When global information and local information collide: a brain potential analysis of the locus of interference effects

Moving beyond response times with accessible measures of manual dynamics

Button-press measures of response time (RT) and accuracy have long served a central role in psychological research. However, RT and accuracy provide limited insight into how cognitive processes unfold over time. To address this limitation, researchers have used hand-tracking techniques to investigate how cognitive processes unfold over the course of a response, are modulated by recent experience, and function across the lifespan. Despite the efficacy of these techniques for investigating a wide range of psychological phenomena, widespread adoption of hand-tracking techniques within the field is hindered by a range of factors, including equipment costs and the use of specialized software. Here, we demonstrate that the behavioral dynamics previously observed with specialized motion-tracking equipment in an Eriksen flanker task can be captured with an affordable, portable, and easy-to-assemble response box. Six-to-eight-year-olds and adults (N = 90) completed a computerized version of the flanker task by pressing and holding a central button until a stimulus array appeared. Participants then responded by releasing the central button and reaching to press one of two response buttons. This method allowed RT to be separated into initiation time (when the central button was released) and movement time (time elapsed between initiation and completion of the response). Consistent with previous research using motion-tracking techniques, initiation times and movement times revealed distinct patterns of effects across trials and between age groups, indicating that the method used in the current study presents a simple solution for researchers from across the psychological and brain sciences looking to move beyond RTs.

Neural Processing of Cognitive Control in an Emotionally Neutral Context in Anxiety Patients

Impaired cognitive control plays a crucial role in anxiety disorders and is associated with deficient neural mechanisms in the fronto-parietal network. Usually, these deficits were found in tasks with an emotional context. The present study aimed at investigating electrophysiological and vascular signatures from event-related brain potentials (ERPs) and functional near-infrared spectroscopy (fNIRS) in anxiety patients versus healthy controls during an inhibition task integrated in an emotionally neutral context. Neural markers were acquired during the completion of a classical Eriksen flanker task. The focus of data analysis has been the ERPs N200 and P300 and fNIRS activations in addition to task performance. No behavioral or neural group differences were identified. ERP findings showed a larger N2pc and a delayed and reduced P300 for incongruent stimuli. The N2pc modulation suggests the reorienting of attention to salient stimuli, while the P300 indicates longer lasting stimulus evaluation processes due to increased task difficulty. FNIRS did not result in any significant activation potentially suggesting a contribution from deeper brain areas not measurable with fNIRS. The missing group difference in our non-emotional task indicates that no generalized cognitive control deficit but rather a more emotionally driven deficit is present in anxiety patients.

Neural Dynamics of Cognitive Control in Various Types of Incongruence

Conflict-control is a core function of cognitive control. Although numerous studies have considered cognitive control to be domain-general, the shared and distinct brain responses to different types of incongruence or conflict remain unclear. Using a hybrid flanker task, the present study explored the temporal dynamics of brain activation to three types of incongruence: flanker interference, rule-based response switch (rule-switch), and action-based response switch (response-alternation). The results showed that: (1) all three types of incongruence evoked larger N2 amplitudes than the congruent condition in the frontal region, with the N2 amplitudes and topographical distribution of the N2 effect differing between the different types of incongruence; and (2) in the P300 time window, the flanker interference condition yielded the most delayed P300 latency, whereas the rule-switch and response-alternation conditions yielded smaller P300 amplitudes with a longer interval from P300 peak to a keypress. These findings suggest that different types of incongruence are first monitored similarly by the cognitive control system and then resolved differently.

