series of patients with gastrointestinal cancer and their impact on outcomes.

Methods

Patients with consecutive cancer who underwent radical gastrointestinal surgery between 2019 and 2020 were analyzed. Age, BMI, comorbidities, ERAS, nutritional screening, and MIS were evaluated to determine their impact on 30-day complications and LOS. Inter-variable correlations were measured, and a latent variable was computed to define the patients' performance status using nutritional screening and comorbidity. Analyses were conducted using structural equation modeling (SEM).

Results

Of the 1,968 eligible patients, 1,648 were analyzed. Univariable analyses documented the benefit of nutritional screening for LOS and MIS and ERAS (≥7 items) for LOS and complications; conversely, being male and comorbidities correlated with complications, while increased age and BMI correlated with worse outcomes. SEM analysis revealed that (a) the latent variable is explained by the use of nutritional screening (p0·004); (b) the variables were correlated (age–comorbidity, ERAS–MIS, and ERAS–nutritional screening, p < 0·001); and (c) their impact on the outcomes was based on direct effects (complications: sex, p0·001), indirect effects (LOS: MIS-ERAS-nutritional screening, p < 0·001; complications: MIS-ERAS, p0·001), and regression-based effects (LOS: ERAS, MIS, p < 0·001, nutritional screening, p0·021; complications: ERAS, MIS, p < 0·001, sex, p0·001). Finally, LOS and complications were correlated (p < 0·001).

Conclusion

Enhanced recovery after surgery (ERAS), MIS, and nutritional screening are beneficial in surgical oncology; however, the inter-variable correlation is reliable, underlying the importance of the multidisciplinary approach.

Ambiguous handedness and visuospatial pseudoneglect in schizotypy in physical and computer-generated virtual environments

Virtual reality (VR) technology has increased clinical attention in the health care of schizophrenia spectrum disorders in both diagnoses of the symptoms and assessment of schizotypal traits. However, the exact nature of VR-induced positive treatment effect in schizotypy is still unknown. In this study, VR technology was used as a non-invasive neurocognitive trigger to test the asymmetric visuospatial representational instability found in individuals with high schizotypy. The study aimed to reveal the brain functional hemispheric laterality in physical and virtual realities in individuals with schizotypal traits. Fifty-one healthy, right-handed participants (24 males and 27 females) were enrolled through public advertisements. Hemispheric functional asymmetry was measured by the Line Bisection Task (LBT). The results revealed that (a) LBT bias in the physical reality showed a handedness-related leftward pseudoneglect, however, similar handedness-related pseudoneglect in VR has not been found. (b) Comparing LBT bias in physically real and VR environments showed rightward drift in VR environments independently to the degree of handedness. (c) The schizotypy has no association with handedness, however, the cognitive schizotypy is related to the LBT bias. Higher cognitive schizotypy in VR associated with left hemispatial pseudoneglect. In conclusion, schizotypy is associated with ambiguous behavioral and cognitive functional laterality. In individuals with high cognitive schizotypy, the VR environment enhanced the representational articulation of the left hemispace. This effect may be originated from the enhancement of the right hemisphere overactivation and is followed by a lower mental control of the overt behavior.

Impact of unilateral stroke on right hemisphere superiority in executive control

In our previous study, we have demonstrated a right hemisphere superiority in executive control of attention, with the right hemisphere being more efficient in dealing with conflict for stimuli presented in the left visual field. However, the unique and synergetic contribution of the two hemispheres to this superiority effect is still elusive. Here, using the lateralized attention network test, we compared the flanker conflict effect for stimuli presented in the left and right visual fields in patients with an ischemic stroke in the right or left hemisphere as the unilateral lesion groups and in patients with a transient ischemic attack without an acute infarction as the control group. In contrast to the transient ischemic attack group, which demonstrated a right hemisphere superiority in conflict processing, there was no evidence for such an effect in both unilateral stroke groups. These results can be explained by our model proposing that there is bilateral hemispheric involvement for conflict processing for information received from the left visual field and unilateral hemispheric involvement for conflict processing for information received from the right visual field, resulting in more efficient processing for the left visual field, i.e., the right hemisphere superiority effect. When there is damage to either hemisphere, the responsibility of conflict processing will largely fall on the intact hemisphere, eliminating the right hemisphere superiority effect.

