Chiew KS, Braver TS. Neural circuitry of emotional and cognitive conflict revealed through facial expressions. PLoS One 6: e17635

Department of Psychology, Washington University in St. Louis, St. Louis, Missouri, United States of America.
PLoS ONE (Impact Factor: 3.23). 03/2011; 6(3):e17635. DOI: 10.1371/journal.pone.0017635
Source: PubMed
Neural systems underlying conflict processing have been well studied in the cognitive realm, but the extent to which these overlap with those underlying emotional conflict processing remains unclear. A novel adaptation of the AX Continuous Performance Task (AX-CPT), a stimulus-response incompatibility paradigm, was examined that permits close comparison of emotional and cognitive conflict conditions, through the use of affectively-valenced facial expressions as the response modality.
Brain activity was monitored with functional magnetic resonance imaging (fMRI) during performance of the emotional AX-CPT. Emotional conflict was manipulated on a trial-by-trial basis, by requiring contextually pre-cued facial expressions to emotional probe stimuli (IAPS images) that were either affectively compatible (low-conflict) or incompatible (high-conflict). The emotion condition was contrasted against a matched cognitive condition that was identical in all respects, except that probe stimuli were emotionally neutral. Components of the brain cognitive control network, including dorsal anterior cingulate cortex (ACC) and lateral prefrontal cortex (PFC), showed conflict-related activation increases in both conditions, but with higher activity during emotion conditions. In contrast, emotion conflict effects were not found in regions associated with affective processing, such as rostral ACC.
These activation patterns provide evidence for a domain-general neural system that is active for both emotional and cognitive conflict processing. In line with previous behavioural evidence, greatest activity in these brain regions occurred when both emotional and cognitive influences additively combined to produce increased interference.


Available from: Kimberly S Chiew
Neural Circuitry of Emotional and Cognitive Conflict
Revealed through Facial Expressions
Kimberly S. Chiew*, Todd S. Braver
Department of Psychology, Washington University in St. Louis, St. Louis, Missouri, United States of America
Neural systems underlying conflict processing have been well studied in the cognitive realm, but the extent to
which these overlap with those underlying emotional conflict processing remains unclear. A novel adaptation of the AX
Continuous Performance Task (AX-CPT), a stimulus-response incompatibility paradigm, was examined that permits close
comparison of emotional and cognitive conflict conditions, through the use of affectively-valenced facial expressions as the
response modality.
Methodology/Principal Findings:
Brain activity was monitored with functional magnetic resonance imaging (fMRI) during
performance of the emotional AX-CPT. Emotional conflict was manipulated on a trial-by-trial basis, by requiring contextually
pre-cued facial expressions to emotional probe stimuli (IAPS images) that were either affectively compatible (low-conflict) or
incompatible (high-conflict). The emotion condition was contrasted against a matched cognitive condition that was
identical in all respects, except that probe stimuli were emotionally neutral. Components of the brain cognitive control
network, including dorsal anterior cingulate cortex (ACC) and lateral prefrontal cortex (PFC), showed conflict-related
activation increases in both conditions, but with higher activity during emotion conditions. In contrast, emotion conflict
effects were not found in regions associated with affective processing, such as rostral ACC.
These activation patterns provide evidence for a domain-general neural system that is active for
both emotional and cognitive conflict processing. In line with previous behavioural evidence, greatest activity in these brain
regions occurred when both emotional and cognitive influences additively combined to produce increased interference.
Citation: Chiew KS, Braver TS (2011) Neural Circuitry of Emotional and Cognitive Conflict Revealed through Facial Expressions. PLo S ONE 6(3): e17635.
Editor: Hans Op de Beeck, University of Leuven, Belgium
Received December 5, 2010; Accepted February 4, 2011; Published March 9, 2011
Copyright: ß 2011 Chiew, Braver. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This work was supported by grant RO1 MH66078 from the National Institutes of Health to T.S.B. and a Natural Sciences and Engineering Research
Council of Canada Postgraduate Scholarship to K.S.C. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of
the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail:
‘Cognitive control’ refers to the coordination and direction of
lower-level cognitive processes critical to complex, goal-directed
behaviour. These processes, including attentional selection,
conflict resolution, and the online maintenance of goal-relevant
information (and inhibition of goal-irrelevant information), may
underlie higher many cognitive functions, permitting the flexibility
and sophistication of human thought and behaviour across a wide
variety of task situations. While cognition has traditionally been
conceptualized as separate from affect, it has been increasingly
recognized that affective significance is a major factor in goal-
directed behaviour, both in establishing goals and in shaping how
information is processed during goal pursuit. Emotionally salient
stimuli in the environment may be prioritized for processing over
non-emotional stimuli [1,2], but it remains unclear whether
qualitatively distinct neural circuitry is engaged for the processing
of affectively-valenced stimulus dimensions. The present study
examines the neural systems engaged in the detection and
management of conflict, a canonical control function, when the
information being processed (i.e., the source of conflict) is
emotional versus non-emotional in nature.
Conflict can be defined mechanistically in terms of cross-talk
caused by the simultaneous concurrent processing of goal-relevant
and goal-irrelevant information competing for common resources
[3]. The Stroop task [4] is a classic conflict task: participants must
name the colour of presented words while ignoring the word’s
meaning. In some trials, goal-irrelevant information is congruent
with goal-relevant information (e.g., the word ‘RED’ printed in
red ink); in other trials, the goal-relevant and irrelevant
information are incongruent (e.g., ‘RED’ printed in green ink),
leading to conflict. Using tasks such as the Stroop (as well as
related incompatibility paradigms such as Simon, flanker and
others, e.g., [5]), conflict has been extensively studied in the
cognitive realm. Functional neuroimaging methods have been
used to identify a number of frontal and parietal brain regions
canonically associated with cognitive control in this and other tasks
[6,7,8,9], with the ACC in particular being associated with conflict
processing functions [10,11,12,13].
