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Consciousness and arousal effects on emotional face processing as revealed by brain oscillations. A gamma band analysis


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It remains an open question whether it is possible to assign a single brain operation or psychological function for facial emotion decoding to a certain type of oscillatory activity. Gamma band activity (GBA) offers an adequate tool for studying cortical activation patterns during emotional face information processing. In the present study brain oscillations were analyzed in response to facial expression of emotions. Specifically, GBA modulation was measured when twenty subjects looked at emotional (angry, fearful, happy, and sad faces) or neutral faces in two different conditions: supraliminal (10 ms) vs subliminal (150 ms) stimulation (100 target-mask pairs for each condition). The results showed that both consciousness and significance of the stimulus in terms of arousal can modulate the power synchronization (ERD decrease) during 150-350 time range: an early oscillatory event showed its peak at about 200 ms post-stimulus. GBA was enhanced by supraliminal more than subliminal elaboration, as well as more by high arousal (anger and fear) than low arousal (happiness and sadness) emotions. Finally a left-posterior dominance for conscious elaboration was found, whereas right hemisphere was discriminant in emotional processing of face in comparison with neutral face.
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Consciousness and arousal effects on emotional face processing as
revealed by brain oscillations. A gamma band analysis
Michela Balconi
, Claudio Lucchiari
Laboratory of Cognitive Psychology, Department of Psychology, Catholic University of Milan, Largo Gemelli, 1 20123 Milan, Italy
Neurological National Hospital C. Besta, Milan, Italy
Received 4 May 2005; received in revised form 29 August 2007; accepted 8 October 2007
Available online 13 October 2007
It remains an open question whether it is possible to assign a single brain operation or psychological function for facial emotion decoding to a
certain type of oscillatory activity. Gamma band activity (GBA) offers an adequate tool for studying cortical activation patterns during emotional
face information processing. In the present study brain oscillations were analyzed in response to facial expression of emotions. Specifically, GBA
modulation was measured when twenty subjects looked at emotional (angry, fearful, happy, and sad faces) or neutral faces in two different
conditions: supraliminal (10 ms) vs subliminal (150 ms) stimulation (100 target-mask pairs for each condition). The results showed that both
consciousness and significance of the stimulus in terms of arousal can modulate the power synchronization (ERD decrease) during 150350 time
range: an early oscillatory event showed its peak at about 200 ms post-stimulus. GBA was enhanced by supraliminal more than subliminal
elaboration, as well as more by high arousal (anger and fear) than low arousal (happiness and sadness) emotions. Finally a left-posterior
dominance for conscious elaboration was found, whereas right hemisphere was discriminant in emotional processing of face in comparison with
neutral face.
© 2007 Elsevier B.V. All rights reserved.
Keywords: Facial expression; EEG; Gamma band; Arousal; Consciousness
1. Introduction
Correlates of affective face processing have been investigat-
ed using a variety of recording techniques. On one side, some
authors studied ERP correlates associated with face compre-
hension. It has been argued that emotional face processing
arises after 200 ms, and that differences between ERPs elicited
by emotional faces and neutral faces were observable
specifically between 250 and 550 ms after stimulus onset
(Krolak-Salmon et al., 2001). An early negative deflection (N2)
of higher amplitude was revealed for arousing facial stimuli
(Balconi and Pozzoli, 2003; Sato et al., 2000; Streit et al., 2000)
in comparison with neutral stimuli. Moreover, there is evidence
that emotion processing is initiated and can proceed without
conscious awareness (Bunce et al., 1999; LeDoux, 1998). An
obvious and well-known example of unconscious perception of
emotion is subliminal stimulation effect. This phenomenon was
studied in a limited number of cases (Wong et al., 1994). Animal
studies suggest that fear-related response are by a direct
subcortical pathway from the thalamus direct to the amygdala,
allowing emotional (and specifically threat) to be processed
automatically and outside awareness. In humans, evidence for
the unconscious perception of masked face has been revealed in
terms of subjective reports (Esteves et al., 1994) autonomic
reaction (Morris et al., 2001), brain imaging measures (Whalen
et al., 1998), as well as ERPs (Kiefer and Spitzer, 2000). In
addition, unconscious stimulation showed to be sensitive to the
emotional content of the stimuli, as revealed by different
behavioural and physiological measures (Lang et al., 1998).
On the other side, brain oscillations were found to be a
powerful tool to analyze the cognitive processes related to
emotion comprehension in general (Başar et al., 1999; Krause,
2003), and, even if less studied, to unconscious perception
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E-mail address: (M. Balconi).
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(Summerfield et al., 2002). Few previous studies on ERD/ERS
responses to emotion-related stimuli have examined the narrow
frequency bands (Aftanas et al., 2001, 2002). Recent researches
showed the event-related theta band power responds specifi-
cally to prolonged visual emotional stimulation (Krause et al.,
2000), and a synchronization was revealed in case of
coordinated response indicating readiness to process informa-
tion (Başar, 1999). Thus, theta EEG power typically increases
with increasing attentional demands and/or task difficulty. Also
the effect of valence in affective picture processing was studied,
showing that valence discrimination is associated with the early
time-locked synchronized theta activity (Aftanas et al., 2001).