Language Lateralization and Auditory Attention Impairment in Young Adults at Ultra-High Risk for Psychosis: A Dichotic Listening Study

Objectives: Impaired attention and language functions are common in psychosis, but have been less explored in subjects with ultra-high risk for psychosis (UHR). The aim of the study was to investigate differences in language lateralization and auditory attention in UHR subjects compared to healthy controls with a dichotic listening paradigm. In addition, symptoms from The Structural Interview for Prodromal Syndromes (SIPS) were explored in relation to performance on dichotic listening.

Methods: The UHR subjects (n = 46, female = 28, mean age = 17.9) were compared to a group of healthy controls (n = 40, female = 20, mean age = 16.8). A split-plot repeated measures analysis of covariance was conducted with group as between-subjects factor and attention conditions (non-forced, forced-right, forced-left) and side (right ear, left ear) as repeated measures factors (2×3×2 design) using gender, age and handedness as covariates. SIPS symptoms were subjected to Spearman’s r correlations with laterality indexes and attentional gain in each ear.

Results: There was a statistically significant three-way interaction of group (UHR, healthy controls) × forced condition (non-forced, forced-right, forced-left) × side (right ear, left ear), p = 0.048. The effect was due to an interaction between group × side in the forced-left condition. There were no significant differences between UHR subjects and healthy controls in the non-forced condition. Right ear gain correlated with “Perceptual abnormalities/Hallucinations” (P4), r = 0.486, p = 0.001.

Conclusion: UHR subjects demonstrated impairment in top-down attentional mechanisms, but showed no language lateralization abnormalities. Impairment in top-down attentional mechanisms are frequently reported from dichotic listening studies in patients with schizophrenia. Higher levels of perceptual abnormalities and hallucinatory experiences were associated with enhanced report from the right ear in the forced-right condition.

A life in academia: My career in brief

In this article I have summarized some of the main trends and topics of my research career, spanning a time period of 50 years, from its start as a master student at the Department of Psychology, University of Uppsala, Sweden to seeing the end of a long career, now at the University of Bergen, Norway. This journey has, apart from having been a journey across various disciplines and topics in experimental psychology, psychophysiology and neuropsychology, functional neuroimaging and cognitive neuroscience, also been a social class journey for me personally. I describe my academic career from my arrival as a young student at the University of Uppsala, Sweden in the late 1960s to my graduation as PhD in 1977 at the age of 29 years, brief postdoc period at the University of Pennsylvania, USA, and finally professor at the University of Bergen, Norway. The article focuses on my view of the research and research findings during these years, including studies of hemispheric asymmetry, dyslexia and language, dichotic listening, fMRI, and during the last years, studies of auditory hallucinations in schizophrenia. I have collaborated with numerous people, both nationally and internationally over the years, far too many to mention in a space-limited overview article. I apologize for this, and wish that I had time and space to mention all the fantastic colleagues and friends that I have met during my career. This article is what I recall of dates, places, encounters, etc., and any errors and misunderstandings are entirely due to my far from perfect memory, for which I also apologize.

Task and resting-state fMRI studies in first-episode schizophrenia: A systematic review

In the last two decades there has been an increase on task and resting-state functional Magnetic Resonance Imaging (fMRI) studies that explore the brain's functional changes in schizophrenia. However, it remains unclear as to whether the brain's functional changes during the resting state are sensitive to the same brain regions during task fMRI. Therefore, we conducted a systematic literature search of task and resting-state fMRI studies that investigated brain pathological changes in first-episode schizophrenia (Fleischhacker et al.). Nineteen studies met the inclusion criteria; seven were resting state fMRI studies with 371 FES patients and 363 healthy controls and twelve were task fMRI studies with 235 FES patients and 291 healthy controls. We found overlapping task and resting-state fMRI abnormalities in the prefrontal regions, including the dorsal lateral prefrontal cortex, the orbital frontal cortex and the temporal lobe, especially in the left superior temporal gyrus (STG). The findings of this systematic review support the frontotemporal hypothesis of schizophrenia, and the disruption in prefrontal and STG might represent the pathophysiology of schizophrenia disorder at a relatively early stage.