Oscillatory Mechanisms of Response Conflict Elicited by Color and Motion Direction: An Individual Differences Approach

Goal-directed behavior requires control over automatic behavior, for example, when goal-irrelevant information from the environment captures an inappropriate response and conflicts with the correct, goal-relevant action. Neural oscillations in the theta band (∼6 Hz) measured at midfrontal electrodes are thought to form an important substrate of the detection and subsequent resolution of response conflict. Here, we examined the extent to which response conflict and associated theta-band activity depend on the visual stimulus feature dimension that triggers the conflict. We used a feature-based Simon task to manipulate conflict by motion direction and stimulus color. Analyses were focused on individual differences in behavioral response conflict elicited across different stimulus dimensions and their relationship to conflict-related midfrontal theta. We first confirmed the presence of response conflict elicited by task-irrelevant motion and stimulus color, demonstrating the usefulness of our modified version of the Simon task to assess different sensory origins of response conflict. Despite titrating overall task performance, we observed large individual differences in the behavioral manifestations of response conflict elicited by the different visual dimensions. These behavioral conflict effects were mirrored in a dimension-specific relationship with conflict-related midfrontal theta power, such that, for each dimension, individual midfrontal theta power was generally higher when experienced response conflict was high. Finally, exploratory analyses of interregional functional connectivity suggested a role for phase synchronization between frontal and parietal scalp sites in modulating experienced conflict when color was the task-relevant visual dimension. Highlighting the importance of an individual differences approach in cognitive neuroscience, these results reveal large individual differences in experienced response conflict depending on the source of visual interference, which are predicted by conflict-related midfrontal theta power.

The effect of interference in the early processing stages on response inhibition in the stop signal task

In the present study, the relation between interference at the early processing stages and response inhibition was investigated. In previous studies, response stopping appeared to be slowed down when irrelevant distracting information was presented. The purpose of the present study was to further explore the relationship between interference control and response inhibition. In Experiment 1, a stop signal paradigm was combined with a global/local task. The typical global-to-local interference effect is generally attributed to early processing stages, such as stimulus perception and identification. Results of this experiment demonstrated a congruency effect for both reaction time data and stopping performance. In Experiment 2, these results were replicated with a flanker task that used stimulus-incongruent but response-congruent flankers. Results of both experiments suggest that response inhibition and interference at the early processing stages interact.

The interplay of goal-driven and stimulus-driven influences on spatial orienting

Search for a target stimulus among distractors is subject to both goal-driven and stimulus-driven influences. Variables that selectively modify these influences have shown strong interaction effects on saccade trajectories toward the target, suggesting the involvement of a shared spatial orienting mechanism. However, subsequent manual response times (RTs) have revealed additive effects, suggesting that different mechanisms are involved. In the present study, we tested the hypothesis that an interaction for RTs is obscured by preceding multisaccade trajectories, promoted by the continuous presence of distractors in the display. In two experiments, we compared a condition in which distractors were removed soon after the presentation of the search display to a standard condition in which distractors were not removed. The results showed additive goal-driven and stimulus-driven effects on RTs in the standard condition, but an interaction when distractors were removed. These findings support the view that both variables influence a shared spatial orienting mechanism.

Probabilistic reward learning in adults with Attention Deficit Hyperactivity Disorder--an electrophysiological study

Attention Deficit Hyperactivity Disorder (ADHD) is hypothesized to be characterized by altered reinforcement sensitivity. The main aim of the present study was to assess alterations in the electrophysiological correlates of monetary reward processing in adult patients with ADHD of the combined subtype. Fourteen adults with ADHD of the combined subtype and 14 healthy control participants performed an active and an observational probabilistic reward-based learning task while an electroencephalogramm (EEG) was recorded. Regardless of feedback valence, there was a general feedback-related negativity (FRN) enhancement in combination with reduced learning performance during both active and observational reward learning in patients with ADHD relative to healthy controls. Other feedback-locked potentials such as the P200 and P300 and response-locked potentials were unaltered in the patients. There were no significant correlations between learning performance, FRN amplitudes and clinical symptoms, neither in the overall group involving all participants, nor in patients or controls considered separately. This pattern of findings might reflect generally impaired reward prediction in adults with ADHD of the combined subtype. We demonstrated for the first time that patients with ADHD of the combined subtype show not only deficient active reward learning but are also impaired when learning by observing other people׳s outcomes.

