Emotional, Temporal, and Spatial Multisensory Integration and Crossmodal Recalibration in Individuals with Psychosis Proneness or Psychosis

Abstract

Since the first phenomenological descriptions of psychosis, severe alterations in sensory processing and perception have been assumed as one key factor at the root of the disorder. Studies on sensory processing in psychosis have repeatedly observed impairments in information processing within individual sensory systems such as vision or audition. It has been discussed that psychosis might be associated with pronounced deficits in multisensory processing, i.e. the processing of stimuli conveyed via multiple senses. Dysfunctions in multisensory integration (MSI) might lead to fragmented or distorted perception and facilitate the development of psychotic disorders via maladaptive perceptual learning mechanisms. Previous studies on MSI in psychosis have observed deficits such as reduced behavioral benefits during processing of congruent crossmodal stimuli or inappropriate integration. Impairments have repeatedly been observed in temporal, sensorimotor, and linguistic processes. However, findings in emotional MSI have been inconsistent, with reports of deficient, intact, and excessive integration. Only a few earlier studies suggested intact spatial MSI in psychosis and their findings require replication. No published study investigated if crossmodal recalibration, i.e. the short- and long-term adaptation to changes in crossmodal characteristics, is altered and as such might contribute to altered perception in psychosis. Further, little is known about the developmental trajectory of multisensory processes in psychosis and no convincing mechanism has been proposed, which describes how impaired multisensory processing might contribute to psychosis.

To address these gaps in the literature, this dissertation project aimed to investigate different aspects of multisensory processes in psychosis. We examined emotional MSI in psychosis proneness as well as MSI and crossmodal recalibration in the temporal and spatial domains in patients with the diagnosis of a psychotic disorder. First, we addressed the question, if impaired MSI might reflect a global underlying deficit or might be rather specific for some domains such as temporal and social information processing. Second, we examined crossmodal spatial and temporal recalibration in order to investigate if both processes might be altered in psychosis. Third, we aimed to contribute to the question if altered MSI might be a consequence of disorder manifestation or if it might play a role in the development of psychosis. Finally, we addressed the issue of a lack of disorder model-based research and aimed to provide initial evidence for a potential mechanism, via which altered multisensory processing might contribute to psychosis.

To investigate these questions, we conducted three different experimental studies. In the first study, we investigated emotional MSI in psychosis proneness by means of an emotion categorization task with affective facial expressions and vocal prosody, expecting impaired emotional MSI in subjects with high psychosis proneness. In the second study, we investigated temporal MSI and crossmodal temporal recalibration in psychosis using an audiovisual (AV) simultaneity judgement (SJ) paradigm. We expected to replicate previous findings on impaired temporal MSI and provide first evidence for impaired crossmodal temporal recalibration in psychosis. In the third study, we conducted a paradigm on the spatial ventriloquist effect and aftereffect to investigate spatial MSI and crossmodal spatial recalibration in psychosis. We expected to replicate previous findings on intact spatial MSI in psychosis and provide first results on crossmodal spatial recalibration in psychosis.

Results showed that high and low proneness subjects did not differ in their emotional categorization performance in unimodal, bimodal emotionally congruent and bimodal emotionally incongruent stimuli. This indicates typical emotional MSI in psychosis proneness. Further, patients with the diagnosis of a psychotic disorder and healthy controls showed comparable performance in judging the synchrony of AV stimuli and similarly adjusted their responses to changes in stimulus asynchrony. This indicates typical temporal MSI and crossmodal temporal recalibration in psychosis. Finally, patients and controls showed similar ventriloquist effects and aftereffects, suggesting intact spatial MSI and crossmodal spatial recalibration in psychosis. In all studies, no correlation between measures of multisensory processes and psychotic symptoms could be observed.

While our findings on emotional MSI in psychosis proneness and temporal MSI in psychosis are in contrast with previous findings in patient samples, we successfully replicated earlier findings on intact spatial MSI. The lack of group differences in all three of our studies neither supports the hypothesis of a global underlying impairment nor of a domain-specificity of multisensory processing dysfunctions in psychosis. Further, our results indicate intact crossmodal recalibration in the spatial and temporal domain, suggesting that patients with the diagnosis of a psychotic disorder are able to adapt to changes in crossmodal spatial and temporal characteristics. Moreover, our findings do not offer support for the assumption that deficient emotional MSI plays a role in the development of psychosis. Taken together, our findings could suggest that altered perception in psychosis might not be generally driven by deficits in multisensory processes.