The role of set-shifting in auditory verbal hallucinations

BACKGROUND

Auditory verbal hallucinations (AVHs) are a cardinal characteristic of psychosis. Recent research on the neuropsychological mechanism of AVHs has focused on source monitoring failure, but a few studies have suggested the involvement of attention, working memory, processing speed, verbal learning, memory, and executive functions. In this study we examined the neuropsychological profile of patients with AVHs, assuming that the mechanism underlying this symptom could be a dysfunction of specific cognitive domains.

METHODS

A large neuropsychological battery including set-shifting, working memory, processing speed, attention, fluency, verbal learning and memory, and executive functions was administered to 90 patients with psychotic disorders and 44 healthy controls. The group of patients was divided into two groups: 46 patients with AVHs in the current episode and 44 who denied auditory hallucinations or other modalities in the current episode. AVHs were assessed with the Psychotic Symptom Rating Scales (PSYRATS); the Launay-Slade Hallucination Scale was used to measure long-term propensity to auditory verbal hallucination-like experiences (HLEs) in the sample.

RESULTS

Patients showed poorer performances on all neuropsychological measures compared to the healthy controls' group. In the original dataset without missing data (n=58), patients with AVHs (n=29) presented poorer set shifting and verbal learning, higher levels of visual attention, and marginally significant poorer semantic fluency compared to patients without AVHs (n=29). In the logistic model on the multiple imputed dataset (n=90, 100 imputed datasets), lower capacity of set shifting and semantic fluency distinguished patients with AVHs from those without them.

CONCLUSIONS

Patients experiencing persistent AVHs might fail to shift their attention away from the voices; poorer semantic fluency could be a secondary deficit of set-shifting failure.

Is duration of illness really influencing outcome in major psychoses?

BACKGROUND

An increasing number of studies identifies the duration of illness (DI) as an important predictor of outcome in patients affected by major psychoses (MP). The aim of the present paper was to revise medical literature about DI and its effects on MP, focusing in particular on the relationship between DI and outcome with particular reference to treatment response, suicidal risk, cognitive impairment and social functioning.

METHODS

A search in the main database sources has been performed to obtain a comprehensive overview. Studies with different methodologies (open and double-blinded) have been included, while papers considering other variables such as duration of untreated episode/illness were excluded. MP included the diagnoses of schizophrenia, bipolar disorder and major depressive disorder.

RESULTS

Available data show that DI influences treatment response, suicidal risk and loss of social functioning in schizophrenic patients, while results are more controversial with regard to cognitive impairment. In bipolar disorder, a long DI has been associated with less treatment response, more suicidal risk and cognitive impairment, but more data are needed to draw definitive conclusions. Finally, studies, regarding DI of illness and its predictive value of outcome in major depressive disorder show contradictory results.

CONCLUSIONS

DI appears a negative outcome factor particularly for schizophrenia, while with regard to mood disorders, more data are needed to draw definitive sound conclusions.

Auditory verbal hallucinations reflect stable auditory attention deficits: a prospective study

INTRODUCTION

Previous studies have shown that auditory verbal hallucinations (AVHs) in psychosis are associated with reduced verbal auditory attention. Whether this is an effect of ongoing AVH or reflects a more stable cognitive vulnerability also present after treating the AVH is unknown. The aim of this study was to follow patients with acute psychosis with and without AVH, and to test their auditory attention in a more stabilised clinical phase.

METHODS

Fifty patients (35 males and 15 females) were examined when admitted to an acute psychiatry ward and tested three months later with a dichotic listening test with attention instructions. The patients were divided into a frequent (n = 33) and non-frequent (n = 17) AVH group based on their score on the Positive and Negative Syndrome Scale item hallucinatory behaviour (≥4 and ≤3, respectively) at baseline.

RESULTS

A significant interaction emerged between AVH group and attention instruction condition; the frequent AVH group failed to control their auditory attention as opposed to the non-frequent AVH group.

CONCLUSIONS

Patients with frequent AVH in an acute psychotic state showed impaired auditory attention three months after their AVH had been treated, indicating a stable cognitive vulnerability factor for experiencing AVH.

