Abstract
The complexity change in brain activity in schizophrenia is an interesting topic clinically. Schizophrenia patients exhibit abnormal task-related modulation of complexity, following entropy of electroencephalogram (EEG) analysis. However, complexity modulation in schizophrenia patients during the sensory gating (SG) task, remains unknown. In this study, the classical auditory paired-stimulus paradigm was introduced to investigate SG, and EEG data were recorded from 55 normal controls and 61 schizophrenia patients. Fuzzy entropy (FuzzyEn) was used to explore the complexity of brain activity under the conditions of baseline (BL) and the auditory paired-stimulus paradigm (S1 and S2). Generally, schizophrenia patients showed significantly higher FuzzyEn values in the frontal and occipital regions of interest (ROIs). Relative to the BL condition, the normalized values of FuzzyEn of normal controls were decreased greatly in condition S1 and showed less variance in condition S2. Schizophrenia patients showed a smaller decrease in the normalized values in condition S1. Moreover, schizophrenia patients showed significant diminution in the suppression ratios of FuzzyEn, attributed to the higher FuzzyEn values in condition S1. These results suggested that entropy modulation during the process of sensory information and SG was obvious in normal controls and significantly deficient in schizophrenia patients. Additionally, the FuzzyEn values measured in the frontal ROI were positively correlated with positive scores of Positive and Negative Syndrome Scale (PANSS), indicating that frontal entropy was a potential indicator in evaluating the clinical symptoms. However, negative associations were found between the FuzzyEn values of occipital ROIs and general and total scores of PANSS, likely reflecting the compensation effect in visual processing. Thus, our findings provided a deeper understanding of the deficits in sensory information processing and SG, which contribute to cognitive deficits and symptoms in patients with schizophrenia.
Highlights
The sensory gating (SG) deficit is considered a core deficit among patients with schizophrenia
We found that schizophrenia patients had significantly larger normalized values of S1 than the normal controls in the frontal and occipital regions of interest (ROIs) (p < 0.05, corrected), values that were in line with the Fuzzy entropy (FuzzyEn) maps
FuzzyEn was used to extract the non-linear feature of EEG signals under BL and paired stimuli, focused on the changes in the complexity of SG between normal controls and schizophrenia patients
Summary
The sensory gating (SG) deficit is considered a core deficit among patients with schizophrenia. SG has usually been studied in a paired-stimulus paradigm: two brief, identical stimuli are presented with a 400 ms stimulus onset asynchrony (Santos et al, 2010; Sánchez-Morla et al, 2013). Both stimuli elicit a positive potential 50 ms post-stimulus (P50), and the amplitude of potential to the second stimulus is normally attenuated. This phenomenon was considered a measure of input inhibitory, called P50 suppression. The poor SG in schizophrenia patients was considered to be more related to the diminished processing of S1 than to the deficient gating of S2 (Blumenfeld and Clementz, 2001; Johannesen et al, 2005)
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