Nonlinear analysis of electroencephalogram at rest and during cognitive tasks in patients with schizophrenia

Nonlinear analysis of electroencephalogram at rest and during cognitive tasks in patients with schizophrenia

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J Psychiatry Neurosci 2012;37(4):259-66

Elisa Carlino, PhD (candidate);* Monica Sigaudo, MD;* Antonella Pollo, MD; Fabrizio Benedetti, MD; TulliaMongini, MD; Filomena Castagna, PhD; Sergio Vighetti, PhD; Paola Rocca, MD

Carlino, Pollo, Benedetti, Vighetti — Department of Neuroscience, University of Turin Medical School, and National Institute of Neuroscience, Turin, Italy; Sigaudo, Mongini, Castagna, Rocca — Department of Neuroscience, Psychiatric Section, University of Turin Medical School, Turin, Italy

*E. Carlino and M. Sigaudo contributed equally to the work.

Abstract

Background: In spite of the large number of studies on schizophrenia, a full understanding of its core pathology still eludes us. The application of the nonlinear theory of electroencephalography (EEG) analysis provides an interesting tool to differentiate between physiologic conditions (e.g., resting state and mathematical task) and normal and pathologic brain activities. The aim of the present study was to investigate nonlinear EEG activity in patients with schizophrenia.

Methods: We recorded 19-lead EEGs in patients with stable schizophrenia and healthy controls under 4 different conditions: eyes closed, eyes open, forward counting and backward counting. A nonlinear measure of complexity was calculated by means of correlation dimension (D2).

Results: We included 17 patients and 17 controls in our analysis. Comparing the 2 populations, we observed greater D2 values in the patient group. In controls, increased D2 values were observed during active states (eyes open and the 2 cognitive tasks) compared with baseline conditions. This increase of brain complexity, which can be interpreted as an increase of information processing and integration, was not preserved in the patient population.

Limitations: Patients with schizophrenia were taking antipsychotic medications, so the presence of medication effects cannot be excluded. Conclusion: Our results suggest that patients with schizophrenia present changes in brain activity compared with healthy controls, and this pathologic alteration can be successfully studied with nonlinear EEG analysis.


Submitted Mar. 26, 2011; Revised Oct. 13, Nov. 17, 2011; Accepted Nov. 17, 2011.

Competing interests: None declared.

Contributors: A. Pollo, F. Benedetti and P. Rocca designed the study. E. Carlino, M. Sigaudo, T. Mongini, F. Castagna and S. Vighetti acquired the data. E. Carlino and M. Sigaudo analyzed the data. E. Carlino, M. Sigaudo and A. Pollo wrote the article. F. Benedetti, T. Mongini, F. Castagna, S. Vighetti and P. Rocca reviewed the article. All authors approved its publication.

DOI: 10.1503/jpn.110030

Correspondence to: E. Carlino, Department of Neuroscience, University of Turin Medical School, and National Institute of Neuroscience,
Corso Raffaello 30, 10125 Turin, Italy; elisa.carlino@unito.it