Controlled shifting of attention in schizophrenia and bipolar disorder through a dichotic listening paradigm

The dichotic listening (DL) task was developed originally to examine bottom-up or "automatic" information processing. More recently, however, it has been used as a tool in the study of top-down or "controlled" information processing. This has been done by including forced-choice conditions, wherein the examinee is required to focus attention on one or the other ear. It has been widely utilized with patients with schizophrenia, who exhibit rather severe deficits in managing their attention, but not with other patient groups, such as patients with bipolar disorder. In the present study, we examined potential performance similarities in the DL listening task. In total, the sample consisted of 38 patients with schizophrenia, 20 patients with psychotic bipolar disorder and 35 healthy individuals, who performed a DL task with verbal stimuli once at the beginning of their hospitalization and again on the last day before discharge. Our findings indicated that both patient groups showed similarly diminished performance when compared to healthy participants at both times of administration. Symptom improvement between the two evaluations did not significantly influence performance in the DL task. In conclusion, impaired automated and controlled information processing appears to be a common deficit in both schizophrenia and bipolar disorder.

Is Central Auditory Processing Disorder Present in Psychosis?

Purpose

The scope of this study was to trace central auditory processing issues in patients with first-episode psychosis using a psychoacoustic test battery approach.

Method

Patients ( n = 17) and volunteer control subjects ( n = 17) with no personal or family history of schizophrenia were included in the study on the basis of normal hearing sensitivity. The authors implemented a central auditory processing battery consisting of monaural and binaural tests with verbal and nonverbal stimuli.

Results

Perceptual deficits in both nonverbal and verbal auditory stimuli are reported in this study, with temporal central auditory processing deficits and a mean left-ear advantage documented in the patient group.

Conclusion

This study points to the possibility of the existence of central auditory processing deficits in first-episode psychosis leading to schizophrenia. Audiologists should be aware of the psychiatric research pointing to enhanced verbal memory as a result of auditory training, linking bottom-up remediation with top-down improvement.

Dichotic listening, executive functions and grey matter cortical volume in patients with schizophrenia and healthy controls

Schizophrenia is characterized by cognitive impairment, especially in relation to executive functions. Brain structural abnormalities are also often seen in schizophrenia although little is known of the relationship between cognitive impairment and structural brain changes. Our aim was therefore to investigate this relationship further using MRI and a dichotic listening (DL) task with simple speech sounds and with instructions to focus attention and report only from the left or right ear stimulus. When instructed to focus attention on the left ear syllable a cognitive conflict is induced requiring the allocation of executive resources to be resolved. Grey matter (GM) volume was measured with MRI from four volumes of interests (VOIs), left and right frontal and temporal cortex, respectively, and correlated with DL performance. The results showed significant differences between the groups in their ability to focus attention on and report the left ear stimulus, which was accompanied by reduced GM volume in the left frontal and right temporal lobe VOIs. There was also a significant positive correlation between left frontal GM volume and performance on the DL task, for the groups combined. The results did not support a conclusion that an impairment in cognitive function in schizophrenia was driven by an corresponding impairment in brain structure, since there were no significant correlations when the groups were analyzed separately. It is however concluded that patients with schizophrenia are impaired in executive functions and that they also show reduced GM volumes in left frontal and right temporal lobe areas, compared to healthy controls.

Failure of attention focus and cognitive control in schizophrenia patients with auditory verbal hallucinations: evidence from dichotic listening

Auditory verbal hallucinations (AVHs) are speech perceptions that lack an external source, phenomenologically experienced as "hearing voices". A perceptual origin of an AVH experience in patients with schizophrenia can however not explain why the "voices" drain the attentional and cognitive capacity of the patients, making them unable to direct attention away from the "voices" and to cognitively suppress the experience. We recently reported how AVHs interfere with the perception of speech sounds, using a dichotic listening experimental paradigm. We now extend this finding by reporting on the interference caused by AVHs on attention and cognitive control, using a slight variation of the same dichotic listening paradigm. The patients (N=148) were instructed to pay attention to and report from either the right or left ear syllable of the dichotic pair. We then correlated their PANSS score for the hallucination item (P3) with the performance score on the dichotic listening task. The results showed that AVHs interfered with the ability to report the right ear syllable when instructed to pay attention to the right side, which is a marker of inability to attend to an external speech stimulus. When instructed to pay attention to the left side, AVHs interfered with the ability to report the left ear syllable, which is a marker of inability to use cognitive control to suppress attending to the "voices". The corresponding correlations for the emotional withdrawal (N2) negative symptom were all non-significant. The correlations were substantiated in an ANOVA with corresponding significant group differences between high versus low symptom score groups. The results thus extend our previous findings of a perceptual origination for AVHs by showing that AVHs interfere with the ability to attend to the outer world around the patient, and the ability to inhibit, or suppress, the "voices" once they occur. Future research should pin down the neuronal basis of both the origination and the attentional and cognitive control aspects of AVHs.

