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

Published online by Cambridge University Press:  26 August 2025

N. Smaoui ,
D. Jardak ,
R. Feki ,
S. Omri ,
I. Gassara ,
N. Charfi ,
J. Ben Thabet ,
M. Maalej ,
M. Bou Ali Maalej  and
L. Zouari
...Show all authors
N. Smaoui
Affiliation:
Psychiatry C, Hedi Chaker University Hospital
D. Jardak*
Affiliation:
Psychiatry C, Hedi Chaker University Hospital
R. Feki
Affiliation:
Psychiatry C, Hedi Chaker University Hospital
S. Omri
Affiliation:
Psychiatry C, Hedi Chaker University Hospital
I. Gassara
Affiliation:
Psychiatry C, Hedi Chaker University Hospital
N. Charfi
Affiliation:
Psychiatry C, Hedi Chaker University Hospital
J. Ben Thabet
Affiliation:
Psychiatry C, Hedi Chaker University Hospital
M. Maalej
Affiliation:
Psychiatry C, Hedi Chaker University Hospital
M. Bou Ali Maalej
Affiliation:
Psychiatry C, Hedi Chaker University Hospital
L. Zouari
Affiliation:
Psychiatry C, Hedi Chaker University Hospital
L. Triki
Affiliation:
Functional Explorations, Habib Bourguiba University Hospital, Sfax, Tunisia
*
*Corresponding author.

Abstract

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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

Schizophrenicsp=Controlsp=
RightLeftRightLeft
At rest
DELTA Occipital30,44± 26,3722,74±19,340,0215127,7±190315111,41±189680,373
THET Occipital58,17±47,6745,67±44,880,0233856,8±124503863,76±124580,721
BETA 1 Occipital7,22±4,256,24±3,770,002497,9±1854498,26±18600,854
After mental calculation task
DELTA Occipital22,62±17,824,84±33,760,7254970,14±150064979,39±150680,762
THETA Occipital46,35±41,4862,62±96,010,4421895,46±53011849,43±52450,766
BETA1 Occipital5,76±3,455,43±3,170,466934,81±3152919,04±30930,328

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

Information

Type
Abstract
Information
European Psychiatry , Volume 68 , Special Issue S1: Abstracts of the 33rd European Congress of Psychiatry , April 2025 , pp. S1044 - S1045
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of European Psychiatric Association
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