Conflicts as aversive signals

Theories of human action control deal with the question of how cognitive control is dynamically adjusted to task demands. The conflict monitoring theory of anterior cingulate (ACC) function suggests that the ACC monitors for response conflicts in the ongoing processing stream thereby triggering the mobilization of cognitive control. Alternatively, the outcome evaluation account of ACC function suggests that the ACC monitors for negative performance outcomes, an information that serves as an aversive learning signal for future action selection. Botvinick (2007) recently suggested that both theories might converge on the detection of aversive signals in general. Here, the authors provide first evidence that conflicts are registered as aversive signals. Congruent and incongruent Stroop color-words served as primes, and positive and negative stimuli as targets in an affective priming paradigm. Negative targets were evaluated faster after incongruent than after congruent Stroop primes, and positive targets were evaluated slower after incongruent than after congruent primes. The finding that conflicts are actually registered as aversive signals bridges the gap between competing theories of ACC function and has broad theoretical and behavioral implications as it makes the conflict monitoring theory applicable to a much wider range of situations and tasks.     

Paying attention to emotion: an fMRI investigation of cognitive and emotional stroop tasks

In this research, we investigated the degree to which brain systems involved in ignoring emotionally salient information differ from those involved in ignoring nonemotional information. The design allowed examination of regional brain activity, using fMRI during color-word and emotional Stroop tasks. Twelve participants indicated the color of words while ignoring word meaning in conditions in which neutral words were contrasted to emotionally negative, emotionally positive, and incongruent color words. Dorsolateral frontal lobe activity was increased by both negative and incongruent color words, indicating a common system for maintaining an attentional set in the presence of salient distractors. In posterior regions of the brain, activity depended on the nature of the information to be ignored. Ignoring color-incongruent words increased left parietal activity and decreased parahippocampal gyrus activity, whereas ignoring negative emotional words increased bilateral occipito-temporal activity and decreased amygdala activity. The results indicate that emotion and attention are intimately related via a network of regions that monitor for salient information, maintain attention on the task, suppress irrelevant information, and select appropriate responses.     

Preattentive processing of audio-visual emotional signals

Previous research has shown that redundant information in faces and voices leads to faster emotional categorization compared to incongruent emotional information even when attending to only one modality. The aim of the present study was to test whether these crossmodal effects are predominantly due to a response conflict rather than interference at earlier, e.g. perceptual processing stages. In Experiment 1, participants had to categorize the valence and rate the intensity of happy, sad, angry and neutral unimodal or bimodal face–voice stimuli. They were asked to rate either the facial or vocal expression and ignore the emotion expressed in the other modality. Participants responded faster and more precisely to emotionally congruent compared to incongruent face–voice pairs in both the Attend Face and in the Attend Voice condition. Moreover, when attending to faces, emotionally congruent bimodal stimuli were more efficiently processed than unimodal visual stimuli. To study the role of a possible response conflict, Experiment 2 used a modified paradigm in which emotional and response conflicts were disentangled. Incongruency effects were significant even in the absence of response conflicts. The results suggest that emotional signals available through different sensory channels are automatically combined prior to response selection.     

Emotional Stroop task: effect of word arousal and subject anxiety on emotional interference

Inconsistent findings regarding the emotional Stroop effect in healthy subjects may be explained by confounding effects of stimulus valence and arousal, as well as individual differences in anxiety. We examined reaction time data in a healthy sample using the emotional Stroop task while carefully matching arousal level of positive and negative words. Independent of valence, emotional relative to neutral words elicited emotional interference, indicating that arousal determines emotional interference. Independent of valence, emotional words were better re-called and recognized than neutral words. Individual differences in state anxiety were associated with emotional interference, that is, emotional interference was enhanced in subjects with high state anxiety. There was no influence of trait anxiety. These findings indicate that word arousal produces emotional interference independent of valence. State anxiety exacerbates interference of emotional words by further biasing attention towards emotionally salient stimuli. Thomas Dresler and Katja Mériau have contributed equally.     

Generalizability of carry-over effects in the emotional Stroop task

The emotional Stroop task has been the most widely used task to examine attentional bias to emotionally salient stimuli. In one format of this task, words are presented to participants in a mixed randomized or quasi-randomized sequence. Using a mixed smoking Stroop task, we have previously demonstrated that smokers are slower to respond to words which follow smoking-related words than words which follow neutral words. Here we show that this carry-over effect is present in heroin addicts-but not control subjects-in a heroin Stroop task, and in normal subjects in a stress Stroop task. Thus, the effect generalizes to other populations. In addition, an examination of the studies that have collected data from both mixed and blocked formats provides converging evidence for the presence of carry-over effects. We discuss the implications of the carry-over effect for research using the emotional Stroop task.     

