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Neuroscience Letters 392 (2006) 118–123
EEG correlates (event-related desynchronization) of emotional
face elaboration: A temporal analysis
Michela Balconia,∗, Claudio Lucchiarib
aLaboratory of Cognitive Psychology, Department of Psychology, Catholic University of Milan, Largo Gemelli 1, 20123 Milan, Italy
bDepartment of Neurology, Neurological National Hospital“C. Besta”, Milan, Italy
Received 31 March 2005; received in revised form 25 August 2005; accepted 2 September 2005
Abstract
AnEEGfrequencybandanalysiswas conducted,inorderto explorethesignificanceofbrain oscillations(delta, theta,alphaand beta)for emotional
face comprehension during different post-stimulus time intervals (50–150; 150–250; 250–350; and 350–450ms). The study was conducted on
twenty adults who looked at emotional (happy, sad, angry, fearful) or neutral faces. The results showed that motivational significance of the
stimulus can modulate the power synchronization (event-related desynchronization (ERD) decrease) within the frequency band of delta and theta.
We propose that delta and theta respond to variations in processing stage of emotional face: whereas, delta reflects updating of the stimulus, theta
responds to the emotional significance of face. The findings revealed that emotional discrimination by theta is observable mainly within 150–250
time interval and that it is more distributed on anterior regions, whereas delta is maximally synchronized within 250–350 interval and more
posteriorly distributed for all the stimulus type. Finally, a right-hemisphere dominance was found for theta during emotional face comprehension.
© 2005 Elsevier Ireland Ltd. All rights reserved.
Keywords: Emotional face; Event-related desynchronization; Temporal analysis; Hemispheric asymmetry
Facial expressions of emotion have an important role in com-
municating the needs and intentions of people and humans must
be specially prepared by evolution and learning to detect and
identify the meaning of emotional faces [8]. When an individual
perceives a motivationally relevant stimulus, such as an emo-
tional face, a variety of specific emotional processes emerge in
the central and peripheral nervous system. Specifically, motiva-
tionalsignificance and relevanceof the emotional face may have
an effect on attentional mechanism [20,21]. The present study
aimedatstudying the brain mechanisms underlying humanemo-
tional processing by measuring frequency band power (delta,
theta, alpha, and beta) changes in response to emotional faces
presented visually. We attended that emotional content may be
indexed by oscillatory activity of the brain that was directly
related to attentional processes and arousal [15,19].
Correlatesofaffectiveface processing havebeeninvestigated
using a variety of recording techniques. On one hand, some
authors studied ERP correlates associated with face processing.
It has been argued that emotional face processing arises early. A
∗Corresponding author. Tel.: +39 02 72342960; fax: +39 02 72342280.
E-mail address: michela.balconi@unicatt.it (M. Balconi).
positive peak was observed at about 100ms post-stimulus (PI),
related to emotional valence of the facial stimulus [23]. It might
demonstrate that emotional perception of faces can take place
pre-attentively and automatically. More recently, the differences
between ERPs elicited by emotional face and neutral faces were
observable specifically between 250 and 550ms after stimulus
onset[20].An early negativedeflection (N2) of higher amplitude
was revealed for arousing facial stimuli [3,24,26] in comparison
with neutral facial stimuli. A successive positive ERP deflection
(P300) was monitored by some authors after an emotional stim-
ulation, even if it does not seem to be exclusive for faces, since
it was observed even in response to adjectives or objects with
an emotional content [6]. Thus, P3 effect seems to be a compo-
nent representing updating aspect of processing, independently
of the nature of the stimuli, since this effect is viewed as reflect-
ing decision or cognitive closure of the recognition processing
[7,13].
