Dopaminergic foundations of schizotypy as measured by the German version of the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE)—a suitable endophenotype of schizophrenia

Abstract

The concept of schizotypy or “psychosis proneness” captures individual differences in perceptual, cognitive, and affective experiences that may relate to a range of psychotic disorders. The concept is an important way to assess the contribution of pre-existing psychological and genetically based biological features to the development of illnesses such as schizophrenia (so called endophenotypes). The Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE) is a widely used multi-dimensional measure of the construct and consists of four scales which mirror several groups of psychotic symptoms: Unusual Experiences (UnEx; positive symptoms), Cognitive Disorganization (CogDis; cognitive symptoms), Introvertive Anhedonia (IntAn; negative symptoms), and Impulsive Nonconformity (ImpNon; impulsive and antisocial symptoms). For the purpose of evaluating the suitability of schizotypy as an endophenotype of schizophrenia the current version of the O-LIFE was translated into German: its psychometric properties (including re-test reliability and construct validity) were examined in a large sample (n > 1200) and compared to those of the English original. The German version was both highly reliable and consistent with the original. The study aimed to show that schizotypy as measured by the O-LIFE can indeed be regarded as an endophenotype of schizophrenia in terms of genetic associations regarding relevant dopamine-related candidate polymorphisms of schizotypy [i.e., Val158Met-polymorphism of the COMT gene, uVNTR of the MAOA gene, Taq1A-polymorphism of the DRD2 gene, VNTR of the SLC6A3 (DAT) gene]. We also wanted to compare the genetic associations of the O-LIFE to those published using other operationalizations of schizotypy. Our results show a large number of significant associations and borderline-significant trends between the O-LIFE sub-scales and a range of genes, thereby supporting using the O-LIFE in the search for endophenotypic markers.

Categories and Their Role in the Science of Emotion

“…So an emotion is not an entity with firm boundaries in nature – it is a category of instances that vary because each one is tailored to the constraints of the immediate environment. For example, an instance of happiness can be pleasant and arousing (e.g., you are finishing a challenging task with no errors and hear applause), pleasant and quiescent (e.g., you feel comfortable and rested after a good night’s sleep), and even unpleasant (e.g., you want to call your friend to share your recent success but he is unreachable) (Wilson-Mendenhall et al, 2013). The actions you make in happiness will depend on the situation (e.g., you might laugh, smile, cry, jump, sigh, shout, slam your fist against a table, and so on.)…”

“…Whenever you ask respondents to report on an experience that has happened in the past, this is also tapping simulation. Simulation during brain scanning produces activity in somatosensory and motor cortices when subjects are completely still, in primary visual cortex when eyes are closed, and even in primary interoceptive cortex (for sensing changes in the core of the body) when there is no real threat or reward immediately present (Wilson-Mendenhall et al, 2013). Understanding the brain dynamics of simulation—how people apply knowledge wired into the brain to create experiences and perceptions in a particular context will reveal how the brain constructs experiences and perceptions of emotion.…”

Schizotypy From a Developmental Perspective

“…50 In a hypothetically similar fashion, stable positive schizotypy may reinforce atypical regulation in the mesolimbic dopaminergic system depending upon transactions with high risk environments (eg bullying), genotype and the constellation of other critical personality dimensions such as negative affect, thereby consolidating increased risk during childhood and adolescence. 51 A second observation, critical to a developmental schizotypy perspective, is that most prospective research fails to examine the multifactorial nature of schizotypy, even if there is general agreement in the field that, at minima, schizotypal traits rest on a triad of relatively stable manifestations encompassing positive schizotypy (unusual perceptual experiences in cognitive-perceptual phenomena), negative schizotypy (flat affect, social withdrawal, anhedonia in the interpersonal domain), and disorganization schizotypy (odd and eccentric speech and behavior as behavioral proxies). However, most research often bypasses the significant and equally predictive value of the negative schizotypy dimension (see Debbané, Schultze-Lutter et al, this issue).…”

Differential Associations of Dopamine-Related Polymorphisms with Discrete Components of Reaction Time Variability: Relevance for Attention Deficit/Hyperactivity Disorder

“…Extraction of DNA from buccal epithelia and genotyping using PCR amplification were performed according to standard protocols previously published by us [20]. …”