The Effects of Visual and Auditory Stimulation on EEG Power
Spectra during the Viewing of Disgust-Eliciting Videos
Mi-Jin Lee, Hae-Lin Kim and Hang-Bong Kang
Dept. of Media Technology & Contents, Catholic University of Korea, Bucheon-si, Korea
Keywords: EEG, Disgust, Auditory Stimuli.
Abstract: Disgust is an affect produced in response to something that is offensive or unpleasant. This emotion is
associated with feelings of dizziness and vomiting and, in severe cases, mental illnesses, such as obsessive
compulsive disorder and depression. Most experimental electroencephalography (EEG) studies on disgust
have identified activated brain areas or disgust elicitors or examined the effects of unimodal stimulation,
such as visual, auditory, olfactory, or haptic stimulation. This EEG study examined the effects of disguste
liciting visual stimuli that were presented with different auditory stimuli in relative power spectrum analyses
of the delta-, theta-, alpha-, beta-, and gamma-wave bands. The EEG data were collected while the
participants watched disgust-eliciting videos of body mutilation and disgusting creatures with the original
soundtrack or auditory stimuli. Two types of auditory stimuli were used: relaxing music or exciting music.
The EEG power spectra of all of the frequency bands were lower in response to videos with auditory stimuli
compared with videos with the original soundtracks. Additionally, the mood of the music aroused different
responses depending on the type of disgust elicitor, and the types of music that reduced disgust differed
according to the different types of disgust elicitors.
1 INTRODUCTION
An emotion is a feeling or mood that arises in
reaction to a situation or an event. A wide variety of
factors, including physiological, physical, and
psychological, cause emotional reactions to cultural
elicitors as diverse as arts, science, and religion.
Affect is an intense emotion that does not last long.
Several studies have suggested different ways to
classify the basic types of affect. Of these, a
categorical model of 6 types of affect (happiness,
surprise, fear, anger, disgust, and sadness) has been
recognized as the basic theory of affect (Lin, 2010).
Previous studies have largely been devoted to
examining the 4 following affects: happiness, fear,
anger, and sadness. These studies, however, have not
investigated elicitors of disgust, which is a type of
negative emotion and which is a recent topic of
interest due to the sharing of internet contents, such
as movies, games, and social networking sites.
From an evolutionary perspective, disgust is a
feeling that is generated in response to things that
might be harmful to us, and it is considered an oral
defense mechanism for excreting or vomiting what is
harmful. In psychiatry, disgust is thought to be
related to obsessive-compulsive disorder or specific
phobias, such as aichmophobia, trypophobia, and
thalassophobia, as well as mental illnesses like
depression and anxiety disorder. There are a variety
of disgust elicitors, and Jonathan Haidt et al. have
classified the 7 main domains of disgust elicitors
(food, specific organisms, sex, body mutilation,
death, hygiene, and body products) into core disgust
and animal reminder disgust. Various studies have
investigated the effects of disgust (Haidt, 1994).
Electroencephalography (EEG) is a methodology
that is used to record changes in the electrical
potentials or brain currents in the cerebral cortex
through the scalp of a human or animal (MIT Press,
2014). Recently, EEG studies have been actively
conducted in diverse research areas, including the
classification of affects; addiction to the internet,
games, or smartphones; and mental illnesses (Gasser,
1982; Schaefer, 2011; Gotlib, 1998).
In this study, we recorded EEGs while subjects
viewed disgust-eliciting video clips and compared
the brain wave data that were collected when the
original video was presented with those collected
when the video was presented with music for
auditory stimulation. For the disgust-eliciting
Lee, M-J., Kim, H-L. and Kang, H-B.
The Effects of Visual and Auditory Stimulation on EEG Power Spectra during the Viewing of Disgust-Eliciting Videos.
DOI: 10.5220/0005758206630669
In Proceedings of the 5th International Conference on Pattern Recognition Applications and Methods (ICPRAM 2016), pages 663-669
ISBN: 978-989-758-173-1
Copyright
c
 2016 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved
663

stimuli, we used videos about body mutilation and
disgusting organisms, which are the disgust elicitors
that show disgust most clearly. The music presented
as the auditory stimuli consisted of relaxing music
and exciting music, and we examined the differences
in the EEGs that resulted from the different moods of
music. The brain wave data were compared with
relative power spectrum analyses across the
following bands: delta (0.5–3 Hz), theta (3–8 Hz),
alpha (8–12 Hz), beta (12–30 Hz), and gamma (30–
70 Hz). Additionally, a survey was administered after
the EEGs were recorded for further data validation.
