title: Spectral EEG abnormalities during vibrotactile encoding and quantitative working memory processing in schizophrenia.
abstract: Schizophrenia is associated with a number of cognitive impairments such as deficient sensory encoding or working memory processing. However, it is largely unclear how dysfunctions on these various levels of cortical processing contribute to alterations of stimulus-specific information representation. To test this, we used a well-established sequential frequency comparison paradigm, in which sensory encoding of vibrotactile stimuli can be assessed via frequency-specific steady-state evoked potentials (SSEPs) over primary somatosensory cortex (S1). Further, we investigated the maintenance of frequency information in working memory (WM) in terms of parametric power modulations of induced beta-band EEG oscillations. In the present study schizophrenic patients showed significantly less pronounced SSEPs during vibrotactile stimulation than healthy controls. In particular, inter-trial phase coherence was reduced. While maintaining vibrotactile frequencies in WM, patients showed a significantly weaker prefrontal beta-power modulation compared to healthy controls. Crucially, patients exhibited no general disturbances in attention, as inferred from a behavioral test and from alpha-band event-related synchronization. Together, our results provide novel evidence that patients with schizophrenia show altered neural correlates of stimulus-specific sensory encoding and WM maintenance, suggesting an early somatosensory impairment as well as alterations in the formation of abstract representations of task-relevant stimulus information.
authors.affiliation: Neurocomputation and Neuroimaging Unit, Freie Universität Berlin, Germany; Berlin School of Mind and Brain, Humboldt-Universität zu Berlin, Germany. Electronic address: simon.ludwig@fu-berlin.de.
authors.forename: Simon
authors.initials: S
authors.lastname: Ludwig
authors.affiliation: Neurocomputation and Neuroimaging Unit, Freie Universität Berlin, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Spitzer
authors.affiliation: Department of Experimental and Neurocognitive Psychology, Freie Universität Berlin, Germany.
authors.forename: Arthur M
authors.initials: AM
authors.lastname: Jacobs
authors.affiliation: Klinik für Psychiatrie und Psychotherapie, Charité - Universitätsmedizin Berlin, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Sekutowicz
authors.affiliation: Klinik für Psychiatrie und Psychotherapie, Charité - Universitätsmedizin Berlin, Germany; Bernstein Center for Computational Neuroscience, Berlin, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Sterzer
authors.affiliation: Neurocomputation and Neuroimaging Unit, Freie Universität Berlin, Germany; Berlin School of Mind and Brain, Humboldt-Universität zu Berlin, Germany; Bernstein Center for Computational Neuroscience, Berlin, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Blankenburg
mesh_terms: D000328:Adult; D001931:Brain Mapping; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000209:etiology*; D008570:Memory, Short-Term / Q000502:physiology*; D009483:Neuropsychological Tests; D010812:Physical Stimulation; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000150:complications*; D013003:Somatosensory Cortex / Q000503:physiopathology; D013057:Spectrum Analysis
keywords: EEG; Schizophrenia; Somatosensory; Steady-state evoked potential (SSEP); Working memory