Multisensory Processing and Anomalous Self Experiences in Schizophrenia
Abnormal multisensory integration is thought to play an important role in anomalous dissociative experiences of the body and self, including out-of-body experiences (OBEs) and feelings-of-presence. Aspects of OBEs including malleable self-boundaries and impaired judgments about self-location overlap with the phenomenology of schizophrenia. We sought to examine the performance of patients with schizophrenia (SZ) and healthy participants on a battery of visuo-tactile tasks designed to tap the underlying multisensory processes that may be abnormal in the schizophrenia spectrum. Methods: 7 patients with schizophrenia and 9 healthy controls participated in a battery of tasks that were designed to probe aspects of self and body integrity. The Mental Rotation Task assessed participants’ abilities to perform mental transformations (perspective taking). The Graphesthesia Task measured participants’ abilities to transform tactile stimuli to visuospatial representation. The Hand Reversal Task measured participants’ abilities to integrate conflicting visuospatial and proprioceptive information. The Pinocchio Illusion task gauged susceptibility to perceive loosened self-boundaries and ambiguous spatial location of the body. The Shape After Effect Illusion measured the tendency to experience tactile illusion. The Two Point Discrimination Task measured the tactile sensitivity and discriminability of the participants. In addition to these behavioral tasks we developed and administered a new self-report questionnaire designed to probe anomalous bodily experiences (BODI). In patients, symptoms were assessed with clinical interviews. In healthy controls, schizotypal personality questionnaire was given to assess schizotypal traits. Results: We found that reported incidence of anomalous phenomenological experience was associated with decreased tactile sensitivity and that SZs were more likely to have reduced tactile sensitivity. Furthermore, higher schizotypal traits in controls were associated with susceptibility to abnormal self-experiences. Discussion: Although there were no statistical differences between patients and controls on most of the illusion tasks, there were trends showing reduced tactile sensitivity in SZ. SZ had preserved perspective-taking abilities in the mental rotation task, which suggests that they are able to perform self-other transformations. Future research should recruit larger, age-matched participant pools and examine neural underpinnings of anomalous self-experiences in schizophrenia.