Moreover, recent research have demonstrated that the modula-
tion of gamma band activity (GBA) in time windows between
200 and 400 ms following the onset of a stimulus is associated
with perception of coherent visual objects (Müller et al., 1996),
and may be a signature of active memory. In parallel, GBA was
found sensitive to emotional vs nonemotional stimuli and more
specifically it was related to the arousal effect: early GBA was
enhanced in response to aversive or highly arousing stimuli
compared to neutral picture (Balconi and Pozzoli, 2007). This
result was revealed in accordance with previous research that
employed ERP measures for arousing pictures (Schupp et al.,
2000) or emotional face (Balconi and Pozzoli, 2003; Sato et al.,
2000), since these studies found a modulation of the increased
arousal on ERP. Interestingly, previous research has found that
gamma frequency band could also be considered a marker of
degree of consciousness during elaboration of a stimulus:
synchronous oscillations in the gamma frequency range may be
necessary for the entry of information into conscious awareness
(Crick and Koch, 1998). Specifically, Summerfield et al. (2002)
have found that gamma activity increases after subjects had
been made aware of the stimulus, and, therefore, synchronous
gamma oscillations occurred in association with awareness
Therefore, gamma band is to be considered of main interest
in exploring the effect of arousal as well as the consciousness in
emotional face elaboration. The present study aims at studying
the brain mechanisms underlying human emotional processing
by measuring GBA changes in response to emotional faces
presented visually in both supraliminal and subliminal stimu-
lation. No previous study has widely explored the effect of
consciousness on the processing of emotional faces, in
conjunction with different types of stimulus (low or high
arousing faces). Actually, although brain oscillations have been
investigated in various sensory modalities, their role for brain
functioning for emotion elaboration remains unclear. Secondly,
it remains an open question whether it is possible to assign a
single brain operation or psychological function for emotion
decoding to a certain type of oscillatory activity. Thus, we
intend to explore functional correlates of brain oscillations with
regard to emotional face processing in supraliminal and
subliminal condition and emphasize the importance of distrib-
uted oscillatory networks in gamma frequency band. We
attended that emotional content may be indexed by oscillatory
activity of the brain that was directly related to awareness or
unawareness of the stimulus. Specifically, we hypothesized that
conscious elaboration of emotional stimuli will be indexed by
GBA synchronization, whereas unconscious condition will be
related to a decreased power intensity of this frequency band.
Secondly, we expected that affective significance of a facial
stimulus may result in changes of subjects' EEG responses
(Lang et al., 1993). Emotion evaluated as highly arousing
should be indexed by an enhanced power of gamma band in
conscious condition. Finally, brain lateralization was found
significant for emotional elaboration. As previously shown,
right dominance was revealed for emotional stimuli compared
to neutral ones, and specifically for face. On the contrary, left
hemisphere was found to be more activated by conscious
elaboration than unconscious. The present experiment based on
ERD measure examined whether emotions would be associated
with band modulation as regard as interhemispheric asymme-
tries in the right direction, whereas left hemisphere is expected
to be discriminant for conscious processing if compared to
2. Method
2.1. Subjects
Twenty healthy volunteers took part in the study (eleven
women, age range1925, mean = 23.37, SD = 2.13). They were
all right-handed and with normal or corrected-to-normal visual
acuity. Exclusion criteria were history of psychopathology for
the subjects or immediate family. They gave informed written
consent for participating in the study.
2.2. Stimulus material
Stimulus materials were taken from the set of pictures of
Ekman and Friesen (1976). They were black and white pictures
of male and female actors, presenting respectively a happy, sad,
angry, fearful, or neutral face.
2.3. Supraliminal/subliminal stimulation
A previous study was conducted in which the duration of
target facial stimulus was varied in order to establish threshold
condition (Liddell et al., 2004). In the current study we
employed both an objective threshold, defined as the stimulus
duration where the stimulus is perceived by the subject in 50%
of the cases (Merikle et al., 2001); and a subjective threshold,
defined as the overt lacking of discrimination of the stimulus
and its emotional content. The pre-experimental study and post-
hoc briefing confirmed that subjects were unable to detect target
stimulus in the subliminal condition.
During the experiment we used a masking procedure. Each
facial stimulus (target) was presented for either 10 (subliminal)
or 150 (supraliminal) ms, followed by a neutral face presented
for 150 ms (interstimulus interval 1.5 s) (Bernat et al., 2001;
Brázdil et al., 1998; Liddell et al., 2004). The short stimulus
presentation in subliminal condition prevents the subjects to
have a clear cognition of the stimulus, but it allows for a semantic
elaboration of the emotional faces. No target and mask pair
42 M. Balconi, C. Lucchiari / International Journal of Psychophysiology 67 (2008) 4146
depicted the same individual. In total there were 100 target-mask
pairs in each threshold condition (each expression type was
presented twenty times for condition). The condition was not
counterbalanced across subjects (Bernat et al., 2001).
2.4. Procedure
Subjects were seated comfortably in a moderately lighted
room with the monitor screen positioned approximately 100 cm in
front of their eyes. Pictures were presented in a randomised order
in the center of a computer monitor, with a horizontal angle of 4°
and a vertical angle of 6° (STIM 4.2 software). During the
examination, they were requested to continuously focus their eyes
on the small fixation point and to minimize blinking. Participants
were required to observe the stimulus during ERP recording
(passive task). In the subliminal condition it was emphasized that
sometimes the target face would be difficult to see, but to
concentrate as best they could on this stimulus, and that they
would be asked question about these stimuli after the ERP
recording. An explicit response to the emotional features of the
stimulus was not required. This was done for three main reasons:
to assure a real passive task (implicit elaboration of emotions); to
not cause them to be more attentive to the emotional stimuli than
the neutral ones; to not introduce an unequal condition between
subliminal and supraliminal stimulation. In addition, the absence
of an explicit response avoids confounding motor potentials in
addition to brain potentials. Prior to recording ERPs, the subject
was familiarized with the overall procedure (training session),
where every subject saw in a random order all the emotional
stimuli presented in the successive experimental session (a block
of 10 trials, each expression type repeated twice).