Previous EEG studies of disgust stimulation have
mostly dealt with disgust elicitors or changes in brain
activity that was related to disgust. Those studies
mainly used unimodal sensory stimulation, such as
visual, olfactory, or haptic stimulation. However,
unlike previous studies, we aimed to investigate the
effects of visual and auditory stimuli that were
presented at the same time.
This paper is organized as follows. In Section 2,
we introduce the existing literature that is relevant to
EEG studies on emotion recognition and the disgust
affect and explain how the current study fills a gap in
the field. In Section 3, the experimental methods,
procedures, and analytical methods are presented. In
Section 4, we analyze the results and further discuss
some notable findings.
2 RELATED WORKS
Many studies have been conducted on emotion
recognition by using EEG, functional magnetic
resonance imaging, and electrocardiography methods
(Lewis, 2010; Palomba, 2000;
Köchel, 2013).
Human beings feel emotions that are aroused
through vision, audition, olfaction, and touch, and all
of these types of stimuli have been studied through
diverse research efforts in order to understand the
elicitation of emotions (Wheaton, 2013; Utama,
2009). The majority of studies of a single stimulation
modality have used visual or auditory stimulation,
which are the primary sensory types. Lin et al. used
auditory stimuli and classified the 4 emotions of joy,
anger, sadness, and pleasure that occur during music
listening with 12 symmetric electrode pairs
(DASM12) (Lin, 2010). Dan Nie et al. used visual
stimuli and EEG recordings and identified the
emotions that occurred while subjects watched
movies (Nie, 2011).
Murugappan et al. have analyzed EEG signals
and identified 6 affects (Murugappan, 2008). Of
these, we focused on disgust and compared it to the
results of previous studies. Michela Sarlo classified
disgust elicitors into body mutilation and
contamination with an EEG alpha power analysis
and compared the levels of activation induced by
each elicitor type (Sarlo
, 2005). Syed Syahril et al.
measured the subgamma band of EEG signals in
subjects while disgust-eliciting stimuli were
presented (Syahril, 2011).
The existing studies on emotion recognition and
disgust are limited because they examined only
single stimulation modalities. In addition, most EEG
studies on disgust distinguished regions of activation
instead of showing clear differences. This study was
meaningful because we examined the effects of
auditory stimuli on disgust-eliciting visual
stimulation. Additionally, in the EEG analysis, we
analyzed data on the regions of activation and the
impact of the videos and music. Finally, we showed
video clips to the participants of a short story that
strongly elicited the disgust affect instead of visual
images that were unidirectional and similar.
3 METHODS
3.1 Experimental Environment
Figure 1: Experimental environment.
As shown in Figure 1, the experiment was
conducted in a dark and isolated room in which the
participants could be tested comfortably away from
any non-experimental stimulation. By placing only
experiment-related equipment in the room, we tried
to provide an experimental environment in which the
participants could focus on the experiment. The
participants were forbidden to drink alcohol before
the study, and they were asked to get enough sleep
on the day prior to the experiment.
ICPRAM 2016 - International Conference on Pattern Recognition Applications and Methods
664

Table 1: The list and categories of the videos and the music used in the study.
Video and music
Category Type A_Original A_Sound B_Original B_Sound
Body
Mutilation
Video
The dentist
<Final Destination5>
The dentist
<Final Destination5>
The gymnast
<Final Destination5>
The gymnast
<Final Destination5>
Music
Yumeji’s Theme
<In the Mood for Love>
Give it up
<Kings man>
Category Type C_Original C_Sound D_Original D_Sound
Disgusting
Organisms
Video The alien <Slither> The alien <Slither> The worm <Slither>
The disgust worm
<Slither>
Music
Yumeji’s Theme
<In the Mood for Love>
Give it up
<Kings man>
3.2 Procedure
In a separate experimental room, the participants
watched 4 disgust-eliciting video clips of body
mutilation and organisms. They watched each video
twice for a total of 8 viewings. After watching the
video clips with the soundtrack on, the participants
watched them again while they were accompanied
with either relaxing music or exciting music and with
the original soundtrack removed. The length of the
video clips was 40 s. There was a 30-s break
between the videos, during which the screen was
black so that the participants could rest and eliminate
any previously experienced emotions. In order to
collect the data as accurately as possible, the
participants were told to sit upright during the
experiment and try not to move while watching the
video. The video clips and the music were taken
from movies. Table 1 lists the videos and music used
in the study. After watching the videos for a total of 5
min, the participants rated their level of disgust for
each video on a 5-point scale.