On the other hand, brain oscillations were found a powerful
tool to analyze the cognitive processes related to emotion com-
prehension [5,18]. Recent researches showed the event-related
thetaband power responds specifically to prolonged visualemo-
tional stimulation [19], and a synchronization was revealed in
case of coordinated response indicating alertness, arousal and
0304-3940/$ – see front matter © 2005 Elsevier Ireland Ltd. All rights reserved.
doi:10.1016/j.neulet.2005.09.004
M. Balconi, C. Lucchiari / Neuroscience Letters 392 (2006) 118–123 119
Fig. 1. Event-related desynchronization (ERD) of frequency band power in response to the stimulus type (emotional vs. neutral) for each time interval.
readiness to process information [4]. Thus, theta EEG power
typically increases with increasing attentional demands and/or
task difficulty. Contrarily, the amplitude of the delta response is
considerably increased as a function of the necessity of stim-
ulus evaluation and memory updating [14]. Nevertheless, at
present no specific data exist on modulation of delta band by
emotional significance of the stimulus. Moreover, as regard of
alpha frequency, it was showed a memory-related alpha oscil-
lations, strongly correlated with working memory and probably
with long-term memory. It was suggested that the responses of
alpha band most probably reflect brain processes associated to
phasic alertness, and it was found an anterior asymmetries in
alpha reduction, that was explained as correlates of changes on
individual affective state [1,9] (Fig. 1).
Although brain oscillations have recently been investigated
in various sensory modalities, their role for brain functioning
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 and
emphasize the importance of distributed oscillatory networks
in a narrow frequency range (between 1 and 20Hz). Another
critical issue of the present research is the comparison of the fre-
quency band changes within different time intervals, since the
distribution of the band frequency along the time appeared more
informative than the peak frequency of the band. Our intent is to
analyze the variability of frequency bands inside some known
time intervals (that is temporal windows around 200ms and
300 ms of latency) that were found as discriminant in emotional
processing. In addition, one question that has been raised con-
cerns asymmetric organization in the cerebral hemisphere of the
mechanisms mediating emotional facial stimulus [10]. A recent
study on generic emotional stimuli showed a significant valence
by hemisphere interaction of theta band in the anterior temporal
areas,showingrelatively greater righthemisphereERSfornega-
tive and left for positive stimuli, and an overall right hemisphere
dominance in theta ERS for valenced versus neutral stimuli [2].
Thus, we expected a significant difference in the hemispheric
response (left-right and anterior-posterior axes) as a function of
the emotional content (emotional versus neutral stimulus).
Twenty healthy volunteers took part in the study (11 women,
age 19–25, mean=23.47, S.D.=2.13) after giving informed
consent. They were all right-handed and with normal or
corrected-to-normalvisual acuity.Stimulus materialsweretaken
from the set of pictures of Ekman and Friesen [11]. They were
blackandwhite pictures of male andfemale(equallydistributed)
actors, presenting respectively a happy, sad, angry, fearful, or
neutral face (resulting in a total of 100 stimuli, twenty for each
category). 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). The stimulus was
presented for 500 ms on the monitor with an interstimulus inter-
val parameter (ISI) of 1500ms, and the inter-stimulus fixation
point was projected at the center of the screen (a white point
on a black background). Subjects were seated comfortably in
a moderately lighted room with the monitor screen positioned
approximately 100cm in front of their eyes. During the exami-
nation, they were requested to continuously focus their eyes on
the small fixation point and to minimize blinking. The EEG was
recorded with a 62-channel DC amplifier (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 place-
ment). 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 0.1–50 Hz. The impedance
of recording electrodes was monitored for each subject prior
to data collection and it was always below 5k. After EOG
correction and visual inspection only artefact-free trials were
considered. Only 14 electrodes were used for the successive sta-
tistical analysis (4 central, Fz, Cz, Pz, Oz; 10 lateral, F3, F4, C3,
120 M. Balconi, C. Lucchiari / Neuroscience Letters 392 (2006) 118–123
C4, T3, T4, P3, P4, 01, 02) [24,25]. The digital EEG data were
band-pass filtered in the following frequency bands: 0.5–4, 4–8,
8–12, and 14–20 Hz. To obtain a signal proportion to the power
of the EEG frequency band, the filtered signal samples were
squared [22]. Successively, the data were epoched, triggered
each second, using four different time windows of 100ms. An
average absolute power value for each electrode for each con-
dition (emotional versus neutral) was calculated separately for
each frequency band. An average of the pre-experimental abso-
lutepowerwasused todeterminethe individualpowerduring no
stimulation. From this reference power value, individual power
changes during face viewing were determined as the relative
stimulus-related decrease (desynchronization). In fact, accord-
ing 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 900ms post-stimulus) as compared to a ref-
erence interval (here 1500ms before picture onset). For each
subject, after band-pass filtering ERD was calculated within the
4 frequency bands for the four intervals of 50–150, 150–250,
250–350, and 350–450ms. The average ERD values across the
respective electrode sites were calculated for each time interval.