2.5. EEG recording
The EEG was recorded with a 62-channel DC amplifer
(SYNAMPS system) and acquisition software (NEUROSCAN
4.2). An ElectroCap with Ag/AgCl electrodes were used to record
EEG from active scalp sites referred to earlobe (10/20 system of
electrode placement). Additionally two EOG electrodes were
sited on the outer side of the eyes. The data were recorded using
sampling rate of 256 Hz, with a frequency band of 0.1 to 60 Hz.
The impedance of recording electrodes was monitored for each
subject prior to data collection and it was always below 5 kΩ.
After EOG correction and visual inspection only artefact-free
trials were considered. Only fourteen electrodes were used for the
successive statistical analysis (four central, Fz, Cz, Pz, Oz; ten
lateral, F3, F4, C3, C4, T3, T4, P3, P4, O1, O2).
2.6. ERD/ERS data reduction
The digital EEG data were bandpass filtered in the gamma
frequency band (3060 Hz). To obtain a signal proportion to the
power of the EEG frequency band, the filtered signal samples
were squared (Pfurtscheller, 1992). Successively, the data were
epoched, triggered each second, using four different time
windows of 100 ms (50150; 150250; 250350; 350
450 ms). An average absolute power value for each electrode
for each condition (five expression types) was calculated. An
average of the pre-experimental absolute power was used to
determine the individual power during no stimulation. From this
reference power value individual power changes during face
viewing were determined as the relative stimulus-related decrease
(desynchronization). In fact, according to ERD/ERS method,
changes in band power were defined as the percentage of a
decrease (ERD) in band power during a test interval (here 900 ms
post-stimulus) as compared to a reference interval (here 1500 ms
before picture onset). For each subject, after band-pass filtering
ERD was calculated within the four time intervals. The average
ERD values across the respective electrode sites were calculated
for each condition, time interval, and emotional category.
2.7. Data analysis
The data were entered into repeated measures analysis of
variance (ANOVA) with four repeated factors: condition (2,
supraliminal and subliminal), time (four time intervals, 4), stimulus
type (emotion type, 5), and electrode sites (cortical sites, 14).
Secondly, in order to analyze widely the cortical distribution of
band modulation, the data were averaged over anterior (F3, Fz, F4),
central (C3, Cz, C4), and posterior (P3, Pz, P4) electrode location,
and secondly over left (F3, C3, T3, P3, O1) and right (F4, C4, T4,
P4, O2) sides. These new values were entered in two distinct
statistical analyses. For all the ANOVAs, degrees of freedom were
GreenhouseGeisser corrected where appropriate.
3. Results
3.1. Behavioral data
The subjects were asked to analyze the stimuli viewed after the
experimental section. Firstly, they evaluated the emotional
significance of each expression by a categorization task. The
five emotional categories were correctly recognized (for happy
96%, sad 94%, angry 97%, fearful 97% and neutral 95% faces).
Successively, in order to distinguish the effect of arousal for
emotional face the subjects evaluated on a Likert scale (5 points)
their responses as a function of the arousing power of each
stimulus (how do you evaluate the arousing power of this
stimulus for you?). Fear (M=4.78), anger (M=4.51), happiness
(M=3.17), sadness (M= 2.76) and neutral (M=2.20) faces differed
in terms of their arousing power. Specifically, ANOVA showed
significant differences between the emotion (F(4, 19)=12.36,
Pb0.001), and post-hoc comparisons (Tukey) revealed that anger
and fear were considered more emotionally arousing than hap-
piness (respectively F(1, 19)= 10.16, Pb0.001; F(1, 19)= 9.74,
Pb0.001) and sadness (F(1, 19)= 11.69, P=0.001; F(1, 19)=
12.36, Pb0.001), as well as than neutral stimuli (F(1, 19)= 14.03,
Pb0.001; F(1, 19) = 15.41, Pb0.001).
3.2. ERD/ERS data
GBA showed sensitivity to Condition (F(1,19)= 7.07, P=
0.001), Type (F(4,19)= 10.12, Pb0.001), Time (F(3,19)= 8.55,
Pb0.001) and Electrodes (F(13,19)=13.09, Pb0.001), as well as
43M. Balconi, C. Lucchiari / International Journal of Psychophysiology 67 (2008) 4146
for Condition× Type, Condition× Time (F(3,19)= 10.98,
Pb0.001), Time×Electrodes (F(39,19) = 14.89, Pb0.001), and
Typ e × Tim e ( F(12,19)= 11.22, Pb0.001).
As shown in Fig. 1, GBA increases in supraliminal condition
compared with subliminal. In addition post-hoc comparison
(contrast analysis) applied to the main effect of Time and Type
revealed that GBA was maximum in 150250 and 250350 time
interval compared with 50150 ms (respectively F(1,19)= 19,03,
Pb0.001), (F(1,19)= 8.70, Pb0.001) and 350450 ms (F(1,19)=
11.24, Pb0.001), (F(1,19)= 9.93, Pb0.001). Moreover, high
arousal emotions have an increased GBA than low arousal emo-
tions (fear vs happiness F(1,19)= 12.96, Pb0.001; vs sadness F
(1,19)= 14.51, Pb0.001; vs neutral F(1,19)=18.73, Pb0.001;
anger vs happiness F(1,19) = 13.08, Pb0.001; vs sadness F
(1,19)=14.11, Pb0.001; vs neutral F(1,19)= 18.16, Pb0.001).
