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

Does chronic nicotine consumption influence visual backward masking in schizophrenia and schizotypy?

Nicotine consumption is higher for people within the schizophrenia spectrum compared to controls. This observation supports the self-medication hypothesis, that nicotine relieves symptoms in, for example, schizophrenia patients. We tested whether performance in an endophenotype of schizophrenia (visual backward masking, VBM) is modulated by nicotine consumption in i) smoking and non-smoking schizophrenia patients, their first-degree relatives, and age-matched controls, ii) non-smoking and smoking university students, and iii) non-smoking, early and late onset nicotine smokers. Overall, our results confirmed that VBM deficits are an endophenotype of schizophrenia, i.e., deficits were highest in patients, followed by their relatives, students scoring high in Cognitive Disorganisation, and controls. Moreover, we found i) beneficial effects of chronic nicotine consumption on VBM performance, in particular with increasing age, and ii) little impact of clinical status alone or in interaction with nicotine consumption on VBM performance. Given the younger age of undergraduate students (up to 30 years) versus controls and patients (up to 66 years), we propose that age-dependent VBM deficits emerge when schizotypy effects are targeted in populations of a larger age range, but that nicotine consumption might counteract these deficits (supporting the self-medication hypothesis).

Hemispheric language asymmetry in first episode psychosis and schizotypy: the role of cannabis consumption and cognitive disorganization

Cannabis use has been related to an elevated psychosis risk and attenuated cognitive functioning. Cannabis-related cognitive impairments are also observed in populations along the psychosis dimension. We here investigated whether a potential behavioral marker of the psychosis dimension (attenuated functional hemispheric asymmetry) is even further attenuated in individuals using cannabis (CU) vs those not using cannabis (nCU). We tested 29 patients with first-episode psychosis (FEP; 11 CU) and 90 healthy controls (38 CU) on lateralized lexical decisions assessing left-hemisphere language dominance. In patients, psychotic symptoms were assessed by Positive & Negative Symptom Scale (PANSS). In controls, self-reported schizotypy was assessed (The Oxford-Liverpool Inventory of Feelings and Experiences: O-LIFE). Results indicated that nCU FEP patients had a relative reduced hemispheric asymmetry, as did controls with increasing cognitive disorganization (CogDis) scores, in particular when belonging to the group of nCU controls. Positive, disorganized and negative PANSS scores in patients and negative and positive schizotypy in controls were unrelated to hemispheric asymmetry. These findings suggest that cannabis use potentially balances rather than exacerbates uncommon hemispheric laterality patterns. Moreover, in healthy populations, the potential stabilization of typical hemispheric asymmetry in CU might be most relevant to individuals with elevated CogDis. We discuss the potential beneficial and harmful effects of cannabis use along the psychosis dimension together with propositions for future studies that should account for the mediating role of additional substances (eg nicotine), cannabis composition (eg cannabidiol content), and individual differences (eg physical health, or absence of significant polysubstance use).

Alcohol and Relatively Pure Cannabis Use, but Not Schizotypy, are Associated with Cognitive Attenuations

Elevated schizotypy relates to similar cognitive attenuations as seen in psychosis and cannabis/polydrug use. Also, in schizotypal populations cannabis and polydrug (including licit drug) use are enhanced. These cognitive attenuations may therefore either be a behavioral marker of psychotic (-like) symptoms or the consequence of enhanced drug use in schizotypal populations. To elucidate this, we investigated the link between cognitive attenuation and cannabis use in largely pure cannabis users (35) and non-using controls (48), accounting for the potential additional influence of both schizotypy and licit drug use (alcohol, nicotine). Cognitive attenuations commonly seen in psychosis were associated with cannabis and alcohol use, but not schizotypy. Future studies should therefore consider (i) non-excessive licit substance use (e.g., alcohol) in studies investigating the effect of cannabis use on cognition and (ii) both enhanced illicit and licit substance use in studies investigating cognition in schizotypal populations.

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.

Effects of risperidone, amisulpride and nicotine on eye movement control and their modulation by schizotypy

RATIONALE

The increasing demand to develop more efficient compounds to treat cognitive impairments in schizophrenia has led to the development of experimental model systems. One such model system combines the study of surrogate populations expressing high levels of schizotypy with oculomotor biomarkers.

OBJECTIVES

We aimed (1) to replicate oculomotor deficits in a psychometric schizotypy sample and (2) to investigate whether the expected deficits can be remedied by compounds shown to ameliorate impairments in schizophrenia.