Schizotypy and hemispheric asymmetry: Results from two Chapman scales, the O-LIFE questionnaire, and two laterality measures

Schizotypy is a multidimensional personality construct representing the extension of psychosis-like traits into the general population. Schizotypy has been associated with attenuated expressions of many of the same neuropsychological abnormalities as schizophrenia, including atypical pattern of functional hemispheric asymmetry. Unfortunately the previous literature on links between schizotypy and hemispheric asymmetry is inconsistent, with some research indicating that elevated schizotypy is associated with relative right over left hemisphere shifts, left over right hemisphere shifts, bilateral impairments, or with no hemispheric differences at all. This inconsistency may result from different methodologies, scales, and/or sex proportions between studies. In a within-participant design we tested for the four possible links between laterality and schizotypy by comparing the relationship between two common self-report measures of multidimensional schizotypy (the O-LIFE questionnaire, and two Chapman scales, magical ideation and physical anhedonia) and performance in two computerised lateralised hemifield paradigms (lexical decision, chimeric face processing) in 80 men and 79 women. Results for the two scales and two tasks did not unequivocally support any of the four possible links. We discuss the possibilities that a link between schizotypy and laterality (1) exists but is subtle, probably fluctuating, unable to be assessed by traditional methodologies used here; (2) does not exist, or (3) is indirect, mediated by other factors (e.g., stress-responsiveness, handedness, drug use) whose influences need further exploration.

Emotional prosody modulates attention in schizophrenia patients with hallucinations

Recent findings have demonstrated that emotional prosody (EP) attracts attention involuntarily (Grandjean et al., 2008). The automat shift of attention toward emotionally salient stimuli can be overcome by attentional control (Hahn et al., 2010). Attentional control is impaired in schizophrenia, especially in schizophrenic patients with hallucinations because the "voices" capture attention increasing the processing load and competing for top-down resources. The present study investigates how involuntary attention is driven by implicit EP in schizophrenia with auditory verbal hallucinations (AVH) and without (NAVH). Fifteen AVH patients, 12 NAVH patients and 16 healthy controls (HC) completed a dual-task dichotic listening paradigm, in which an emotional vocal outburst was paired with a neutral vocalization spoken in male and female voices. Participants were asked to report the speaker's gender while attending to either the left or right ear. NAVH patients and HC revealed shorter response times for stimuli presented to the attended left ear than the attended right ear. This laterality effect was not present in AVH patients. In addition, NAVH patients and HC showed faster responses when the EP stimulus was presented to the unattended ear, probably because of less interference between the attention-controlled gender voice identification task and involuntary EP processing. AVH patients did not benefit from presenting emotional stimuli to the unattended ear. The findings suggest that similar to HC, NAVH patients show a right hemispheric bias for EP processing. AVH patients seem to be less lateralized for EP and therefore might be more susceptible to interfering involuntary EP processing; regardless which ear/hemisphere receives the bottom up input.

Hemispheric asymmetry and theory of mind: is there an association?

INTRODUCTION

In autism and schizophrenia attenuated/atypical functional hemispheric asymmetry and theory of mind impairments have been reported, suggesting common underlying neuroscientific correlates. We here investigated whether impaired theory of mind performance is associated with attenuated/atypical hemispheric asymmetry. An association may explain the co-occurrence of both dysfunctions in psychiatric populations.

METHODS

Healthy participants (n=129) performed a left hemisphere (lateralised lexical decision task) and right hemisphere (lateralised face decision task) dominant task as well as a visual cartoon task to assess theory of mind performance.

RESULTS

Linear regression analyses revealed inconsistent associations between theory of mind performance and functional hemisphere asymmetry: enhanced theory of mind performance was only associated with (1) faster right hemisphere language processing, and (2) reduced right hemisphere dominance for face processing (men only).