By analyzing interaction effects, high arousal stimuli showed
increased power GBA in conscious condition than in uncon-
scious condition (for fear F(1,19) = 10.99, Pb0.001; for anger
F(1,19)= 14.04, Pb0.001). Secondly, larger synchronization
was found for anger and fear in 150250 and 250350 post-
stimulus than 50150 (F(1,19) = 12.16, Pb0.001; F(1,19)=
15.05, Pb0.001) and 350450 ms (F(1,19) = 9.07, Pb0.001; F
(1,19)= 10.91, Pb0.001). Finally, enhanced brain gamma
oscillations were observed for conscious condition in second
and third time intervals than unconscious condition (respec-
tively F(1,19)= 8.83, Pb0.001; F(1,19)= 8.03, Pb0.001). No
other post-hoc comparison was statistically significant. We can
summarize these results pointing out that 150350 ms post-
stimulus was significant in distinguishing GBA modulation,
and that it was during this time that types of emotion (high/low
arousing) and condition (conscious/unconscious) differences
The second order of analysis took into account Laterality (2)
and Location (3) effects. The analysis revealed differences for
Laterality × Condition (F(1,19)= 7.78, P=0.001), as well as
Type× Laterality (F(4,19)= 10.99, Pb0.001). The second
ANOVA revealed a significant Location ×Condition (F(2,19) =
9.15, Pb0.001) and Location× Type (F(8,19) =11.34,
Pb0.001) interaction effects. Specifically, as revealed by the
contrast analysis, GBA synchronizes mainly in the left
hemisphere than in the right hemisphere in supraliminal
condition (F(1,19)= 6.85, P=0.002). Moreover, emotional
faces (both high and low arousing) elicited a dominance in
power synchronization of right hemisphere than neutral faces (F
(1,19)= 9.06, Pb0.001). Finally, as shown in Fig. 2, post-hoc
comparisons showed that supraliminal stimuli induced an
increased GBA in posterior than in the anterior (F(1,19) =5.09,
P=0.002) or central (F(1,19) =6.73, P= 0.002) sites. In parallel,
all the emotional faces differed from the neutral faces in terms of
local distribution on the scalp of GBA: emotional stimuli were
more posterior (Pz) distributed than neutral stimuli.
4. Discussion
The first main result of the study was that GBA was
increased by presentation of a supraliminal emotional face in
Fig. 1. ERD % for Emotion × Time interaction in gamma band. (a) Supraliminal; (b) Subliminal.
Fig. 2. Supraliminal/subliminal comparison (ERD decreasing) as a function of: (a) right/left hemisphere; (b) anterior/central/posterior site.
44 M. Balconi, C. Lucchiari / International Journal of Psychophysiology 67 (2008) 4146
comparison with a subliminal presentation. Indeed for each type
of emotions we revealed that increasing in gamma band
synchronization was significantly higher for conscious emo-
tional stimuli than for unconscious. Moreover, we observed an
enhanced activity of gamma band during 150350 ms post-
stimulus onset, such as an early oscillatory event that showed its
peak at about 200 ms post-stimulus. This time range was found
to be of main importance in emotional face processing, since it
was found to be discriminant in distinguishing between types of
emotion (low or high arousing power). Therefore, we can
suppose that GABA modulation could represent conscious
processing of the subjects for the emotional face during this
early time (Keil et al., 2001).
Secondly, in both supraliminal and subliminal condition we
found that GBA modulation increased linearly as a function of the
degree of arousal that subjects experienced for each facial
stimulus. Indeed, we noticed a similar increasing of GBA for
anger and fear in comparison with happiness, sadness and neutral
stimuli despite the subthreshold or suprathreshold stimulation,
and this increasing was more pronounced between 250350 ms.
We can hypothesize that GBA could be considered not only a
marker of conscious elaboration of emotional expression but even
an index of an enhanced activation (high level of perceived
arousal) of the subject in elaborating significant stimuli, even if
they prevent to reach the level of awareness. Moreover, this
emotional-effect is observable mainly in the early time of stimulus
elaboration. This suggestion is supported by ERP studies on
emotion, and taken together these results demonstrate that
difference in affective significance of a stimulus influences the
brain activity during 150350 time range (Balconi and Pozzoli,
2003; Sato et al., 2000). A related and interesting point is that
information presented to subjects under subliminal condition may
be processed ona high level even if the subject is not aware of this
information. This is in line with studies that have examined
psychophysiological responses to unconscious emotional stimuli:
they were effective both in capturing attention and in eliciting
autonomic response. Subliminal process appears to have a
preattentive origin, because it can be observed to stimuli that
are prevented from reaching conscious recognition. This fast
processing has adaptive value because it allows an immediate
response to a relevant and potentially threatening stimulus, and
this system can operate even prior to the conscious appraisal of the
With regard of the lateralization effect, we found that the left
hemisphere more than the right can mediate conscious
elaboration, since a clear dominance of left side was found in
the supraliminal condition. This result is in line with previous
research, that underlined a left-conscious/right-unconscious
dichotomy. Moreover, supraliminal faces were mainly elabo-
rated in posterior sites if compared to subliminal faces. Clearly
defined synchronization increase over posterior cortical sites in
response to affective stimuli presented supraliminally could be
attributed to specific function of posterior sites for conscious
stimulation (Summerfield et al., 2002). To summarize, a left-
posterior localization is supposed for consciousness.
A second interesting result on cortical distribution of GBA is
that both types of emotions (high or low arousing) induced greater
synchronization over right-posterior regions of the scalp than
neutral stimuli, and this is the case of both supra- and subliminal
condition. This result may elucidate a different role of the two
hemispheres in comprehending the emotional significance of a
facial stimulus. As it was underlined, whereas anterior brain
regions may be important for the modulation of the valence
(pleasant/unpleasant), posterior regions of the right hemisphere
may be involved in the modulation of arousal dimension. Indeed
emotional (and more arousing stimuli) are preferentially
elaborated in the posterior (and right) side than neutral
(nonemotional) stimuli: for example Aftanas et al. (2002) pointed
out a more posterior emotional vs nonemotional distribution of
gamma oscillations, even it was observed specifically for the
narrow bands (theta).
