Rationale: Hallucinations occur in many patients with different kinds of diseases, including psychiatric, neurological and perceptual impairment. The origin of these hallucinations is only partly understood. This prevents correct prediction of treatment response and hampers the development of new, more effective treatment strategies.

Different subtypes of hallucinations resulting from different neuropathology may exist across diagnostic entities, and be responsive to different treatment strategies. Understanding the origin of these subtypes with use of fMRI and EEG can help to make rational treatment decisions on an individual basis and enhance the development of innovative treatment paradigms.

Objective: The primary objective is to find specific abnormalities on resting state fMRI related to the pathophysiology of different subtypes of hallucinations. Secondary objectives are to find EEG connectivity measures that are related to the pathophysiology of different subtypes of hallucinations, reveal correlating patterns of EEG and fMRI that underlie the experience of hallucinations across different disorders, and to examine the frequency of spontaneous synchronized burst activations in auditory and visual cortices using fMRI.

Study design: The investigators intend to examine neural correlates of hallucinations over different disorders using resting state EEG, fMRI and sMRI in an observational study.

Study population: A total of 140 hallucinating patients will be included, 20 of each of the 7 different diagnostic groups. As a control group, 140 non-hallucinating patients with the same disorder of similar severity will be included.

Main study parameters/endpoints: The main study endpoint is the difference in resting state correlates as measured with fMRI between hallucinating and non-hallucinating participants and between hallucinating individuals of different subtypes, namely: connectivity within the DMN and connectivity of the DMN to sensory cortices and the hippocampal-amygdala complex.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Participation in the study will entail an MRI scan of 40 minutes and an EEG measurement of 5 minutes. Total visit time, including preparations, will be approximately 2,5 hours. The risks associated with participation and the benefits to the individuals are negligible. The potential benefit to society in the future is considerable if the findings lead to optimization of treatment strategies and treatment response.

Inclusion Criteria:

• Previous participation in the phenomenology/cognition study 13-059.
• Belong to one of the diagnostic groups as described above in 4.1.
• Written informed consent

Exclusion Criteria:

• < 18 years of age
• Any contraindication for a 3Tesla MRI scan

The participants will consist of 7 different diagnostic categories. Individuals with hallucinations will have to experience at least one episode of hallucinations over the last month. The control group will consist of non-hallucinating individuals who have the same disorder as the hallucinating individuals and are matched group-wise for severity of the disease, medication, age, sex, handedness and education.