title: Early somatosensory processing in individuals at risk for developing psychoses.
abstract: Human cortical somatosensory evoked potentials (SEPs) allow an accurate investigation of thalamocortical and early cortical processing. SEPs reveal a burst of superimposed early (N20) high-frequency oscillations around 600 Hz. Previous studies reported alterations of SEPs in patients with schizophrenia. This study addresses the question whether those alterations are also observable in populations at risk for developing schizophrenia or bipolar disorders. To our knowledge to date, this is the first study investigating SEPs in a population at risk for developing psychoses. Median nerve SEPs were investigated using multichannel EEG in individuals at risk for developing bipolar disorders (n = 25), individuals with high-risk status (n = 59) and ultra-high-risk status for schizophrenia (n = 73) and a gender and age-matched control group (n = 45). Strengths and latencies of low- and high-frequency components as estimated by dipole source analysis were compared between groups. Low- and high-frequency source activity was reduced in both groups at risk for schizophrenia, in comparison to the group at risk for bipolar disorders. HFO amplitudes were also significant reduced in subjects with high-risk status for schizophrenia compared to healthy controls. These differences were accentuated among cannabis non-users. Reduced N20 source strengths were related to higher positive symptom load. These results suggest that the risk for schizophrenia, in contrast to bipolar disorders, may involve an impairment of early cerebral somatosensory processing. Neurophysiologic alterations in schizophrenia precede the onset of initial psychotic episode and may serve as indicator of vulnerability for developing schizophrenia.
authors.affiliation: The Zurich Program for Sustainable Development of Mental Health Services (ZInEP), Psychiatric Hospital, University of Zurich Zurich, Switzerland ; Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich Zurich, Switzerland.
authors.forename: Florence
authors.initials: F
authors.lastname: Hagenmuller
authors.affiliation: The Zurich Program for Sustainable Development of Mental Health Services (ZInEP), Psychiatric Hospital, University of Zurich Zurich, Switzerland ; Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich Zurich, Switzerland.
authors.forename: Karsten
authors.initials: K
authors.lastname: Heekeren
authors.affiliation: The Zurich Program for Sustainable Development of Mental Health Services (ZInEP), Psychiatric Hospital, University of Zurich Zurich, Switzerland ; Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich Zurich, Switzerland.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Theodoridou
authors.affiliation: The Zurich Program for Sustainable Development of Mental Health Services (ZInEP), Psychiatric Hospital, University of Zurich Zurich, Switzerland ; Department of Child and Adolescent Psychiatry, University of Zurich Zurich, Switzerland.
authors.forename: Susanne
authors.initials: S
authors.lastname: Walitza
authors.affiliation: The Zurich Program for Sustainable Development of Mental Health Services (ZInEP), Psychiatric Hospital, University of Zurich Zurich, Switzerland ; Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich and ETH Zurich Zurich, Switzerland.
authors.forename: Helene
authors.initials: H
authors.lastname: Haker
authors.affiliation: The Zurich Program for Sustainable Development of Mental Health Services (ZInEP), Psychiatric Hospital, University of Zurich Zurich, Switzerland ; Laboratory of Neuroscience (LIM 27), Institute of Psychiatry, University of Sao Paulo Sao Paulo, Brazil.
authors.forename: Wulf
authors.initials: W
authors.lastname: Rössler
authors.affiliation: The Zurich Program for Sustainable Development of Mental Health Services (ZInEP), Psychiatric Hospital, University of Zurich Zurich, Switzerland ; Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich Zurich, Switzerland.
authors.forename: Wolfram
authors.initials: W
authors.lastname: Kawohl
keywords: cannabis; high-frequency oscillations; risk; schizophrenia; somatosensory evoked potentials; thalamus dysfunction