The counting stroop: An interference task specialized for functional neuroimaging-validation study with functional MRI

Meta-analytic evidence for a superordinate cognitive control network subserving diverse executive functions

Classic cognitive theory conceptualizes executive functions as involving multiple specific domains, including initiation, inhibition, working memory, flexibility, planning, and vigilance. Lesion and neuroimaging experiments over the past two decades have suggested that both common and unique processes contribute to executive functions during higher cognition. It has been suggested that a superordinate fronto-cingulo-parietal network supporting cognitive control may also underlie a range of distinct executive functions. To test this hypothesis in the largest sample to date, we used quantitative meta-analytic methods to analyze 193 functional neuroimaging studies of 2,832 healthy individuals, ages 18-60, in which performance on executive function measures was contrasted with an active control condition. A common pattern of activation was observed in the prefrontal, dorsal anterior cingulate, and parietal cortices across executive function domains, supporting the idea that executive functions are supported by a superordinate cognitive control network. However, domain-specific analyses showed some variation in the recruitment of anterior prefrontal cortex, anterior and midcingulate regions, and unique subcortical regions such as the basal ganglia and cerebellum. These results are consistent with the existence of a superordinate cognitive control network in the brain, involving dorsolateral prefrontal, anterior cingulate, and parietal cortices, that supports a broad range of executive functions.

A review of neurofeedback treatment for pediatric ADHD

OBJECTIVE

The aim of this paper was to review all randomized published trials and unpublished conference presentations on the neurofeedback (NF) treatment of pediatric ADHD, and their relevance, strengths, and limitations.

METHOD

Via PsychInfo and Medline searches and contacts with NF researchers 14 studies were identified and reviewed.

RESULTS

The majority were conducted from 1994 to 2010, with 5- to 15-year-olds, usually male and White with the combined type of ADHD. Most studies used theta/beta NF with a unipolar-electrode placement at Cz and demonstrated, where reported, an overall ADHD mean effect size of d = 0.69, a medium effect. Main study strengths, within some studies, include use of randomization, treatment control conditions, Diagnostic and Statistical Manual of Mental Disorders criteria, evidence-based assessment of ADHD, standard treatment outcome measures, multidomain assessment, and, for some studies, moderate sample size, some type of blind and the identification of medication as a concomitant treatment. Main study limitations (and directions for future research) include the lack of adequate blinding of participants, raters and NF trainers, a sham-NF/blinded control treatment condition, posttreatment follow-up, generalizability, specific details about delivery of NF, identification and control of comorbidity, and the identification, measurement, and control of concomitant treatments and potential side effects.

CONCLUSION

Based on the results and methodologies of published studies, this review concludes that NF for pediatric ADHD can be currently considered as "probably efficacious."

Brain circuitries involved in semantic interference by demands of emotional and non-emotional distractors

BACKGROUND

Previous studies have indicated that the processes leading to the resolution of emotional and non-emotional interference conflicts are unrelated, involving separate networks. It is also known that conflict resolution itself suggests a considerable overlap of the networks. Our study is an attempt to examine how these findings may be related.

METHODOLOGY/PRINCIPAL FINDINGS

We used functional magnetic resonance imaging (fMRI) to study neural responses of 24 healthy subjects to emotional and non-emotional conflict paradigms involving the presentation of congruent and incongruent word-face pairs based on semantic incompatibility between targets and distractors. In the emotional task, the behavioral interference conflict was greater (compared to the non-emotional task) and was paralleled by involvement of the extrastriate visual and posterodorsal medial frontal cortices. In both tasks, we also observed a common network including the dorsal anterior cingulate, the supplemental motor area, the anterior insula and the inferior prefrontal cortex, indicating that these brain structures are markers of experienced conflict. However, the emotional task involved conflict-triggered networks to a considerably higher degree.

CONCLUSIONS/SIGNIFICANCE

Our findings indicate that responses to emotional and non-emotional distractors involve the same systems, which are capable of flexible adjustments based on conflict demands. The function of systems related to conflict resolution is likely to be adjusted on the basis of an evaluation process that primarily involves the extrastriate visual cortex, with target playing a significant role.

Resiliency in adolescents at high risk for substance abuse: flexible adaptation via subthalamic nucleus and linkage to drinking and drug use in early adulthood

INTRODUCTION

The personality trait resiliency is the ability to flexibly adapt impulse control relative to contextual demand. Low resiliency has been linked to later alcohol/drug problems. The underlying psychological and neural mechanisms are unknown, but neurocomputational models suggested relations between resiliency and working memory. Cortical-striatal connectivity has been proposed to underlie adaptive switches between cautious and risky behaviors.