CONCLUSIONS

The majority of non-significant findings suggest that theory of mind and functional hemispheric asymmetry are unrelated. Instead of "overinterpreting" the two significant results, discrepancies in the previous literature relating to the problem of the theory of mind concept, the variety of tasks, and the lack of normative data are discussed. We also suggest how future studies could explore a possible link between hemispheric asymmetry and theory of mind.

Minor physical anomalies in patients with schizophrenia in a Chinese population

Studies have shown that minor physical anomalies (MPAs) may be associated with schizophrenia. However, it remains unclear whether any items of MPAs are more associated with schizophrenia than the others. We aimed to examine which specific MPAs are more associated with schizophrenia than others. A total of 154 patients with schizophrenia and 152 healthy controls were assessed using candidate MPAs items along with items from the Waldrop scale. Significant differences were found between the patients and controls in inner canthal distance, epicanthus, adherent ear lobe, cuspidal ear and length difference from section index to ring finger (2D:4D length difference) as well as gap between the first and the second toes. These six items were selected by the logistic regression model, which correctly classified 89.0% of patients with schizophrenia (sensitivity) and 96.7% of healthy controls (specificity). The overall classification success rate was 92.8%. MPAs are associated with neurodevelopment, especially 2D:4D associated with cerebral lateralisation. Hence, our present findings support that it is necessary to evaluate MPAs beyond the Waldrop scale, as some item, such as 2D:4D length difference may reflect the more detailed aberrant neurodevelopment of schizophrenia.

Digit ratio (2D:4D) asymmetry and Schneiderian first rank symptoms: implications for cerebral lateralisation theories of schizophrenia

Schneiderian first rank symptoms (FRS) in schizophrenia have been hypothesised to be secondary to aberrant cerebral lateralisation over the course of human evolution. The ratio of length of second digit to fourth digit (2D:4D) has been put forward as a potential indicator of cerebral lateralisation. This study examined 2D:4D and its asymmetry in antipsychotic-naïve schizophrenia patients (N=79) in comparison with healthy controls (N=75). Psychopathology was assessed using Scales for Assessment of Positive and Negative Symptoms. FRS assessment was performed as per established descriptions. The digit lengths (2D & 4D) were measured using a digital vernier caliper with good inter-rater reliability. Female schizophrenia patients showed significantly lower 2D:4D than female healthy controls. Mean 2D:4D asymmetry index was significantly lower in male schizophrenia patients than male healthy controls. FRS status had significant effect on left 2D:4D as well as 2D:4D asymmetry index, the patients with FRS having the lowest values. Our study findings support association between schneiderian FRS and low 2D:4D as well as low 2D:4D asymmetry index. Since 2D:4D is linked with limbic asymmetry, our study findings offer further support to the cerebral lateralisation theories of schizophrenia.

Stressing schizotypy: the modulating role of stress-relieving behaviours and intellectual capacity on functional hemispheric asymmetry

Relative cognitive impairments are common along the schizophrenia spectrum reflecting potential psychopathological markers. Yet stress, a vulnerability marker in schizophrenia (including its spectrum), is likewise related to cognitive impairments. We investigated whether one such cognitive marker (attenuated functional hemispheric asymmetry) during stressful life periods might be linked to individuals' schizotypal features or rather to individuals' stress-related experiences and behaviours. A total of 58 students performed a left hemisphere dominant (lateralised lexical decisions) and right hemisphere dominant (sex decisions on composite faces) task. In order to account for individual differences in stress sensitivity we separated participants into groups of high or low cognitive reserve according to their average current marks. In addition, participants filled in questionnaires on schizotypy (short O-LIFE), perceived stress, stress response, and a newly adapted questionnaire that enquired about potential stress compensation behaviour (elevated substance use). The most important finding was that enhanced substance use and cognitive disorganisation contributed to a right and left hemisphere shift in language dominance, respectively. We discuss that (i) former reports on right hemisphere shifts in language dominance with positive schizotypy might be explained by an associated higher substance use and (ii) cognitive disorganisation relates to unstable cognitive functioning that depend on individuals' life circumstances, contributing to published reports on inconsistent laterality-schizotypy relationships.