In sum, gamma band can be represented as a marker of
consciousness as well as of the subject's evaluation of the arousing
power of emotional stimuli. In fact it is not only increased by an
aware processing but it appears to differentiate high from low-
arousing emotional faces. This effect was found in both
supraliminal and subliminal condition. Moreover, GBA resulted
more right-posterior distributed for emotional vs nonemotional
stimuli, and more left-posterior localized in case of conscious
elaboration in comparison with unconscious. More generally
posterior sites appear to be discriminant for emotions, indepen-
dently from the type of facial expression. Finally, methodologi-
cally the present results indicate that gamma frequency band
analysis offers a powerful tool for studying cortical activation
patterns during emotional information processing.
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46 M. Balconi, C. Lucchiari / International Journal of Psychophysiology 67 (2008) 4146
... However, only a few studies have investigated the correlation between cue-induced cravings and gamma oscillations. Some studies reported that low-frequency EEG signals are related to alertness and motor imagery, whereas high-frequency signals are related to memory, attention, and emotion [21][22][23][24][25]. Thus, such high-frequency oscillations are not specific to a particular cognitive function, but represent global binding across various neurons and networks [26][27][28][29]. ...
... Evidence from previous studies suggested that gamma oscillations represent activation-related markers of neural communication and are important in complex multisensory perceptual paradigms (e.g., watching a video) as well as in high-order cognitive processes such as attention, memory, and emotion [26,28,[30][31][32][33][34]. Since these functions influence cue-induced craving, extracting the features of gamma activity might help us understand how the brains of METH abusers react to drug-related cues. ...
... Some studies have demonstrated that fast oscillations reflect the synchronous activity of large ensembles of neurons [30]. A reasonable explanation is that such high-frequency oscillations are not specific to a particular cognitive process, but rather represent the functional communication between various neurons and networks [26][27][28][29]. Together, both these processes could lead to the observed effects of gamma oscillation. ...
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Background This study explored the feasibility of using EEG gamma-band (30–49 Hz) power as an index of cue-elicited craving in METH-dependent individuals. Methods Twenty-nine participants dependent on methamphetamine (METH) and 30 healthy participants were instructed to experience a METH-related virtual reality (VR) social environment. Results Individuals with METH dependence showed significantly stronger self-reported craving and higher gamma power in a VR environment than healthy individuals. In the METH group, the VR environment elicited a significant increase in gamma power compared with the resting state. The METH group then received a VR counterconditioning procedure (VRCP), which was deemed useful in suppressing cue-induced reactivity. After VRCP, participants showed significantly lower self-reported craving scores and gamma power when exposed to drug-related cues than the first time. Conclusions These findings suggest that the EEG gamma-band power may be a marker of cue-induced reactivity in patients with METH dependence.
... Previous studies indicated that enhanced gamma activity was involved in the increased neural processing of emotional information (Balconi, M., & Lucchiari, C., 2008;Maffei et al., 2019;Müller et al., 1999). Balconi, M. and Lucchiari, C. (2008) found that gamma power in the prefrontal cortex was higher during the processing of emotional stimuli compared to neutral stimuli (Balconi, M., & Lucchiari, C., 2008). ...
... Previous studies indicated that enhanced gamma activity was involved in the increased neural processing of emotional information (Balconi, M., & Lucchiari, C., 2008;Maffei et al., 2019;Müller et al., 1999). Balconi, M. and Lucchiari, C. (2008) found that gamma power in the prefrontal cortex was higher during the processing of emotional stimuli compared to neutral stimuli (Balconi, M., & Lucchiari, C., 2008). They found that gamma band oscillations were enhanced when participants were consciously aware of emotional stimuli and were in an aroused state. ...
... Previous studies indicated that enhanced gamma activity was involved in the increased neural processing of emotional information (Balconi, M., & Lucchiari, C., 2008;Maffei et al., 2019;Müller et al., 1999). Balconi, M. and Lucchiari, C. (2008) found that gamma power in the prefrontal cortex was higher during the processing of emotional stimuli compared to neutral stimuli (Balconi, M., & Lucchiari, C., 2008). They found that gamma band oscillations were enhanced when participants were consciously aware of emotional stimuli and were in an aroused state. ...
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In recent years, there has been a growing interest in investigating the influence of biophilic design on occupants’ psychological comfort and well-being in the built environment. Biophilic principles aim to leverage the therapeutic effects of nature to alleviate distress, depression, anxiety, and pain. The impact of biophilic design can vary depending on the outcome measures and the design context, but studies examining diverse forms of biophilic design in hospital rooms have been limited. The study investigated how the incorporation of biophilic design elements in a virtual reality (VR) hospital patient room affects emotional and brain responses. The purpose of this experiment was to measure interactive emotions in an experimental setting, using a combination of electroencephalogram (EEG) and VR methods. A machine learning approach and statistical analysis were applied to differentiate emotional changes related to biophilic design. Seventy-five participants were divided into three groups to investigate the distinct effects of three types of biophilic design. EEG recordings were taken during experimental conditions to determine how biophilic design affects brain and emotional states. The Positive and Negative Affect Scale (PANAS) and State-Trait Anxiety Inventory - state (STAI-s) were used to measure changes in emotion and anxiety state. The results of the machine learning application on EEG data showed that classification accuracy above 90% included the frontal region in all classification conditions, indicating that biophilic design causes changes in brain function in this region. For the classification of the control room and digital wall room, and the control room and both plant and digital wall room, alpha power for frontal regions was included with above 90% classification accuracy. The results of the statistical analysis of the EEG data found that low-frequency band, which is associated with a relaxed state, was increased by biophilic design, while high- frequency band, which is associated with high arousal state, was reduced. These findings suggested that bio- philic design in a hospital room can reduce tension. The results from PANAS and STAI-s showed that biophilic design can induce positive emotional changes. The results of PANAS suggested that adding plant walls can reduce negative emotions due to their calming effect on the human nervous system. Using both plant walls and digital elements in healthcare environments can have a complementary effect on emotional well-being by reducing negative emotions while enhancing positive emotions. The study can potentially contribute to building a deeper and unified knowledge base for developing evidence-based designs to improve mental health and well-being. Moreover, the study provides insights into the potential benefits of different forms of biophilic design and their impact on human well-being.