METHODS

Working memory was probed in sixty-seven 18- to 22-year-olds from a larger community study of alcoholism, using the n-back task during functional magnetic resonance imaging. Functional connectivity between task-related regions was investigated with psychophysiological interaction analysis. Resiliency was measured in early teen years and related to early adulthood measures of drinking/drug use, task activation, and connectivity. Relationships with risk factors, including family history, age of drinking onset, and number of alcohol problems, were also investigated.

RESULTS

Higher resiliency was related to lower levels of substance use, fewer alcohol problems, and better working memory performance. Whole-brain regression revealed resiliency negatively correlated with activation of subthalamic nucleus (STN) and pallidum during the n-back. High and Low resiliency quartile groups (n = 17 each) differed in coupling strength between STN and median cingulate cortex, a region of reduced activation during working memory. The high resiliency group had later onset of drinking, fewer alcohol problems, had used fewer illicit drugs, and were less likely to smoke cigarettes than their low resiliency counterparts.

CONCLUSIONS

These findings suggest that resiliency in early adolescence may protect against alcohol problems and drug use, although the direction of this effect is currently unknown. This protective factor may relate to executive functioning as supported by the finding of a neural link shared between resiliency and working memory in basal ganglia structures. The STN, a key basal ganglia structure, may adaptively link flexible impulse control with cognitive processing, potentially modulating substance use outcomes.

Practice on conflict tasks promotes executive function of working memory in the elderly

Effects of practice on a conflict task in elderly individuals are examined with a focus on its impact on executive function in working memory. During a short-term practice period, healthy elderly participants practiced switching attention using a Stroop task that involved a conflict between a task relevant stimulus and an irrelevant stimulus. To explore neural substrates underlying practice effects, two working memory tasks were used: a focus reading span test (F-RST) and a non-focus reading span test (NF-RST); the NF-RST test demanded greater switching attention due to a conflict between the relevant task stimulus and an irrelevant task stimulus, thus requiring an attention switch from the latter to the former. Following the Stroop task practice, fMRI data showed that participants who had engaged in practice had significant increases in activation in the anterior cingulate cortex (ACC), the left inferior parietal lobule (IPL), the left dorsolateral prefrontal cortex (DLPFC) and the precuneus regions during the NF-RST. By contrast, a control group, which did not practice, showed no significant increases in these regions. Results suggest that practice on conflict tasks in elderly individuals activated regions related to conflict perceiving and attention switching regions as well as attention-maintenance regions thereby improving performance on tasks requiring a high degree of attention control of working memory.

Neural correlates of attention bias to threat in post-traumatic stress disorder

Attentional biases have been proposed to contribute to symptom maintenance in posttraumatic stress disorder (PTSD), although the neural correlates of these processes have not been well defined; this was the goal of the present study. We administered an attention bias task, the dot probe, to a sample of 37 (19 control, 18 PTSD+) traumatized African-American adults during fMRI. Compared to controls, PTSD+ participants demonstrated increased activation in the dorsolateral prefrontal cortex (dlPFC) in response to threat cue trials. In addition, attentional avoidance of threat corresponded with increased ventrolateral prefrontal cortex (vlPFC) and dorsal anterior cingulate cortex (dACC) activation in the PTSD group, a pattern that was not observed in controls. These data provide evidence to suggest that relative increases in dlPFC, dACC and vlPFC activation represent neural markers of attentional bias for threat in individuals with PTSD, reflecting selective disruptions in attentional control and emotion processing networks in this disorder.

Basolateral amygdala encodes upcoming errors but not response conflict

Adaptive behavior depends on the detection of potential errors so that ongoing behavior might be corrected. Here, we ask whether basolateral amygdala (ABL) might serve this function by examining activity in rats performing a task in which errors were induced by pitting two behavioral responses against each other. This response competition or conflict was created by forcing rats to respond away from the direction in which they were freely choosing on the majority of trials. Rats were slower and less accurate on these incongruent trial types. We found that activity in ABL fired more strongly prior to errant responses, but did not signal the potential for errors on correctly performed incongruent trials. These data support a role for ABL in processing errors prior to their occurrence and suggest that ABL is not involved in monitoring conflict so that ongoing behavior might be corrected.