Developmental mechanisms underlying improved contrast thresholds for discriminations of orientation signals embedded in noise

We combined an external noise paradigm with an efficient procedure for obtaining contrast thresholds (Lesmes et al., 2006) in order to model developmental changes in the effect of noise on contrast discrimination during childhood. Specifically, we measured the contrast thresholds of 5-, 7-, 9-year-olds and adults (n = 20/age) in a two alternative forced-choice orientation discrimination task over a wide range of external noise levels and at three levels of accuracy. Overall, as age increased, contrast thresholds decreased over the entire range of external noise levels tested. The decrease was greatest between 5 and 7 years of age. The reduction in threshold after age 5 was greater in the high than the low external noise region, a pattern implying greater tolerance of the irrelevant background noise as children became older. To model the mechanisms underlying these developmental changes in terms of internal noise components, we adapted the original perceptual template model (Lu and Dosher, 1998) and normalized the magnitude of performance changes against the performance of 5-year-olds. The resulting model provided an excellent fit (r² = 0.985) to the contrast thresholds at multiple levels of accuracy (60, 75, and 90%) across a wide range of external noise levels. The improvements in contrast thresholds with age were best modeled by a combination of reductions in internal additive noise, reductions in internal multiplicative noise, and improvements in excluding external noise by template retuning. In line with the data, the improvement was greatest between 5 and 7 years of age, accompanied by a 39% reduction in additive noise, 71% reduction in multiplicative noise, and 45% improvement in external noise exclusion. The modeled improvements likely reflect developmental changes at the cortical level, rather than changes in front-end structural properties (Kiorpes et al., 2003).

Spatial frequency information modulates response inhibition and decision-making processes

We interact with the world through the assessment of available, but sometimes imperfect, sensory information. However, little is known about how variance in the quality of sensory information affects the regulation of controlled actions. In a series of three experiments, comprising a total of seven behavioral studies, we examined how different types of spatial frequency information affect underlying processes of response inhibition and selection. Participants underwent a stop-signal task, a two choice speed/accuracy balance experiment, and a variant of both these tasks where prior information was given about the nature of stimuli. In all experiments, stimuli were either intact, or contained only high-, or low- spatial frequencies. Overall, drift diffusion model analysis showed a decreased rate of information processing when spatial frequencies were removed, whereas the criterion for information accumulation was lowered. When spatial frequency information was intact, the cost of response inhibition increased (longer SSRT), while a correct response was produced faster (shorter reaction times) and with more certainty (decreased errors). When we manipulated the motivation to respond with a deadline (i.e., be fast or accurate), removal of spatial frequency information slowed response times only when instructions emphasized accuracy. However, the slowing of response times did not improve error rates, when compared to fast instruction trials. These behavioral studies suggest that the removal of spatial frequency information differentially affects the speed of response initiation, inhibition, and the efficiency to balance fast or accurate responses. More generally, the present results indicate a task-independent influence of basic sensory information on strategic adjustments in action control.

Enhancement of perceptual representations by endogenous attention biases competition in response selection

Perception and response selection are core processes in the generation of overt behavior. Selective attention is known to facilitate behavioral performance by altering perceptual processes. It remains unclear, however, whether selective attention can aid the resolution of response conflict, and if so, at what stage of processing this takes place. In two experiments, an endogenous cuing task was combined with a flanker task to assess the interaction of selective attention with response selection. The results of Experiment 1 show that cuing reduces the flanker-congruency effect when the cue and flanker are presented in close temporal proximity to each other. The results of Experiment 2 demonstrate that pre- but not post-cuing the target reduced the congruency effect, showing that selective attention can affect performance, but is ineffective once stimulus processing has proceeded to response selection. Our results provide evidence that selective attention can aid the resolution of response conflict by altering early perceptual processing stages.

