Quantifying clinical improvements in patients with depression under the treatment of transcranial direct current stimulation using event related potentials
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The main goal of this study was to assess the changes in brain activities of patients with severe depression by applying transcranial direct current stimulation (tDCS) using event related potentials (ERPs). Seven patients (four males, with the mean age 34.85 ± 4.25) were asked to fill out Beck’s depression questionnaires. EEG signals of subjects were recorded during Stroop test. This test entailed 360 stimulations, which included 120 congruent, 120 incongruent, and 120 neutral stimulations lasting for 12 min. Subsequently, the dorso lateral prefrontal cortex in patients’ left hemisphere was stimulated for six sessions using tDCS. At the end of tDCS treatment period, subjects filled out Beck’s depression questionnaires again and EEG signal recordings were repeated simultaneously with Stroop test. Wavelet coefficients of EEG frequency bands in every stimulation type were extracted from ERP components. The changes in Beck score before and after tDCS were estimated using neural network model. The ERP results showed that the latency period of N400 component after applying tDCS decreased significantly. Moreover, a significant correlation was observed between percentage changes of congruent and incongruent accuracy and the increase in the average energy of wavelet coefficients in alpha band in Pz electrode with p = 0.0128, r = 0.9060 and p = 0.0037, r = 0.95, respectively. Additionally, the results of neural network model revealed that the changes in Beck score were estimated with an average error of 0.0519. Consequently, the improvement of depressed patients treated with tDCS could be estimated with good accuracy using average energy of wavelet coefficients in alpha band.
KeywordsDepression Transcranial direct current stimulation Stroop test Event related potentials Dorso lateral prefrontal cortex
Financial support from the Cognitive Technology and Science Development Staff is greatly appreciated.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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