Complexity-based analysis of the coupling between facial muscle and brain activities

Abstract The human body consists of different muscles. Investigation of facial muscle activities is very important since they are responsive to different kinds of stimuli that humans receive. The brain controls and regulates the activities of human’s muscles. In this work, we evaluated the coupling among the facial muscles and brain activities for twelve subjects (7 M and 5 F) that were stimulated using three odors (pineapple, banana, and vanilla flavors as olfactory stimuli) with different molecular complexities. Using fractal theory and sample entropy, we studied how the complexity of facial muscles’ reaction through Electromyography (EMG) signals is linked to the complexity of the brain’s response through Electroencephalography (EEG) signals due to olfactory stimulation. The results showed significant changes ( P 0.05 ) in the complexities of EMG and EEG signals in response to the applied odors. Besides, the changes in the complexity of EEG and EMG signals are strongly correlated in the case of fractal dimension (r=-0.947) and sample entropy (r=-0.774). This analysis method can be applied to other physiological signals to investigate the coupling between the activities of other organs and brain activity.