CHANGES IN CARDIOVASCULAR, RESPIRATORY, AND NEURAL ACTIVITY BY MUSIC: EFFECTS OF BREATHING PATHWAY ON FEELING EMOTIONS

Listening to music can induce emotional and physiological changes. Increasing recognition of the palliative effects of music has led to its use as an adjuvant therapeutic tool in the treatment of various diseases. It is also well known that autonomic nervous activities and some cardiorespiratory rhythms change in correspondence with music. However, less is known about how these effects triggered by music come about. Listening to music affects synchronization between electroencephalograms (EEGs) and cardiac rhythmic activity. This interaction between cardiac and electrical responses led us to investigate whether EEG segments synchronized to different portions of the cardiac cycle can better reveal the effects produced while listening to music. In this dissertation, we investigated the effects of music from two different perspectives. Effects of the tempo of music, which has a relatively stronger effect on physiological variables compared to the other structural features, and effects of cognition of music were considered to compare the effects of a strong acoustical feature of music with effects of a feature not related to the structure of music to determine whether these effects were better revealed within certain portion of the cardiac cycle. We use effects of cognition to mean as those not directly resulting from structural features of music. 14 subjects participated in this study. In a second study, we investigated how the breathing pathway can affect the processing of emotion induced by music. There is evidence of the presence of respiratory entrainment of local field potential activity in human limbic brain networks and the importance of nasal airflow in shaping this entrainment, but the effects of breathing pathway (nasal vs. oral) on the processing of various emotions, which happens in the limbic region, are not yet well-understood, we compared the degree of various emotions triggered by different pieces of music during purely oral breathing (OB) and purely nasal breathing (NB). Also, changes in some physiological parameters during OB and NB were compared, and the correlation of different structural musical features with different emotions was investigated. 12 subjects participated in this study. Results showed, as indicated by eigenvalue decomposition, an increase in complexity of brain response by an increase in the tempo of the music, specifically in the parietal lobe, and triggering the smallest changes by slow tempo song, possibly explaining the calming effects of slow music. A stronger effect of cognition of music was observed in frequencies \u3e 38 Hz, particularly in the temporal lobe, and a stronger response to slower tempo music was observed in frequencies \u3c 38 Hz. The larger sensitivity of EEGs to portions of the cardiac cycle was in frequency bands \u3c 38 Hz. Alpha and Beta bands were the most sensitive bands to auditory stimuli and cardiac phases, respectively, and in both of them, effects of tempo were larger than cognition of music. Overall, we observed that the EEG portion which contained data points that were temporally farthest from R-waves of ECG showed the effects of music in a much more pronounced way than the other two portions. This observation was consistently supported by all of the used features and statistical indices which were based on eigenvalue decomposition, the effect size of changes, and p values. In the study related to investigating the effects of breathing pathway on processing emotion, our results revealed that during NB, subjects found songs happier and more relaxing, and they felt more arousal states from songs when compared to the same songs during OB. On the other hand, during OB, subjects’ average rate of more negative emotions was higher when compared to NB. We observed that the consonance degree of songs had significantly high positive correlations with positive emotions and significantly high negative correlations with negative emotions, while the higher complexity rate of songs had a positive correlation with negative emotions. Also, our results demonstrated slightly higher synchronization of respiration with various EEGs and with heartrate variations during NB in both control and listening to music