Developmental changes during childhood in single-letter acuity and its crowding by surrounding contours

Crowding refers to impaired target recognition caused by surrounding contours. We investigated the development of crowding in central vision by comparing single-letter and crowding thresholds in groups of 5-year-olds, 8-year-olds, 11-year-olds, and adults. The task was to discriminate the orientation of a Sloan letter E. Single-letter thresholds, defined as the stroke width forming the smallest discriminable E, were worse than those of adults (0.83 arcmin) at 5 years of age (1.05 arcmin) but not at older ages (8-year-olds: 0.81 arcmin; 11-year-olds: 0.78 arcmin). The maximum distances over which crowding occurred, as measured in multiples of threshold stroke width, were smaller in adults (2.83) than in the three groups of children, who did not differ from each other (5-year-olds: 7.03; 8-year-olds: 7.84; 11-year-olds: 7.13). Thus, even 11-year-olds are more affected than adults by surrounding contours despite having single-letter acuity that has been mature for several years. The stronger influence of crowding in children may be caused by immaturities in the brain areas beyond the primary visual cortex (V1) where early visual inputs are combined and may contribute to their slower reading speed.

Global-local interference is related to callosal compromise in alcoholism: a behavior-DTI association study

BACKGROUND

Visuospatial ability is a multifactorial process commonly impaired in chronic alcoholism. Identification of which features of visuospatial processing are affected and which are spared in alcoholism, however, has not been clearly determined. We used a global-local paradigm to assess component processes of visuospatial ability and MR diffusion tensor imaging (DTI) to examine whether alcoholism-related microstructural degradation of the corpus callosum contributes to disruption of selective lateralized visuospatial and attention processes.

METHODS

A hierarchical letter paradigm was devised, where large global letters were composed of small local letters. The task required identification of target letters among distractors presented at global, local, both, or neither level. Attention was either selectively directed to global or local levels or divided between levels. Participants were 18 detoxified chronic alcoholics and 22 age-matched healthy controls. DTI provided quantitative assessment of the integrity of corpus callosal white matter microstructure.

RESULTS

Alcoholics generally had longer reaction times than controls but obtained similar accuracy scores. Both groups processed local targets faster than global targets and showed interference from targets at the unattended level. Alcoholics exhibited moderate compromise in selectively attending to the global level when the global stimuli were composed of local targets. Such local interference was less with longer abstinence. Callosal microstructural integrity compromise predicted degree of interference from stimulus incongruency in the alcoholic group. This relationship was not observed for lateral or third ventricular volumes, which are measures of nonspecific cortical volume deficits.

CONCLUSION

Global-local feature perception was generally spared in abstinent chronic alcoholics, but impairments were observed when directing attention to global features and when global and local information interfered at stimulus or response levels. Furthermore, the interference-callosal integrity relationship in alcoholics indicates that compromised visuospatial functions include those requiring bilateral integration of information.

Anterior cingulate cortex and conflict detection: an update of theory and data

The dorsal anterior cingulate cortex (ACC) and associated regions of the medial frontal wall have often been hypothesized to play an important role in cognitive control. We have proposed that the ACC's specific role in cognitive control is to detect conflict between simultaneously active, competing representations and to engage the dorsolateral prefrontal cortex (DLPFC) to resolve such conflict. Here we review some of the evidence supporting this theory, from event-related potential (ERP) and fMRI studies. We focus on data obtained from interference tasks, such as the Stroop task, and review the evidence that trial-to-trial changes in control engagement can be understood as driven by conflict detection; the data suggest that levels of activation of the ACC and the DLPFC in such tasks do indeed reflect conflict and control, respectively. We also discuss some discrepant results in the literature that highlight the need for future research.

Age-group differences in set-switching and set-maintenance on the Wisconsin Card Sorting Task

This study examined developmental change in set-switching and set-maintenance on the Wisconsin Card Sorting Task (WCST), and sought to determine how executive function (EF) components (i.e., Working Memory, Shifting and Inhibition) may contribute to the observed changes on WCST performance. To this end, performance in four age groups (7-year-olds, 11-year-olds, 15-year-olds, and 21-year-olds) was measured on the WCST, and on three EF tasks assumed to tap Working Memory, Shifting, and Inhibition. The results showed that adult levels of performance were reached in 11-year-olds for set-switching, and in 15-year-olds for set-maintenance. A subsequent principal component analysis revealed that set-switching and set-maintenance loaded on two factors for 7-year-olds, but a single factor in the other age groups. Finally, regression analyses yielded a complex pattern of results concerning the prediction of set-switching and set-maintenance by the performance on tasks used to assess the EF components. The results were interpreted to suggest distinct developmental trends in set-switching and set-maintenance abilities required by the WCST.