3.3 Analytical Methods
For the brain wave measurements, we used a
NeuroScan EEG device and Curry 7 software
program. We examined 12 participants, including 6
males and 6 females, and their average age was 22.7
years. The average ages of the males and females
were 23.25 years and 22 years, respectively. The data
from 10 of the 12 participants were included in the
final analysis after the data of 2 participants were
excluded due to errors resulting from large body
movements and the participants’ falling asleep
during the experiment. The brain waves were
recorded with 64-channel electrodes that were placed
according to the 10-20 system. The EEG signals
were recorded with a 1-kHz sampling rate and later
downsampled to 500 Hz. Impedance was maintained
below 10 kΩ during the experiment.
All of the EEG data were divided into 4
segments according to the type of video and mood of
the music and then extracted for 40 s, after which a
baseline correction was performed by matching the
baselines of the raw data to a constant with Curry 7.
To remove signal noise from eye blinks, the data in
the area outside of the amplitude threshold were
replaced with the covariance of the area 200 ms
before and the area 800 ms after the affected data
area. Band-pass filters were applied. To compare
power spectra, the delta (0.5–3 Hz), theta (3–8 Hz),
alpha (8–12 Hz), beta (12–30 Hz), and gamma (30–
70 Hz) bands, as well as the full frequency range
(0.5–70 Hz), were extracted. In the analysis, we
compared the peak relative power, which was the
ratio of a frequency band power to the total
frequency band power.
4 RESULTS
For the body mutilation category of disgusteliciting
stimuli, we used the following labels: AO to indicate
the first video with the original soundtrack, AS to
indicate the first video but with relaxing music,
BO to indicate the second video with the original
soundtrack, and, finally, BS to indicate the second
video with exciting music. For the disgusting
The Effects of Visual and Auditory Stimulation on EEG Power Spectra during the Viewing of Disgust-Eliciting Videos
665

organism category, we used CO to indicate the first
video with the original soundtrack, CS to indicate the
first video with relaxing music, DO to indicate the
second video with the original soundtrack, and,
finally, DS to indicate the second video with exciting
music. The data from 4 electrodes (FZ, CZ, PZ, and
OZ) were used to analyze the relative power spectra.
The relative power spectrum values were expressed
by category. The relative power spectra data are
expressed in μV.
4.1 Body Mutilation
4.1.1 FZ
Table 2: The relative power spectra at the FZ electrode.
Delta/
Total
Theta/
Total
Alpha/
Total
Beta/
Total
Gamma
/ Total
A
O
2.710951 -1.44074 -0.6693 -0.06018 -0.00096
A
S
2.71096 -1.44076 -0.66931 -0.06018 -0.00096
B
O
2.13304 -1.13358 -0.52662 -0.04735 -0.00075
B
S
2.02069 -1.13372 -0.52667 -0.04735 -0.00075
Table 2 shows the values for the relative power
spectra recorded at the FZ electrode during AO, AS,
BO, and BS. For the first video, the relative power
spectrum of the theta- and alpha-frequency bands
was higher during AO compared to that during AS.
For the second video, the relative power spectrum of
the delta-, theta-, and alpha-frequency bands was
higher during BO than that during BS. The relative
power spectra of the beta- and gamma-frequency
bands were similar during AO, AS, BO, and BS.
4.1.2 CZ
Table 3: The relative power spectra at the CZ electrode.
Delta/
Total
Theta/
Total
Alpha/
Total
Beta/
Total
Gamma
/ Total
A
O
1.555454 -0.82667 -0.38404 -0.03453 -0.00055
A
S
1.555407 -0.82665 -0.38402 -0.03453 -0.00055
B
O
2.711577 -1.44115 -0.55665 -0.17304 -0.00096
B
S
2.598958 -1.44109 -0.66947 -0.06019 -0.00096
Table 3 shows the values for the relative power
spectra recorded at the CZ electrode during AO, AS,
BO, and BS. For the first video, the relative power
spectrum of the delta- and alpha-frequency bands
was higher during AO compared to that during AS.
Likewise, for the second video, the relative power
spectrum for the delta-, alpha-, and beta-frequency
bands was higher during BO than that during BS. In
addition, the relative power spectra of the
gammafrequency bands were similar during AO, AS,
BO, and BS.
4.1.3 PZ
Table 4: The relative power spectra at the PZ electrode.