... Thus, enhanced GBA synchronization may be directly linked to an attentional selection of relevant stimuli. Cortical GBA increases are often stronger for emotionally arousing than neutral expressions (Balconi & Lucchiari, 2008;Balconi & Pozzoli, 2009;Keil et al., 1999;Luo et al., 2009;Müsch et al., 2017). Those increases were localized in the visual cortex by magnetoencephalogram (MEG) source reconstructions (Luo et al., 2009;Müsch et al., 2017). ...
... We anticipate a differentiation of emotional from neutral faces, with the strongest GBA increase for angry faces at ~150-300 ms. We base our assumptions on previous studies which showed that both amygdala (Luo et al., 2007;Guex et al., 2020) and scalp GBA (Balconi & Lucchiari, 2008;Luo et al., 2007) differentiated emotional, primarily negative facial expressions, from neutral expressions in early to mid-latencies. We test to what extent these effects are further modified by the participants' attentional focus. ...
... We show that top-down attention to faces does not universally enhance amygdala GBA activity but interacts with affective relevance of the attended to face. Our data potentially reflect parallel gamma synchronizations in cortical and subcortical networks (Balconi & Lucchiari, 2008;Luo et al., 2007, Luo et al., 2009) that are specifically tuned by attention to negative stimuli. This aligns with Herz et al. (2020), who theorize that negative affect narrows cerebral processing in favor of negative stimuli, while positive affect broadens it. ...
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The amygdala is assumed to contribute to a bottom-up attentional bias during visual processing of emotional faces. Still, how its response to emotion interacts with top-down attention is not fully understood. It is also unclear if amygdala activity and scalp EEG respond to emotion and attention in a similar way. Therefore, we studied the interaction of emotion and attention during face processing in oscillatory gamma-band activity (GBA) in the amygdala and on the scalp. Amygdala signals were recorded via intracranial EEG (iEEG) in 9 patients with epilepsy. Scalp recordings were collected from 19 healthy participants. Three randomized blocks of angry, neutral, and happy faces were presented, and either negative, neutral, or positive expressions were denoted as targets. Both groups detected happy faces fastest and most accurately. In the amygdala, the earliest effect was observed around 170 ms in high GBA (105-117.5 Hz) when neutral faces served as targets. Here, GBA was higher for emotional than neutral faces. During attention to negative faces, low GBA (< 90 Hz) increased specifically for angry faces both in the amygdala and over posterior scalp regions, albeit earlier on the scalp (60 ms) than in the amygdala (210 ms). From 570 ms, amygdala high GBA (117.5-145 Hz) was also increased for both angry and neutral, compared to happy, faces. When positive faces were the targets, GBA did not differentiate between expressions. The present data reveal that attention-independent emotion detection in amygdala high GBA may only occur during a neutral focus of attention. Top-down threat vigilance coordinates widespread low GBA, biasing stimulus processing in favor of negative faces. These results are in line with a multi-pathway model of emotion processing and help specify the role of GBA in this process by revealing how attentional focus can tune timing and amplitude of emotional GBA responses.
... Motivationally relevant stimuli, such as the perception of a face with specific intrinsic features, are able to generate a transitory and automatic enhancement of arousal [36,37], that entails a prioritized processing of the stimulus in the visual stream [35]. This mechanism is associated with a series of physiological changes, including a top-down (i.e., endogenous) affective influence on sensory gain control [35], an increase in the amplitude of frequencyspecific brain oscillations [32,38] and in the magnitude of ERP components [34,35]. In this light, testing for the actual occurrence of enhanced arousal is crucial to ensure that a face has been successfully perceived, thus maximizing the SNR of ERP responses and the consequent effect size of odors' modulation. ...
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This study examines the modulatory effect of contextual hedonic olfactory stimuli on the visual processing of neutral faces using event-related potentials (ERPs) and effective connectivity analysis. The aim is to investigate how odors' valence influences the cortical connectivity underlying face processing, and the role arousal enhanced by faces plays on such visual-odor multimodal integration. To this goal, a novel methodological approach combining electrodermal activity (EDA) and dynamic causal modeling (DCM) was proposed to examine cortico-cortical interactions changes. The results revealed that EDA sympathetic responses were associated with an increase of the N170 amplitude, which may be suggested as a marker of heightened arousal to faces. Hedonic odors had an impact on early visual ERP components, with increased N1 amplitude during the administration of unpleasant odor and decreased vertex positive potential (VPP) amplitude during the administration of both unpleasant and neutral odors. On the connectivity side, unpleasant odors strengthened the forward connection from the inferior temporal gyrus (ITG) to the middle temporal gyrus (MTG), involved in processing changeable facial features. Conversely, the occurrence of sympathetic responses was correlated with an inhibition of the same connection, and with an enhancement of the backward connection from ITG to the fusiform face gyrus. These findings suggest that negative odors may enhance the interpretation of emotional expressions and mental states, while faces capable of enhancing sympathetic arousal prioritize the processing of identity. The proposed methodology provides insights into the neural mechanisms underlying the integration of visual and olfactory stimuli in face processing.