The data were entered into repeated measures analysis of
variance (ANOVA) with three repeated factors: stimulus type
(neutral versus emotional), frequency band (4 levels) and elec-
trode sites (14 levels). Four ANOVAs were conducted, one for
each time interval. Thereafter, four ANOVAs were calculated
separately for each frequency band, with two within subject fac-
tors, the stimulus type (2) and the time interval (4). Finally,
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 loca-
tion, and secondly over left (F3, C3, T3, P3, 01) and right (F4,
C4, T4, P4, 02) sides. These new values were entered in two
distinctstatisticalanalyses. For all the ANOVAs, degreesoffree-
dom were Greenhouse–Geisser corrected where appropriate. In
the first time interval, ANOVA showed the statistical signifi-
cance for only Band (F(3,19) =8.60, P< 0.001) main effect. As
showed by the contrast analysis, the alpha and beta frequency
bands showed a higher ERD in comparison with delta (respec-
tively for alpha/delta (F(l,19)= 4.88, P= 0.007) and beta/delta
(F(l,19) = 6.91, P= 0.002) and theta (alpha/theta (F(l,19)= 4.12,
P=0.009) and beta/theta (F(l,19)=5.58, P=0.006) bands. On
the contrary, theta and delta were not differentiated each other.
In the 150–250 time window, main effects for Type
(F(l,19) =5.41, P= 0.006) Band (F(3,19)= 7.44, P=0.001) and
Electrodes (F(13,19)=8.02, P<0.001) were found. For the
Band effect, it was showed a greater decrease of alpha and
beta power, whereas delta and theta showed an increased
power. The contrast comparison verified that this was due
to the significant difference for alpha/theta (F(l,19)= 9.40,
P<0.001), alpha/delta (F(l,19)=8.81, P<0.001), as well
as for beta/theta (F(l,19)=10.05, P<0.001) and beta/delta
(F(l,19)=9.40, P<0.001). In addition, an increased syn-
chronization was found for theta band if compared to
delta (F(l,19)=4.26, P=0.005). A higher synchronization of
the oscillations was found in this time interval for theta
band. Moreover Band×Type interaction was also significant
(F(3,19)=5.29, P=0.002). Contrast effects showed a signifi-
cant difference for alpha/theta (F(l,19)= 3.49, P= 0.041) and
alpha/delta (F(l,19)=3.32, P=0.043) comparisons in emo-
tional face processing, as well as for beta/theta (F(l,19)=3.76,
P=0.038) and beta/delta (F(l,19)=4.05, P=0.028) compar-
isons. The synchronization was varied as a function of stim-
ulus type. In particular, theta and delta band synchronization
was due to the emotional content of the stimulus, whereas
desynchronization for alpha and beta was observed for all the
facial stimuli. The significant interaction Band×Electrodes
(F(39,19) =12.86, P< 0.001) was explored more deeply by two
successiveANOVAs, in order to analyze Location (anterior,cen-
tral, posterior) and Side (right, left) contribution to the cortical
distribution of the frequency bands. The first ANOVA revealed
a significant interaction effect for Location×Type×Band
(F(6,19) =6.16, P= 0.001). Specifically, post-hoc analysis indi-
cated that theta frequency band synchronizes mainly in the
frontal regions of the scalp during emotional stimulus elab-
oration, whereas delta band was concentrated in the pos-
terior regions for the entire stimulus. The second ANOVA
showed a significant interaction effect for Side×Type×Band
(F(3,19)=8.53, P<0.001).
A higher right synchronization was observed only for theta
bandduringelaborationofemotionalstimuli in comparison with
neutral stimuli.