Perceptual factors contribute to akinesia in Parkinson's disease

Parkinson's disease (PD) patients have longer reaction time (RT) than age-matched control subjects. During the last decades, conflicting results have been reported regarding the source of this deficit. Here, we addressed the possibility that experimental inconsistencies originated in the composite nature of RT responses. To investigate this idea, we examined the effect of PD on different processes that compose RT responses. Three variables were manipulated: the signal quality, the stimulus-response compatibility and the foreperiod duration. These variables have been shown to affect, respectively, the ability to extract the relevant features of the stimulus (perceptual stage), the intentional selection of the motor response (cognitive stage) and the implementation of the muscle command (motor stage). Sixteen PD patients were tested on and off-medication and compared with an age and gender-matched control group. Results indicated that degrading the legibility of the response stimulus affected the latency of simple key-press movements more dramatically in the off-medication PD group than in the control population. The stimulus-response compatibility and the foreperiod duration had similar effects in the two groups. Interestingly, the response slowing associated with the degradation of the stimulus was the same whether the patients were on or off dopaminergic medication. This suggests that the high-level perceptual deficits observed in the present study do not have a dopaminergic origin.

Speed-accuracy modulation in case of conflict: the roles of activation and inhibition

This study investigated how the speed-accuracy balance is modulated by changes in the time course of motor activation and inhibition of a primed response. Responses and event-related brain potentials were recorded in a paradigm in which the first stimulus indicated the correct response with 80% validity. The remaining 20% of the trials required no response (no-go) or a response opposite to the cued hand (change trials). Subjects were instructed either to balance speed and accuracy or to emphasize speed at the cost of accuracy. Analyses of error patterns, reaction time distributions and brain potentials show that subjects can modulate the amount of activation of the primed response. More surprisingly, the engagement of inhibition of the response also varied with the speed-accuracy instruction. The results are consistent with a model where the frontothalamic loop actively controls both the activation and the inhibition of responses, depending on the current task requirements.

Global precedence and response activation: evidence from LRPs

Lateralized readiness potentials (LRPs) were measured in left/right/no-go tasks using compound global/local stimuli. In Experiment 1, participants responded to local target shapes and ignored global ones. RTs were affected by the congruence of the global shape with the local one, and LRPs indicated that irrelevant global shapes activated the responses with which they were associated. In Experiment 2, participants responded to conjunctions of target shapes at both levels, withholding the response if a target appeared at only one level. Global shapes activated responses in no-go trials, but local shapes did not. The results are consistent with partial-output models in which preliminary information about global shape can partially activate responses that are inconsistent with the local shape. They also demonstrate that part of the global advantage arises early, before response activation begins and probably before recognition of the local shape.

Attention and selection in the growing child: views derived from developmental psychophysiology

Our understanding of developmental changes in attentional selection in the growing child has been advanced substantially by the results of (a relatively small number of) studies undertaken from a psychophysiological perspective. The basic outcome of these studies is that, in attentional filtering as well as selective set (the two basic paradigms in attention research), the processes necessary for attentional selection are in essence available even to the young child; however, the speed and efficiency of these processes tends to increase as the child grows into an adolescent. Under optimal conditions, filtering is performed at early stages of information processing, but less optimal stimulus characteristics and task requirements may induce a shift in the locus of selection to later processing stages for young children whereas older individuals are better able to preserve their early locus of selection. When early selection is constrained, young children are substantially more sensitive to the adverse effects of response competition. In selective set, sub-optimal conditions lead not so much to a shift in locus of selection processes, but to a shift in the age at which asymptote efficiency is attained. We have proposed hierarchical regression analysis as a useful technique to examine whether age-related differences in attention effects, as observed in specific ERP components and in RT, are reflections of an age effect on a single source of attentional selection or of separate sources that each contribute uniquely to the developmental trends seen in (attention effects on) RT. Re-analyses of existing data demonstrated that (again depending on task specifics) many but not all of the different component processes involved in attentional selection contributed unique variance to the age-related changes in attention effects.