... Listening to rhythmic sound may entails local and/or distant neural networks and affect different EEG frequency bands (Bhattacharya and Petsche, 2005) such as changes in the frontal/temporal region in the alpha (Samhani et al., 2018), occipital lobe in beta and the right parietal region in gamma (Balconi & Lucchiari, 2008). Beta rhythms are always dominant in adults' wakefulness, in addition to being a sign of conscious thought and behaviour, alertness, and a focused mind. ...
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Spiritual healing and Quranic sound therapy has long accompanied human tradition since decades. Quranic sound is perceived as rhythmical cues that portrays psychospiritual effects although it was not recited with external melodic intonation (tarannum). Its internal rhythms were believed to activate and synchronize its listeners’ brain rhythms hence modulating their brainwaves to give the psychospiritual effect. However, there is lack of scientific investigation that elucidates source of Quranic linguistic rhythms which contributes to the greater neural activation in the Quran’s listeners. This study aimed to evaluate a Quranic linguistic feature that contributes to high rhythmicity, and high energy that activates its listeners neural ensembles. As a result, Electroencephalography (EEG)’s electrode correlation will be presented as a predictive measure for neural connectivity compared with Arabic News listening. Fatihah Chapter recitation (tajweed without tarannum) was selected, representing the Holy Quran, while Arabic News was selected representing human speech. Spectrogram analysis was performed by using Praat: Doing Phonetics by Computer (PRAAT) software. The continuous brain electrical charges from twenty-eight normal subjects (14 male:14 female) with inclusion criteria of habitual daily Quran listeners were recorded by 128-channel EEG. These brain electrical data were pre-processed and analysed by Fast Fourier Transform (FFT) followed by multivariate analysis. Discriminant Analysis results which compare the mean values of the groups were followed by Multiple Linear Regression. From spectrogram analysis, we found that Fatihah Chapter sound is more rhythmic compared to Arabic news and brings higher energy. The correlation spectral power between EEG electrodes showed three types of relationship: short, long, and inversely correlated, indicating communication flow among brain regions. Comparatively, larger-scale integration of neural ensembles from the fronto-temporo-parieto-occipital areas was observed while listening to Quranic Fatihah Chapter recitation than the fronto-temporo-parieto regions from Arabic News listening, indicated of higher synchronisation and integration in neuronal communication during Quranic listening. We found that listening to the Quranic sound may induce neural activation and reorganisation in the global brain regions involving the frontal, temporal, parietal, motor and occipital areas. Dynamic brain network interaction is postulated in a desynchronised pattern, essential for normal brain functioning, reduced pathological tendencies, and emotion-health-cognition stability, offering psychospiritual effects.
... Similar broadband brain activities can also be found on the brain's emotion response [43,44]. The θ frequency can decrease with the increasing positive valence [45,46]. α frequency is proved to increase with the increasing positive emotional arousal [45]. ...
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Autonomous sensory meridian response is believed as a perceptual phenomenon to specific sensory stimuli. To explore the underlying mechanism and emotional effect, the EEG under video and audio triggers of autonomous sensory meridian response was analyzed. The differential entropy and power spectral density by Burg method on δ, θ, α, β, γ and high γ frequencies were employed as quantitative features. The results indicate that the modulation of autonomous sensory meridian response on brain activities is broadband. Video trigger owns better performance of autonomous sensory meridian response than other triggers. Moreover, the results also reveal that autonomous sensory meridian response has a close relationship with neuroticism and its three sub-dimensions, anxiety, self-consciousness and vulnerability, with the scores of self-rating depression scale, but without emotions, happiness, sadness, or fear. This suggests that the responders of autonomous sensory meridian response may have the tendencies of neuroticism and depressive disorder.
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Introduction Women with premenstrual syndrome (PMS) suffer heavily from emotional problems, the pathogenesis of which is believed to be related to the hypothalamic-pituitary-adrenal (HPA) axis, autonomic nervous system (ANS) and central nervous system (CNS). We took into account all 3 aspects to observed the psychological, physiological and biochemical correlations under anger and sadness in college students with and without PMS. Methods 33 students with PMS and 24 healthy students participated in the emotion induction experiment, and were required to fill out self-report scales. Their salivary cortisol (SCort), skin conductivity level (SCL), heart rate variability (HRV), blood pressure (BP) and electroencephalogram (EEG) data were collected at the resting stage and 10-15 minutes after each video. Results Compared to healthy controls, students with PMS showed lower SCort level and higher VLF at rest, and no statistic difference in activities of ANS and HPA axis after emotional videos, but different results in EEG in all conditions. The decreases in SBP during angry video, SCort after angry and neutral videos, and increases in θ band power during sad video were moderately correlated with increases in PMS score. No intergroup differences were found in self-report emotions. Discussion Students with PMS had lower activity of HPA axis and possibly higher activity of PNS at rest, and different response patterns in CNS in all conditions. Several EEG frequencies, especially θ band, in specific encephalic regions during emotional videos, as well as declined HPA activities in dealing with angry and neutral stressors, in which γ activity in frontal lobe may play a role, showed moderate correlations with more severe PMS.
