Source localization of sensory gating: a combined EEG and fMRI study in healthy volunteers |
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Authors: | Bak Nikolaj Glenthoj Birte Y Rostrup Egill Larsson Henrik B Oranje Bob |
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Affiliation: | a Center for Neuropsychiatric Schizophrenia Research (CNSR), Faculty of Health Sciences, University of Copenhagen, University Psychiatric Center Glostrup, Glostrup, Denmark;b Functional Imaging Unit, Glostrup Hospital, University of Copenhagen, Denmark;c Department of Clinical Physiology and Nuclear Medicine, Glostrup Hospital, University of Copenhagen, Denmark;d The Lundbeck Foundation Center for Neuropsychiatric Schizophrenia Research (CINS), Psychiatric University Center Glostrup, University of Copenhagen, Denmark;e Department of Radiology, Glostrup Hospital, University of Copenhagen, Denmark |
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Abstract: | Reduced sensory gating appears to be among the core features in schizophrenia. The sources of sensory gating however are largely unknown. The aim of the current study was to identify these sources, with concurrent EEG and fMRI methodology. Twenty healthy male volunteers were tested with identical P50 suppression paradigms in two separate sessions: an EEG setting, and an EEG concurrent with fMRI setting. The stimuli in the P50 paradigm consisted of weak electrical stimulation of the left median nerve. The stimuli were presented in pairs with either 500 ms or 1000 ms interstimulus intervals (ISI). No difference was found between the EEG setting and the concurrent EEG and fMRI setting. P50 suppression was, in both settings, found only in the 500 ms trials, not in the 1000 ms trials. EEG-dipole modeling resulted in 4 sources located in the medial frontal gyrus, the insula, the hippocampus, and primary somatosensory cortex. These sources corresponded to significant fMRI clusters located in the medial frontal gyrus, the insula, the claustrum, and the hippocampus. Activity in the hippocampus and the claustrum was higher in the trials with suppression, suggesting that these brain areas are involved in the inhibitory processes of P50 suppression. The opposite was found for activity in the medial frontal gyrus and the insula, suggesting that these brain areas are involved in the generation of the P50 amplitude. To our knowledge, this is the first study demonstrating that P50 suppression can be reliably assessed inside an MRI scanner. |
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Keywords: | P50 suppression fMRI EEG Source localization Sensory gating Concurrent assessment |
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