The 250–350 time window showed a significant main
effect for Band (F(3,19)= 11.53, P< 0.001), and Electrodes
(F(13,19)=8.81, P<0.001) as well as for the interaction
Type×Band (F(13,19)=8.02, P<0.001) and Type×Band×
Electrodes (F(39,19)=9.12, P<0.001). Specifically, the post-
hoc comparison showed that alpha and beta frequency bands
desynchronize for each type of stimulus, on the contrary that
beta and theta synchronize during this time interval, but whereas
the delta synchronization was found for all the stimulus (emo-
tional and neutral) theta showed a more decreased ERD for
emotional face if compared with neutral faces. In addition,
theta and delta were differentiated each other (F(l,19)= 5.99,
P=0.002),since delta showed the higher increased power (max-
imum of synchronization). Moreover, the successive ANOVAs
revealed a Type×Side ×Band (F(3,19) = 7.12, P= 0.001) and
Type×Location×Band effect (F(6,19)= 8.62, P< 0.001): a
right anterior synchronization was revealed during emotional
face elaboration in comparison with neutral face elaboration
for theta band, whereas delta was preferentially located in the
posterior sites. Finally, in the Time interval 350–450ms, Band
effect was significant (F(3,19)= 4.02, P= 0.008). Specifically,
as showed by post-hoc comparison, delta frequency band syn-
chronizes within 350–450 time window, if compared with alpha
(F(l,19)=9.11, P=0.001), beta (F(l,19)=8.06, P=0.001) and
theta (F(l,19)=3.88, P=0.033) that showed a greater desyn-
chronization. This effect was revealed for all stimulus type (both
emotional and neutral stimuli).
In order to reveal power variation for each frequency band
within the overall 0–450 temporal duration, specific ANOVAs
Type (2)×Time (4)×Electrodes (14) were conducted sepa-
rately for each frequency band. In the alpha band only the
Time main effect was statistically significant (F(3,19)= 6.05,
M. Balconi, C. Lucchiari / Neuroscience Letters 392 (2006) 118–123 121
P= 0.001). Contrast analysis showed a significant increasing of
ERDfor the firstintervalincomparisonwiththe others(1/2inter-
vals (F(l,19)= 4.47, P= 0.006), 1/3 (F(l,19) = 5.12, P= 0.002),
and 1/4 (F(l,19)=5.50, P=0.002). No other effect resulted
statistically significant. In fact, a higher desynchronization of
alpha band was observed during the early latency, whereas
ERD reduces gradually inside the successive intervals for both
the emotional and neutral stimuli. As in the alpha frequency
band, ANOVA applied to beta revealed the significance for only
one of the main effect, Time (F(3,19)= 6.03, P= 0.003). The
post-hoc analysis showed a gradual desynchronization within
the four time intervals. Delta frequency band showed sensi-
tivity to Type (F(l,19)= 6.01, P=0.002), Time (F(3,19)=8.96,
P<0.001) and Electrodes (F(13,19)=8.08, P<0.001) fac-
tors, as well as to Time×Electrodes (F(39,19) = 11.22,
P<0.001), and Type×Time×Electrodes (F(39,19) = 13.05,
P<0.001). Specifically, ERD showed a significant decrease
within 150–450ms. Moreover, a maximum of synchroniza-
tion of the oscillations was revealed during the third time
interval (250–350ms), with a peak of the band power around
320 ms. This synchronization appears due to the emotional con-
tent of the stimulus during 150–250 time interval (significant
differences between emotional versus neutral faces), whereas
it responds to the facial stimulus in general in the succes-
sive time intervals. ANOVAs revealed differences in Loca-
tion (F(2,19)=5.18, P=0.001). Specifically, as revealed by
the contrast analysis, delta band power synchronizes mainly
in the posterior than in the anterior (F(l,19)=4.88, P=0.012)
or central (F(l,19)=4.60, P=0.010) sites. A similar statis-
tical result was observed for theta band (significant effects
for Time (F(3,19)= 9.60, P< 0.001), Type (F(l,19)= 8.14,
P< 0.001) and Electrodes (F(13,19)= 14.08, P< 0.001), as well
as for the interactions Type×Time (F(3,19)= 5.16, P=0.001)
and Type×Time×Electrodes (F(39,19) =11.28, P< 0.001), it
beingassociatedwithaselectiveERD reduction within 150–250
timewindow,and agradualincreasing ofERDduringthe succes-
sive time intervals (350–450 time). An interesting result of the
analysiswasthat the synchronization of theta band was observed
mainly for emotional stimuli compared with neutral stimuli in
thesecondandthirdtime interval. SuccessiveANOVAs revealed
a Side×Type×Time effect (F(3,19)= 7.78, P< 0.001), and
a Type×Time×Location effect (F(9,19) = 9.35, P< 0.001).
