Abstract
The aim of the present study was to characterize the neural network reorganization during a cognitive task in schizophrenia (SCH) by means of wavelet entropy (WE). Previous studies suggest that the cognitive impairment in patients with SCH could be related to the disrupted integrative functions of neural circuits. Nevertheless, further characterization of this effect is needed, especially in the time-frequency domain. This characterization is sensitive to fast neuronal dynamics and their synchronization that may be an important component of distributed neuronal interactions; especially in light of the disconnection hypothesis for SCH and its electrophysiological correlates. In this work, the irregularity dynamics elicited by an auditory oddball paradigm were analyzed through synchronized-averaging (SA) and single-trial (ST) analyses. They provide complementary information on the spatial patterns involved in the neural network reorganization. Our results from 20 healthy controls and 20 SCH patients showed a WE decrease from baseline to response both in controls and SCH subjects. These changes were significantly more pronounced for healthy controls after ST analysis, mainly in central and frontopolar areas. On the other hand, SA analysis showed more widespread spatial differences than ST results. These findings suggest that the activation response is weakly phase-locked to stimulus onset in SCH and related to the default mode and salience networks. Furthermore, the less pronounced changes in WE from baseline to response for SCH patients suggest an impaired ability to reorganize neural dynamics during an oddball task.
Highlights
Schizophrenia (SCH) is a psychiatric disorder characterized by positive and negative symptoms, frequently accompanied by impaired cognitive processing [1]
Non-significant differences were found between baseline and response windows in SCH patients (p > 0.05, Wilcoxon signed-rank test)
We found that SCH patients showed lower changes in their irregularity patterns during the active response compared to controls for the two analyzed approaches: ST and SA
Summary
Schizophrenia (SCH) is a psychiatric disorder characterized by positive and negative symptoms, frequently accompanied by impaired cognitive processing [1]. It is noteworthy that neural mechanisms underlying cognitive dysfunctions in SCH are related to fast changes in the spatiotemporal patterns of neuronal modulation [12] These techniques do not provide enough time resolution to study brain dynamics. EEG can be used to study fast interactions (e.g., changes from baseline to response windows) In this regard, event-related potentials (ERPs) have been used to assess cognitive processing in SCH. MMN is an important paradigm for SCH research, because it could be linked to altered dopaminergic neurotransmission [17] It is necessary a deep study of the spectral and spatial brain dynamics to further understand the neural substrates underlying this pathology [12,18,19,20,21]
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