Face processing impairments in schizophrenia and other psychiatric disorders

Abstract

The ability to recognise and interpret the facial expressions of others is shown to be impaired in individuals with schizophrenia and may contribute to poor social functioning. In contrast, it remains unclear whether other aspects of face processing (such as identity recognition) are also impaired, and whether such deficits correlate with specific symptoms. This thesis explores face processing in schizophrenia and other psychiatric disorders. To test this, a novel set of video-based tasks were designed to improve upon traditional image-based tasks, as these have been criticised for lacking ecological validity. We show that these video-based tasks are recognised more easily than image-based versions and are sensitive to schizophrenia-like experiences in a study of healthy individuals (n=82). Eighty-six psychiatric inpatients and an additional twenty healthy controls completed a series of five video-based tasks: Emotion Discrimination (same or different), Emotion Labelling (fear or disgust), Identity Discrimination (same or different), Sex Labelling (male or female), and a non-face control task – Car Discrimination (same or different). Schizophrenia patients (n=36) were impaired compared to healthy controls across all tasks except for Identity Discrimination (which showed marginal impairment), and Sex Labelling. When all patient groups were compared, it was revealed that the schizophrenia (n=36) and bipolar disorder groups (n=15) were significantly impaired on the emotion-processing tasks and Car Discrimination compared to both healthy controls (n=20) and patients with non-psychotic diagnoses (n=18). There were no significant differences between patients and healthy controls on the general face tasks (Identity Discrimination and Sex Labelling). These findings hint that the “emotion-specific” processing deficits reported in previous studies may represent a more general cognitive or perceptual impairment. Correlational analyses revealed that non-cognitive positive symptoms – such as delusions and suspiciousness – were negatively correlated with emotion-processing ability and car discrimination, but not identity-processing ability. In contrast, more severe cognitive symptoms were associated with generally reduced performance across tasks. Overall, results suggest that deficits in emotion processing reflect symptom pathology independent of diagnosis and support the idea of a generalised cognitive deficit that is particularly prominent in patients showing positive symptoms of psychosis. These findings are discussed in terms of dimensional models of psychosis. Furthermore, they highlight the importance of including appropriate control tasks when assessing allegedly specific deficits.