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Color is a visual cue that can convey emotions and attract attention, and there is no doubt that brightness is an important element of color differentiation. To examine the effect of art training on color perception, 44 participants with or without art training were assigned to two groups for an experiment. They scored emotional responses to color stimuli of different brightness levels based on the Munsell color system, and their EEG data was recorded simultaneously. The behavioral results revealed that high-brightness colors were rated more positively than low-brightness colors for both groups. Additionally, evoked event-related oscillation results showed that the high-brightness stimuli for the artist group also elicited large delta, theta, alpha, and low gamma responses. Similarly, event-related potential results for the artist group showed that high-brightness colors enhanced P2 and P3 amplitudes. Furthermore, non-artists had a shorter P2 latency and a longer N2 latency than artists, and there was a significant group × brightness interaction for the N2 and P3 components separately. Simple-effect analysis showed that N2 and P3 amplitudes for the artistic group were substantially higher for high-brightness stimuli than for lower-brightness stimuli, but not for the non-artist group. These results imply that high-brightness color stimuli trigger more positive emotions and attract stronger attention, and artistic training has a positive effect on top-down visual perception.
Electroencephalogram (EEG) based emotion recognition has received considerable attention from many researchers. Methods based on deep learning have made significant progress. However, most of the existing solutions still need to use manually extracted features as the input to train the network model. Neuroscience studies suggest that emotion reveals asymmetric differences between the left and right hemispheres of the brain. Inspired by this fact, we proposed a hemispheric asymmetry measurement network (HAMNet) to learn discriminant features for emotion classification tasks. Our network is end-to-end and reaches the average accuracy of 96.45%, which achieves the state-of-the-art (SOTA) performance. Moreover, the visualization and analysis of the learned features provides a possibility for neuroscience to study the mechanism of emotion.KeywordsDeep learningConvolution neural networkEEGEmotion recognition
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Recently, numerous novel methods have flourished in brain research and cognitive sciences, increasing our knowledge of the ways in which the human brain processes information. Experimental studies utilizing modern neurophysiological and neuroimaging techniques (EEG; electroencephalogram, MEG; magnetoencephalogram; fMRI; functional magnetic resonance imaging, PET; positron emission tomography) in association with cognitive processing have provided an opportunity to approach subtle brain-behavior relationships in a more direct and empirical manner than ever before. Although being one of the oldest psychophysiological methods to study brain activity, the electroencephalogram (EEG) can successfully be utilized in modern brain research in order to assess brain activity during cognitive functioning. In this chapter, the role of brain electric oscillations in revealing the neural basis of human cognitive and memory processes will be discussed.
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Objective: The present study aimed at examining the time course and topography of oscillatory brain activity and event-related potentials (ERPs) in response to laterally presented affective pictures. Methods: Electroencephalography was recorded from 129 electrodes in 10 healthy university students during presentation of pictures from the international affective picture system. Frequency measures and ERPs were obtained for pleasant, neutral, and unpleasant pictures. Results: In accordance with previous reports, a modulation of the late positive ERP wave at parietal recording sites was found as a function of emotional arousal. Early mid gamma band activity (GBA; 30-45 Hz) at 80 ms post-stimulus was enhanced in response to aversive stimuli only, whereas the higher GBA (46-65 Hz) at 500 ms showed an enhancement of arousing, compared to neutral pictures. ERP and late gamma effects showed a pronounced right-hemisphere preponderance, but differed in terms of topographical distribution. Conclusions: Late gamma activity may represent a correlate of widespread cortical networks processing different aspects of emotionally arousing visual objects. In contrast, differences between affective categories in early gamma activity might reflect fast detection of aversive stimulus features.
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Visual presentation of an object produces firing patterns in cell assemblies representing the features of the object. Based on theoretical considerations and animal experiments, it has been suggested that the binding of neuronal representations of the various features is achieved through synchronization of the oscillatory firing patterns. The present study demonstrates that stimulus-induced gamma-band responses can be recorded non-invasively from human subjects attending to a single moving bar. This finding indicates the synchronization of oscillatory activity in a large group of cortical neurons. Gamma-band responses were not as apparent in the presence of two independently moving stimuli, suggesting that the neuronal activity patterns of different objects are not synchronized. These results open a new paradigm for investigating the mechanisms of feature binding and association building in relation to subjective perception.
Recent studies have shown that the late positive component of the event-related-potential (ERP) is enhanced for emotional pictures, presented in an oddball paradigm, evaluated as distant from an established affective context. In other research, with context-free, random presentation, affectively intense pictures (pleasant and unpleasant) prompted similar enhanced ERP late positivity (compared with the neutral picture response). In an effort to reconcile interpretations of the late positive potential (LPP), ERPs to randomly ordered pictures were assessed, but using the faster presentation rate, brief exposure (1.5 s), and distinct sequences of six pictures, as in studies using an oddball based on evaluative distance. Again, results showed larger LPPs to pleasant and unpleasant pictures, compared with neutral pictures. Furthermore, affective pictures of high arousal elicited larger LPPs than less affectively intense pictures. The data support the view that late positivity to affective pictures is modulated both by their intrinsic motivational significance and the evaluative context of picture presentation.
The main purposes of this review are to set out for neuroscientists one possible approach to the problem of consciousness and to describe the relevant ongoing experimental work. We have not attempted an exhaustive review of other approaches.
Functional activity in the visual cortex was assessed using functional magnetic resonance imaging technology while participants viewed a series of pleasant, neutral, or unpleasant pictures. Coronal images at four different locations in the occipital cortex were acquired during each of eight 12-s picture presentation periods (on) and 12-s interpicture interval (off). The extent of functional activation was larger in the right than the left hemisphere and larger in the occipital than in the occipitoparietal regions during processing of all picture contents compared with the interpicture intervals. More importantly, functional activity was significantly greater in all sampled brain regions when processing emotional (pleasant or unpleasant) pictures than when processing neutral stimuli. In Experiment 2, a hypothesis that these differences were an artifact of differential eye movements was ruled out. Whereas both emotional and neutral pictures produced activity centered on the calcarine fissure (Area 17), only emotional pictures also produced sizable clusters bilaterally in the occipital gyrus, in the right fusiform gyrus, and in the right inferior and superior parietal lobules.