Co-occurring anxiety influences patterns of brain activity in depression

Brain activation associated with anhedonic depression and co-occurring anxious arousal and anxious apprehension was measured by fMRI during performance of an emotion word Stroop task. Consistent with EEG findings, depression was associated with rightward frontal lateralization in the dorsolateral prefrontal cortex (DLPFC), but only when anxious arousal was elevated and anxious apprehension was low. Activity in the right inferior frontal gyrus (IFG) was also reduced for depression under the same conditions. In contrast, depression was associated with more activity in the anterior cingulate cortex (dorsal ACC and rostral ACC) and the bilateral amygdala. Results imply that depression, particularly when accompanied by anxious arousal, may result in a failure to implement top-down processing by appropriate brain regions (left DLPFC, right IFG) due to increased activation in regions associated with responding to emotionally salient information (right DLPFC, amygdala).     

Adding fear to conflict: A general purpose cognitive control network is modulated by trait anxiety

Studies of cognitive control show that the dorsal anterior cingulate cortex (dACC) and dorsolateral prefrontal cortex are involved in the detection and resolution of cognitive conflict. However, the neural and behavioral mechanisms underlying emotional interference effects are less consistent. We used fMRI during emotional and nonemotional versions of a facial Stroop task to investigate the effects of emotional stimuli on cognitive control. In the full group there was limited evidence that different prefrontal circuits manage conflict arising from emotional and nonemotional distractors. However, individual differences in trait anxiety affected both behavioral performance and neural activity during the emotional task. Relative to low-anxiety (LA) subjects, high-anxiety (HA) subjects showed greater amygdala activity to task-relevant emotional information and impaired performance and greater conflict-related activity in the dACC when emotional content was task-irrelevant. Only LA subjects activated rostral ACC during the emotional task. This is consistent with cognitive models of individual differences that hypothesize deficient control of task-irrelevant emotional information in HA subjects. Additional behavioral and fMRI results from this study may be downloaded from http://cabn.psychonomic-journals .org/content/supplemental.     

Exploring emotional and cognitive conflict using speeded voluntary facial expressions

Affective conflict and control may have important parallels to cognitive conflict and control, but these processes have been difficult to quantitatively study with emotionally naturalistic laboratory paradigms. The current study examines a modification of the AX-Continuous Performance Task (AX-CPT), a well-validated probe of cognitive conflict and control, for the study of emotional conflict. In the Emotional AX-CPT, speeded emotional facial expressions measured with electromyography (EMG) were used as the primary response modality, and index of emotional conflict. Bottom-up emotional conflict occurred on trials in which precued facial expressions were incongruent with the valence of an emotionally evocative picture probe (e.g., smiling to a negative picture). A second form of top-down conflict occurred in which the facial expression and picture probe were congruent, but the opposite expression was expected based on the precue. A matched version of the task was also performed (in a separate group of participants) with affectively neutral probe stimuli. Behavioral interference was observed, in terms of response latencies and errors, on all conflict trials. However, bottom-up conflict was stronger in the emotional version of the task compared to the neutral version; top-down conflict was similar across the two versions. The results suggest that voluntary facial expressions may be more sensitive to indexing emotional than nonemotional conflict, and importantly, may provide an ecologically valid method of examining how emotional conflict may manifest in behavior and brain activity.     

Evidence for task conflict in the Stroop effect

C. M. MacLeod and P. A. MacDonald (2000) suggested that congruent and incongruent Stroop stimuli cause more task conflict than neutral stimuli because the anterior cingulate cortex is more activated with these stimuli. This study investigated behavioral expression for this pattern. Experiment 1 reduced task conflict control by increasing the proportion of nonword neutrals. Additionally, half the trials had conflict or neutral cues. The control reduction revealed the task conflict. For noncued trials, response time was longer for congruent stimuli than for neutral stimuli (reverse facilitation effect). In addition, response time for congruent stimuli was longer when stimuli were uncued vs. cued. Experiment 2 increased task conflict control by changing the neutral stimuli to noncolor words. Consequently, the task conflict expression disappeared.     