Evidence from early neuroimaging studies examining conflict
elicited by emotional versus non-emotional distracters resulted in an
influential hypothesis postulating that emotional and cognitive
conflict detection are mediated by distinct rostral and dorsal
subdivisions of the ACC, respectively (Bush et al., 2000). However,
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subsequent investigations of emotional and cognitive conflict
processing have yielded mixed evidence regarding the domain-
specificity of their underlying neural systems. Most studies focusing
on emotion conflict using Stroop-like variants tend to find activation
in dorsal rather than ventral ACC, as well as other areas associated
with cognitive control, such as the lateral PFC [14,15]. In a recent
study comparing activity in closely matched emotion and non-
emotional variants of a face-word Stroop paradigm, Egner and
colleagues [16] again reported that conflict detection was associated
with dorsal ACC in both conditions; activation was observed in the
rostral ACC (and amygdala) only during conditions examining
emotional conflict resolution (i.e., modulation based on previous
trial conflict). Ochsner and colleagues [17] compared an emotional
versus non-emotional flanker task, and also found a number of areas
commonly engaged by conflict in both tasks, including the dorsal
ACC. However, consistent with the cognitive/emotion division
hypothesis, they also observed that affective conflict selectively
engaged the rostral medial PFC, with brain-behavior correlations
observed in rostral ACC. Likewise, another recent study [18]
reported distinct patterns of conflict-related neural activity in
conditions involving emotional stimulus-response (S-R) incompat-
ibility (emotion expression interference; elicited via making facial
expressions incongruent with those of presented faces) with
cognitive S-R incompatibility (elicited via the Simon task).
A major challenge in this research area has been to utilize
appropriate paradigms that enable valid and closely matched
comparisons of emotional and cognitive forms of conflict. The
hypothesis that emotional versus cognitive conflict may depend on
distinct subdivisions of the ACC was based on evidence from
emotional adaptations of the Stroop task, which examine
interference from emotional distracters (e.g., performance of the
colour-naming task for emotional relative to non-emotional words;
[19]). However, it has been asserted that interference in the
colour-naming emotional Stroop task may occur because of lower-
level lexical effects [20] or general attention capture [21] rather
than the direct conflict effects present in the traditional Stroop. To
improve upon this design, face-word Stroop variants have been
utilized, in which positive and negatively valenced words (e.g.,
‘HAPPY’ or ‘FEAR’) are superimposed on compatible or
compatible facial expressions [15,16,22,23]. This design improves
on the colour-naming emotional Stroop in that the responses
require affective classification and the task-relevant and irrelevant
information are semantically related, leading to affective incom-
patibility effects more closely related to the direct conflict present
in the traditional cognitive Stroop. However, all of these tasks
involve an incompatibility between a task-relevant stimulus and a
task-irrelevant stimulus (thus, stimulus-stimulus [S-S] incompati-
bility). In contrast, studies of cognitive conflict have explored both
S-S and S-R incompatibilities [5]. The emotion expression
interference paradigm developed by Lee and colleagues [18] is a
first step in exploring S-R incompatibility in the context of
emotional conflict: this paradigm examines interference when
participants make emotional facial expressions as a behavioral
response, capitalizing on their role as an index of emotional
experience and expression [24]. However, the Lee et al paradigm
requires participants to make an expression in response to a
presented face. As such, it leaves open the possibility that
interference effects in the task may be caused by overriding
imitation tendencies instead of being due to conflicting emotional
influences, per se. In view of these considerations, our goal was to
examine emotional conflict with a paradigm that similarly
capitalized on emotional facial expressions to index stimulus-
response incompatibility, but that improved upon this paradigm
by avoiding possible imitative influences.
Accordingly, we developed a new paradigm to examine
emotional conflict via S-R incompatibility using emotional facial
expressions to emotional, but non-face stimuli [25]. This task was
adapted from the AX Continuous Performance Task (AX-CPT), which
has been repeatedly established as a robust probe of context
processing, cognitive conflict, and cognitive control [13,26,27,28].
The emotional AX-CPT requires participants to respond to
emotionally evocative cue-probe combinations with emotionally
congruent or incongruent facial expressions. This task was
developed on the rationale that interference elicited by a mismatch
between evoked emotion and required facial response may more
closely approximate situations of emotional conflict that people
experience in ‘real-life’ (e.g., acting pleasant to a rude customer;
smiling graciously after a defeat), thus achieving a higher level of
ecological validity. In prior work using facial electromyography
(EMG) to index expression responses in this task, we demonstrated
that behavioural interference can be robustly elicited, and
furthermore, that such interference was greater when emotional
influences were present relative to when they were absent [25].
In the AX-CPT, conflict and cognitive control are varied on a
trial-by-trial basis through the use of contextual pre-cues. Certain
cue-probe combinations require a target response (e.g., ‘A’
followed by ‘X’), whereas all other cue-probe combinations
require a non-target response. The target (‘AX’) combination
occurs with high frequency, which leads to high levels of
interference in two low-frequency cue-probe combinations: AY
(target cue, non-target probe) and BX (non-target cue, target
probe). In AY trials, interference arises from expectancy
established by the target cue, while in BX trials interference arises
via a dominant target response bias to the probe. In both trial
combinations, target-related response biases produce stimulus-
response interference because a non-target response is required. In
the emotional AX-CPT we developed, text instructions (‘SMILE’
and ‘FROWN’) were used as cues and emotionally evocative
pictures (from the International Affective Picture System
[IAPS];[29] served as probes; participants were required to smile
or frown in response. The target cue-probe-response combination
was always emotionally congruent (i.e., smiling to ‘SMILE’+plea-
sant picture, or frowning to ‘FROWN’+unpleasant picture). BX
trials (non-target cue, target probe) involved incompatibility
between the probe presented and the required facial response
(e.g., smiling to an unpleasant picture); in contrast, interference in
AY trials (target cue, non-target probe) was due to incompatibility
between the instructions of the cue and the required facial
response (e.g., frowning after ‘SMILE’ cue). When contrasting
performance in the emotion AX-CPT relative to a tightly matched
non-emotional condition (in which probes were emotionally
neutral), utilizing EMG measures to quantify the facial expression
response, we observed that interference effects were present under
both emotional and non-emotional conditions, but were strongest
in the emotional AX-CPT, when both emotional and non-
emotional sources of incompatibility were present [25]. In this
condition, interference was due not only to standard sources of S-
R incompatibility, but also because of the automatic, but
inappropriate affective response to the target (e.g. being cued to
smile to a negative IAPS picture).
This paradigm is unique among present tasks probing emotional
conflict, in that it requires integrated processing of both cue and
probe in order to perform successfully, as opposed to requiring
inhibition of the emotional information. Additionally, a major
strength of the paradigm is the ability to create a closely matched
analog task that permits a direct comparison of emotional vs. non-
emotional conflict. Specifically, by changing probe stimuli to be
affectively neutral (i.e., arbitrary symbol categories instead of
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emotionally evocative pictures), but retaining the other aspects of
the task structure (including using facial expressions as response
modality), sources of S-R incompatibility in the affective
dimension are eliminated, while the standard non-affective S-R
association effects driving AX-CPT effects remain (i.e., probe-
driven biases and cue-driven expectancies). By comparing effects
in the two conditions, it is possible to isolate the additive conflict
effects specifically associated with S-R incompatibility in the
affective dimension.
