Applied Mechanics and Materials Vol. 311 (2013) pp 502-506 Online available since 2013/Feb/27 at www.scientific.net © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMM.311.502
Effect of Music Listening on Frontal EEG Asymmetry Yi-Yeh Lee1,a, Aaron Raymond See2,b, Shih-Chung Chen2,c, Chih-Kuo Liang3,d 1Department of Graphic Communication Arts, National Taiwan University of Arts, New Taipei City, Taiwan 2
Department of Electrical Engineering, Southern Taiwan University, Tainan, Taiwan 3
Department of Electrical Engineering, National Taitung College, Taitung, Taiwan a
[email protected],
[email protected],
[email protected], d
[email protected]
Keywords: Frontal EEG Asymmetry, Sad Music Video, Audio-Video Stimulation.
Abstract. Frontal EEG asymmetry has been recognized as a useful method in determining emotional states and psychophysiological conditions. For the current research, resting prefrontal EEG was measured before, during and after listening to sad music video. Data were recorded and analyzed using a wireless EEG module with digital results sent via Bluetooth to a remote computer for further analysis. The relative alpha power was utilized to determine EEG asymmetry indexes. The results indicated that even if a person had a stronger right hemisphere in the initial phase a significant shift first occurred during audio-video stimulation and was followed by a further inclination to left EEG asymmetry as measured after the stimulation. Furthermore the current research was able to use prefrontal EEG to produce results that were mostly measured at the frontal lobe. It was also able to provide significant changes in results using audio and video stimulation as to previous experiments that made use of audio stimulation. In the future, more experiments can be conducted to obtain a better understanding of a person’s appreciation or dislike toward a certain video, commercial or other multimedia contents through the aid of convenient EEG module. Introduction Music has been a main source of entertainment that crosses boundaries and cultures. And in the past few decades, its purpose has grown from simply entertainment to medical purposes. Then in the recent two decades researches on EEG asymmetry in relation to emotional and psychological states has been on the increase. Previous researches associated resting EEG asymmetries inhibiting a greater right than left frontal activity to traits and behaviors indicative of withdrawal behaviors. One of these withdrawal behaviors is fear wherein the negative thoughts produce a greater right frontal resting EEG activity [1, 2]. In measuring frontal EEG, a common index computes difference between the natural logarithm of the left hemisphere alpha power from the natural logarithm of the right hemisphere alpha power. The higher the score means that EEG power demonstrates a greater right frontal activity and vice versa [1, 3]. Cross-referencing with several other researches showed that base from these figures, a relatively greater left frontal activity correlates to a general appetitive, approach or behavioral activation motivational system while relatively greater right frontal activity is associated with tendencies favoring general avoidance or withdrawal system [1, 4]. From this hypothesis, the factor mentioned above may be considered as an index for the risk of anxiety or depression. In addition, other studies on EEG showed that a person with depression has exhibited a left frontal hypo-activation and an increase of beta power in the right frontal region [5-7]. But there was a research that indicated EEG asymmetry could be found in both healthy and depressive subjects [8]. In other research, music was found to correlate with emotional experience. It was also discussed that the frontal-central areas were diagnosed to determine effects on emotion through the use of EEG, wherein distinct changes were able to be observed on the theta and delta band at different emotional All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 114.33.176.240, Department of Electrical Engineering, Southern Taiwan University, No.1, Nantai St., Yung Kang Dist., Tainan, Taiwan, Tainan, Taiwan-04/03/13,09:52:44)
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states [9]. It was known that both positive and negative music exerted positive modulatory effects on cardiovascular and respiratory activity during the post-stress recovery and it was also able to restore physiological signals to baseline levels [10]. In the present work, the effects of sad music on EEG asymmetry and EEG power relationships would be studied to compare its effect on the theory that sad or negative music could also relieve stress and restore physiological signals to baseline levels as well. In particular, a study on the prefrontal EEG channels Fp1 and Fp2 would be further studied as it has the most convenient channels to measure EEG for practical purposes. In the future, the goal of the research is to use two channel prefrontal EEG to measure a person’s reaction to a certain music, advertisement or movie. Materials and Methods In order to simulate the effect of music videos and other possible entertainment type of stimulus, several subjects were requested to test the model and examine the pair of EEG channels that would exhibit asymmetrical changes due to the introduction of sad music. The experiment was carried out with a group of volunteers composed of 9 male university students with a mean age of 22.67±2.75 years. Subjects were normal healthy students without any known psychological disorders. A total of 10 trials were performed to evaluate the effect of affective music on the EEG of each subject. For the experimental design, the procedure was divided into three parts including Baseline, AVS (Audio-Visual Stimulation), Post-AVS for 5, 15, 5 minutes respectively, with a total of 25 minutes. Measurements were done in the laboratory while sitting in a relaxed position. The Neurosky Dual-channel Mindband was used to record the EEG signals. Data were transmitted via Bluetooth and are saved in text files. These would be utilized for further analysis. Asymmetry and Engagement Index In accordance to several previous studies, the difference of the natural logarithm of the right alpha power and left alpha power were calculated (ln[right alpha]-ln[left alpha]). EEG Asymmetry=ln(right alpha)-ln(left alpha)
(1)
On the other hand, the engagement index (EI) was calculated using the relative theta, alpha and beta power and stated as: EI=relative beta power/(relative theta power+relative alpha power)
(2)
This EI index was used to determine if the subject was able to suppress slow wave theta+alpha (8-12Hz) and enhance beta (12-20Hz) needed for attention improvement. Results and Discussion In accordance to previous researches frontal EEG asymmetry could be utilized to measure whether a person has an inclination toward a certain emotional state or possible mental disorder [1-4]. However, in the current research, normal subjects were used and as shown in Fig. 1 there was very minimal change between Fp1 and Fp2 for each of the experimental procedures. In addition, the two channels were found to be close to symmetric during baseline and AVS in almost all the subjects. It was observed that from the experiment there was a 9~13% increase in the relative alpha power when comparing the baseline to the post experiment with a slight inclination to the right hemisphere. In addition, the relative alpha power was reduced by almost 50% and had the lowest values when the subject was undergoing AVS. The results suggested that such a significant change in alpha power was due to the difference in eyes open and eyes close situation of the subject. The baseline and post-experiment were both done with eyes close. However, it also found that such a decrease brought in a significant increase in the relative theta power amplitude, hence it indicated that such increase in lower frequency bands was correlated to meditation that reflected a positive emotional state and internalized attention [11].
