Executive control over response priming and conflict: a transcranial magnetic stimulation study

The neural dynamics of conflict adaptation induced by conflict observation: Evidence from univariate and multivariate analysis

Conflict adaptation can be expressed as greater performance (shorter response time and lower error rate) after incongruent trials when compared to congruent trials. It has been observed in designs that minimize confounding factors, i.e., feature integration, contingency learning, and temporal learning. Our current study aimed to further elucidate the temporal evolution mechanisms of conflict adaptation. To address this issue, the current study employed a combination of behavioral, univariate, and multivariate analysis (MVPA) methods in a modified color-word Stroop task, where half of the trials required button presses (DO trials), and the other half only required observation (LOOK trials). Both behavioral and the ERP results (N450 and SP) in the LOOK-DO transition trials revealed significant conflict adaptation without feature integration, contingency learning, and temporal learning, providing support for the conflict monitoring theory. Furthermore, during the LOOK trials, significant Stroop effect in the N450 and SP components were observed, indicating that conflict monitoring occurred at the stimulus level and triggered reactive control adjustments. The MVPA results decoded the congruent-incongruent and incongruent-incongruent conditions during the conflict adjustment phase but not during the conflict monitoring phase, emphasizing the unique contribution of conflict adjustment to conflict adaptation. The current research findings provided more compelling supporting evidence for the conflict monitoring theory, while also indicating that future studies should employ the present design to elucidate the specific processes of conflict adaptation.

Head movement direction in football - a field study on visual scanning activity during the UEFA-U17 and -U21 European Championship 2019

Visual exploration (scanning) of one's environment is a key aspect in team sports. Based on Gibson's (1979) ecological approach of visual perception, this study aims to advance the understanding of scanning by focusing on the direction of head movements in football and its implications for subsequent on-ball actions. The video-based data analysis consisted of nine selected matches and 162 players of the Union of European Football Associations (UEFA) U17 and U21 European Championship 2019. The results indicate that the direction of the last scan prior to receiving the ball is related to the foot used for the first ball contact. This relationship was further analysed in view of the game context (direction of play and opponent pressure) and with information about the player's dominant foot. The findings reveal a relationship between the direction of the last scan before receiving the ball and the direction the game is proceeded in. Further, when a player performs the last scan to the side of their dominant foot, the probability increases that their dominant foot is used for the subsequent first ball contact. Depending on the direction of the last scan, opponent pressure had various effects on the foot used for the first contact.

Dissociable effects of positive feedback on the capture and inhibition of impulsive behavior in adolescents with ADHD versus typically developing adolescents

The present study investigated how enhancing motivation by delivering positive feedback (a smiley) after a successful trial could affect interference control in adolescents with Attention Deficit Hyperactivity Disorder (ADHD) and in their typically developing (TD) peers. By using a Simon task within the theoretical framework of the "activation-suppression" model, we were able to separately investigate the expression and the inhibition of impulsive motor behavior. The experiment included 19 adolescents with ADHD and 20 TD adolescents in order to explore whether data found in adolescents with ADHD were similar to those found in TD adolescents. Participants performed the Simon task in two conditions: a condition with feedback delivered after each successful trial and a condition with no feedback. The main findings were that increasing motivation by delivering positive feedback increased impulsive response in both groups of adolescents. It also improved the efficiency of impulsive motor action inhibition in adolescents with ADHD but deteriorated it in TD adolescents. We suggest that 1/increased motivation could lead adolescents to favor fast responses even if incorrect, and 2/the differential effect of feedback on the selective suppression of impulsive motor action in both groups could be due to different baseline DA levels.

Multiple Routes to Control in the Prime-Target Task: Congruence Sequence Effects Emerge Due to Modulation of Irrelevant Prime Activity and Utilization of Temporal Order Information

In interference tasks, the magnitude of the congruency effect is reduced in trials that follow an incongruent trial. This congruence sequence effect (CSE) reflects cognitive control processes, yet accounts disagree when and how control is exerted. Here, we address these questions in the context of the prime-target task. In this task, control can either modulate early prime or late target information. Furthermore, control can utilize information specific to the stimulus (perceptual features) or relational information between stimuli (temporal order). Two experiments (N = 41 | N = 62) were conducted using a prime-target task with arrows (prime) and letters (target). We presented either the prime before the target or the target before the prime. For both trial-type transitions, the CSE was assessed. Regarding the first question, when is control exerted, results showed a larger CSE for prime→target relative to target→prime trials. This suggests that control in the prime-target task modulates prime activity. Regarding the second question, how is control exerted, a combined analysis of both experiments showed a larger CSE for repetition of the same prime and target order across two trials (e.g., previous trial: prime→target; current trial: prime→target) compared to changes (e.g., previous trial: prime→target; current trial: target→prime), suggesting that control in the prime-target task can employ temporal selection.

