EEG Changes Induced by Odor Effects after Stress of Long Monotonous Work; Application of Nonlinear Analysis Based on Chaos Dynamics

Based on the findings of previous studies, we used nonlinear analysis of EEGs to investigate the effects of odor stimuli applied after the stress of monotonous work. Eight healthy adults who took the Uchida-Kraepelin test of working capability as mental working stress were subjects. Immediately after a post-stress session, subjects were exposed to odor or control stimuli. EEGs were concurrently recorded for 2 minutes. Psychological tests indicated that subjective fatigue and trait anxiety levels increased after stress loading, suggesting that subjects were placed under mental and physical stress. Both subjective Nonlinear analysis of EEGs indicated that Dc in the post-stress session was lower than in the pre-stress session. The subsequent odor stimuli induced an increase in Dc. Correlations were observed between DDc and stress and stimuli, and changes were significant in the occipital and left parietal regions of the cerebral hemispheres. Our study demonstrated that the effect of odor stimuli on the human body might be associated with higher cerebral function, such as favorite odors and psychological changes including emotional alteration.