Postdoc Section coordinator: Section Psychopathology of developmental disorders
Department of Psychiatry
email
i.sommer@umcutrecht.nltel +31-88 75 56756
Project
Structure, activity and connectivity of cortical language areas in healthy hallucinators
Background
Although auditory hallucinations occur with a lifetime prevalence of 10 to 15% in persons without neuropsychiatric diseases, they are most common in schizophrenia, with an average prevalence of 60%. Therefore, recent models of auditory hallucinations are based on results gained from investigations of patients with schizophrenia. Three cerebral deviations have been found in schizophrenia patients which may underlie their tendency to misinterpret inner speech as external: functional magnetic resonance imaging (fMRI) studies showed that schizophrenia patients have lower degrees of language lateralization and Diffusion Tension Imaging (DTI) studies reported an imbalance in directionality of the white matter tracts that connect the language areas in schizophrenia patients. Third, local volume decreases of the right hemisphere homologue of Broca’s area and the left temporal lobe have been correlated to the severity of hallucinations in patients with schizophrenia. All three mechanisms, altered language representation, altered connectivity and structural deficit of the frontotemporal language system, may be predisposing factors for hallucinations. However, they have been shown to correlate with schizophrenia, which is a complex syndrome consisting of psychotic, cognitive and negative symptoms and not to auditory hallucinations per see.
AimIn order to learn whether either of these mechanisms plays a causal role in the pathophysiology of auditory hallucinations the pure form of hallucinations should be investigated. This can be done by studying healthy subjects who experience hallucinations, without other psychotic or cognitive symptoms and who have no history of hospitalisation or chronic medication use.
Design
In the proposed project, language activation and connectivity will be assessed in healthy individuals who sometimes experience auditory hallucinations. A large group of healthy volunteers will be asked to answer a short questionnaire on our website on hallucinatory experiences. From these individuals, 50 persons with high scores and 50 persons with low scores will be invited to participate in the MRI study. If the healthy hallucinating subjects can be demonstrated to show similar abnormalities as described above, a causal role for these cerebral deviations can be presumed in the occurrence of hallucinations, which elucidates part of the pathophysiology.