空间-数字反应编码联合效应下冲突适应过程的ERP研究

为了考察被试在不能意识到任务中包含冲突的情况下的认知控制过程,将产生SNARC效应的奇偶判断任务看作是一种潜在的冲突任务。大小与反应手一致的视为一致的试次,大小与反应手不一致的视为不一致的试次。根据不一致试次之前一个试次的类型将其划分为iI(不一致—不一致,incongruent-incongruent)试次和cI(一致—不一致,congruent-incongruent)试次两种类型。对冲突适应过程的分析表明iI试次的反应时显著快于cI试次,iI试次和cI试次相比,两者的脑电在大约260~300ms的时间段内在FCz位置上差异最大。偶极子分析表明差异波的产生源定位于背侧前扣带回(dorsal anterior cingulate cortex),这些结果与前扣带回的意识监测理论并不一致。最后结合冲突监测理论和其他解释前扣带回功能的理论对研究结果做了相应的解释,认为冲突适应可以是一个无意识的过程     

Cognitive Control in the Face of Fear: Reduced Cognitive-Emotional Flexibility in Women with a History of Child Abuse

Child abuse can negatively affect neurobiological systems involved in regulating emotions. Adults who were maltreated as children show diminished capacity to flexibly integrate the prefrontal and limbic circuits underlying emotion regulation. Using a facial identification Stroop task with nonemotional and emotional stimuli, we found that women who reported more childhood abuse (N = 44) were no different from women reporting less childhood abuse (N = 45) on nonemotional conflict adaptation, but were significantly less able to adapt to emotional conflict. Women who reported more abuse were especially impaired in adapting to emotional conflict when incongruent stimuli involved a fearful face. These results help characterize the relation between cognitive control and emotion regulation and highlight the far-reaching effects of childhood abuse on cognitive-emotional flexibility.     

Time course analysis of the Stroop phenomenon

Dyer (1971) investigated the response competition hypothesis of the Stroop phenomenon by temporally separating the color and word components of single stimuli (incongruent, control, and congruent). This line of research was continued in a series of five experiments that generalized Dyer's study: (a) In addition to the color-naming task, a reading task was included; (b) the irrelevant stimulus component was presented before and after the relevant one; (c) the probabilities of congruent and incongruent stimuli were varied; (d) besides color-word/color stimuli, color-color and word-word stimuli were used; and (e) the functional discrimination (color naming or reading) was compared with a sequential discrimination task. The data suggest the following temporal relations: (a) a slow facilitation due to response bias; (b) its inhibitory counterpart; and (c) a fast, strong inhibition with no facilitatory complement that seems to correspond to the usual Stroop conflict but that seems to occur earlier than the response execution stage.     

Cognitive control: dynamic, sustained, and voluntary influences

The cost of incongruent stimuli is reduced when conflict is expected. This series of experiments tested whether this improved performance is due to repetition priming or to enhanced cognitive control. Using a paradigm in which Word and Number Stroop alternated every trial, Experiment 1 assessed dynamic trial-to-trial changes. Incongruent trials led to task-specific reduction of conflict (trial n + 2) without cross-task modulation (trial n + 1), but this was fully explained by repetition priming. In contrast, an increased ratio of incongruent words did lead to sustained task-specific enhancement, above and beyond repetition priming (Experiment 2). Experiments 3 and 4 assessed the voluntary modulation of cognitive control: A cue predicted the congruency of the incoming trial, allowing participants to establish the correct mindset (Word Stroop in Experiment 3, Flanker task in Experiment 4). Preparing oneself to process an incongruent word (or flanker) enhanced conflict resolution in the subsequent Number Stroop, an example of cross-task modulation. Taken together, these experiments reveal the multifaceted aspects of conflict resolution: Trial-to-trial changes are often due to repetition priming; sustained modulations brought about by task demands are task specific; and voluntary modulations are task general.     

Age-related differences in the involvement of the prefrontal cortex in attentional control

We investigated the relative involvement of cortical regions supporting attentional control in older and younger adults during performance on a modified version of the Stroop task. Participants were exposed to two different types of incongruent trials. One of these, an incongruent-ineligible condition, produces conflict at the non-response level, while the second, an incongruent-eligible condition, produces conflict at both non-response and response levels of information processing. Greater attentional control is needed to perform the incongruent-eligible condition compared to other conditions. We examined the cortical recruitment associated with this task in an event-related functional magnetic resonance imaging paradigm in 25 older and 25 younger adults. Our results indicated that while younger adults demonstrated an increase in the activation of cortical regions responsible for maintaining attentional control in response to increased levels of conflict, such sensitivity and flexibility of the cortical regions to increased attentional control demands was absent in older adults. These results suggest a limitation in older adults’ capabilities for flexibly recruiting the attentional network in response to increasing attentional demands.     