The present study builds on our previous behavioural work by
using event-related fMRI to examine whether brain activity
associated with processing emotional vs. non-emotional conflict
involves the same general control-related regions or qualitatively
different neural circuits. Such a comparison may help to clarify
further some of the outstanding contradictions present in previous
emotion conflict research. On the basis of previous neuroimaging
evidence, we hypothesized that both emotional and non-emotional
versions of this task would engage common control-related regions
including the dorsal ACC and lateral PFC. Further, based on our
previous behavioural evidence, we predicted that conflict-related
interference would be greater in the emotional task than in the
non-emotional task, and that this would be reflected in increased
levels of elicited activity within these control-related brain regions.
Finally, we tested whether the emotional task was associated with
the activation of potentially affectively-specialized regions, such as
the rostral ACC/ventromedial PFC and amygdala, that might be
selectively recruited to detect emotional conflict.
Ethics Statement
Ethics approval to conduct this study was granted by the
Institutional Review Board of Washington University. Each
participant provided written, informed consent prior to participa-
tion, in accordance with the human subjects guidelines established
by Washington University.
Twenty-four healthy young adults (8 males, 16 females; mean
age = 25.5 years, SD = 5.63) were scanned using fMRI while
participating in the task. All fMRI participants were right-handed,
native English speakers, and screened to ensure no neurological or
psychiatric disorders, psychotropic medications, or other factors
were present that contraindicated fMRI.
Task Procedure
Participants performed an emotional (Emotion condition) and
non-emotional (Neutral condition) variant of the AX-CPT. The
AX-CPT paradigm follows a cue-probe trial structure, in which
cue stimuli set a context that is needed for appropriate response
selection to the subsequent probe. The Emotion and Neutral
conditions were identical in all respects except for the category of
stimuli used as probes. Cue stimuli in the task were the words
‘SMILE’ and ‘FROWN’. For probes, the Emotion condition used
IAPS pictures as probes and the Neutral condition used
alphanumeric symbols (i.e., letters served as target probes, and
digits served as nontarget probes). New pictures/symbols were
used as probes on each trial, except for a pre-specified neutral
picture/punctuation mark on no-go trials (described below).
Across participants the particular cue-probe combination that
comprised the ‘‘AX’’ target trial type was counter-balanced. Thus,
for approximately half of the participants (11/24) the AX target
was ‘SMILE’/positive picture (‘‘SMILE’’/letter in Neutral)
requiring a smile response (facial expression) and the other half
(13/24) the AX target was ‘FROWN/negative picture
(‘‘FROWN’’/letter in Neutral) requiring a frown response.
However, on nontarget trials (AY, BX, BY), the opposite facial
expression was required. All other details of the task paradigms
described below were identical for the Emotion and Neutral
conditions, and for both participant groups.
Trials were presented in pseudorandom sequence, with target
(AX) trials occurring at a 7:1 frequency compared to all non-target
task trials, leading to a total of 84 AX trials, 12 AY trials (target
cue, non-target probe), 12 BX trials (non-target cue, target probe),
12 BY trials (non-target cue, non-target probe). Although the
absolute numbers of high conflict (BX and AY) trials is somewhat
low, our prior results suggest that this number was sufficient to
robustly detect significant interference effects. In addition to
primary task trials, no-go trials were also included to ensure that
participants responded on the basis of the cue-probe combination
and not solely and prematurely to the cue. No-go trials were
indicated by a pre-specified neutral picture in Emotion (punctu-
ation mark in Neutral), to which no response was to be made (24
no-go trials total; occurring both after target and non-target cues).
Participants performed four scanning runs each of the Emotion
and Neutral conditions of the AX-CPT (eight runs in total). Within
each run, task blocks (three per run; 135 seconds each) alternated
with short fixation blocks (four per run; 30 seconds each). Each
scanning run began with 10 seconds of rest (later discarded) to
allow the scanner to reach steady state; total run duration was
,9 minutes. Each of the three task blocks within a scanning run
consisted of 12 trials; thus participants performed eight runs of 36
AX-CPT trials each for 288 trials in total (144 Emotion, 144
Neutral). AX-CPT trials consisted of cue-probe pairs shown in
sequence. Trial structure (Figure 1) was as follows: cue (750 ms),
inter-stimulus-interval (ISI; 3250 ms), probe (2500 ms), and
minimum inter-trial-interval (ITI) of 1000 ms (for a minimum
total trial length of 7.5 seconds). ITIs included additional jittering
to facilitate event-related response estimation, in increments of
2500 ms (no jitter, 2500 ms, 5000 ms, or 7500 ms). 72 trials were
presented at each of the four ITI lengths.
fMRI Data Collection
Structural and functional imaging data was collected on a 3T
Siemens TIM Trio whole-body scanner at Mallinckrodt Institute
of Radiology at Washington University School of Medicine. High-
resolution anatomical images were acquired for each participant
using a sagittal T1-weighted MP-RAGE sequence (TE = 3.16 ms,
TR = 2400 ms, flip angle = 8u 176 slices, 16161 mm voxels).
Anatomical images were aligned with each individual’s functional
images. To facilitate registration of the T1 and functional scans, a
T2-weighted image was also acquired in the same space as the
functional scans [TE = 96 ms, TR = 5000 ms, 1896256 acquisi-
tion matrix, 48 slices, 1.026163 mm voxels]. The functional
images were collected in eight 210TR (,9 minutes) runs using an
asymmetric spin-echo echo-planar sequence sensitive to blood
oxygenation level-dependent (BOLD) contrast (T2*) [TE = 27 ms,
TR = 2500 ms, flip angle = 90u, FOV = 256 mm, skip = 0 mm, 36
slices, 46464 mm voxels].