METHODS

In this randomized double-blind, placebo-controlled study 233 healthy participants performed prosaccade (PS), antisaccade (AS) and smooth pursuit eye movement (SPEM) tasks after being randomly assigned to one of four drug groups (nicotine, risperidone, amisulpride, placebo). Participants were classified into medium- and high-schizotypy groups based on their scores on the Schizotypal Personality Questionnaire (SPQ, Raine (Schizophr Bull 17:555-564, 1991)).

RESULTS

AS error rate showed a main effect of Drug (p < 0.01), with nicotine improving performance, and a Drug by Schizotypy interaction (p = 0.04), indicating higher error rates in medium schizotypes (p = 0.01) but not high schizotypes under risperidone compared to placebo. High schizotypes had higher error rates than medium schizotypes under placebo (p = 0.03). There was a main effect of Drug for saccadic peak velocity and SPEM velocity gain (both p ≤ 0.01) indicating impaired performance with risperidone.

CONCLUSIONS

We replicate the observation of AS impairments in high schizotypy under placebo and show that nicotine enhances performance irrespective of group status. Caution should be exerted in applying this model as no beneficial effects of antipsychotics were seen in high schizotypes.

Inferring about individual drug and schizotypy effects on cognitive functioning in polydrug using mephedrone users before and after clubbing

OBJECTIVE

Mephedrone has been recently made illegal in Europe, but little empirical evidence is available on its impact on human cognitive functions. We investigated acute and chronic effects of mephedrone consumption on drug-sensitive cognitive measures, while also accounting for the influence of associated additional drug use and personality features.

METHOD

Twenty-six volunteers from the general population performed tasks measuring verbal learning, verbal fluency and cognitive flexibility before and after a potential drug-taking situation (pre-clubbing and post-clubbing at dance clubs, respectively). Participants also provided information on chronic and recent drug use, schizotypal (Oxford-Liverpool Inventory of Feelings and Experiences) and depressive symptoms (Beck Depression Inventory), sleep pattern and premorbid IQ.

RESULTS

We found that (i) mephedrone users performed worse than non-users pre-clubbing and deteriorated from the pre-clubbing to the post-clubbing assessment; (ii) pre-clubbing cannabis and amphetamine (not mephedrone) use predicted relative cognitive attenuations; (iii) post-clubbing, depression scores predicted relative cognitive attenuations; and (iv) schizotypy was largely unrelated to cognitive functioning, apart from a negative relationship between cognitive disorganisation and verbal fluency.

CONCLUSION

Results suggest that polydrug use and depressive symptoms in the general population negatively affect cognition. For schizotypy, only elevated cognitive disorganisation showed potential links to a pathological cognitive profile previously reported along the psychosis dimension.

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.

Cognitive disorganisation in schizotypy is associated with deterioration in visual backward masking

To understand the causes of schizophrenia, a search for stable markers (endophenotypes) is ongoing. In previous years, we have shown that the shine-through visual backward masking paradigm meets the most important characteristics of an endophenotype. Here, we tested masking performance differences between healthy students with low and high schizotypy scores as determined by the self-report O-Life questionnaire assessing schizotypy along three dimensions, i.e. positive schizotypy (unusual experiences), cognitive disorganisation, and negative schizotypy (introvertive anhedonia). Forty participants performed the shine-through backward masking task and a classical cognitive test, the Wisconsin Card Sorting Task (WCST). We found that visual backward masking was impaired for students scoring high as compared to low on the cognitive disorganisation dimension, whereas the positive and negative schizotypy dimensions showed no link to masking performance. We also found group differences for students scoring high and low on the cognitive disorganisation factor for the WCST. These findings indicate that the shine-through paradigm is sensitive to differences in schizotypy which are closely linked with the pathological expression in schizophrenia.

The facial evolution: looking backward and moving forward

Three-dimensional (3D) facial analysis is ideal for high-resolution, nonionizing, noninvasive objective, high-throughput phenotypic, and phenomic studies. It is a natural complement to (epi)genetic technologies to facilitate advances in the understanding of rare and common diseases. The face is uniquely reflective of the primordial tissues, and there is evidence supporting the application of 3D facial analysis to the investigation of variation and disease including studies showing that the face can reflect systemic health, provides diagnostic clues to disorders, and that facial variation reflects biological pathways. In addition, facial variation has been related to evolutionary factors. The purpose of this review is to look backward to suggest that knowledge of human evolution supports, and may instruct, the application and interpretation of studies of facial morphology for documentation of human variation and investigation of its relationships with health and disease. Furthermore, in the context of advances of deep phenotyping and data integration, to look forward to suggest approaches to scalable implementation of facial analysis, and to suggest avenues for future research and clinical application of this technology.

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.