A role of the lateral prefrontal cortex in the congruency sequence effect revealed by transcranial direct current stimulation

Congruency effect is the increase in response time when relevant and irrelevant cues indicate incongruent rather than congruent responses. The congruency effect is smaller in the trial after an incongruent trial than after a congruent trial: this difference is known as the congruency sequence effect (CSE). Psychophysical and neural studies have suggested that the lateral prefrontal cortex (LPFC) and the medial prefrontal cortex are associated with the CSE. In the present study, we applied anodal and cathodal transcranial direct current stimulation, which is thought to result in excitation and inhibition, respectively, on the LPFC, while human participants were performing a flanker task. We found that the CSE was increased under cathodal stimulation (inhibition) of the LPFC. Moreover, the LPFC stimulation modulated the congruency effect after a congruent trial. Further analyses suggested that the results cannot be explained by any of the currently prevailing hypotheses of the CSE, including the conflict monitoring hypothesis, feature integration hypothesis, and temporal learning account. Based on our findings, we propose that a new distinct mechanism might be involved in the CSE. Specifically, the LPFC might contribute to the CSE by maintaining the attention to the task-relevant information, which is an endogenous goal-oriented function and reduces the carry-over of the task-irrelevant information after a congruent trial.

The neurocognitive underpinnings of the Simon effect: An integrative review of current research

For as long as half a century the Simon task - in which participants respond to a nonspatial stimulus feature while ignoring its position - has represented a very popular tool to study a variety of cognitive functions, such as attention, cognitive control, and response preparation processes. In particular, the task generates two theoretically interesting effects: the Simon effect proper and the sequential modulations of this effect. In the present study, we review the main theoretical explanations of both kinds of effects and the available neuroscientific studies that investigated the neural underpinnings of the cognitive processes underlying the Simon effect proper and its sequential modulation using electroencephalogram (EEG) and event-related brain potentials (ERP), transcranial magnetic stimulation (TMS), and functional magnetic resonance imaging (fMRI). Then, we relate the neurophysiological findings to the main theoretical accounts and evaluate their validity and empirical plausibility, including general implications related to processing interference and cognitive control. Overall, neurophysiological research supports claims that stimulus location triggers the creation of a spatial code, which activates a spatially compatible response that, in incompatible conditions, interferes with the response based on the task instructions. Integration of stimulus-response features plays a major role in the occurrence of the Simon effect (which is manifested in the selection of the response) and its modulation by sequential congruency effects. Additional neural mechanisms are involved in supporting the correct and inhibiting the incorrect response.

Conflict monitoring and the affective-signaling hypothesis-An integrative review

Conflict-monitoring theory proposes that conflict between incompatible responses is registered by a dedicated monitoring system, and that this conflict signal triggers changes of attentional filters and adapts control processes according to the current task demands. Extending the conflict-monitoring theory, it has been suggested that conflict elicits a negative affective reaction, and that it is this affective signal that is monitored and then triggers control adaptation. This review article summarizes research on a potential signaling function of affect for cognitive control. First, we provide an overview of the conflict-monitoring theory, discuss neurophysiological and behavioral markers of monitoring and control adaptation, and introduce the affective-signaling hypothesis. In a second part, we review relevant studies that address the questions of (i) whether conflict elicits negative affect, (ii) whether negative affect is monitored, and (iii) whether affect modulates control. In sum, the reviewed literature supports the claim that conflict and errors trigger negative affect and provides some support for the claim that affect modulates control. However, studies on the monitoring of negative affect and the influence of phasic affect on control are ambiguous. On the basis of these findings, in a third part, we critically reassess the affective-signaling hypothesis, discuss relevant challenges to this account, and suggest future research strategies.