Stimuli were presented using E-Prime (Psychology Software
Tools, Pittsburgh, PA) on a Dell PC. As described in the Task
Procedure section, participants responded to each trial using
emotional facial expressions. A custom-built mirror apparatus
positioned over the head coil served both to reflect the projected
image of the task screen towards the participant and to reflect the
view of the participant’s face such that it could be recorded using a
videocamera positioned at the head end of the bore. Video
recording served to ensure participant compliance in the task and
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Page 3
was visually inspected to verify that such compliance was
occurring. However, due to technical difficulties and poor video
quality, this video was not quantitatively evaluated for measures of
behavioural performance. A fiber-optic button box interfaced with
E-Prime facilitated communication with the participant.
fMRI Data Analysis
The fMRI data were analyzed with in-house software. Data
analysis was conducted with a general linear model (GLM),
including nuisance regressors for linear trends within runs and
baseline shifts between runs. Additionally, the GLM contained
task-related regressors for block and event-related activity. Block-
related activity related to each task condition (Emotion and
Neutral) were modeled as boxcar functions, but because
examining sustained activity did not permit the examination of
conflict effects in the data, these functions were also treated as
regressors of no interest. Our experimental design follows the
specifications of Visscher et al. [30] in permitting the dissociation
of block and event-related fMRI activity (using alternating blocks
of task and rest, as well as jittered trials within each task block);
using event-related regressors that are estimated (using delta or
FIR functions) rather than assumed via a model of the
hemodynamic response function. With this estimation approach,
multicollinearity between the sustained and event-related regres-
sors has been shown not to be a major concern.
The primary task-related analysis focused on event-related
activity as a function of trial type and task condition. Event-related
estimates were created for each trial type within task conditions
(AX, AY, BX, BY, no-go within Emotion and Neutral task
versions). Given the complex trial structure, event-related effects
were analyzed without reference to a fixed hemodynamic response
function, using a delta-function estimation approach. Thus, within
a 25-second response epoch following trial onset, independent
values were estimated for each of 10 timepoints (corresponding to
the 10 TR frames). The estimates from the individual subject
GLMs were analyzed using appropriately designed analyses of
variance (ANOVAs) that treated participants as a random factor.
Regions of interest identification. We examined event-
related brain activity in analyses within a priori defined regions of
interest (ROIs). Analyses were conducted within two ‘networks’ of
interest (selected not on the basis of functional connectivity but as
coherent sets of regions observed in prior literature to be
functionally related to cognitive control and reward processing).
The first analysis examined activity within regions associated with
cognitive control and working memory (established using meta-
analyses; primarily including dorsal medial and lateral prefrontal
and parietal regions [8,9]. The ROI mask for the cognitive control
network (CCN) was created by using anatomical coordinates
identified by the aforementioned meta-analyses as seed points with
10 mm radius spheres drawn around them. The second analysis
examined activity within anatomical regions associated with
emotion and reward processing (hereafter EMO network)
including the amygdala, portions of the basal ganglia (putamen,
caudate, substantia nigra and nucleus accumbens), anterior insula,
medial orbitofrontal cortex, and ventromedial prefrontal cortex,
with regions drawn according to anatomical criteria identified
using the Talaraich atlas [31], and previous studies
[32,33,34,35,36,37,38,39,40]. A separate region of interest
included the rostral ACC, defined anatomically, which was near
to, but not overlapping the ventromedial PFC ROI [41]. For
coordinates for ROIs in both networks, please refer to Table S1
and Table S2. The exact masks for both networks are available
from the authors by request.
Significant activity within each network mask was corrected for
multiple comparisons using a cluster size criterion based on Monte
Carlo simulations [42,43], via the AlphaSim software within AFNI
[44]. To assure a multiple comparisons corrected p,.05 criteria,
significant regions were identified based on a per-voxel minimum
z.2.32 and minimum cluster size of 37 voxels within the CCN
mask (or 30 voxels within the EMO mask).
Within each mask, we were interested in identifying regions
demonstrating general sensitivity to conflict (e.g., across both the
emotional and non-emotional tasks) and then examining whether
brain activity within these conflict-associated regions differed as a
function of emotional task content. Thus, the first stage analysis
consisted of the following voxelwise contrast: high conflict trials (AY +
BX collapsed, averaged across timepoints 4–7) . low conflict trials
(AX + BY collapsed, averaged across timepoints 4–7). This analysis
further collapsed across the Emotion and Neutral conditions, in order
to enable unbiased identification of regions. Timepoints 4–7 were
selected to capture probe-related activity, which is necessary for the
elicitation of conflict in the AX-CPT paradigm.
In the second stage of analysis, we conducted ROI-based
ANOVAs on significant regions identified as sensitive to conflict in
Figure 1. Trial structure with timing. (A) Example of the target (AX) cue-probe-response for the smile-AX condition of the Emotion AX-CPT; (B)
Example of BX (non-target cue, target probe) and (C) AY (target cue, non-target probe) conflict trials for smile-AX condition of the task.
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the first-stage analysis. Two different kinds of region-wise analyses
were carried out. In the first ANOVA, we examined which, if any,
of these conflict-defined regions showed independent differences in
brain activity as a function of task condition, i.e., Emotion vs.
Neutral, and time (the ANOVA included all 10 timepoints). This
analysis enabled a direct test of whether conflict-related regions
showed increased responsivity under emotion conditions. In the
second ANOVA, we only included the high-conflict trials AY and
BX, to examine whether task condition effects were still exhibited
selectively during conflict. Additionally, by including trial-type as a
factor, we tested whether condition effects differed by the type of
conflict elicited (AY = cue-based; BX = probe-based; again, time-
point was also included as a factor in the ANOVA).
In addition to analyses within these networks of interest, we
conducted more focused analyses within the rostral ACC and
amygdala ROIs, as these regions have been specifically implicated
in emotional conflict processing [16,45]. The amygdala was part of
the general EMO mask, but the additional analyses focused
exclusively on amygdala and rACC regions, and as such utilized a
more liberal corrected threshold specific to the size of each ROI
(i.e., small-volume correction). Thus, for these analyses a reduced
cluster-size criterion of 12 voxels for rostral ACC and 9 voxels for
amygdala was employed (again with voxelwise minimum z.2.32).
In addition to the analyses described above, we also conducted a
focused test with the rACC and amygdala ROIs to examine
whether these regions show a selective response to conflict only
under Emotion conditions. As such, a voxelwise contrast of high
conflict (AY + BX, timepoints 4–7) . low conflict (AX + BY,
timepoints 4–7) was conducted, but only using trials from the
Emotion condition.
Behavioural Performance
As described in Methods, participants performed the emotional
AX-CPT with voluntary emotional facial expressions as the
response modality. Facial expressions were monitored in the
scanner using video recording and video footage was inspected
following each participant to ensure compliance with the task, but
poor video quality and technical difficulties rendered this video
unusable for the purposes of evaluating behavioural performance.