Age-related differences in the involvement of the prefrontal cortex in attentional control

We investigated the relative involvement of cortical regions supporting attentional control in older and younger adults during performance on a modified version of the Stroop task. Participants were exposed to two different types of incongruent trials. One of these, an incongruent-ineligible condition, produces conflict at the non-response level, while the second, an incongruent-eligible condition, produces conflict at both non-response and response levels of information processing. Greater attentional control is needed to perform the incongruent-eligible condition compared to other conditions. We examined the cortical recruitment associated with this task in an event-related functional magnetic resonance imaging paradigm in 25 older and 25 younger adults. Our results indicated that while younger adults demonstrated an increase in the activation of cortical regions responsible for maintaining attentional control in response to increased levels of conflict, such sensitivity and flexibility of the cortical regions to increased attentional control demands was absent in older adults. These results suggest a limitation in older adults’ capabilities for flexibly recruiting the attentional network in response to increasing attentional demands.     

Motivational and cognitive determinants of control during conflict processing

Previous studies suggest that both reward anticipation and expected or experienced conflicts activate cognitive control. The present study investigated how these factors interact during conflict processing. In two experiments, participants performed a variant of the Stroop task, receiving performance-dependent monetary rewards in some blocks. In addition, we manipulated the level of conflict-triggered reactive and expectancy-driven proactive control: In Experiment 1, we compared the Stroop effect after previously congruent and incongruent trials to examine the conflict adaptation effect (reactive control). We found that the level of motivation did not interact with conflict adaptation. In Experiment 2, we varied the proportion of congruent and incongruent trials to manipulate conflict expectancy (proactive control). The data suggest the effects of motivation to be less pronounced under conditions of high conflict expectancy. We conclude that the interaction of motivation with cognitive determinants of control depends on whether these activate proactive or reactive control processes.     

Errors without conflict: implications for performance monitoring theories of anterior cingulate cortex

Recent theories of the neural basis of performance monitoring have emphasized a central role for the anterior cingulate cortex (ACC). Replicating an earlier event-related potential (ERP) study, which showed an error feedback negativity that was modeled as having an ACC generator, we used event-related fMRI to investigate whether the ACC would differentiate between correct and incorrect feedback stimuli in a time estimation task. The design controlled for response conflict and frequency and expectancy effects. Although participants in the current study adjusted their performance following error feedback, we did not observe error feedback-evoked ACC activity. In contrast, we did observe ACC activity while the same subjects performed the Stroop task, in which an area of the ACC activated during both conflict and error trials. These findings are inconsistent with previous dipole models of the error feedback negativity, and suggest the ACC may not be involved in the generation of this ERP component. These results question involvement of the ACC in the detection of errors per se when controlling for conflict.     

冲突观察能诱发冲突适应

重复启动效应和一致试次所占的比例都会影响冲突适应效应。采用词-色Stroop任务, 本研究在控制了重复启动效应和一致试次的比例之后, 通过三个实验共同探讨反应执行和冲突观察对冲突适应效应的影响。实验一发现当前试次的Stroop干扰效应, 但没有得到冲突适应效应; 在实验二中, 先前试次为四选一的选择反应时任务, 当前试次为词-色Stroop任务, 得到反转的冲突适应效应; 实验三和实验一程序相似, 但在先前试次上不执行反应, 得到了稳定的冲突适应效应。这些结果证明, 冲突观察能够诱发冲突适应机制, 提升当前的操作表现。     

Investigating hemispheric specialization in a novel face-word Stroop task

We examined hemispheric specialization in a lateralized Stroop facial identification task. A 2 (presentation side: left or right visual field [LVF or RVF])x2 (picture emotion: happy or angry)x3 (emotion of distractor word: happy, angry, or blank) factorial design placed the right hemispheric specialization for emotional expression processing and the left hemispheric specialization for verbal processing in conflict. Faces (from ) and emotion words were briefly displayed, and participants responded with keypresses corresponding to the picture emotion. As predicted, greater Stroop interference in identification accuracy was found with incongruent displays of facial expression in the LVF and emotion words in the RVF, and females exhibited less Stroop interference. Reaction times were moderated by emotion and visual field.     

Does incongruence of lexicosemantic and prosodic information cause discernible cognitive conflict?

We are often required to interpret discordant emotional signals. Whereas equivalent cognitive paradigms cause noticeable conflict via their behavioral and psychophysiological effects, the same may not necessarily be true for discordant emotions. Skin conductance responses (SCRs) and heart rates (HRs) were measured during a classic Stroop task and one in which the emotions conveyed by lexicosemantic content and prosody were congruent or incongruent. The participants’ task was to identify the emotion conveyed by lexicosemantic content or prosody. No relationship was observed between HR and congruence. SCR was higher during incongruent than during congruent conditions of the experimental task (as well as in the classic Stroop task), but no difference in SCR was observed in a comparison between congruence effects during lexicosemantic emotion identification and those during prosodic emotion identification. It is concluded that incongruence between lexicosemantic and prosodic emotion does cause notable cognitive conflict. Functional neuroanatomic implications are discussed.