Brain Activity Measurement during a Mental Arithmetic Task in fNIRS Signal Using Continuous Wavelet Transform

Farzaneh  Aliabadi Farahani; Mehrdad  Dadgostar; Zahra  Einalou

doi:10.18502/fbt.v8i4.7755

Farzaneh Aliabadi Farahani Department of Biomedical Engineering, Central Tehran Branch, Islamic Azad University, Tehran, Iran
Mehrdad Dadgostar Department of Biomedical Engineering, Central Tehran Branch, Islamic Azad University, Tehran, Iran
Zahra Einalou Department of Biomedical Engineering, North Tehran Branch, Islamic Azad University, Tehran, Iran

DOI: https://doi.org/10.18502/fbt.v8i4.7755

Keywords: functional Near-Infrared Spectroscopy; Mental Arithmetic Task; Prefrontal Cortex; Continuous Wavelet Transform.

Abstract

Purpose: Functional Near-Infrared Spectroscopy (fNIRS) is a non-invasive imaging technology with widespread use in cognitive sciences and clinical studies. It indirectly measures neural activation by measuring alterations of oxyhemoglobin (HbO₂) and deoxyhemoglobin (Hb) in tissues. This study used mental arithmetic task for analyzing the activation of the frontal cortex.

Materials and methods: The fNIRS instrument was used for measuring the alterations of HbO₂ and Hb in healthy subjects during the task. Then the recorded signals were filtered in the frequency range of 3 to 80 mHz. The Continuous Wavelet Transform (CWT) of each of the HbO₂ and Hb signals in each channel was calculated in the intended frequency range, followed by the calculation of the energy of obtained coefficients. Finally, for the performed tasks, the average energy of each channel in each region was obtained. Then the energies of spatially symmetric channel pairs in the two hemispheres were compared using the t-test.

Results: Results demonstrated that the average energy of HbO₂ signal for corresponding channels in the temporal, Medial Prefrontal Cortex (MPFC), and Dorsolateral Prefrontal Cortex (DLPFC) regions had significant differences (P<0.05). Also, a significant difference was observed in the temporal, medial prefrontal, and Ventrolateral Prefrontal Cortex (VLPFC) regions for Hb signal.

Conclusion: The obtained results indicate activation in both HbO2 and Hb signals in the DLPFC, temporal, and MPFC regions, considering the performance of memory and the frontal cortex under mental arithmetic tasks. Therefore, it can be concluded that this technique is effective and appropriate for analyzing alterations of brain oxygen levels during cognitive activity.