Effects of Non-invasive Brain Stimulation on Stimulant Craving in Users of Cocaine, Amphetamine, or Methamphetamine: A Systematic Review and Meta-Analysis

Dopamine system plays a pivotal role in specific kinds of substance use disorders (SUD, i. e., cocaine and methamphetamine use disorders). Many studies addressed whether dopamine-involved craving could be alleviated by non-invasive brain stimulation (NIBS) techniques. Nevertheless, the outcomes were highly inconsistent and the stimulating parameters were highly variable. In the current study, we ran a meta-analysis to identify an overall effect size of NIBS and try to find stimulating parameters of special note. We primarily find 2,530 unduplicated studies in PubMed, Psychology and Behavioral Sciences Collection, PsycARTICLES, PsycINFO, and Google Scholar database involving “Cocaine”/“Amphetamine”/“Methamphetamine” binded with “TMS”/“tDCS”/“non-invasive stimulation” in either field. After visual screening, 26 studies remained. While 16 studies were further excluded due to the lack of data, invalid craving scoring or the absence of sham condition. At last, 16 units of analysis in 12 eligible studies were coded and forwarded to a random-effect analysis. The results showed a large positive main effect of stimulation (Hedge's g = 1.116, CI = [0.597, 1.634]). Further subgroup analysis found that only high-frequency repetitive transcranial magnetic stimulation (rTMS) could elicit a significant decrease in craving, while the outcome of low-frequency stimulation was relatively controversial. Moreover, univariate meta regression revealed that the number of pulses per session could impose negative moderation toward the intervention. No significant moderation effect was found in types of abuse, overall days of stimulation and other variables of stimulating protocol. In conclusion, this meta-analysis offered a persuasive evidence for the feasibility of using NIBS to remit substance addictive behavior directly based on dopamine system. We also give clear methodological guidance that researchers are expected to use high-frequency, sufficiently segmented rTMS to improve the efficacy in future treatments.

Lunching for Relaxation or Cognitive Control? After-Effects of Social and Solitary Meals

Meals, especially when taken in company, may affect the diner’s mood. In line with findings that mood may alter cognitive control, a previous study by the authors found that after solitary meals, the Simon effect was diminished as compared to a premeal condition, whereas a social meal did not reduce the Simon effect. Here, we investigated whether this finding generalizes across different demands in cognitive control and, therefore, applied a flanker task. Obtained questionnaire data indicated differential effects in mood and relaxation of a social as compared to a solitary meal. Replicating our previous findings, the flanker compatibility effect decreased after a solitary meal but increased after a social meal. The present results support our previous findings with new evidence that a meal taken in a social context attenuates subsequent cognitive control processes compared with a solitary meal.

Distinct Roles for the Anterior Cingulate and Dorsolateral Prefrontal Cortices During Conflict Between Abstract Rules

Distinct patterns of activity within the anterior cingulate cortex (ACC) and dorsolateral prefrontal cortex (dlPFC) reported in neuroimaging studies during tasks involving conflict between competing responses have often been cited as evidence for their key contributions to conflict-monitoring and behavioral adaptation, respectively. However, supporting evidence from neuropsychological patients has been scarce and contradictory. We administered a well-studied analog of the Wisconsin Card Sorting Test, designed to elicit conflict between 2 abstract rules, to a cohort of 6 patients with damage to ACC or dlPFC. Patients who had sustained more significant damage to the ACC were not impaired either on a measure of "conflict cost" nor on measures of "conflict-induced behavioral adaptation." In contrast, damage to dlPFC did not affect the conflict cost measure but abolished the patients' ability to adapt their behavior following exposure to conflict, compared with controls. This pattern of results complements the findings from nonhuman primates with more circumscribed lesions to ACC or dlPFC on the same task and provides converging evidence that ACC is not necessary for performance when conflict is elicited between 2 abstract rules, whereas dlPFC plays a fundamental role in behavioral adaptation.

Phasic valence and arousal do not influence post-conflict adjustments in the Simon task

According to theoretical accounts of cognitive control, conflict between competing responses is monitored and triggers post conflict behavioural adjustments. Some models proposed that conflict is detected as an affective signal. While the conflict monitoring theory assumed that conflict is registered as a negative valence signal, the adaptation by binding model hypothesized that conflict provides a high arousal signal. The present research induced phasic affect in a Simon task with presentations of pleasant and unpleasant pictures that were high or low in arousal. If conflict is registered as an affective signal, the presentation of a corresponding affective signal should potentiate post conflict adjustments. Results did not support the hypothesis, and Bayesian analyses corroborated the conclusion that phasic affects do not influence post conflict behavioural adjustments in the Simon task.