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Fig. 1. EEG Harmonic parameters for the 3 different experimental procedures as measured from electrode1 (Fp1) and electrode 2 (Fp2).Odd numbers for Fp1 while even for Fp2. After undergoing the experiment, the EEG asymmetry was calculated and it was noticed that there is an upward trend as shown in Fig. 2. Besides, it was discovered that a large difference in the post EEG asymmetry was manifested after watching the sad music video. It may be said that it was insufficient to just use the relative power to display the asymmetry but through the work of previous researchers it was proven that this function could display changes in the EEG asymmetry even if the pre-frontal EEG was measured instead of the frontal EEG.
Fig. 2. Alpha EEG Asymmetry of the 3 procedures. On the other hand, in Fig. 3 the engagement index showed that the mean of the indices shifted from a larger right index at baseline to a greater left pre-frontal EEG. And interestingly pre-frontal EEG dropped and was nearly symmetric at the post-AVS procedure. Therefore, the results of this study showed that although sad music videos were utilized, the subjects tended to have a more appreciative response toward the video, moreover, the engagement index presented that the left pre-frontal EEG index was the highest during the experiment showing involvement of the subject that was motivated by the AVS. According to the course of the experiment, the subjects tended to exhibit a more meditative state as compared to an attentive state. In Fig. 4, it showed that among all three procedures the meditation index was significantly higher showing that the subjects were brought into a relax and meditative state by listening and watching the videos. Furthermore, it also coinhered with the research on long-term AVS wherein the theta and alpha bands in the frontal region were significantly increased. Based on the results, although there was a significant decrease in the alpha power during AVS results, post measurements showed an ascending trend from the index estimations.
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Fig. 3. Changes in the Engagement Index (EI).
Fig. 4. Comparison of attention and meditation as seen from each experiment.
Conclusion The research had successfully used fronto-polar EEG to study the effects of sad music video on EEG. It was shown that sad music videos has the tendency to produce greater right pre-frontal EEG asymmetry, but there was not any significant values to prove that normal subjects can be strongly affected by these videos. In addition, the engagement index showed that the subjects manifested an inclination to the left pre-frontal EEG as they were watching the music videos. It showed that people watching the videos are generally in an appreciative mood when watching videos even if these were sad music videos. It also suggested that once the video over, post measurements revealed that the subjects were less engaged or more relaxed compared to the baseline measurement. It could be interpreted as a sympathetic or withdrawal tendency but could also mean a more relax and meditative state due to a stronger theta and alpha condition. Moreover, subjects also exhibited a more meditative state thus bringing them into a more relaxed state and indicated that such videos could aid in relaxation if viewed at a limited time. The 15-minute time frame may not be considered short or long but from previous researches a 20-30 minute video could be used to train, stimulate or provide relaxation to the subject.
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The research has also proven that the use of pre-frontal EEG could be utilized in studying the EEG changes on whether a person was appreciative and motivated or not. The engagement index and asymmetry index could both be used in future experiments with the possibility of innovating new indices that could further provide a more convenient and accurate form of satisfaction evaluation system for multimedia products through the easy use of EEG device. Acknowledgments The authors would like to thank the financial support from National Science Council of Taiwan through grant NSC 99-2221-E-218-012. References [1] R.E. Wheeler, R.J. Davidson and A.J. Tomarken: Psychophysiology Vol. 30 (1996), p. 82-89 [2] J.A. Coan and J.J.B. Allen: Biol. Psychol. Vol. 67(1-2) (2004), p. 7-49 [3] N.A. Jones, T. Field and M. Davalos: Infant Behavior & Development Vol. 21(3) (1998), p. 527-530 [4] E. Harmon-Jones, J.J.B. Allen and J. Abnorm: Psychol. Vol. 106(1) (1997), p. 159-163 [5] H. Hinrikus, A. Suhhova, M. Bachmann, K. Aadamsoo and U. Vohma: Med. Biol. Eng. Comput. Vol. 47(12) (2009), p. 1291-1299 [6] V.A. Grin-Yatsenko, I. Baas, V.A. Ponomarev and J.D. Kropotov: Clinical Neurophysiology Vol. 121(3) (2010), p. 281-289 [7] E. Harmon-Jones, P.A. Gable and C.K. Peterson: Biol. Psychol. Vol. 84(3) (2010), p. 451-462 [8] S. Debener, A. Beauducel, D. Nessler, B. Brocke, H. Heilemann and J. Kavser: Neuropsychobiology Vol. 41(1) (2000), p. 31-37 [9] Y.P. Lin, J.R. Duann, J.H. Chen and T.P. Jung: Neuroreport Vol. 21(6) (2010), p. 410-415 [10] E. Sokhadze: App. Pyschophysiology and Biofeedback Vol. 32(1) (2007), p. 31-50 [11] M. Teplan, A. Krakovska and S. Stolc: International Journal of Psychophysiology Vol. 59(2) (2006), p. 81-90
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Effect of Music Listening on Frontal EEG Asymmetry 10.4028/www.scientific.net/AMM.311.502