Previously published data from our laboratory [25] investigating
the Emotion and Neutral versions of the AX-CPT used here found
no significant main effects of task condition on performance
(indexed by error rates and response onsets), suggesting that the
overall difficulty of emotional and non-emotional versions of the
task may be comparable. Additionally, that study indexed
performance using facial electromyography (EMG), which enables
a much more fine-grained behavioural analysis than video coding
would have permitted in the present study. We discuss issues with
the present study’s behavioural data and present behaviour from
our previous EMG study in Text S1 and Figure S1. We compared
areas defined by task conflict (high . low conflict) within the CCN
and EMO networks with and without discernable errors, and found
relatively few differences. These results are shown in Table S3.
Imaging Results: ROI Analyses
As described in the Methods section, event-related brain activity
was examined within two ‘networks’ of interest: the cognitive
control network (CCN) and the emotion/reward processing
network (EMO). We also analyzed brain activity within more
focused ROIs of the rostral ACC and bilateral amygdala.
Conflict-defined regions within CCN and EMO
Within each ROI, we identified regions showing
conflict-related increases in activity through the high-conflict .
low-conflict contrast, collapsing across Emotion and Neutral
conditions to provide an unbiased test. Fourteen regions within
the CCN, as well as five regions within the EMO network, were
identified as showing conflict responses. These conflict-defined
regions are summarized in Table 1, with cortical regions shown in
Figure 2. As expected, conflict-related regions within the CCN
included the dorsal ACC and bilateral PFC, along with additional
activation in the inferior parietal lobule, precuneus, thalamus, and
cerebellum. The EMO regions showing sensitivity to conflict
included bilateral dopaminergic midbrain, bilateral anterior
insula, and left putamen. However, in this contrast, conflict-
related activation was not observed in ventromedial PFC or
Condition-related effects within the high versus low
conflict contrast.
In the next stage of analysis, each of these
conflict-defined ROIs was subjected to an ANOVA that tested for
effects of condition type, using timepoint as an additional factor to
define event-related effects (i.e., in terms of a condition 6 time
interaction). Nine ROIs showed such condition 6 time effects
these areas are marked in a column in Table 1. The areas showing
sensitivity to both conflict and emotional task content included,
most prominently, the dorsal ACC, right dorsolateral PFC, and
bilateral posterior PFC, near the inferior frontal junction. The
examination of timecourses in these nine regions revealed that, in
all of them, the condition 6 time interaction was due to Emotion
. Neutral activation, especially in the middle timepoints where
activity peaked (approximately timepoints 4–7). The timecourse of
the effect within the dorsal ACC is shown in Figure 3, as a
representative illustration of this pattern. In this and the other
regions, the effects of condition did not interact with conflict, but
instead were present as an additive increase in activation. In only
one region, the right dopaminergic (DA) midbrain, was there
evidence of a condition*conflict interaction (at trend-level,
p = .057). However, this interaction was due to increased activity
in both the high and low conflict trials of the Emotion condition
(i.e., with a reduced conflict-related increase), compared to the
Neutral condition.
Emotion and trial-type effects under high
Because the ANOVA described above showed
Emotion effects that did not interact with conflict, we conducted
a follow-up ANOVA to address two additional questions: 1) Was
the Emotion-related increase in activation present even when only
considering high-conflict trials (i.e., AY and BX)? 2) Were there
any differential effects of Emotion related to the type of conflict
experienced, i.e., cue-based (AY trials) versus probe-based (BX
trials)? To address these questions, the second ANOVA included
only the high-conflict trial types (AY, BX) and excluded the low-
conflict trials (AX,BY), to examine potential effects of condition
(Emotion, Neutral) and high-conflict trial-type (AY,BX) as primary
factors of interest (additional factors again included timepoint, and
target expression).
The primary pattern observed in the first ANOVA, a condition
6 time interaction, was replicated in the second ANOVA. Eight
regions showed this effect, denoted in Table 1; again, these
included dorsal ACC, right dorsolateral PFC, and bilateral PFC
regions. Importantly, the same Emotion . Neutral pattern was
observed in these regions, confirming that high emotion-conflict
trials increased activation of the cognitive control system relative to
non-emotion conflict conditions.
A second pattern that was observed in the ANOVA was a trial-
type 6 time interaction, which was significant in 11 ROIs. In all of
these regions, the pattern was due to increased activation on BX
trials relative to AY, during the early part of the trial (timepoints
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2–5), but then comparable activation later in the trial (timepoints
6–10). Figure 4 demonstrates this timecourse pattern in an
example region, the right lateral PFC. Although a BX . AY
pattern is consistent with conflict being increased under probe-
based conditions, the early, rather than late timecourse of the
effect suggests that the trial-type effect might be anticipatory or
expectancy-related. Note that the expectancy for high conflict is
significantly greater following a B-cue (probability BX | B-
cue,0.4) than following an A-cue (probability AY | A-cue,0.1).
Thus, differential conflict anticipation or expectancy may account
for the trial-type effects, rather than a differential response to
experienced conflict during probe processing. Similar conflict
expectancy effects have been observed in prior studies of the AX-
CPT [46,47] and other conflict paradigms [48].
Although effects of condition and trial-type were present, the
two factors did not appear to interact, as no regions showed
evidence of condition 6 trial-type or condition 6 trial-type 6 time
interactions. Thus, the BX . AY pattern did not differ
significantly between Emotion & Neutral conditions.
Focused analysis of rostral ACC and amygdala activity:
conflict and condition effects.
As done previously within the
CCN and EMO masks, we computed contrasts (high . low
conflict) within the rostral ACC and amygdala ROIs. However, to
test whether these regions were particularly sensitive to emotion
conflict per se, we conducted a follow-up ANOVA using a high .
low conflict contrast, but restricting to the Emotion condition only.
No voxels within the rostral ACC or amygdala survived this
contrast, contrary to evidence from previous studies suggesting
their sensitivity to emotional conflict.
As a final test to ensure that we did not produce any false
negatives, we tested the high . low conflict contrast, using all the
data (Emotion and Neutral), but with lowered statistical thresholds,
utilizing a small-volume correction for each region individually.
