Pleasant mood intensifies brain processing of cognitive control: ERP correlates

The present study investigated the impact of auditory-induced mood on brain processing of cognitive control using a Stroop color-word interference task. A total of 135 positive, negative, and neutral sounds (45 of each) were presented in separate blocks for a mood induction procedure, which was then followed by a Stroop color-word task in each trial. Event-related potentials (ERPs) were recorded for color-word congruent, incongruent and neutral (color-word irrelevant) words and subjects named the printed colors of the words by pressing the appropriate key (irrespective of word meaning). Response latency was delayed during incongruent vs. neutral trials, and this cost did not interact significantly with mood states. ERP data showed prolonged peak latencies in the P200 component and more negative deflections in the Late Positive Component (LPC, 450-550 ms) during incongruent vs. neutral conditions, regardless of mood states. Moreover, the negative deflections (N450) in the 450-550 ms interval of the incongruent- neutral difference waves, which index cognitive control effect in brain potentials, was more pronounced in the pleasant, but not in the unpleasant, mood state when compared with the neutral mood state. These data suggest that, pleasant mood intensifies brain processing of cognitive control, in a situation requiring effective inhibition of task-irrelevant distracting information. In addition, N450 component serves as an affective marker, embodying not only cognitive control effect in the brain but also its interaction with mood states.     

Event-related potential correlates of sound organization: Early sensory and late cognitive effects

We tested whether incoming sounds are processed differently depending on how the preceding sound sequence has been interpreted by the brain. Sequences of a regularly repeating three-tone pattern, the perceived organization of which spontaneously switched back and forth between two alternative interpretations, were delivered to listeners. Occasionally, a regular tone was exchanged for a slightly or moderately lower one (deviants). The electroencephalogram (EEG) was recorded while listeners continuously marked their perception of the sound sequence. We found that for both the regular and the deviant tones, the early exogenous P1 and N1 amplitudes varied together with the perceived sound organization. Percept-dependent effects on the late endogenous N2 and P3a amplitudes were only found for deviant tones. These results suggest that the perceived sound organization affects sound processing both by modulating what information is extracted from incoming sounds as well as by influencing how deviant sound events are evaluated for further processing.     

Event-related potential correlates of interference between cognitive performance and tonic experimental pain

In this study, we examined cognitive function during experimental pain induced by an ischemic upper-arm tourniquet. During pain and control conditions, individuals performed a memory search task and an oddball task. Reaction time, errors, and event-related potentials in response to task stimuli were evaluated. Pain reduced accuracy and changed the response-type dependency of errors and the reaction time within the memory search task: false rejections but not false acceptances increased, and rejections were faster than acceptances during pain, whereas the opposite occurred during control conditions. The memory probes elicited an N275 that increased and a P300 that decreased in amplitude during pain. Pain also reduced amplitudes of P200 and P300 from the oddball task. N275 enhancement was greater in nonaffected than affected individuals, suggesting its association with focused attention that inhibited disruption by pain. P300 attenuation is interpreted as an indication that cognitive involvement in pain diminishes the attention resources allocated to a concurrent cognitive task.     

Event-related potential correlates of task switching and switch costs

Studies of task switching demonstrate that task switches are associated with response costs and that these costs are reduced when a cue is presented in advance of a switch. The present study examined cortical event-related potential correlates of task switching and switch costs in 39 participants during a cued match/mismatch discrimination task. Compared with non-switch trials, switch trials were associated with a larger cue-related, anticipatory P3b-like waveform. Switch trials were also associated with smaller target-related, stimulus-dependent P2 and P3-like components. Moreover, the switch-related amplitude variability in the P3b to the cue and the P2 to the target were associated with unique components of the residual switch costs. The results support an integrated model of task switching with complementary yet distinct roles for anticipatory and stimulus-dependent processes in task switching and switch costs.     

Event-related potential correlates of impaired visuospatial working memory in schizophrenia

Previous studies have reported that patients with schizophrenia demonstrate impaired performance during working memory (WM) tasks. The current study aimed to determine whether WM impairments in schizophrenia are accompanied by reduced slow wave (SW) activity during on-line maintenance of mnemonic information. Event-related potentials were obtained from patients with schizophrenia and well controls as they performed a visuospatial delayed response task. On 50% of trials, a distractor stimulus was introduced during the delay. Compared with controls, patients with schizophrenia produced less SW memory negativity, particularly over the right hemisphere, together with reduced frontal enhancement of SW memory negativity in response to distraction. The results indicate that patients with schizophrenia generate less maintenance phase neuronal activity during WM performance, especially under conditions of distraction.     