Cognitive control activity is modulated by the magnitude of interference and pre-activation of monitoring mechanisms

The Simon task is used to study interference from irrelevant spatial information. Interference is manifested by longer reaction times when the required response -based on non-spatial features- is spatially incompatible with stimulus position. Interference is greater when incompatible trials are preceded by compatible trials (compatible-incompatible sequence) than when they are preceded by incompatible trials (incompatible-incompatible sequence). However, the relationships between spatial attention, interference and cognitive control have not been investigated. In the present study, we distinguished three experimental conditions according to sequential effects: same mappings (SM, compatible-compatible/incompatible-incompatible sequences: low interference), opposite mappings (OM, compatible-incompatible/incompatible-compatible sequences: high interference) and unrelated mappings (UM, central-compatible/central-incompatible sequences: intermediate interference). The negativity central contralateral (N2cc, a correlate of prevention of spatial response tendencies) was larger in OM than in SM, indicating greater cognitive control for greater interference. Furthermore, N2cc was larger in UM than in SM/OM, indicating lower neural efficiency for suppressing spatial tendencies of the response after central trials. Attentional processes (negativity posterior contralateral) were also delayed in UM relative to SM/OM, suggesting attentional facilitation by similar sets of attentional shifts in successive trials. Overall, the present findings showed that cognitive control is modulated by the magnitude of interference and pre-activation of monitoring mechanisms.

Transcranial magnetic stimulation to dorsolateral prefrontal cortex affects conflict-induced behavioural adaptation in a Wisconsin Card Sorting Test analogue

A substantial body of literature has proposed a role for dorsolateral prefrontal cortex (dlPFC) in supporting behavioural adaptation during conflict tasks. The vast majority of the evidence in support of this interpretation comes from neuroimaging studies. However, in order to unequivocally ascribe such a role to dlPFC, it is important to determine whether or not it is essential for this mechanism, and this can only be achieved by lesioning the area or interfering with its activity. In this study, we investigated the effects of repeated Transcranial Magnetic Stimulation (rTMS) to dlPFC on performance on a conflict version of a Wisconsin Card Sorting Test analogue (used previously in circumscribed lesion studies in monkeys) in neurologically healthy human participants. Our results supported the view of dlPFC as a fundamental structure for optimal conflict-induced behavioural adaptation, as stimulation cancelled out the adaptation effect normally observed on control trials. We show that there is some indication of differential modulation of trial types by stimulation and we hypothesize that this might suggest a role for dlPFC in conflict-induced adaptation that is more specifically concerned with the maintenance of conflict-history information online across trials.

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Dorsolateral prefrontal cortex stimulation abolishes conflict-induced adaptation.

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Adaptation is abolished via differential modulation of trial types.

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Dorsolateral prefrontal areas may aid adaptation via conflict history maintenance.

Practice-induced and sequential modulations in the Simon task: evidence from pupil dilation

Recent evidence showed that pupil dilation (PD) reflects modulations in the magnitude of the Simon interference effect due to correspondence sequence. In the present study we used this measure to assess whether these modulations, thought to result from cognitive control mechanisms, are influenced by prior practice with an incompatible stimulus-response (S-R) mapping. To this end, PD and reaction times (RTs) were recorded while participants performed a Simon task before and after executing a spatially incompatible practice. The sequential analysis revealed that PD mirrored the conflict-adaptation pattern observed in RTs. Crucially, sequential modulations were not affected by prior practice. These findings support the view that the modulations of the Simon effect due to prior practice and those due to correspondence sequence result from two different mechanisms, and suggest that PD can help to better understand the mechanisms underlying response selection and cognitive control in the Simon task.

Tracking Visual Events in Time in the Absence of Time Perception: Implicit Processing at the ms Level

Previous studies have suggested that even if subjects deem two visual stimuli less than 20 ms apart to be simultaneous, implicitly they are nonetheless distinguished in time. It is unclear, however, how information is encoded within this short timescale. We used a priming paradigm to demonstrate how successive visual stimuli are processed over time intervals of less than 20 ms. The primers were two empty square frames displayed either simultaneously or with a 17ms asynchrony. The primers were followed by the target information after a delay of 25 ms to 100 ms. The two square frames were filled in one after another with a delay of 100 ms between them, and subjects had to decide on the location of the first of the frames to be filled in. In a second version of the paradigm, only one square frame was filled in, and subjects had to decide where it was positioned. The influence of the primers is revealed through faster response times depending on the location of the first and second primers. Experiment 1 replicates earlier results, with a bias towards the side of the second primer, but only when there is a delay of 75 to 100 ms between primers and targets. The following experiments suggest this effect to be relatively independent of the task context, except for a slight effect on the time course of the biases. For the temporal order judgment task, identical results were observed when subjects have to answer to the side of the second rather than the first target, showing the effect to be independent of the hand response, and suggesting it might be related to a displacement of attention. All in all the results suggest the flow of events is followed more efficiently than suggested by explicit asynchrony judgment studies. We discuss the possible impact of these results on our understanding of the sense of time continuity.

