Behavioral and imaging studies of hallucinations

Prosjektet er del av pågående forskning kring audiutive hallusinasjoner ved schizofreni, der hjernemarkører og kognitve funksjon blir brukt for å avdekke de underliggende nevronale faktorer bak opplevelsen av å "høre stemmer" som er et av de viktigste sym ptomene for en diagnose av schizofreni. Et nytt moment er bruk av MRspektroskopi (MRS) for måling av glutamat-konsentrasjon i utvalgte edeler av hjernen som en biomarkør for hørselshallusinasjoner

The experience of "hearing voices", i. e. auditory hallucinations in the absence of an external acoustic input is a perplexing phenomenon. In addition to being a defining core characteristic of schizophrenia, experiences of "hearing voices" are not uncomm on in the general population which poses a theoretical challenge from a neuropsychological point of view. The overall goal is to track auditory hallucinations from the cognitive (phenomenological) to the neuronal (brain systems and synaptic) levels of exp lanation, by drawing on my previous research on hemispheric asymmetry and attention-modulation of dichotic listening and functional neuroimaging. From the phenomenology of what patients and healthy individuals "hearing voices" actually report led me to qu estion current models and theories that auditory hallucinations are "inner speech" or "traumatic memories". Since both patients and healthy individuals "hearing voices" subjectively report experiencing someone "speaking to them" it seems that a perceptual model with a left temporal lobe focus would better fit the actual phenomenology. A speech perceptual model can however not explain why patients and healthy individuals differ in the way they cope with and interpret the "voice". An expanded model is there fore advanced that sees auditory hallucinations as a break-down of the dynamic interplay between bottom-up (perceptual) and top-down (inhibitory control) cognitive processes. It is suggested that while both patients and healthy individuals show deficient perceptual processing, the patients in addition have impaired inhibitory control functions which prevents them from interpreting the "voices" as coming from inner thought processes. A series of four experiments are proposed to test the model.