Opposite effect of conflict context modulation on neural mechanisms of cognitive and affective control

This study investigated the neural effect of conflict context modulation of cognitive and affective conflict processing by recording evoked‐response potentials in cognitive and affective versions of a flanker task. By varying the proportion of congruent and incongruent trials in a block, we found different patterns of the context effect on evoked potentials during cognitive and affective conflict processing. For posterior N1 amplitude, frequent incongruent trials produced a larger effect only in the affective task. The opposite pattern of the context effect was observed for the central N450, which was enhanced by frequent cognitive but reduced by frequent affective contexts. We found similar context effect on the parietal sustained potential in both tasks. Overall, our findings suggest that cognitive and affective conflict processing engage a context‐dependent attentional control mechanism but a common conflict response system.     

On the role of conflict and control in social cognition: Event‐related brain potential investigations

Numerous social‐cognitive models posit that social behavior largely is driven by links between constructs in long‐term memory that automatically become activated when relevant stimuli are encountered. Various response biases have been understood in terms of the influence of such “implicit” processes on behavior. This article reviews event‐related potential (ERP) studies investigating the role played by cognitive control and conflict resolution processes in social‐cognitive phenomena typically deemed automatic. Neurocognitive responses associated with response activation and conflict often are sensitive to the same stimulus manipulations that produce differential behavioral responses on social‐cognitive tasks and that often are attributed to the role of automatic associations. Findings are discussed in the context of an overarching social cognitive neuroscience model in which physiological data are used to constrain social‐cognitive theories.     

Event-related potential correlates of proactive interference in schizophrenic patients and controls

Performance and event-related potentials (ERPs) were examined in a proactive interference (PI) task with 15 male schizophrenic patients and 15 matched healthy controls. Within a paired-associate task, 30 pairs of semantically unrelated words (A-B) were presented twice, followed by cued recall, in which the paired-associate B had to be named upon cue A. Subsequently, 50% of the A-words were paired with new words (A-C) and presented in random order together with 15 novel pairings (D-E). Slower responses and poorer recall of C- than of E-words in the final recall indicated PI in both groups. During acquisition, the paired-associates (C/E) evoked larger P3 and positive slow wave in controls than in patients. During recall, cues (A/D) evoked a slow wave with predominating anterior negativity in controls and posterior positivity in patients. The group-specific ERP pattern suggests deviant encoding and retrieval processes in schizophrenic individuals.     

The instructed context of a motor task modulates covert response preparation and shifts of spatial attention

We investigated how covert response preparation is modulated by the instructed cognitive context of a motor task. Participants prepared left-hand or right-hand movements toward or away from the body midline, as indicated by a response cue (S1) presented prior to a go/no-go stimulus (S2). Different participants were instructed that response cues specified the response hand or movement direction, respectively. This emphasis on effector versus movement direction selection modulated lateralized ERP components triggered during the S1–S2 interval. Attention shifts during movement preparation were assessed by measuring ERPs to irrelevant visual probes. Enhanced N1 components were found for probes near the effector when effector selection was emphasized, but for probes near the movement target location when movement direction selection was emphasized. Results demonstrate strong top-down contextual biases on motor control and on the locus of spatial attention during response preparation.     

Event-related potential correlates of perceptual and functional categories: comparison between stimuli matching by identity and equivalence

Event-related potentials (ERPs) correlates of two test criteria of an abstract category task were dissociated. In a stimulus equivalence task, 10 subjects observed pairs of figures presented serially in three conditions: reflexivity (generalized identity), equivalence (arbitrary derived relations from a previous training), and unrelated pairs. They were instructed to decide whether the second item in a pair matched or mismatched the first one. Participants' performance in reflexivity matching tests was faster and more accurate than in equivalence matching or mismatching responses. In the three conditions, an occipital P2, a frontal N2 and a parietal P3 ERP component were elicited. The earlier components P2 and N2 exhibited reflexivity matching effects, while the later component (P3) exhibited the only equivalence matching effect. In addition, the subtracted ERP components from unrelated minus identity and unrelated minus equivalence trials were computed within two time windows: 150-250ms (dN300) and 350-450ms (dN400). While both dN300 waves were not significantly different, the comparison of both dN400 waves showed statistical differences. Correlates of partially perceptual (but contextually abstract) concepts are elicited earlier than those of pure abstract concepts. These ERPs correlates of stimulus equivalence relation tests of semantic categories are in concordance with the behavioral data.     

