Neurological soft signs, temperament and schizotypy in patients with schizophrenia and unaffected relatives: An fMRI Study

Abstract

Schizophrenia is a severe psychiatric disorder that has a profound effect on both the individuals affected and society. This common mental illness is a complex, heterogeneous behavioural and cognitive syndrome that seems to originate from disruption of brain development caused by genetic or environmental factors, or both. The genetic basis may be present in individuals without disease, as in the case of relatives of patients, being detectable through biological markers. Neurological soft signs (NSS) are discrete sensorimotor impairments associated with deviant brain development that were postulate as an endophenotype of schizophrenic spectrum disorder. Also the personality traits have been proposed as a vulnerability marker in schizophrenia. A specific profile of temperament and character and the schizotypal personality traits have also been correlated with schizotypal personality traits. These traits and some neurological abnormalities have been shown to aggregate in the relatives of schizophrenia patients. The etiopathogenesis of schizophrenia suggests it may be a "progressive neurodevelopmental disorder". This view postulates a disruption in functional circuits involving hetero modal association areas rather than a specific abnormality in a single brain region._x000D_ The aim of this study is to explore the abnormalities in the functional connectivity of the default mode network related to the association between neurological soft signs and personality in schizophrenia._x000D_ To investigate this a cross-sectional study is proposed, comparing a group of patients with schizophrenia, a group of unaffected relatives and a group of healthy controls._x000D_ In order to explore the association of these potential biomarkers of schizophrenia the study was composed of two parts:_x000D_ a) To explore the association between neurological soft signs and personality traits in schizophrenia, two personality examinations (Temperament and Character Inventory and the Schizotypal Personality Questionnaire) and an evaluation of Neurological Soft Signs were performed._x000D_ b) To explore the association between cerebral connectivity changes in the default mode network with the presence of neurological soft signs in schizophrenia a functional magnetic resonance scan was performed on participants in a resting state._x000D_ The major finding in this study was that patients with schizophrenia and non-psychotic relatives display a unique profile of temperament and character and more schizotypal traits that correlate with higher presence of NSS._x000D_ Our results reveal an association between these hypothesized vulnerability markers, as temperament (especially harm avoidance, reward dependence and persistence) and character (especially self-directedness and cooperativeness) correlated with the presence of NSS in the entire sample. Also the schizotypal traits (total scores and subscores) showed a very strong correlation with the presence of NSS in the entire sample._x000D_ The results showed that susceptibility to NSS and to schizophrenia are both related to individual differences in personality features in non-psychotic relatives of patients with schizophrenia. These findings highlight the value of using both assessments to study high risk populations._x000D_ The neuroimaging results showed connectivity changes in the default mode network with a possible association with the presence of neurological soft signs. These findings support the theory of cognitive dysmetria as a possible dysfunction in cortical-thalamic-cerebellar connectivity. This model also could explain the diversity of symptoms in schizophrenia and their associations (like this study that includes personality and sensory and motor functions)._x000D_ One strength of the study is that the relatives of patients with schizophrenia had no familial ties to the patients used, thus decreasing the possibility that similar upbringing would confound the results.

Date of Award	24 Apr 2017
Original language	Undefined/Unknown
Awarding Institution	Consorci Parc de Recerca Biomèdica de Barcelona (PRBB)
Supervisor	Victor Pérez Solà (Director), Oscar Vilarroya Oliver (Tutor) & Daniel Berge Baquero (Director)