Auditory Processes and Emotional Perception in Schizophrenia

Overview

Schizophrenia is a mental illness with a variety of clinical symptoms that can be regrouped into 2 categories: positive and negative symptoms. This mental illness is also characterised by cognitive alterations in various fields, including social cognition difficulties and self / non-self-discrimination difficulties. Self and non-self-discrimination abilities have been regrouped under a function called source memory. This source memory enables a person to identify the source of an information previously encoded. In our everyday life, these processes are necessary to distinguish events generated by an external source from imagined events. It is called reality monitoring. A number of studies have evidenced reality-monitoring alterations in patients suffering from schizophrenia. More specifically, patients would present with an externalisation bias, they would assign more imagined events to an external source. The knowledge of these deficits encourages the study of the processes involved in order to better understand the alterations, particularly including auditory processes. A recent study has shown that discrimination errors concerning certain sound characteristics (e.g. frequency) were associated to reality monitoring errors. However, the links between reality-monitoring and basic auditory processes have rarely been explored. The dysfunction of the auditory "where" path, especially the possibility to discriminate between the intra and extra cephalic localisation of sounds, could lead to difficulties to discern between what is produced by one self and what is produced by another or the local environment.

The main objective of this study is to study the links between source memory deficits and externalization abilities in schizophrenic patients and healthy subjects. Also, this study will: * evaluate the impact of emotional content on the ability to externalize an auditory perception * evaluate the abilities to separate sources concerning vocal stimuli * evaluate the basic auditory processes In order to meet the objectives, the correlation between the percentage of good attributions in the reality monitoring task and the percentage of correct perceptions in/out (sound perceived as coming from inside or outside the head) will be analyzed in the externalization task in patients suffering from schizophrenia. Will also be analyzed: * the number of correct perceptions In/Out in the externalization task * the number of correct perceptions In/Out for the emotional stimuli * the detection level of difference in pitch between 2 vocal sources pour the height discrimination task * the number of correctly identified words in the speech-in-speech task The tasks : Subjects will undergo a battery of cognitive and auditory experiments in order to answer the objectives and hypothesis. The duration of the entire experiments will be 3.30 hours. \- Subjects will undergo the source monitoring task (30 min): This task is divided in 2 parts: * one part that will evaluate the reality monitoring performances (LISTENING task). Subjects either have to listen to words or imagine themselves listening to words * another part evaluating internal source monitoring performances (SAY task). Subjects either have to pronounce words or imagine themselves pronouncing words. * In order to measure perception abilities, all subjects will undergo a battery of psychoacoustic tests (30 min) including the Tone Matching Task (TMT) which evaluates the capacity of discriminating static pitch. The battery is also composed of tasks measuring length, amplitude, etc… * A yes / no discrimination task will be used to measure the externalization abilities: subjects will have to discern whether a sound is perceived as coming from inside or outside the head * the ability to separate sources will be measured using 2 paradigms: * a pitch discrimination task (30 min): it will evaluate the capacity to discern sources based on voice pitch * a speech-in-speech task (30 min): target words are presented simultaneously to masks (composed of words time reversed so that have lost the semantic content). The subject has to listen and repeat the words heard.