The influence of tobacco consumption on the relationship between schizotypy and hemispheric asymmetry

Tobacco use is positively associated with severity of symptoms along the schizophrenia spectrum. Accordingly it could be argued that neuropsychological performance, formerly thought to be modulated by schizotypy, is actually modulated by drug use or an interaction of drug use and schizotypy. We tested whether habitual cigarette smokers as compared to non-smokers would show a neuropsychological profile similar to that observed along the schizophrenia spectrum and, if so, whether smoking status or nicotine dependence would be more significant modulators of behavior than schizotypy. Because hemispheric dominance has been found to be attenuated along the schizophrenia spectrum, 40 right-handed male students (20 non-smokers) performed lateralized left- (lexical decisions) and right- (facial decision task) hemisphere dominant tasks. All individuals completed self-report measures of schizotypy and nicotine dependence. Schizotypy predicted laterality in addition to smoking status: While positive schizotypy (Unusual Experiences) was unrelated to hemispheric performance, Cognitive Disorganization predicted reduced left hemisphere dominant language functions. These latter findings suggest that Cognitive Disorganization should be regarded separately as a potentially important mediator of thought disorganization and language processing. Additionally, increasing nicotine dependence among smokers predicted a right hemisphere shift of function in both tasks that supports the role of the right hemisphere in compulsive/impulsive behavior.

Structural equation modeling in medical research: a primer

Background

Structural equation modeling (SEM) is a set of statistical techniques used to measure and analyze the relationships of observed and latent variables. Similar but more powerful than regression analyses, it examines linear causal relationships among variables, while simultaneously accounting for measurement error. The purpose of the present paper is to explicate SEM to medical and health sciences researchers and exemplify their application.

Findings

To facilitate its use we provide a series of steps for applying SEM to research problems. We then present three examples of how SEM has been utilized in medical and health sciences research.

Conclusion

When many considerations are given to research planning, SEM can provide a new perspective on analyzing data and potential for advancing research in medical and health sciences.

Disorganization and reality distortion in schizophrenia: a meta-analysis of the relationship between positive symptoms and neurocognitive deficits

BACKGROUND

Factor analytic studies have shown that in schizophrenia patients, disorganization (e.g., conceptual disorganization and bizarre behavior) is a separate dimension from other types of positive symptoms such as reality distortion (delusions and hallucinations). Although some studies have found that disorganization is more strongly linked to neurocognitive deficits and poor functional outcomes than reality distortion, the findings are not always consistent.

METHODS

A meta-analysis of 104 studies (combined n=8015) was conducted to determine the magnitude of the relationship between neurocognition and disorganization as compared to reality distortion. Additional analyses were conducted to determine whether the strength of these relationships differed depending on the neurocognitive domain under investigation.

RESULTS

The relationship between reality distortion and neurocognition was weak (r=-.04; p=.03) as compared to the moderate association between disorganization and neurocognition (r=-.23; p<.01). In each of the six neurocognitive domains that were examined, disorganization was more strongly related to neurocognition (r's range from -.20 to -.26) than to reality distortion (r's range from .01 to -.12).

CONCLUSIONS

The effect size of the relationship between neurocognition and disorganization was significantly larger than the effect size of the relationship between neurocognition and reality distortion. These results hold across several neurocognitive domains. These findings support a dimensional view of positive symptoms distinguishing disorganization from reality distortion.

Dichotic listening impairments in early onset schizophrenia are associated with reduced left temporal lobe volume

Dichotic listening (DL) impairments, in particular the loss or reduction of right ear advantage (REA) in people with schizophrenia have been variously interpreted as both a state and trait marker for schizophrenia. To date, there has been no comprehensive investigation of dichotic language impairments in relation to the structural integrity of the temporal cortex--the likely neural substrate for such impairments. In this study of 39 early onset patients and matched controls we used a dichotic listening procedure and examined the findings in relation to MRI measurements of gross and regional cerebral volumes. No overall group difference in ear advantage was found between patients and controls but patients who showed absence of REA also demonstrated an accompanying reduction of left temporal lobe volume compared with patients who showed normal ear advantage and controls. The findings suggest that impaired DL performance is a correlate of structural change in the temporal lobe and that this is apparent in early onset cases.

