Abstract

This study aims to investigate the appearance of brainwaves due to mental stress caused by memory recall and mental calculation, and physical stress caused by noises. We obtainedElectroencephalography (EEG) data from 34 healthy subjects while they were at memory test interrupted by noises. Noise was accompanied by instability as it significantly decreased the relative power of the alpha wave of the left parietal lobe as compared to the rest state. In the word or picture memory recall, judging from the significant facts at the occipital and parietal lobes, the relative power of the alpha wave was more decreased, while the relative power of the theta wave was more increased at the occipital and parietal lobes; more so, the relative power of theta was more increased and the relative power of alpha was more decreased when solving the problems than when the problems were given only. Memorizing the process of words and pictures could also be considered as a stress factor like noises. When carrying out the mental calculation, the significant decrease of the relative power of the alpha wave at the occipital and parietal lobes showed instability during problem solving when compared to the rest state. This implies that mental calculation can also be considered as a stress factor. From the point that right-biased alpha wave was analyzed as significantly high in noises that are sometimes generated during the mental calculating process, it is possible to consider asymmetrical interpretation. As a result, noises (a physical stress factor) and memory recall (a mental stress factor) showed reduction of relative power of Alpha wave in the parietal and occipital lobes, and in case of the mental stress factor, even an increase of the relative power of theta wave was observed. Therefore, the appearance of brainwaves due to stresses is used as data to investigate mental activities.

Key words: Stress, noise, memory, electroencephalogram, power.