A transcranial magnetic stimulation study on response activation and selection in spatial conflict

In choice reaction tasks, subjects typically respond faster when the relative spatial positions of stimulus and response correspond than when they do not, even when spatial information is irrelevant to the task (e.g. in the Simon task). Cognitive models attribute the Simon effect to automatic response activation elicited by spatial information, which facilitates or competes with the controlled selection of the correct response as required by task demands. In the present study, we investigated the role of the dorsal premotor cortex (PMd) in response activation and selection during spatial conflict. We applied single-pulse transcranial magnetic stimulation (TMS) to the PMd of the right and left hemispheres during the execution of a Simon task, at different times after the onset of the visual stimulus. The results showed that TMS produced a different effect on subjects' performance in two separate time windows. When TMS was applied at an early time [160-ms stimulus onset asynchrony (SOA)], we observed suppression of the Simon effect, resulting from a delay of corresponding trials. When TMS was applied at a late time (220 and 250-ms SOA), we observed an increase in the Simon effect, resulting from a delay of non-corresponding trials. These outcomes revealed that the PMd is involved both in the activation of the spatially triggered response and in response selection during spatial conflict.

Fronto-parietal network oscillations reveal relationship between working memory capacity and cognitive control

Executive-attention theory proposes a close relationship between working memory capacity (WMC) and cognitive control abilities. However, conflicting results are documented in the literature, with some studies reporting that individual variations in WMC predict differences in cognitive control and trial-to-trial control adjustments (operationalized as the size of the congruency effect and congruency sequence effects, respectively), while others report no WMC-related differences. We hypothesized that brain network dynamics might be a more sensitive measure of WMC-related differences in cognitive control abilities. Thus, in the present study, we measured human EEG during the Simon task to characterize WMC-related differences in the neural dynamics of conflict processing and adaptation to conflict. Although high- and low-WMC individuals did not differ behaviorally, there were substantial WMC-related differences in theta (4–8 Hz) and delta (1–3 Hz) connectivity in fronto-parietal networks. Group differences in local theta and delta power were relatively less pronounced. These results suggest that the relationship between WMC and cognitive control abilities is more strongly reflected in large-scale oscillatory network dynamics than in spatially localized activity or in behavioral task performance.

The heterogeneous world of congruency sequence effects: an update

Congruency sequence effects (CSEs) refer to the observation that congruency effects in conflict tasks are typically smaller following incongruent compared to following congruent trials. This measure has long been thought to provide a unique window into top-down attentional adjustments and their underlying brain mechanisms. According to the renowned conflict monitoring theory, CSEs reflect enhanced selective attention following conflict detection. Still, alternative accounts suggested that bottom-up associative learning suffices to explain the pattern of reaction times and error rates. A couple of years ago, a review by Egner (2007) pitted these two rivalry accounts against each other, concluding that both conflict adaptation and feature integration contribute to the CSE. Since then, a wealth of studies has further debated this issue, and two additional accounts have been proposed, offering intriguing alternative explanations. Contingency learning accounts put forward that predictive relationships between stimuli and responses drive the CSE, whereas the repetition expectancy hypothesis suggests that top-down, expectancy-driven control adjustments affect the CSE. In the present paper, we build further on the previous review (Egner, 2007) by summarizing and integrating recent behavioral and neurophysiological studies on the CSE. In doing so, we evaluate the relative contribution and theoretical value of the different attentional and memory-based accounts. Moreover, we review how all of these influences can be experimentally isolated, and discuss designs and procedures that can critically judge between them.

Neural systems for preparatory control of imitation

Humans have an automatic tendency to imitate others. Previous studies on how we control these tendencies have focused on reactive mechanisms, where inhibition of imitation is implemented after seeing an action. This work suggests that reactive control of imitation draws on at least partially specialized mechanisms. Here, we examine preparatory imitation control, where advance information allows control processes to be employed before an action is observed. Drawing on dual route models from the spatial compatibility literature, we compare control processes using biological and non-biological stimuli to determine whether preparatory imitation control recruits specialized neural systems that are similar to those observed in reactive imitation control. Results indicate that preparatory control involves anterior prefrontal, dorsolateral prefrontal, posterior parietal and early visual cortices regardless of whether automatic responses are evoked by biological (imitative) or non-biological stimuli. These results indicate both that preparatory control of imitation uses general mechanisms, and that preparatory control of imitation draws on different neural systems from reactive imitation control. Based on the regions involved, we hypothesize that preparatory control is implemented through top-down attentional biasing of visual processing.

