Analysis of interhemispheric EEG spectral variation at rest and after mental arithmetic task in schizophrenic patients compared to healthy controls

Résumé

Introduction Electroencephalogram (EEG) has emerged to be valuable for understanding the neurophysiological mechanisms underlying cognitive dysfunctions in psychiatric disorders. EEG mental arithmetic enables to assesse cognitive abilities in schizophrenic patients, by inducing brain activity that can be observed through frequency band analysis Objectives This study aimed to assess the absolute spectral density (ASD) of various EEG frequency bands in schizophrenic patients and healthy controls, at rest and during a mental arithmetic task, in order to identify specific neural differences Methods We conducted a cross-sectional, descriptive, and analytical case-control study involving 15 schizophrenic patients and 15 healthy controls. The study was carried out at the outpatient unit of Psychiatry Department “C” at Hedi Chaker University Hospital in Sfax, Tunisia. Participants underwent a standard wakefulness EEG with eyes closed at the Functional Explorations Department of Habib Bourguiba Hospital in Sfax, Tunisia. Each participant also performed a mental calculation test during the EEG recording Results The ASD of the different EEGs was studied for each frequency band in the different cerebral lobes (Table 1). At rest, in schizophrenic patients, a significant difference was found between the mean ASD of the delta, theta, and beta1 frequency bands in the right and left occipital regions. Also, frequency band activity was more diminished in the left occipital regions than in the right. After mental calculation, the interhemispheric asymmetry disappeared in schizophrenic patients. In the control group, no significant differences were found between the mean ASD for any frequency band in the right and left frontal, temporal, and occipital regions, either at rest or after mental calculation (Table 1) Table 1 : Comparison of EEG absolute spectral density between hemispheres in schizophrenics and controls at rest and after mental calculation task Schizophrenics p= Controls p= Right Left Right Left At rest DELTA Occipital 30,44± 26,37 22,74±19,34 0,021 5127,7±19031 5111,41±18968 0,373 THET Occipital 58,17±47,67 45,67±44,88 0,023 3856,8±12450 3863,76±12458 0,721 BETA 1 Occipital 7,22±4,25 6,24±3,77 0,002 497,9±1854 498,26±1860 0,854 After mental calculation task DELTA Occipital 22,62±17,8 24,84±33,76 0,725 4970,14±15006 4979,39±15068 0,762 THETA Occipital 46,35±41,48 62,62±96,01 0,442 1895,46±5301 1849,43±5245 0,766 BETA1 Occipital 5,76±3,45 5,43±3,17 0,466 934,81±3152 919,04±3093 0,328 Conclusions These results underline the importance of considering cerebral lateralization in the diagnostic and therapeutic approach to schizophrenia. It is important to note that mental arithmetic involves complex cognitive processing, essentially working memory. Hence the importance of adopting a therapeutic approach incorporating not only pharmacological treatments, but also cognitive remediation therapies Disclosure of Interest None Declared

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