Even with these more liberal thresholds, no rostral ACC clusters
were observed; however, a small voxel cluster within the left
amygdala was identified (see Table 1). Within this conflict-sensitive
left amygdala region, there was a significant effect of task condition
in the full ANOVA (i.e., involving conflict, condition and timepoint
as factors; see Figure 3). This interaction was due to a similar pattern
of activity to that observed in several other regions within the CCN
and EMO networks (i.e., Emotion . Neutral activity). Similarly, as
with these other regions, no condition*conflict interaction was
observed. Indeed, if anything, the high . low conflict effect was
weaker in the Emotion condition relative to Neutral (Figure 3),
consistent with the absence of a significant conflict effect in this
region when only the Emotion condition was examined. Addition-
ally, in this left amygdala region, no effects of trial type were
observed in the ANOVA contrasting AY and BX trials. Together,
these results confirm that the rostral ACC and amygdala did not
show any selective emotion conflict effects, and the small left
amygdala region that was identified showed a pattern of activation
that was very similar to other regions within cognitive control
network, i.e., sensitivity to both to the presence of task conflict and
to emotional processing, but no preferential response to emotional
conflict (e.g., these factors did not interact with one another).
With the present study, we examined neural activity associated
with emotional versus non-emotional conflict using a novel
paradigm: the emotional AX-CPT. This paradigm capitalized
on the use of controlled facial expressions as a response modality to
generate S-R incompatibility that was either emotional or non-
emotional in nature. The examination of brain activity associated
with the processing of these two forms of S-R incompatibility helps
clarify the extent to which emotional conflict relies on neural
circuitry common to that associated with more traditionally
studied forms of cognitive conflict. Specifically, the current
findings suggest that both emotional and non-emotional conflict
commonly engage a number of brain regions associated with
cognitive control, including the dorsal ACC and lateral PFC, as
well as certain areas implicated in both emotional processing and
cognitive control, such as bilateral anterior insula. Additionally,
most of these common regions demonstrated higher activity when
Figure 2. Cortical areas sensitive to the High
Low conflict contrast. These areas fall within the CCN and REW masks and were identified as
showing significant (AY + BX) . (AX + BY) activation, collapsed across Emotion and Neutral conditions.
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processing emotional (versus non-emotional) conflict; in contrast,
we observed no conflict-sensitive regions where the non-emotional
task elicited greater activity than the emotional task.
Our findings are in line with several other studies examining the
neural basis of emotional versus non-emotional conflict. Processing
of both kinds of conflict may rely on cognitive control-related
brain areas [17,49]. In particular, mechanisms underlying both
emotional and non-emotional conflict detection have been
localized to the dorsal ACC [15,16,50]. However, the present
results are inconsistent with the older hypothesis that rostral and
dorsal subdivisions of the ACC are devoted to processing
emotional and cognitive conflict, respectively [45]. In particular,
although we observed robust conflict-related activation in the
dorsal ACC in both Emotion and Neutral conditions, no such
patterns were observed in the rostral ACC, even when focusing
exclusively on Emotion conflict.
The absence of emotion-specific conflict regions in the ACC
during task processing may be surprising from the perspective of
classic theoretical distinctions, but is actually relatively consistent
with the prior literature. As discussed previously, original variants of
the emotion Stroop actually target emotional distraction or even
non-affective variables, and as such may not be appropriate for the
study of emotional conflict, as suggested by recent conceptual
analyses [14]. More recent studies that utilize conflict-based variants
of the emotional Stroop and related tasks have been equivocal as to
whether rostral ACC is either engaged, or associated with the
detection (rather than resolution) of emotional conflict [15,16].
Additionally, in one recent study rostral ACC activity during the
emotion-conflict Stroop was dependent on the trait anxiety level of
participants [23]. Thus, the current study adds to prior literature in
suggesting that caution is warranted regarding whether the rostral
ACC should in fact be associated with emotion conflict processing
per se. Instead, further investigation of this region is needed, that
focus on examining potential alternative accounts such as emotional
distraction, conflict resolution, and individual trait anxiety.
In contrast to the pattern in the rostral ACC, there were
significant effects of emotion on activation in a number of regions
associated with cognitive control functions, including the dorsal
ACC and lateral PFC. Interestingly, these effects were observed as
significant condition (Emotion . Neutral) and conflict (Conflict .
No Conflict) effects, without a significant condition 6 conflict
interaction. In other words, the emotion effects were additive to
conflict, rather than interactive, which suggests two independent
mechanisms. At first glance, this pattern seems somewhat counter-
intuitive, since the presence of affectively-valenced content did not
selectively modulate the magnitude of the conflict effect, but
instead increased activation equivalently on both high and low-
conflict trials. Nevertheless, the pattern may actually be fairly
consistent with interpretations regarding the nature of emotional
conflict and control.
Table 1. Activity in areas defined by task conflict (high.low conflict) within anatomically defined ROIs.
Cluster Size
) ROI Z BA Area
Sig. Condition*
Time effect in
High vs. Low
Conflict Contrast
Sig. Condition*
Time effect
in AY vs. BX
Trial Contrast
Sig. Condition*
Time effect in
AY vs. BX Trial
0, 11, 48 7722 CCN 3.63 32 Dorsal ACC * **
41, 28, 35 1512 CCN 2.88 9 R DLPFC * * *
244, 8, 33 5589 CCN 3.48 9 L IFJ * **
45, 5, 32 2673 CCN 2.93 9 R IFJ * * *
249, 13, 3 2457 CCN 3.20 47 L IFG *
28, 0, 54 7155 CCN 4.15 8 R superior
frontal (FEF)
* *
228, 21, 55 7938 CCN 3.83 8 L superior
frontal (FEF)
18, 260, 43 23031 CCN 4.83 7 R precuneus *
237, 252, 40 6534 CCN 4.24 40 L IPL * *
10, 212, 4 3915 CCN 3.88 ---- R thalamus *
29, 211, 6 1215 CCN 2.89 ---- L thalamus *
231, 267, 245 2052 CCN 3.08 ---- L cerebel lum
32, 260, 244 1215 CCN 3.07 ---- R cerebel lum
33, 262, 226 999 CCN 4.27 ---- R cerebellum * * *
39, 20, 0 3996 EMO 4.83 47/13 R anterior insula *
236, 17, 0 3051 EMO 4.02 47/13 L anterior insula * *
216, 5, 22 1161 EMO 3.36 ---- L putamen * *
8, 217, 210 1026 EMO 3.12 ---- R DA midbrain
26, 218, 210 1242 EMO 3.35 ---- L DA midbrain
216, 21, 211 324 EMO 2.84 ---- L amygdala * *
Significant effects of interest within these areas (condition*time interactions within high vs. low conflict contrast and AY vs. BX trials contrast; trial*time interactions
within AY vs. BX trials contrast) are marked by asterisks in their respect ive columns.