Dopamine agonists and the suppression of impulsive motor actions in Parkinson disease

The suppression of spontaneous motor impulses is an essential facet of cognitive control that is linked to frontal-BG circuitry. BG dysfunction caused by Parkinson disease (PD) disrupts the proficiency of action suppression, but how pharmacotherapy for PD impacts impulsive motor control is poorly understood. Dopamine agonists improve motor symptoms of PD but can also provoke impulsive-compulsive behaviors (ICB). We investigated whether dopamine agonist medication has a beneficial or detrimental effect on impulsive action control in 38 PD patients, half of whom had current ICB. Participants performed the Simon conflict task, which measures susceptibility to acting on spontaneous action impulses as well as the proficiency of suppressing these impulses. Compared with an off-agonist state, patients on their agonists were no more susceptible to reacting impulsively but were less proficient at suppressing the interference from the activation of impulsive actions. Importantly, agonist effects depended on baseline performance in the off-agonist state; more proficient suppressors off agonist experienced a reduction in suppression on agonist, whereas less-proficient suppressors off agonist showed improved suppression on agonist. Patients with active ICB were actually less susceptible to making fast, impulsive response errors than patients without ICB, suggesting that behavioral problems in this subset of patients may be less related to impulsivity in motor control. Our findings provide further evidence that dopamine agonist medication impacts specific cognitive control processes and that the direction of its effects depends on individual differences in performance off medication.

The premotor theory of attention as an account for the Simon effect

The Simon effect refers to the phenomenon that responses are faster when the irrelevant location of a stimulus corresponds with the response location than when these locations do not correspond. In the current paper we examined the viability of an updated version of the premotor theory of attention (PMTA) as an account for the Simon effect. Two predictions were evaluated. First, in the case of focused attention at the relevant target position a strong reduction of the Simon effect should be observed as the Simon effect according to PMTA crucially depends on attentional orienting. Secondly, if attention is directed towards a location then this orienting by itself should already be sufficient for producing a Simon effect, as stimulus presence is not required. Our data confirmed these predictions thereby supporting the relevance of the PMTA for the Simon effect.

TMS of the FEF interferes with spatial conflict

In the Simon task, a conflict arises because irrelevant spatial information competes for response selection either facilitating or interfering with performance. Responses are faster when stimulus and response position correspond than when they do not. The FEFs, which have long been characterized for their role in oculomotor control, are also involved in the control of visuospatial attention when eye movements are not required. This study was aimed at investigating whether the FEFs contribute to spatial conflict. Double-pulse TMS was applied to the FEF of either left or right hemisphere during the execution of a Simon task at different time windows after the onset of the visual stimulus. A suppression of the Simon effect was observed after stimulation of the FEF for stimuli appearing in the contralateral hemifield when TMS was applied to the left hemisphere after stimulus onset (0-40 and 40-80 msec). A reduction of the correspondence effect was observed after right FEF TMS for stimuli presented in the left visual hemifield when stimulation was delivered in the 80-120 msec range after stimulus onset. These outcomes indicate that the FEF play a critical role in encoding spatial attribute of a stimulus for response priming, which is the prerequisite for response conflict in the Simon task. Moreover, our finding that the left FEF have a dominant role during spatial conflict extends the idea of the left-hemisphere lateralization of the motor network in action selection by suggesting that the FEF may constitute part of this network.

Accessory Stimuli Affect the Emergence of Conflict, Not Conflict Control

Accessory signals that precede stimuli in interference tasks lead to faster overall responses while conflict increases. Two opposing accounts exist for the latter finding: one is based on dual-route frameworks of response preparation and proposes amplification of both direct response activation and indirect response selection processes; the other refers to attentional networks and suggests inhibition of executive attention, thereby hampering conflict control. The present study replicated previous behavioral findings in a Simon task and extended them by electrophysiological evidence. Accessory tones facilitated stimulus classification and attentional allocation in the Simon task as reflected by an increased N1 amplitude and an overall decrease of the N2 amplitude, respectively. The conflict-related N2 amplitude, which is larger in conflict trials compared with nonconflict trials, was not modulated by accessory tones. Moreover, accessory tones did not affect sequence-dependent conflict adaptation. In terms of a dual-route framework present results suggest amplification of both response preparation routes by accessory stimuli. An executive attention approach proposing accessory stimuli to hamper control of conflict is not supported.