The functional interaction of visual-perceptual and response mechanisms during selective attention in young adults, young-old adults, and old-old adults

A response compatibility paradigm was employed to address how the perceptual and response activation processes functionally interact during selective attention and how they may be influenced by aging. The results showed that increasing the visual similarity of targets within response sets reduced the magnitude of the interference effect, but only with a narrow interletter distance. In a dissimilar condition, the magnitude of the interference effect did not vary with age. However, in a similar condition, the magnitude of the interference effect was larger for both young (18-30 years) and young-old adults (55-79 years) than for old-old adults (> or = 80 years). In contrast, all three groups showed similar facilitation effects. These results failed to provide support for the notion that enhanced spatial filtering of the target from the flankers produces a corresponding decrease in response competition. Rather, the decrease in the interference effect can be attributed to a functional interaction between the perceptual availability of partial information and the magnitude of response competition. The results also suggest that age does not impair response activation but that advanced age diminishes the availability of local, but not global, feature information.

Electrophysiological evidence of a perceptual precedence of global vs. local visual information

Aim of the present study was to investigate the mechanisms of attentional selection of hierarchically organized visual patterns (compound letter stimuli), while subjects were engaged in target selection at either the global or local level. Event-related brain potentials (ERPs) were recorded using a high density electrode montage. Reaction times (RTs) to target stimuli were also recorded. RT data indicated the interference effect of global incongruent information with the local one. ERP data were consistent with behavioral data. In fact, the early sensory N115 component recorded at the primary visual areas exhibited smaller responses to locally attended elements when the global configuration was incongruent rather than congruent, suggesting an interference effect of the global with the local level. Conversely, no interference effect was found for globally attended configurations. These results strongly support the view of a perceptual advantage of globally conveyed information, very likely mediated by low spatial frequency channels. At later processing levels, N1 and P3 components were faster and larger when attention was paid to the global configuration. The difference between target and nontarget responses, indexing the attentional target selection, yielded a broad occipital-temporal negativity focused onto the left hemisphere in the attend-local, and over the right hemisphere in the attend-global condition. The present findings indicate a hemispheric asymmetry in cerebral activation during local/global processing. In addition, they provide robust evidence of a sensory precedence of global information.

Shifting attention between global features and small details: an event-related potential study

In two experiments, large letters H or Z composed of small letters (also H or Z) were presented. Subjects had to make a two-choice motor response (e.g. H--left key, Z--right key). A cue presented 500 ms before the letter indicated which level (global or local) was relevant. In Experiment I, a third letter (T) sometimes appeared either at the cued or the non-cued level; in the former case, subjects had to shift their attention and to respond to stimulus features located at the non-cued level. The interference effect (RT delay in response to incongruent stimuli as compared to congruent ones) was larger when the local, rather than global, level was cued. A slow anterior negativity preceding globally-cued stimuli and shorter N1 and P2 ERP component latencies to these stimuli indicated better preparation for processing of global, as compared to local, stimulus features. The shift from local to global focus yielded a larger increase of RT, error rate, and of the P600 latency than the global-to-local shift. The P600 latency changes were parallel to those of RT. In Experiment II, the attentional shift was provoked by stimulus color red-colored letters meant that the cue was invalid, and thus, subjects had to respond to the non-cued level. Neither the interference nor the attentional shift demonstrated any asymmetry between the global and local levels. ERPs also did not differ substantially after local and global cues. In the condition demanding a shift of focus (invalid cue, incongruent letter), a positive deflection of the lateralized readiness potential indicated the activation of the wrong response channel. The large RT increment in this condition was not accompanied by an increase of the P600 latency. Two possible mechanisms of attentional shift may be proposed, the first related to perceptual processes (e.g. an additional visual search), and the second, to the competition between two response intentions.