Development of the time course for processing conflict: an event-related potentials study with 4 year olds and adults

Background

Tasks involving conflict are widely used to study executive attention. In the flanker task, a target stimulus is surrounded by distracting information that can be congruent or incongruent with the correct response. Developmental differences in the time course of brain activations involved in conflict processing were examined for 22 four year old children and 18 adults. Subjects performed a child-friendly flanker task while their brain activity was registered using a high-density electroencephalography system.

Results

General differences were found in the amplitude and time course of event-related potentials (ERPs) between children and adults that are consistent with their differences in reaction time. In addition, the congruency of flankers affected both the amplitude and latency of some of the ERP components. These effects were delayed and sustained for longer periods of time in the children compared to the adults.

Conclusions

These differences constitute neural correlates of children's greater difficulty in monitoring and resolving conflict in this and similar tasks.

Individual differences in executive attention predict self-regulation and adolescent psychosocial behaviors

This study examined temperament, executive attention, parental monitoring and relationships, and involvement in pro- and antisocial behaviors in an ethnically diverse sample of adolescents. We sought to relate parent- and self-reported effortful control to performance on measures of executive attention and to better understand the relative contributions of individual-difference variables and environmental variables in predicting behaviors in adolescence. The results indicated a relationship between poor executive attention and mother-reported effortful control. Inclusion of individual-difference variables significantly increased prediction of problem-behavior scores, suggesting the importance of including such variables in studies of adolescent deviance.

See clearly: suggestion, hypnosis, attention, and visual acuity

Some reports claim that positive suggestion (e.g., using hypnosis) can significantly improve visual acuity (e.g., in myopes). Based on behavioral, neurocognitive, and ophthalmological findings, the authors provide a critical account to review and challenge some of these data. While acknowledging the relative merits of hypnosis for investigating visual phenomena, an array of arguments converges to propose caveats to the apparent influence suggestion can exert on visual acuity. The authors argue that neither suggestion nor hypnotic phenomena are likely to significantly improve myopic vision and contend that a responsible scientific attitude should carefully outline what hypnosis and suggestion cannot do in addition to what they can. It seems likely that the small apparent influence of suggestion on visual acuity is mediated by changes in attention. The authors outline how attention can affect visual acuity.

Developing mechanisms of temperamental effortful control

Studies of temperament from early childhood to adulthood have demonstrated inverse relationships between negative affectivity and effortful control. Effortful control is also positively related to the development of conscience and appears as a protective factor in the development of behavior disorders. In this study, the development of attentional mechanisms underlying effortful control was investigated in 2- to 3-year-old children, as indexed by their performance in a) making anticipatory eye movements to ambiguous locations and b) resolving conflict between location and identity in a spatial conflict task. The ability to make anticipatory eye movements to ambiguous locations within a sequence was clearly present at 24 months. By 30 months, children could also successfully perform a spatial conflict task that introduced conflict between identity and location, and at that age, children's success on ambiguous anticipatory eye movements was related to lower interference from conflict in the spatial conflict task. Children's performance on the eye-movement task was correlated with performance and reaction time on spatial tasks, and both were related to aspects of effortful control and negative affect as measured in children's parent-reported temperament.

Synaptogenesis and heritable aspects of executive attention

In humans, changes in brain structure and function can be measured non-invasively during postnatal development. In animals, advanced optical imaging measures can track the formation of synapses during learning and behavior. With the recent progress in these technologies, it is appropriate to begin to assess how the physiological processes of synapse, circuit, and neural network formation relate to the process of cognitive development. Of particular interest is the development of executive function, which develops more gradually in humans. One approach that has shown promise is molecular genetics. The completion of the human genome project and the human genome diversity project make it straightforward to ask whether variation in a particular gene correlates with variation in behavior, brain structure, brain activity, or all of the above. Strategies that unify the wealth of biochemical knowledge pertaining to synapse formation with the functional measures of brain structure and activity may lead to new insights in developmental cognitive psychology.