Neural correlates of cue retrieval, task set reconfiguration, and rule mapping in the explicit cue task switching paradigm

Event-related brain potentials (ERPs) were used in two experiments to examine the neural correlates of processes underlying task switching in the information-reduction task switching paradigm. Each experiment included 22 participants. The paradigm included two cues for each task. This element of the design allowed us to differentiate the ERP correlates of cue retrieval, task set reconfiguration, and rule mapping. The ERP data revealed a parietal slow wave that was sensitive to processes associated with cue retrieval and task set reconfiguration and a frontal-polar slow wave that was sensitive to processes associated with rule mapping. These findings further the proposal that an endogenous act of control supporting processes related to task set reconfiguration and rule mapping may facilitate performance of the explicit cue task switching paradigm.     

Cognitive performance and electrophysiological indices of cognitive control: a validation study of conflict adaptation

Psychiatric and neurologic disorders are associated with deficits in the postconflict recruitment of cognitive control. The primary aim of this study was to validate the relationship between cognitive functioning and indices of conflict adaptation. Event-related potentials were obtained from 89 healthy individuals who completed an Eriksen flanker task. Neuropsychological domains tested included memory, verbal fluency, and attention/executive functioning. Behavioral measures and N2 amplitudes showed significant conflict adaptation (i.e., previous-trial congruencies influenced current-trial measures). Higher scores on the attention/executive functioning and verbal fluency domains were associated with larger incongruent-trial N2 conflict adaptation; measures of cognitive functioning were not related to behavioral indices. This study provides initial validation of N2 conflict adaptation effects as cognitive function-related aspects of cognitive control.     

Sex differences in electrophysiological indices of conflict monitoring

The purpose of this study was to investigate sex differences in cognitive control as measured by the stimulus-locked N2 component of the event-related potential (ERP). High-density ERPs were obtained from 114 healthy individuals (60 females, 54 males) who completed a modified Eriksen Flanker Task. Behavioral measures (i.e., error rates, reaction times) and N2 amplitudes were analyzed. On the flanker task, females responded significantly slower and committed more errors than males. For N2 amplitude, there was a significant main effect of congruency, with increased amplitude to incongruent trials. Importantly, sexes differed as a function of congruency, with males showing significantly larger incongruent N2 amplitudes than females. Sex differences in N2 amplitude remained in a subgroup of participants that did not differ for behavioral, demographic, and affective variables. No sex differences were shown for electrophysiological or behavioral indices of conflict adaptation. Results indicate sex differences in brain activation associated with conflict monitoring. Findings may be explained by two contradictory possibilities: (1) females more effectively monitor conflict as indicated by less neural activation than males for similar behavioral performance in a matched subsample, or, (2) females less effectively monitor conflict than males.     

Electrophysiological evidence for different effects of working memory load on interference control in adolescents than adults

The present study investigated how the development of interference control is influenced by the development of working memory (WM) capacity during adolescence. In a dual-task, 17 adolescents (12-16 years) and 19 adults (18-48 years) performed a gender word-face Stroop task, while WM-capacity was manipulated by a concurrently performed N-back task. Behavior (reaction times, % errors and % misses) and event-related potentials associated with the detection (N450) of the Stroop conflict and response selection (sustained positivity; SP) were measured without or with a concurrent WM load. Adolescents had lower accuracy on N-back and Stroop trials than adults. N450 results showed Stroop conflict above temporal-occipital cortex which was suggested to be caused by processing of distracter faces. This N450 conflict response was smaller in adults and only present when holding a simultaneous WM-load, whereas adolescents' N450 conflict responses were already present without a concurrent WM-load and did not further increase with load. These N450 results indicate poorer distracter suppression in adolescence which is suggested to be due to insufficient attentional resources for top-down control. Irrespective of WM-load, adolescents also had larger parietal SP conflict responses than adults, suggesting inefficient response selection in case of activation of two conflicting responses. The main conclusion is that adolescents have worse distracter suppression than adults, caused by lower availability of resources for top-down control.     

Behavioral and ERP indices of response conflict in Stroop and flanker tasks

We investigated effects of different proportions of incongruent trials on behavioral and event-related potential (ERP) interference measures associated with response conflict in the Stroop and flanker task. From the literature, we hypothesized that response conflict is greater when incongruent trials are rare compared to when incongruent trials are frequent. In support, the behavioral results on both tasks and the ERP results on the Stroop task (N450) showed that interference effects were significantly larger when incongruent trials were rare than frequent. In contrast, the ERP results on the flanker task N200 showed a larger interference effect when incongruent trials were frequent than rare. Because results for the flanker N200 were opposite to behavioral effects and theoretical predictions, our findings challenge the notion of the flanker N200 as a valid index of response conflict.     