Duration of Illness, Regional Brain Morphology and Neurocognitive Correlates in Schizophrenia

Introduction: Previous studies examining brain effects of duration of illness in schizophrenia have focused on either cortical or subcortical structures. Hence this study sought to elucidate the regional grey matter changes (both cortical and subcortical) and neurocognitive correlates with increased duration of illness in a large sample of patients with schizophrenia using voxel-based morphometry. Materials and Methods: Ninety patients (72 males and 18 females) with DSM-IV diagnosis of schizophrenia were recruited and assessed using magnetic resonance imaging and a battery of neuropsychological tests. Results: A longer duration of illness was associated with smaller grey matter volumes in the left superior frontal gyrus, bilateral putamen, right superior temporal gyrus, right superior occipital gyrus as well as the right thalamus. No region showed increased grey matter volume above threshold with longer duration of illness. Longer duration of illness was correlated with poorer attention. Conclusions: The grey matter reductions in different brain regions highlighted that a distributed network of cortical and subcortical regions was associated with duration of illness. This is consistent with neural models that implicate involvement of thalamo-cortical circuitry as the disruption in these neural pathways can result in specific deficits such as poorer attention. The results have implications for the understanding of brain changes in schizophrenia, and with further studies, may guide better tailored and targeted clinical management in terms of reducing the impact of duration of illness on neural substrates in schizophrenia in the future. Key words: Duration of Illness, Grey Matter, Magnetic resonance imaging, Voxel-based Morphometry

Left temporal lobe structural and functional abnormality underlying auditory hallucinations in schizophrenia

In this article, we have reviewed recent findings from our laboratory, originally presented in Hugdahl et al. (2008). These findings reveal that auditory hallucinations in schizophrenia should best be conceptualized as internally generated speech mis-representations lateralized to the left superior temporal gyrus and sulcus, not cognitively suppressed due to enhanced attention to the 'voices' and failure of fronto-parietal executive control functions. An overview of diagnostic questionnaires for scoring of symptoms is presented together with a review of behavioral, structural, and functional MRI data. Functional imaging data have either shown increased or decreased activation depending on whether patients have been presented an external stimulus during scanning. Structural imaging data have shown reduction of grey matter density and volume in the same areas in the temporal lobe. We have proposed a model for the understanding of auditory hallucinations that trace the origin of auditory hallucinations to neuronal abnormality in the speech areas in the left temporal lobe, which is not suppressed by volitional cognitive control processes, due to dysfunctional fronto-parietal executive cortical networks.

A comparison of the effects for sustained versus shifted attention on dichotic listening performance

We measured the effect of two types of directed attention instructions, sustained by a verbal cue or shifted by a tone cue with different time intervals (150, 450, and 750 ms), on a consonant-vowel dichotic listening (C-V DL) test for a large group of right- and left-handed participants of both sexes. An increasing of the hits and a decreasing of the intrusions from the baseline DL test scores was evident for both types of attentional manipulations, with no differences regarding sex or handedness. Increasing the time from 150 to 450 ms benefited the focusing of attention but this advantage was markedly attenuated at the longer 750-ms interval. The improving effect was seen for the hits of both the left and right ears and so a right ear advantage was evident for the three time intervals.

Evidence of normal hearing laterality in familial schizophrenic patients and their relatives

Dichotic listening (DL) has been used as a tool to investigate possible left cerebral dysfunction in schizophrenia. However, the wide range of DL tests (e.g., words, emotions, sentences) as well as patient groups ("heterogeneity") has introduced several confounders. Assessing relatives of patients with schizophrenia may overcome some of these problems, and may be more useful in determining if loss of functional cerebral laterality in schizophrenia is a state or a trait phenomenon. The fused consonant-vowel DL test was administered to 114 subjects: 20 individuals with familial schizophrenia, 42 of their healthy relatives, and 52 healthy volunteers. We did this to investigate whether the normal language processing asymmetry-a right ear advantage (REA)-is present, and whether it could serve as a marker for genetic liability. General performance accuracy level was lower in schizophrenia patients and their relatives but the expected REA was present in all groups. Adjusting for age, accuracy, and obligate status made no difference. In conclusion, familial schizophrenic patients and their relatives have normal REA and hearing laterality on the fused DL test.