Development of attentional networks in childhood

Recent research in attention has involved three networks of anatomical areas that carry out the functions of orienting, alerting and executive control (including conflict monitoring). There have been extensive cognitive and neuroimaging studies of these networks in adults. We developed an integrated Attention Network Test (ANT) to measure the efficiency of the three networks with adults. We have now adapted this test to study the development of these networks during childhood. The test is a child-friendly version of the flanker task with alerting and orienting cues. We studied the development of the attentional networks in a cross-sectional experiment with four age groups ranging from 6 through 9 (Experiment 1). In a second experiment, we compared children (age 10 years) and adult performance in both child and adults versions of the ANT. Reaction time and accuracy improved at each age interval and positive values were found for the average efficiency of each of the networks. Alertness showed evidence of change up to and beyond age 10, while conflict scores appear stable after age seven and orienting scores do not change in the age range studied. A final experiment with forty 7-year-old children suggested that children like adults showed independence between the three networks under some conditions.

Developing mechanisms of temperamental effortful control

Studies of temperament from early childhood to adulthood have demonstrated inverse relationships between negative affectivity and effortful control. Effortful control is also positively related to the development of conscience and appears as a protective factor in the development of behavior disorders. In this study, the development of attentional mechanisms underlying effortful control was investigated in 2- to 3-year-old children, as indexed by their performance in a) making anticipatory eye movements to ambiguous locations and b) resolving conflict between location and identity in a spatial conflict task. The ability to make anticipatory eye movements to ambiguous locations within a sequence was clearly present at 24 months. By 30 months, children could also successfully perform a spatial conflict task that introduced conflict between identity and location, and at that age, children's success on ambiguous anticipatory eye movements was related to lower interference from conflict in the spatial conflict task. Children's performance on the eye-movement task was correlated with performance and reaction time on spatial tasks, and both were related to aspects of effortful control and negative affect as measured in children's parent-reported temperament.

An approach to the psychobiology of personality disorders

Human variability in temperament allows a unique natural experiment where reactivity, self-regulation, and experience combine in complex ways to produce an individual personality. Personality disorders may result from changes in the way past memories filter new information in situations of emotional involvement with others. According to this view, disorders are specific to their initiating circumstances rather than a general difficulty that might extend to classes of information processing remote from triggers for the disorder. A different view suggests a more general deficit in attentional control mechanisms that might extend to a wide range of situations far from those related to the core abnormality. This paper outlines methods for examining these views and presents data from the study of borderline personality disorder, arguing in favor of high negative emotionality being combined with a deficit in an executive attentional control network. Because this attentional network has already been well described in terms of anatomy, the cognitive operations involved, development, chemical modulators, and effects of lesions and candidate genes, these findings may have implications for understanding the disorder and its treatment. We consider these implications in terms of a general approach to the study of personality development and its disorders.

Imaging a science of mind

I believe that the study of neuroimaging has supported localization of mental operations within the human brain. Most studies have shown a small number of widely distributed brain areas that must be orchestrated to carry out a cognitive task. Although, as in all sciences, there are disagreements, the convergence of results in areas of attention and language in particular seem impressive. Moreover, the anatomical data has helped us to specify the computations that are used by the brain to carry out cognitive tasks. Building upon localization of cognitive operations, imaging methods are being applied to studies of the circuitry, plasticity and individual development of neural networks. Working together with cellular and genetic methods, there is movement towards a more unified view of the role of the human brain in supporting the mind.

Posthypnotic suggestion and the modulation of Stroop interference under cycloplegia

Recent data indicate that under a specific posthypnotic suggestion to circumvent reading, highly suggestible subjects successfully eliminated the Stroop interference effect. The present study examined whether an optical explanation (e.g., visual blurring or looking away) could account for this finding. Using cyclopentolate hydrochloride eye drops to pharmacologically prevent visual accommodation in all subjects, behavioral Stroop data were collected from six highly hypnotizables and six less suggestibles using an optical setup that guaranteed either sharply focused or blurred vision. The highly suggestibles performed the Stroop task when naturally vigilant, under posthypnotic suggestion not to read, and while visually blurred; the less suggestibles ran naturally vigilant, while looking away, and while visually blurred. Although visual accommodation was precluded for all subjects, posthypnotic suggestion effectively eliminated Stroop interference and was comparable to looking away in controls. These data strengthen the view that Stroop interference is neither robust nor inevitable and support the hypothesis that posthypnotic suggestion may exert a top-down influence on neural processing.