Sensitivity of medial frontal cortex to response and nonresponse conflict

The anterior cingulate cortex (ACC) holds a prominent place in models of the neural architecture supporting cognitive control and conflict processing. The findings of empirical and computational work lead to the prediction that the ACC is sensitive to response conflict and insensitive to nonresponse conflict. We tested this prediction in two experiments using event-related brain potentials in combination with a task in which some trials included only nonresponse conflict and others included nonresponse and response conflict. A N450 associated with the activity of neural generators in the ACC and anterior frontal region was elicited on trials including only nonresponse and nonresponse and response conflict. This finding is inconsistent with the hypothesis that activation of the ACC is limited to response conflict and may identify one avenue of development in future applications of conflict theory.     

Attentional set mixing: Effects on target selection and selective response activation

Performance is impaired under set mixing conditions that require frequent readjustments of attentional focus over an extended time period. We compared set repetitions within pure blocks (constant focus of attention) to physically identical repetitions within mixed blocks (changing focus of attention). The aim was to investigate how set mixing affects target selection, indexed by the N2pc component, and selective response activation, indexed by the lateralized readiness potential (LRP). We found that set mixing prolonged the evolution of the N2pc while leaving its onset unaffected. Impaired target selection indicated by the N2pc mixing effect also delayed the start of response planning indexed by an onset delay of the stimulus-locked LRP, explaining one part of the behavioral mixing cost. A larger part of mixing cost could be attributed to a prolonged response planning phase, indexed by an earlier onset of the response-locked LRP.     

Multiple cognitive control mechanisms associated with the nature of conflict

Cognitive control is required to regulate conflict. The conflict monitoring theory suggests that the dorsal anterior cingulate cortex (dACC) is involved in detecting response conflict and the dorsolateral prefrontal cortex (DLPFC) plays a critical role in regulating conflict. Recent studies, however, have suggested that rostral dACC (rdACC) responds to response conflict whereas caudal dACC (cdACC) is associated with perceptual conflict. Moreover, DLPFC has been engaged only in regulation of response conflict. A neural network involved in perceptual conflict, however, remains unclear. In this study, we used functional magnetic resonance imaging (fMRI) in an attempt to reveal monitor–controller networks corresponding to either perceptual conflict or response conflict. A version of the Stroop color matching task was used to manipulate perceptual conflict, response conflict was manipulated by an arrow. The results demonstrated that rdACC and DLPFC were engaged in response conflict whereas cdACC and the dorsal portion of premotor cortex (pre-PMd) were involved in perceptual conflict. Interestingly, the posterior parietal cortex (PPC) was activated by both types of conflict. Correlation analyses between behavioral conflict effects and neural responses demonstrated that rdACC and DLPFC were associated with response conflict whereas cdACC and pre-PMd were associated with perceptual conflict. PPC was not correlated with either perceptual conflict or response conflict. We suggest that cdACC and pre-PMd play critical roles in perceptual conflict processing, and this network is independent from the rdACC/DLPFC network for response conflict processing. We also discussed the function of PPC in conflict processing.     

An event-related potential study of supramodal attentional control and crossmodal attention effects

We conducted two audiovisual experiments to determine whether event-related potential (ERP) components elicited by attention-directing cues reflect supramodal attentional control. Symbolic visual cues were used to direct attention prior to auditory targets in Experiment 1, and symbolic auditory cues were used to direct attention prior to visual targets in Experiment 2. Different patterns of cue ERPs were found in the two experiments. A frontal negativity called the ADAN was absent in Experiment 2, which indicates that this component does not reflect supramodal attentional control. A posterior positivity called the LDAP was observed in both experiments but was focused more posteriorly over the occipital scalp in Experiment 2. This component appears to reflect multiple processes, including visual processes involved in location marking and target preparation as well as supramodal processes involved in attentional control.     

Resisting recently acted-on cues: compatibility of Go/NoGo responses to response history modulates (frontal P3) event-related potentials

Using event-related potentials to investigate compatibility between past and present cue-response interactions, an experiment combined elements of selective-attention and Go/NoGo tasks. In the selective-attention part of each trial, participants responded to one of two visible numerical digits. Immediately afterward, in the Go/NoGo part of each trial, one of the same two digits appeared, with participants required to press the corresponding key on Go trials and to withhold responding on NoGo trials. Higher-amplitude anterior P3 responses on NoGo than on Go trials emerged when participants withheld responding to a recently selected cue but were greatly diminished when participants withheld responding to a recently ignored cue. The findings suggest that episodic traces of past Go/NoGo responses guide future action decisions, such that increased response control is needed to overcome bias to respond to recently acted-on NoGo cues.