Specifically post-hoc comparison verified a higher right ante-
rior synchronization of theta frequency band during the second
and third time interval, and this effect was related to emotional
stimuli.
Three major effects were found in the present research.
First, the results support the view that the responses of differ-
ent EEG frequencies to emotional face differ from each other
systematically as a function of stimulus type. Secondly, band
frequency modulation arises in concomitance with some critical
time intervals that were observed to be discriminant for emotion
in previous analysis based on ERPs. Third, location differences
(right–left hemisphere, frontal–posterior sites) were observed
for some frequency bands in emotional face elaboration.
Firstly, some of the frequency bands were revealed to be sen-
sitive to emotional content of face. Especially theta and delta
EEG frequencies responded specifically to visual emotional
stimulation, whereas alpha and beta frequencies are modulated
by all the stimulus types. Thus, these two sub-categories of fre-
quency band power were differentiated as a function of their
higher (delta/theta) and lower (alpha/beta) sensitivity to emo-
tional significance of face. For the alpha band power an interest-
ing features is the spectral changes in response to the stimulus as
compared to baseline in the first time interval, showing an inter-
action between stimulus elaboration and this frequency band.
Specifically, alpha showed a greater decrease (desynchroniza-
tion) selectively up 150ms for all the stimulus, whereas a more
stableERDis observed duringtheotherstagesof stimulus elabo-
ration(from 150 ms). Previousstudy foundthatalpha power(and
more specifically lower-1 alpha frequency) desynchronizes as a
response to a presented warning stimulus, and it could be linked
to attentional demand and habituation [16,17]. Thus, in the
presentresearch alpha variationmaybea marker of thefirststage
ofstimulus elaboration thatisrelated toalertnessmechanism. On
thecontrary,narrowfrequencybands(deltaandtheta)showedto
synchronizeespecially duringemotion-relatedinformation elab-
oration.Weobserved that this effect was most pronounced in the
last part of the post-stimulus interval, that is the second and third
time windows (up to about 350ms), where the increase of theta
and delta power reached a maximum of intensity. Specifically,
delta showed a higher synchronization at about 320ms post-
stimulus. Moreover, the synchronization effect was sustained
from 150 up 350, then it begins a gradual desynchronization of
delta oscillations. In parallel, theta band synchronized mainly
within the second time window (with a peak at about 240ms
of latency). In comparison with delta power, theta showed an
earlier synchronization, an anticipated increased power and it
more quickly desynchronized (at about 250 latency). In addi-
tion a significant difference between delta and theta must be
considered. In fact, whereas during 150–250 time interval both
the frequency bands synchronized in correspondence with the
emotional more than with the neutral stimulus elaboration, the
successive response (250–350 interval) of the two frequency
bands differed, since only for theta band the synchronous oscil-
lations were related to the emotional content of face, whereas
deltarespondedsimilarly (synchronously) to emotional andneu-
tral stimuli.
What mechanisms can we suppose to be underlying these
frequency band variations? We have showed that in the present
experiment the EEG is modulated as a function of time, and it
is assumable that the power changes between different tempo-
ral windows are specifically due to the evolving of stimulus
elaboration. In particular, time course of affective theta and
beta synchronization during facial expression comprehension
showeddiscrimination between early and later processing stages
ofstimulus. Deltabandreached a gradualsynchronizationwithin
the temporal sequences, with a peak at about 300ms. Contrar-
ily, theta was enhanced during the 150–250ms, reaching greater
synchronizationatabout 200 ms post-stimulus. This pattern sug-
gests that band modulation of this early time-locked response
reflects processing of the features of the facial stimuli but in
different manner. In the first case, delta synchronization could
be a marker of novelty of the stimulus, and it can respond to
122 M. Balconi, C. Lucchiari / Neuroscience Letters 392 (2006) 118–123
the exigency of stimulus updating in memory [12]. This cogni-
tive process need a longer time to be concluded and it appears
not to be exclusively sensitive to the emotional content of the
stimulus but generalized to the overall facial stimuli. Never-
theless, it is likely that the higher complexity of the emotional
than the neutral stimuli is signalled in the first time (150–250
post-stimulus interval) of updating process and it is not present
successively (250–350ms) when the subject have familiarized
with the stimulus. In the second case, theta appears to vary in
concomitance with motivational significance of face that is it
synchronizes mainly as a function of the emotional expressions
and not of the neutral ones. More generally, it was found that
theta band was related to the function of orienting and atten-
tion for emotional significance of the stimulus, representing the
first stage of conceptual stimulus processing of a short-term
conceptual memory-system, in which stimuli reach meaningful
representation rapidly [2]. It was also observed that in compari-
son to delta band, there is a general tendency in theta to exhibit
negative ERD values with increasing attentional demand. Thus,
here enhanced synchronization of theta might index selective
attention for arousing stimuli and a concomitant increased moti-
vational significance of the emotional faces.