Timing spatial conflict within the parietal cortex: a TMS study

Orienting and motor attention are known to recruit different regions within right and left parietal lobes. However, the time course and the role played by these modules when visual information competes for different motor response are still unknown. To deal with this issue, single-pulse TMS was applied over the angular (AG) and the supramarginal (SMG) gyri of both hemispheres at several time intervals during the execution of a Simon task. Suppression of the conflict between stimulus and response positions (i.e., the Simon effect) was found when TMS pulse was applied 130 msec after stimulus onset over the right AG and after 160 msec when applied over the left AG and SMG. Interestingly, only stimulation of the left SMG suppressed the asymmetry in conflict magnitude between left- and right-hand responses, usually observed in the Simon task. The present data show that orienting attention and motor attention processes are temporally, functionally, and spatially separated in the posterior parietal cortex, and both contribute to prime motor response during spatial conflict.

Conflict and error adaptation in the Simon task

We present recent empirical and theoretical advances in conflict and error monitoring in the Simon task. On the basis of the adaptation by binding account for conflict adaptation and the orienting account for post-error slowing, we predict a dissociation between conflict and error monitoring. This prediction is tested and confirmed as conflict adaptation is task-specific while post-error slowing is not.

Post-error behavioral adjustments are facilitated by activation and suppression of task-relevant and task-irrelevant information processing

Error monitoring by the posterior medial frontal cortex (pMFC) has been linked to post-error behavioral adaptation effects and cognitive control dynamics in lateral prefrontal cortex (LPFC). It remains unknown, however, whether control adjustments following errors produce post-error behavioral adjustments (PEBAs) by inhibiting inappropriate responses or facilitating goal-directed ones. Here we used functional magnetic resonance imaging to investigate the hemodynamic correlates of PEBAs in a stimulus-response compatibility task. Our task was designed to test whether PEBAs are implemented by suppressing motor responses primed by irrelevant stimulus features (face location), redirecting attention to relevant features (face gender), or both or neither of these possibilities. Independent of PEBAs, error-related pMFC activation was followed by post-error recruitment of prefrontal and parietal control regions and, crucially, both (1) suppressed response-related activity in sensorimotor cortex and (2) enhanced target processing in face-sensitive sensory cortex ("fusiform face area"). More importantly, by investigating the covariation between post-error hemodynamic activity and individual differences in PEBAs, we showed that modulation of task-related motor and sensory processing was dependent on whether participants produced generally slower responses ("post-error slowing"; PES) or selectively reduced interference effects ("post-error reduction of interference"; PERI), respectively. Each of these behaviorally dependent effects was mediated by distinct LPFC control mechanisms (PES: inferior frontal junction; PERI: superior frontal sulcus). While establishing relationships between PEBAs and cognitive control, our findings suggest that the neural architecture underlying sequential behavioral adaptation may be determined primarily by how control is executed by the individual when adjustments are needed.

Generalized signaling for control: evidence from postconflict and posterror performance adjustments

Goal-directed behavior requires cognitive control to effect online adjustments in response to ongoing processing demands. How signaling for these adjustments occurs has been a question of much interest. A basic question regarding the architecture of the cognitive control system is whether such signaling for control is specific to task context or generalizes across contexts. In this study, the authors explored this issue using a stimulus-response compatibility paradigm. They examined trial-to-trial adjustments, specifically, the findings that incompatible trials elicit improved performance on subsequent incompatible trials and that responses are slower after errors. The critical question was, Do such control effects-typically observed within a single task context-occur across task contexts? The paradigm involved 2 orthogonal, stimulus-response sets: Stimuli in the horizontal direction mapped only to responses in the horizontal direction, and likewise for the vertical direction. Cues indicated that either compatible (same direction as stimulus) or incompatible (opposite to stimulus) responses were required. The results showed that trial-to-trial adjustments exist for both direction-repeat and direction-switch trials, demonstrating that signaling for control adjustments can extend beyond the task context within which they arise.

Attention control and susceptibility to hypnosis

The present work aimed at assessing whether the interference exerted by task-irrelevant spatial information is comparable in high- and low-susceptible individuals and whether it may be eliminated by means of a specific posthypnotic suggestion. To this purpose high- and low-susceptible participants were tested using a Simon-like interference task after the administration of a suggestion aimed at preventing the processing of the irrelevant spatial information conveyed by the stimuli. The suggestion could be administered either in the absence or following a standard hypnotic induction. We showed that, outside from the hypnotic context, the Simon effect was similar in high and low-susceptible participants and it was significantly reduced following the posthypnotic suggestion in high-susceptible participants only. These results show that a specific posthypnotic suggestion can alter information processing in high-susceptible individuals and reduce the interfering effect exerted by arrow stimuli.