Delta/
Total
Theta/
Total
Alpha/
Total
Beta/
Total
Gamma
/ Total
A
O
1.811968 -0.96294 -0.44734 -0.04022 -0.00064
A
S
2.133065 -1.13363 -0.52663 -0.04735 -0.00075
B
O
2.132629 -1.13336 -0.52648 -0.04734 -0.00075
B
S
2.020075 -1.13335 -0.52649 -0.04734 -0.00075
Table 4 shows the values of the relative power
spectra recorded at the PZ electrode during AO, AS,
BO, and BS. For the first video, the relative power
spectrum of the theta-, alpha-, beta-, and
gammafrequency bands was higher during AO
compared to that during AS. Likewise, for the second
video, the relative power spectrum of the delta- and
alphafrequency bands was higher during BO than
that during BS. In addition, the relative power
spectra of the beta- and gamma-frequency bands
were similar during BO and BS.
4.1.4 Oz
Table 5: The relative power spectra at OZ electrode.
Delta/
Total
Theta/
Total
Alpha/
Total
Beta/
Total
Gamma
/ Total
A
O
0.977283 -0.51938 -0.24128 -0.02169 -0.00035
A
S
0.977522 -0.51954 -0.24134 -0.0217 -0.00035
B
O
-2.28066 -0.13037 -0.01172 -0.00019 -0.00055
B
S
-0.28055 -0.13032 -0.01172 -0.00019 -0.00055
Table 5 shows the values of the relative power
spectra recorded at the OZ electrode during AO, AS,
BO, and BS. For the first video, the relative power
spectrum of the theta-, alpha-, and beta-frequency
bands was higher during AO compared to that during
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666

AS. Likewise, for the second video, the relative
power spectrum of the delta- and thetafrequency
bands was higher during BO than that during BS. In
addition, the relative power spectra of the gamma-
frequency bands were similar during AO and AS,
and that of the alpha-, beta-, and gammafrequency
bands were similar during BO and BS.
4.2 Disgusting Organisms
4.2.1 FZ
Table 6: The relative power spectra at the FZ electrode.
Delta/
Total
Theta/
Total
Alpha/
Total
Beta/
Total
Gamma
/ Total
A
O
3.288796 -1.74784 -0.81197 -0.073 -0.00116
A
S
3.288853 -1.74794 -0.81199 -0.073 -0.00116
B
O
2.711133 -1.44084 -0.66934 -0.06018 -0.00096
B
S
2.711128 -1.44083 -0.66935 -0.06018 -0.00096
Table 6 shows the values of the relative power
spectra recorded at the FZ electrode during CO, CS,
DO, and DS. For the third video, the relative power
spectrum of the theta- and alpha-frequency bands
was higher during CO compared to that during CS.
Likewise, for the fourth video, the relative power
spectrum of the delta-frequency band was higher
during DO than that during DS. In addition, the
relative power spectra of the beta- and
gammafrequency bands were similar during CO, CS,
DO, and DS.
4.2.2 CZ
Table 7: The relative power spectra at the CZ electrode.
Delta/
Total
Theta/
Total
Alpha/
Total
Beta/
Total
Gamma
/ Total
A
O
2.712979 -1.44205 -0.66993 -0.06023 -0.00096
A
S
2.708993 -1.43947 -0.66866 -0.06012 -0.00096
B
O
2.709902 -1.44009 -0.66897 -0.06015 -0.00096
B
S
2.710961 -1.44074 -0.6693 -0.06018 -0.00096
Table 7 shows the values of the relative power
spectra recorded at the CZ electrode during CO, CS
DO, and DS. For the third video, the relative power
spectrum of the delta-frequency bands was higher
during CO compared to that during CS. For the
fourth video, the relative power spectrum of the
theta-, alpha-, and beta-frequency bands was higher
during DO than that during DS. In addition, the
relative power spectra of the gamma-frequency
bands were similar during CO, CS, DO, and DS.
4.2.3 PZ
Table 8: The relative power spectra at the PZ electrode.
Delta/
Total
Theta/
Total
Alpha/
Total
Beta/
Total
Gamma
/ Total
A
O
0.977341 -0.63517 -0.25877 -0.02169 -0.00035
A
S
0.977569 -0.51954 -0.24134 -0.0217 -0.00035
B
O
-1.30416 -0.60587 -0.05447 -0.00087 -0.00075
B
S
-1.30421 -0.60588 -0.05447 -0.00087 -0.00075
Table 8 shows the values of the relative power
spectra recorded at the PZ electrode during CO, CS,
DO, and DS. For the third video, the relative power
spectrum of the beta-frequency bands was higher
during CO compared to that during CS. For the
fourth video, the relative power spectrum of the
delta-frequency bands was higher during DO than
that during DS. The relative power spectra of the
gamma-frequency bands were similar during CO and
CS, and those of the alpha-, beta-, and
gammafrequency bands were similar during DO and
DS.