Moregenerally,an interesting result ofthe present research is
that each oscillation appears to respond to variations in process-
ing stage of emotional face by variations in latency. As we have
stated the latency (different time intervals) and content sensitiv-
ity (emotional versus neutral content) of delta and theta differed
and it appears to be likely that they are related (or contribute to)
the correspondent N2 and P3 ERP correlates. In this view, oscil-
latory neural assemblies effect on event-related potentials were
supposed [14]. Previous study found that N2 have an emotional
significance [3,24,26]. Specifically, it was related to arousing
stimulation and thus differentiated as a function of the moti-
vational value of the stimulus [25]. Contrarily, P3 was more
generally linked to the decisional aspect of processing, indepen-
dently of the nature of the stimuli, since this effect is viewed
as reflecting decision or cognitive closure of the recognition
processing. Taking into consideration our results, whereas theta
could represent a complex set of cognitive processes whereby
selective attention becomes focused on an emotional-relevant
stimulus that is maintained in short-term memory, on the con-
trary delta activity could reflect at least in part P3, and it is
elicited whenever there is a need to update context.
Moreover, the modulation of the narrow frequency bands
was revealed at both the anterior (theta) and posterior (delta)
recording sites. Nevertheless, two different cortical preferen-
tial distributions were supposed for theta and delta: theta was
anterior-distributed in response to emotional face, whereas delta
was more posterior-distributed independently from the stimulus
type. Previously it was showed that attentional aspect of theta
is obtained from the frontal locations, with the probable gen-
erators lying in corticohippocampal and frontolimbic structures
[14]. The topographical distribution of theta band modulation
suggests that emotional content comprehension is related to
alterations in anterior areas. A vigilance mechanism activated in
concomitance of detection and evaluation of facial expression is
likelyto be locatedattheanterior sites thatareanetwork of atten-
tion consisting of the frontal site is argued to maintain a state of
alertness when salient stimuli are encountered. In addition, the
cortical sides (left and right) have an effect in modulating band
distribution on the scalp, being theta most pronounced on the
right hemisphere than the left, and this effect revealed for theta
could be involved in the modulation of emotion-related arousal.
This effect regarding hemisphere differences is in line with pre-
vious study, that underlined the lateralization of emotional face
processing, since aright hemisphere dominance for emotional
face comprehension was pointed out [10,20]. In parallel, corti-
cal asymmetries were reported for some of the ERP variations
related to emotion elaboration that is N2 and P3, with maximal
effects over the right region. Specifically, the N2 amplitude was
increased for negative compared to neutral stimuli at right hemi-
sphere side [3]. Nevertheless our results present some limits due
to the necessity to analyze in a more systematic manner the spe-
cific effect of different emotional content on band variations as a
function of the valence – positive versus negative – and arousal
– high versus low – of each face [2]. Moreover, the it is likely
thatthe emotional valenceof face (negativeversus positive) may
have an effect on cortical distribution of band modulation, as it
was pointed out by Pizzagalli et al. [23]. Indeed, it was found
that recognition of specific emotions would depend on the exis-
tence of partially distinct systems. For example, amygdala is
required for processing fear but not happiness. Thus, the inci-
dence of this variable on the attentional and motivational levels,
and therefore, on the brain oscillations must be tested systemat-
ically in the future.
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