Abbreviations: ROI = region of interest; CCN = cognitive control network; EMO = emotion/reward network; BA = Brodmann area; IFG = inferior frontal gyr us; IFJ = inferior
frontal junction; DLPFC = dorsolateral prefrontal cortex; ACC = anterior cingulate cortex; IPL = inferior parietal lobule; DA = dopaminergic.; FEF = frontal eye fields.
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Figure 3. Timecourses illustrating High
Low Conflict and Emotion
Neutral effects. Representative regions demonstrating both a high .
low conflict and Emotion . Neutral pattern (due to a condition*time interaction), but no conflict* condition interaction: (A) dorsal ACC; (B) left amygdala.
Figure 4. Timecourse illustrating BX
AY trial-type effect. Representative region in right lateral PFC exhibiting BX . AY activity early, and
comparable levels of activity in both trial types later in the timecourse.
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In particula r, a key feature of the Emotional AX-CPT i s that
in the Emotion condition, there shoul d be a relatively automatic,
but task-irrelevant, subjective emotional reaction to t he affective
con tent present in the probe. This emotional reaction is task-
irrelevant because correct respons e selection requ ires consider-
ati on only o f the cognitive classification of the probe as having
positive or neg ative content (and in integrating thi s information
with cue classi fication). Indeed, the subjective emot ional response
to the probe, which may automatically trigger a tendency to
activate the associated facial expression, can lead to an addition al
source of res ponse uncertainty. For exampl e, if viewing a
negatively valenced probe stimulus triggers a tendency to make
a frown expression (or likewis e, if viewing a positively valenced
probe stimulus triggers a tendency to smile), confusion can be
generated r egarding whethe r this ‘‘expression tendency’ is
app ropriate for the current trial (i.e., correc t on AX but incorrect
on BX trials). Under such circumstances, from a cognitive
con trol perspective, the optimal task strategy would be to
suppress any subjective emotional responses that might b e
experienced in order to reduce response uncerta inty. Because
suc h task-irrelevant emotional response tendencies can occur on
all trials in the E motion condition, there would be generally
hig her cognitiv e contro l dem ands in this condition relativ e to
In addition to the additive effects of emotion and conflict
observed in regions associated with cognitive control, this same
pattern was also present in the left amygdala, at least under an
adjusted statistical threshold. The amygdala has typically been
thought of as an emotion processing region whose activity, in
conflict, distraction, and regulation paradigms, will reflect the
emotional valence of stimuli, rather than tracking cognitive control
demands [16,51,52]. However, prior findings of amygdala activity
associated with increased cognitive control have also been
repeatedly observed, although they typically receive less attention
in the literature. For example, in one study increased amygdala
activation was associated with improved behavioral performance
during working memory, selectively under high-load conditions
[53]. This finding, and others [54,55,56], supports alternative
theoretical views of amygdala function, in which this regions is
postulated to mediate general vigilance/goal-relevance-detection
processes that contribute to enhanced cognitive performance as
well as processing of emotional demands [57,58]. The pattern of
left amygdala activation in the present task associated with both
emotion and conflict-processing might be better characterized by
such an explanation, especially considering that emotional
information must be evaluated for valence, while at the same
time suppressing subjective emotional responses, in order to
optimally perform the task.
Beyond the main effects of condition and conflict, a number of
regions also exhibited distinct patterns of activity as a function of
the type of interference presen t. As in the original AX-CPT, the
emotional AX-CPT involves non-target trials eliciting conf lict via
two different forms of in terference: AY trials, where interference
is cue-based and relatively top-down in nature, and BX trials,
where interference is probe-based and relatively bottom-up in
nature. A number of frontal and parietal regions associa ted with
cognitive control de monstrated significant trial effects in the
present study, primarily because of BX . AY activity early in the
trial (with comparable activity levels late in the trial). Previous
studies of the AX-CPT have observed similar patterns of
activation within the lateral PFC and other regions, demonstrat-
ing the robustness of the effect [46,47]. The pattern of activity is
typically interpreted as reflecting the higher degree of interf er-
ence expectan cy associated with B-cues (i.e., associated with non-
target responses) relative to A-cues (i.e., associated with target
responses) , and thus increased demands for proactive cognitive
control [28]. The current study extends this finding by
demonstrating that this interference expectancy effects can be
exhibited during emotional as well as non-emotional AX-CPT
conditions. As such, the current results support the general notion
that participants utili ze the same types of proactive control
strategies even when experiencing high demands for such control
as a result of emotional conflict.
The emotional AX-CPT paradigm presented in the present
study, and the use of emotional facial expressions as a response
modality more generally, have the potential to provide a more
naturalistic technique from which to probe emotional conflict,
relative to the previous laboratory paradigms that have been used.
Facial expressions have direct, automatic associations with
different emotional experiences [59]; thus, they potentially provide
a performance measure that is a more sensitive index of both trial-
by-trial fluctuations and individual differences in emotional
processing. In the present study we were not able to obtain
behavioural performance measures due to technical difficulties,
but future studies capitalizing on this technique should explore this
possibility (e.g., via simultaneous EMG and fMRI recordings).
Additionally, using facial expressions as responses permits
elicitation of conflict via S-R interference, which is a robust form
of interference that has nevertheless been understudied (relative to
S-S interference) in the domain of emotion. The utilization of
facial expressions as a response modality provides a potential
means to probe emotional conflict via S-R interference in other
paradigms as well, such as the Stroop adaptations utilized by
Egner and colleagues [16,22]. For example, in Stroop conditions
that require participants to make facial expressions to semantically
associated words (e.g., ‘‘smile’’, ‘‘frown’’) while ignoring irrelevant
but superimposed affectively-valenced pictures, it would be
possible to manipulate congruency in an analogous manner to
that examined here.
One of the advantages of developing adaptations of the Stroop
and related paradigms (e.g., Flankers, Simon) that include facial
expressions as a response modality is that it would permit
exploration of experimental manipulations not easily implemented
in the AX-CPT. In particular, conflict-related shifts in control state
(e.g., conflict adaptation or resolution effects) have been profitably
examined through manipulation and examination of trial-by-trial
sequential effects [60], changes in relative trial frequencies [61],
and other similar effects. As a means of eliciting emotional conflict
in a naturalistic, ecologically valid manner, the S-R incompatibil-
ity elicited through facial expression-based responding has the
potential to be exploited in a similar variety of experimental
manipulations, contributing to our knowledge of the behavioural
and neural mechanisms underlying emotional conflict processing.
It is our hope that this technique may provide one direction by
which investigations of emotional conflict may approach the rigor
and sophistication of similar research within the more traditional
realm of cognitive control.
