Abnormal sensory gating in schizophrenia: The evidence from Lempel-Ziv complexity analysis in EEG

The abnormality of sensory gating is one of the important mechanisms in schizophrenia. The present study aims to discuss the auditory sensory gating effect on the dynamical complexity of brain activity in schizophrenia compared to normal control groups. Event-related Electroencephalograms (EEG) during the standard P50 sensory gating test were recorded from 9 schizophrenia and 14 normal controls. A nonlinear dynamic method, Lempel-Ziv complexity (LZC) measure was used in this study. LZC can explore the dynamical complexity of brain activity under mental task. The research discovered that the schizophrenia showed significantly different LZC effects on the paired stimuli (s1 and s2) from normal group at certain area (Cz, p=0.000; T7, p=0.002; and Fz, p=0.034). Normal subjects have significant lower complexities for s1 than that for s2. However, the schizophrenia group did not show obvious LZC differences between s1 and s2. We also did classical analysis of event-related potential (ERP). The P50 component was analyzed and the consistent results were found with LZC. The P50 suppression shows obvious inhibition when s2 comes for the normal group but not for the schizophrenia group. The neurophysiological theory tells that, the first stimuli s1 activates an inhibitory system, suppressing the response to s2 for normal people. While, the schizophrenia show reduced suppression when s2 comes, which indicate the abnormality of auditory sensory gating. The schizophrenia was unable to filter out irrelevant stimuli, resulting in perceptual abnormalities. We therefore deduced that, the increase of LZC represented the order of neurons activities declined while brain disregarding irrelevant stimuli. In conclusion, LZC analysis may be another important way to understand the sensory gating in future studies.