Dorsolateral prefrontal cortex and Stroop performance: tackling the lateralization

Neuroscience research has identified the involvement of the dorsolateral prefrontal cortex (DLPFC) in cognitive control. Questions remain, however, about its lateralization correlates during Stroop task performance, an experimental cornerstone on which a large amount of cognitive control research is based. After reviewing the literature, we find that three Stroop variants have been used in an attempt to uncover different aspects of cognitive control related to DLPFC involvement. In sum, rapid and sequential up-regulation of the attentional set seems to be related to the left DLPFC. These attentional adjustments are based on participants' expectancies regarding the conflicting nature of the upcoming trial, and not on the conflict itself. In contrast, the right DLPFC is associated with an overall up-regulation of the attentional set when attentional conflict is experienced.

Co-occurrence of sequential and practice effects in the Simon task: Evidence for two independent mechanisms affecting response selection

The Simon effect refers to the observation that responses to a relevant stimulus dimension are faster and more accurate when the stimulus and response spatially correspond than when they do not, even though stimulus position is irrelevant. Recent findings have suggested that the Simon effect can be strongly modulated by prior practice with a spatially incompatible mapping and by correspondence sequence. Although practice is thought to influence conditional stimulus-response (S-R) processing, leaving response priming through the unconditional route unaffected, sequential effects are thought to represent trial-by-trial adaptations that selectively involve unconditional S-R processing. In the present study, we tested this assumption by assessing the effects of correspondence sequence both when the Simon task alone was performed and when it was preceded by a spatial compatibility task with either incompatible (Experiments 1-2) or compatible (Experiment 2) instructions. The observation that practice and correspondence sequence co-occur and exert additive effects strongly demonstrates that the two factors affect different processing routes.

Memory impairment induced by an interfering task is reverted by pre-frontal cortex lesions: a possible role for an inhibitory process in memory suppression in mice

Interference theory refers to the idea that forgetting occurs because the recall of certain items interferes with the recall of other items. Recently, it has been proposed that interference is due to an inhibitory control mechanism, triggered by competing memories, that ultimately causes forgetting [Anderson MC (2003) Rethinking interference theory: Executive control and the mechanisms of forgetting. J Mem Lang 49:415-4453]. In the present research we study the interference process by submitting CD1 mice to two different hippocampal-dependent tasks: a place object recognition task (PORT) and a step-through inhibitory avoidance task (IA). Our results show a mutual interference between PORT and IA. To elucidate the possible neural mechanism underlying the interference process, we submit hippocampus- and prefrontal cortex-lesioned mice to PORT immediately before IA training. Results from these experiments show that prefrontal cortex lesions completely revert the impairing effect exerted by PORT administration on IA memory, while hippocampus lesions, that as expected impair memory for both PORT and IA, increase this effect. Altogether our results suggest that interference-induced forgetting is driven by an inhibitory control mechanism through activation of hippocampus-prefrontal cortex circuitry. The hippocampus seems to be crucial for storing information related to both behavioral tasks. Competition between memories triggers the inhibitory control mechanism, by activating prefrontal cortex, and induces memory suppression.

Executive functioning component mechanisms and schizophrenia

BACKGROUND

Executive functioning refers to a set of processes involved in complex, goal-directed thought and behavior involving multiple brain regions (e.g., prefrontal cortex, parietal cortex, basal ganglia) and multiple neurotransmitters (e.g., dopamine, glutamate, gamma-aminobutyric acid). People with schizophrenia exhibit executive functioning deficits that are associated with treatment-refractory aspects of the disorder. Although there is general consensus about what cognitive tasks involve executive functioning, there is disagreement about the specific cognitive mechanisms that comprise executive functioning.

METHODS

This article discusses a number of possible candidate executive functioning mechanisms and provides a summary of the consensus reached by the executive functioning discussion group at the first CNTRICS (Cognitive Neuroscience for Treatment Research to Improve Cognition in Schizophrenia) meeting in Washington, DC.

RESULTS

The consensus was that two constructs have a well-founded basis in basic cognitive neuroscience research and seem to be impaired in schizophrenia: 1) rule generation and selection; and 2) dynamic adjustments in control (i.e., after conflict and errors).

CONCLUSIONS

The consensus of the first CNTRICS meeting was that immediate translation of measures of these constructs for use in schizophrenia should be pursued. A number of other constructs (e.g., scheduling, sequencing) could also be very important for schizophrenia and are in need of more basic and more clinical research.