Supporting Information
Figure S1 (a) Error rates and (b) response onset times measured via
EMG in the Emotion AX-CPT, from Chiew & Braver (2010), as a
function of Condition (Emotion vs. Neutral) and Conflict (high vs. low).
Table S1 Centres of mass for cognitive control network (CCN)
regions of interest (ROIs) used to mask the neuroimaging data.
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Table S2 Coordinates for hand-drawn emotion/reward-related
(EMO) regions of interest (ROIs) used to mask the neuroimaging
Table S3 Activity in areas defined by task conflict (high . low
conflict) within anatomically defined ROIs with discernable errors
eliminated, and comparable areas with all trials included (from
Table 1).
Text S1
Author Contributions
Conceived and designed the experiments: KSC TSB. Performed the
experiments: KSC. Analyzed the data: KSC TSB. Wrote the paper: KSC
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Neural Circuitry of Emotional & Cognitive Conflict
PLoS ONE | 11 March 2011 | Volume 6 | Issue 3 | e17635
Page 11
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    • "The anterior cingulate cortex has an evaluative function that monitors for current control demands and allows for appropriate , context-sensitive control adjustments (Botvinick et al., 2004). So far, studies of healthy people have found evidence for activation of both dorsolateral prefrontal and anterior cingulate cortex when processing conflicting emotion cues (Haas et al., 2006; Wittfoth et al., 2010; Zaki et al., 2010; Chiew and Braver, 2011; Kanske and Kotz, 2011a, b). "
    [Show abstract] [Hide abstract] ABSTRACT: Our ability to make sense of emotional cues is of paramount importance for understanding state of mind and communicative intent. However, emotional cues often conflict with each other; this presents a significant challenge for people with schizophrenia. We conducted a theoretical review to determine the extent and types of impaired processing of emotion-related conflict in schizophrenia; we evaluated the relationship with medication and symptoms, and considered possible mediatory mechanisms. The literature established that people with schizophrenia demonstrated impaired function: (i) when passively exposed to emotion cues whilst performing an unrelated task, (ii) when selectively attending to one source of emotion cues whilst trying to ignore interference from another source, and (iii) when trying to resolve conflicting emotion cues and judge meta-communicative intent. These deficits showed associations with both negative and positive symptoms. There was limited evidence for antipsychotic medications attenuating impaired emotion perception when there are conflicting cues, with further direct research needed. Impaired attentional control and context processing may underlie some of the observed impairments. Neuroanatomical correlates are likely to involve interhemispheric transfer via the corpus callosum, limbic regions such as the amygdala, and possibly dorsolateral prefrontal and anterior cingulate cortex through their role in conflict processing.
    Full-text · Article · Aug 2014 · Psychiatry Research
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    • "Moreover, the current N2 activation was mainly distributed over the frontal and central areas, which suggested that neural function of monitoring processing on affect conflicts might be also relied on the frontal lobe, especially the ACC [1,2,4,23]. Chiew and Braver [24] adopted an emotional AX Continuous Performance Task (AX-CPT) to investigate the neural circuitry of emotional conflict control processing, in which the cue stimuli ( " A " ) offered a context for appropriate response selection to the subsequent probe ( " X " ), and it was reported that ACC and lateral prefrontal cortex (PFC) were activated during the affective conflict control processing. "
    [Show abstract] [Hide abstract] ABSTRACT: Conflict control is an important cognitive control ability and it is also crucial for human beings to execute conflict control on affective information. To address the neural correlates of cognitive control on affective conflicts, the present study recorded event-related potentials (ERPs) during a revised Eriksen Flanker Task. Participants were required to indicate the valence of the central target expression while ignoring the flanker expressions in the affective congruent condition, affective incongruent condition and neutral condition (target expressions flanked by scramble blocks). Behavioral results manifested that participants exhibited faster response speed in identifying neutral target face when it was flanked by neutral distractors than by happy distractors. Electrophysiological results showed that happy target expression induced larger N2 amplitude when flanked by sad distractors than by happy distractors and scramble blocks during the conflict monitoring processing. During the attentional control processing, happy target expression induced faster P3 response when it was flanked by happy distractors than by sad distractors, and sad target expression evoked larger P3 amplitude when it was flanked by happy distractors comparing with sad distractors. Taken together, the current findings of temporal dynamic of brain activity during cognitive control on affective conflicts shed light on the essential relationship between cognitive control and affective information processing.
    Preview · Article · Jul 2013 · PLoS ONE
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    • "In brief, we found that the spontaneous occurrence (experiment 1) or induction (experiment 2) of autonomic arousal during free association led to subsequent memory failure and was associated with increased activation of the anterior cingulate cortex. In both experiments, activations were within the anterior dorsal ACC (adACC), which shows rich connectivity with limbic regions (i.e., amygdala, periaqueductal gray and hypothalamus) and plays a major role in emotional processing151617181922], although ACC activations in the second experiment were slightly more posterior and ventral as compared to the first experiment. These results are consistent with the hypothesis that free association of words reactivates internal conflicts, which generates autonomic arousal and impairs subsequent conscious memory access. "
    [Show abstract] [Hide abstract] ABSTRACT: The psychodynamic theory of repression suggests that experiences which are related to internal conflicts become unconscious. Previous attempts to investigate repression experimentally were based on voluntary, intentional suppression of stimulus material. Unconscious repression of conflict-related material is arguably due to different processes, but has never been studied with neuroimaging methods. We used functional magnetic resonance imaging (fMRI) in addition with skin conductance recordings during two free association paradigms to identify the neural mechanisms underlying forgetting of freely associated words according to repression theory. In the first experiment, free association to subsequently forgotten words was accompanied by increases in skin conductance responses (SCRs) and reaction times (RTs), indicating autonomic arousal, and by activation of the anterior cingulate cortex. These findings are consistent with the hypothesis that these associations were repressed because they elicited internal conflicts. To test this idea more directly, we conducted a second experiment in which participants freely associated to conflict-related sentences. Indeed, these associations were more likely to be forgotten than associations to not conflict-related sentences and were accompanied by increases in SCRs and RTs. Furthermore, we observed enhanced activation of the anterior cingulate cortex and deactivation of hippocampus and parahippocampal cortex during association to conflict-related sentences. These two experiments demonstrate that high autonomic arousal during free association predicts subsequent memory failure, accompanied by increased activation of conflict-related and deactivation of memory-related brain regions. These results are consistent with the hypothesis that during repression, explicit memory systems are down-regulated by the anterior cingulate cortex.
    Full-text · Article · Apr 2013 · PLoS ONE
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