Attempt to Evaluate Comfort Level Using EEG Before and After Sugar Intake: Examination of EOG by Principal Component Analysis

Background and objectives: It has been reported that sugar produces positive emotions in psychological questionnaire studies. However, some reports show no effect on mood, and others show increased depressed mood. Questionnaire surveys are not sufficient for subjective mood evaluation. Recently, electroencephalography (EEG), a simple measurement of central nervous system activity, has been used as an objective method for estimating mood. The Comfort Vector (CV) model based on the 1/f characteristics of alpha wave fluctuations in the frontal lobe is used as a mood evaluation index using EEG. In contrast, EEG is contaminated with Electrooculography (EOG). EOG-contaminated EEG makes the accuracy of the results of the CV model unstable. A method for removing EOG artifacts from EEG is proposed using principal component analysis (PCA). In this study, we propose a new CV model combined with PCA for objective and real-time evaluation of mood on sugar intake. Methods: Two healthy young males participated in this double-blind crossover study. Experiments were conducted in the morning after a 12-hour fast. The subjects consumed fructose or placebo (sodium saccharin) with water. EEG and EOG were measured for 6 min 7 times before and every 10 minutes after intake with eyes closed at resting-state. The EEG and EOG signals were divided into 2.048-second segments, and the segments were graded based on the maximum amplitude of the EOG signals. PCA was applied to the EEG contaminated with EOG artifacts. Then, the analytical procedure for the CV model was performed. Results: We report about the percentage of the region where the length of the vector in the second quadrant is greater than 50%. This percentage increased 20 min after intake for subject A and 10 min after intake for subject B in both intakes. Then, this percentage did not increase or decrease 40-50 min after placebo intake, whereas it increased after fructose intake.