Interwined study on brain bio-electrical signal and salivary protein for mental stress level indicator

Abstract

Lifetime exposure to stress can have significant impact on health that increase the risk of having diseases that may lead to death. In this project, inter-relationship between brain activity and salivary alpha-amylase (sAA) as stress marker is investigated in response to induced mental-stress activities. By using psychophysics experiment to alter normal mental condition, several mental tasks with different levels of difficulty (baseline level: 100% correct answer, easy level: 65-75% correct answer; medium level: 20-40% correct answer, and hard level: 0% correct answer) are presented to 20 healthy participants (10 male; 10 female). In this study, participants' normal mental condition is defined using results from perceived stress scale (PSS-IO) questionnaire given to them before experimental procedure with total score of 40. Participant with PSS-IO total score lower than 30 is considered in their normal mental condition. Brain activity from participants were recorded using electroencephalogram (EEG) and their saliva samples were also collected during experimental procedure. The characteristic of sAA is a biomarker for autonomic nervous system reacting sensitively to stress-related changes. A correlation analysis was conducted to see the significant correlation between specific activated brain area and sAA concentration level during alpha and beta frequency band specifically focusing on superior frontal gyrus, middle frontal gyrus, inferior frontal gyrus, orbital gyrus, anterior cingulate, and insula areas. Positive correlation that was statistically significant between brain activities in beta frequency band and sAA concentration level was found in insula area (F 0.998, rr- 3, p~0.042<0.05) for fJz band and anterior cingulate (F 0.997, rr- 3, p=0.047<0.05) and insula area (r= 0.999, n= 3, p= 0.031 <0.05) for fJ3 band. However, alpha-band activities and sAA level did not show any statistically significant correlation in all six desired brain area. These areas were significantly more active under stimuli with highest level of difficulties compared with that of the lowest level. Saliva analysis using ANOVA also showed statistically significant difference in concentration level of sAA for 4 different groups: (F (3, 8) =55.76509, p~0.00001<0.05) where only medium (M=1l0.79, SD=3.97); t (4) = 2.78, p= 0.002<0.0083 (two-tailed) and hard level (M~123.56, SD~2.50); t (4) ~ 2.78, p~O.OOOI <0.0083 (two-tailed) has significantly differ from baseline level (control group). In conclusion, brain activity in anterior cingulate and insula area within beta frequency band and sAA level showed statistically positive correlation, as it altered normal mental condition in regards to different levels of stress.