Impairments of event-related magnetic fields in schizophrenia patients with predominant negative symptoms.

Recently there is a growing understanding that patients suffering from negative symptoms of schizophrenia represent a distinct patient population. However, despite the abundance of EEG studies characterizing schizophrenia patients in general, only a handful of studies have focused on the electrophysiological correlates of negative symptoms. The current study examined whether the impairments in event-related magnetic fields (ERFs) commonly reported in heterogeneous groups of patients with mixed positive and negative symptoms also occur in patients with predominantly negative symptoms, and investigated their correlation to clinical symptoms and cognitive deficits. Twenty schizophrenia patients suffering from predominant negative symptoms and 25 healthy subjects underwent neuropsychological and electromagnetic assessments. ERFs were recorded during a three-stimuli novelty oddball and a sensory gating paradigm, and M50, P300m and Novelty-P3m components were investigated. Patients displayed impaired M50 ratios, reduced left P300m and frontal Novelty-P3m amplitudes. These electromagnetic measures correlated significantly with the severity of negative symptoms (SANS scale). The electrophysiological abnormalities which have been proposed as candidate biomarkers for schizophrenia are also manifested in patients with predominantly negative symptoms.