4.2.4 OZ
Table 9: The relative power spectra at the OZ electrode.
Delta/
Total
Theta/
Total
Alpha/
Total
Beta/
Total
Gamma
/ Total
A
O
-0.28066 -0.13037 -0.01172 -0.00019 -0.00075
A
S
-0.28055 -0.13032 -0.01172 -0.00019 -0.00075
B
O
-0.62189 -0.28889 -0.02597 -0.00041 -0.00096
B
S
-0.62174 -0.28882 -0.02597 -0.00041 -0.00096
Table 9 shows the values of the relative power
spectra recorded at the OZ electrode during CO, CS,
DO, and DS. For the third video, the relative power
spectrum of the delta-frequency bands was higher
during CO compared to that during CS. For the
fourth video, the relative power spectrum of the
theta-, alpha, and beta-frequency bands was higher
The Effects of Visual and Auditory Stimulation on EEG Power Spectra during the Viewing of Disgust-Eliciting Videos
667

during DO than that during DS. In addition, the
relative power spectra of the beta- and
gammafrequency bands were similar during CO and
CS, and those of the alpha-, beta-, and gamma-
frequency bands were similar during DO and DS.
4.3 Survey
After watching the videos, the participants rated their
level of disgust for each video on a 5-point scale.
The survey results for 7 participants were used in the
final analysis. For body mutilation, all of the
participants responded that the first and second
original videos (AO and BO) were more disgusting
than the same videos with easy listening and exciting
music (AS and BS). In addition, for the disgusting
organisms, all of the participants responded that the
third and fourth original videos (CO and DO) were
more disgusting than the same videos with easy
listening and exciting music (CS and DS).
4.4 Overall Results
In this study, we investigated the differences in the
relative power spectra of the brain waves while the
participants watched disgust-eliciting videos with
auditory stimuli for different moods. The results of
the experiment showed that the relative power
spectra of the delta-, theta-, and alphafrequency
bands were mostly higher for the disgusteliciting
videos with the original soundtracks compared to the
same videos with extraneous auditory stimuli and
that the relative power spectra of the beta- and
gamma-frequency bands were almost similar for the
disgust-eliciting videos with the original soundtracks
compared to the same videos with extraneous
auditory stimuli. These results were consistent with
the results of the survey that was administered
following the experiment. These findings suggest
that the participants may have felt less disgust when
they watched the disgusteliciting videos with
background music compared to when they watched
them with the original soundtracks.
5 CONCLUSIONS
This study was conducted to examine the effects of
auditory stimulation on disgust-eliciting visual
stimulation. We selected videos of two categories of
disgust elicitors, added auditory stimulation to them
with music, and then examined the changes in brain
waves. The categories of the disgust elicitors were
body mutilation and disgusting organisms. For the
auditory stimuli, easy listening and exciting music
were used to provide contrasting moods of music.
The relative power spectra of the brain waves
were lower when the videos were shown with
auditory stimulation compared with its original
soundtrack. That is, the participants experienced less
disgust while they watched disgust-eliciting videos
with auditory stimulation. Additionally, we found
differences between the stimulation of body
mutilation videos and that of disgusting organism
videos, which suggests that the responses to the
mood of music may differ depending on the type of
disgust elicitors. The significance of this study was
that that it utilized visual and auditory stimulation
together to study a specific type of affect.
The study materials were limited to the disgust
elicitors of body mutilation and disgusting
organisms. Thus, future research of a variety of
disgust elicitors is needed. Furthermore, future
research needs to investigate other stimulation
modalities other than auditory stimuli.
In the present study, we investigated disgust
elicitors, which were limited to body mutilation and
disgusting organisms. In our follow-up studies, we
plan to examine a wider range of disgust elicitors
and investigate different kinds of auditory
stimulation that may arouse different responses
depending on the type of disgust elicitor.
ACKNOWLEDGEMENTS
This research was supported by Basic Science
Research Program through the National Research
Foundation of Korea(NRF) funded by the Ministry
of Science, ICT and future Planning(No.
2015R1A2A1A10056304).
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