Mapping the genetic variation of executive attention onto brain activity

Brain imaging data have repeatedly shown that the anterior cingulate cortex is an important node in the brain network mediating conflict. We previously reported that polymorphisms in dopamine receptor (DRD4) and monoamine oxidase A (MAOA) genes showed significant associations with efficiency of handling conflict as measured by reaction time differences in the Attention Network Test (ANT). To examine whether this genetic variation might contribute to differences in brain activation within the anterior cingulate cortex, we genotyped 16 subjects for the DRD4 and MAOA genes who had been scanned during the ANT. In each of the two genes previously associated with more efficient handling of conflict in reaction time experiments, we found a polymorphism in which persons with the allele associated with better behavioral performance showed significantly more activation in the anterior cingulate while performing the ANT than those with the allele associated with worse performance. The results demonstrate how genetic differences among individuals can be linked to individual differences in neuromodulators and in the efficiency of the operation of an appropriate attentional network.

Cognitive and brain consequences of conflict

Tasks involving conflict between stimulus dimensions have been shown to activate dorsal anterior cingulate and prefrontal areas. It has been proposed that the dorsal anterior cingulate is involved a domain general process of monitoring conflict, while prefrontal areas are involved in resolving conflict. We examine three tasks that all require people to respond based on one stimulus dimension while ignoring another conflicting dimension, but which vary in the source of conflict. One of the tasks uses language stimuli (Stroop effect) and two use nonlanguage spatial conflicts appropriate for children and nonhuman animals. In Experiment 1, 12 participants were studied with event-related functional magnetic resonance imaging (fMRI) while performing each of the three tasks. Reaction times for each of the three tasks were significantly longer in the incongruent condition compared with the congruent condition, demonstrating that each task elicits a conflict. By studying the same people in the same session, we test the hypothesis that conflict activates a similar brain network in the three tasks. Significant activations were found in the anterior cingulate and left prefrontal cortex for all three conflict tasks. Within these regions, the conflict component demonstrated evidence for significant common activation across the three tasks, although the peak activation point and spatial extent were not identical. Other areas demonstrated activation unique to each task. Experiments 2-4 provide behavioral evidence indicating considerable independence between conflict operations involved in the tasks. The behavioral and fMRI results taken together seem to argue against a single unified network for processing conflict, but instead support either distinct networks for each conflict task or a single network that monitors conflict with different sites used to resolve the conflict.

Attentional mechanisms of borderline personality disorder

We consider whether disruption of a specific neural circuit related to self-regulation is an underlying biological deficit in borderline personality disorder (BPD). Because patients with BPD exhibit a poor ability to regulate negative affect, we hypothesized that brain mechanisms thought to be involved in such self-regulation would function abnormally even in situations that seem remote from the symptoms exhibited by these patients. To test this idea, we compared the efficiency of attentional networks in BPD patients with controls who were matched to the patients in having very low self-reported effortful control and very high negative emotionality and controls who were average in these two temperamental dimensions. We found that the patients exhibited significantly greater difficulty in their ability to resolve conflict among stimulus dimensions in a purely cognitive task than did average controls but displayed no deficit in overall reaction time, errors, or other attentional networks. The temperamentally matched group did not differ significantly from either group. A significant correlation was found between measures of the ability to control conflict in the reaction-time task and self-reported effortful control.

Hypnotic suggestion and the modulation of Stroop interference

BACKGROUND

Hypnosis has been used clinically for hundreds of years and is primarily a phenomenon involving attentive receptive concentration. Cognitive science has not fully exploited hypnosis and hypnotic suggestion as experimental tools. This study was designed to determine whether a hypnotic suggestion to hinder lexical processing could modulate the Stroop effect.

METHODS

Behavioral Stroop data were collected from 16 highly suggestible and 16 less suggestible subjects; both naturally vigilant and under posthypnotic suggestion. Subjects were urged to only attend to the ink color and to impede reading the stimuli under posthypnotic suggestion.

RESULTS

Whereas posthypnotic suggestion eliminated Stroop interference for highly suggestible subjects, less suggestible control subjects showed no significant reduction in the interference effect.

CONCLUSIONS

This outcome challenges the dominant view that word recognition is obligatory for proficient readers, and may provide insight into top-down influences of suggestion on cognition.

Assessing the molecular genetics of attention networks

BACKGROUND

Current efforts to study the genetic underpinnings of higher brain functions have been lacking appropriate phenotypes to describe cognition. One of the problems is that many cognitive concepts for which there is a single word (e.g. attention) have been shown to be related to several anatomical networks. Recently, we have developed an Attention Network Test (ANT) that provides a separate measure for each of three anatomically defined attention networks.

RESULTS

In this study we have measured the efficiency of neural networks related to aspects of attention using the ANT in a population of 200 adult subjects. We then examined genetic polymorphisms in four candidate genes (DRD4, DAT, COMT and MAOA) that have been shown to contribute to the risk of developing various psychiatric disorders where attention is disrupted. We find modest associations of several polymorphisms with the efficiency of executive attention but not with overall performance measures such as reaction time.

CONCLUSIONS

These results suggest that genetic variation may underlie inter-subject variation in the efficiency of executive attention. This study also shows that genetic influences on executive attention may be specific to certain anatomical networks rather than affecting performance in a global or non-specific manner. Lastly, this study further validates the ANT as an endophenotypic assay suitable for assessing how genes influence certain anatomical networks that may be disrupted in various psychiatric disorders.

Mental chronometry in the study of individual and group differences

The papers in this issue are excellent examples of the many uses of measuring reaction time in the exploration of nervous system pathologies. In our commentary we consider mental chronometry as a field that seeks to measure the time course of mental operations in the human nervous system. We draw upon diverse methods such as neuroimaging, electrical recording and reaction time to illustrate the use of chronometry in conjunction with anatomy and genetics to approach both normal individual differences and pathologies. The goal is to examine general and specific changes in neural networks that underlie both variations in normal function and changes due to pathology. Although much remains to be done along these lines, it is now possible to see how the various chronometric contributions outlined in this special issue can converge to provide a basis for improved understanding of the genetic and experiential basis of cognitive and emotional processes.

Convergence of psychological and biological development

The special issue provides an opportunity to assess the degree of integration that has been achieved between studies of psychological and biological development. This commentary uses the material in the special issue to address integration of the two fields and to suggest some future developments.

Testing the efficiency and independence of attentional networks

In recent years, three attentional networks have been defined in anatomical and functional terms. These functions involve alerting, orienting, and executive attention. Reaction time measures can be used to quantify the processing efficiency within each of these three networks. The Attention Network Test (ANT) is designed to evaluate alerting, orienting, and executive attention within a single 30-min testing session that can be easily performed by children, patients, and monkeys. A study with 40 normal adult subjects indicates that the ANT produces reliable single subject estimates of alerting, orienting, and executive function, and further suggests that the efficiencies of these three networks are uncorrelated. There are, however, some interactions in which alerting and orienting can modulate the degree of interference from flankers. This procedure may prove to be convenient and useful in evaluating attentional abnormalities associated with cases of brain injury, stroke, schizophrenia, and attention-deficit disorder. The ANT may also serve as an activation task for neuroimaging studies and as a phenotype for the study of the influence of genes on attentional networks.

Attentional phenotypes for the analysis of higher mental function

We outline a strategy to relate normal cognitive processes to candidate genes. First, brain imaging is used to specify a cognitive process "attention" in terms of the neural networks involved. Next, evidence is presented showing that the operation of each network involves a dominant neuromodulator. Then we discuss development of a task designed to measure the efficiency of each network in normal individuals and consider evidence on the independence, reliability, and heritability of the networks. DNA from cheek swabs of subjects who performed the task are then used to examine candidate polymorphisms in genes related to the transmitters. We then examine the ability of these candidate alleles to predict the efficiency of relevant networks. This process has demonstrated that candidate genes are related to specific networks of attention to a greater degree than to overall performance as measured by reaction time and accuracy. These findings require replication and possible extension to other cognitive processes.

Assessing the heritability of attentional networks

BACKGROUND

Current efforts to study the genetics of higher functions have been lacking appropriate phenotypes to describe cognition. One of the problems is that many cognitive concepts for which there is a single word (e.g. attention) have been shown to be related to several anatomical networks. Recently we have developed an Attention Network Test (ANT) that provides a separate measure for each of three anatomically defined attention networks. In this small scale study, we ran 26 pairs of MZ and DZ twins in an effort to determine if any of these networks show sufficient evidence of heritability to warrant further exploration of their genetic basis.

RESULTS

The efficiency of the executive attention network, that mediates stimulus and response conflict, shows sufficient heritability to warrant further study. Alerting and overall reaction time show some evidence for heritability and in our study the orienting network shows no evidence of heritability.

CONCLUSIONS

These results suggest that genetic variation contributes to normal individual differences in higher order executive attention involving dopamine rich frontal areas including the anterior cingulate. At least the executive portion of the ANT may serve as a valid endophenotype for larger twin studies and subsequent molecular genetic analysis in normal subject populations.