Gray matter volume abnormalities in individuals with cognitive vulnerability to depression: a voxel-based morphometry study

BACKGROUND

The hopelessness theory of depression posits that individuals with negative cognitive styles are at an increased risk for depression following negative life events. In neuroimaging studies, brain gray matter volume abnormalities correlate with the presence of depressive disorders. However, it is unknown whether changes in gray matter volume also appear in healthy individuals with cognitive vulnerability to depression (CVD).

METHODS

30 subjects diagnosed with CVD, 33 first-episode patients with major depressive disorder (MDD), and 32 healthy controls were examined using voxel-based morphometry following magnetic resonance imaging (MRI).

RESULTS

We found significant volumetric differences between three groups in the left precentral gyrus, right fusiform gyrus and the right thalamus. In these regions, compared to controls, CVD subjects showed reduced gray matter volumes in the left precentral gyrus and right fusiform gyrus. MDD patients demonstrated reduced gray matter volume in the left precentral gyrus and increased gray matter volume in the right thalamus. Additionally, CVD individuals had significantly smaller right fusiform gyrus and right thalamus than MDD patients. The weakest-link scores on CSQ were negatively correlated with gray matter volumes in the left precentral gyrus.

CONCLUSIONS

Reductions in brain gray matter volume exist widely in individuals with CVD. In addition, there exist similar abnormalities in gray matter volume in both CVD subjects and MDD patients. Reductions of gray matter volume in the left precentral gyrus might be correlated to the negative cognitive styles, as well as an increased risk for depression.

Executive function and PTSD: disengaging from trauma

Neuropsychological approaches represent an important avenue for identifying susceptibility and resiliency factors relating to the development and maintenance of posttraumatic stress disorder (PTSD) symptoms post-trauma. This review will summarize results from prospective longitudinal and retrospective cross-sectional studies investigating executive function associated with PTSD. This research points specifically towards subtle impairments in response inhibition and attention regulation that may predate trauma exposure, serve as risk factors for the development of PTSD, and relate to the severity of symptoms. These impairments may be exacerbated within emotional or trauma-related contexts, and may relate to dysfunction within dorsal prefrontal networks. A model is presented concerning how such impairments may contribute to the clinical profile of PTSD and lead to the use of alternative coping styles such as avoidance. Further neuropsychological research is needed to identify the effects of treatment on cognitive function and to potentially characterize mechanisms of current PTSD treatments. Knowledge gained from cognitive and neuroscientific research may prove valuable for informing the future development of novel, more effective, treatments for PTSD. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.

Impaired executive functions in paediatric obsessive-compulsive disorder patients

Isık Taner Y, Erdogan Bakar E, Oner O. Impaired executive functions in paediatric obsessive-compulsive disorder patients.

Objective: There are only few studies which investigated the neuropsychological performances of paediatric patients with obsessive-compulsive disorder (OCD). Previous studies show that most of adult OCD patients had an onset of their first symptoms before the age of 15. Our objective was to evaluate the neuropsychological functions in paediatric patients with OCD.

Methods: We compared the executive functions and general intelligence of child and adolescent OCD patients (n = 20) with age- and gender-matched healthy controls (n = 20). To compare mentioned skills, a neuropsychological test battery including Wechsler Intelligence Scale for Children-Revised (WISC-R), Wisconsin Card Sorting Test (WCST), Stroop Test and Verbal Fluency Test was performed.

Result: Performances of the OCD and control subjects on neuropsychological tests were statistically analysed by using multivariate analysis of covariance (MANCOVA), in which Full Scale Intelligence Quotient (FSIQ) results were taken into consideration as a covariate to observe FSIQ's effect on test scores. Our results showed that the differences in WISC-R Picture Arrangement and Coding scores remained significant when co-analysed with FSIQ scores. In a similar manner, the OCD group exhibited worse performances on STR1-duration, STR3-duration, STR3-error, STR4-duration, STR4-error, STR5-correct response, and STR5-error as compared with the control group when FSIQ scores were taken into calculation. Some variables of the WCST (perseverative responses, percent errors, abstraction-flexibility and categories completed) also yield lower test scores in the OCD group. There was no significant difference between the groups regarding Verbal Fluency Test scores.

Conclusion: Our results suggested that paediatric OCD patients had worse abstraction-flexibility, mental set-shifting, verbal comprehension and visuospatial/construction abilities.

Lower activation in the right frontoparietal network during a counting Stroop task in a cocaine-dependent group

Dysregulation in cognitive control networks may mediate core characteristics of drug addiction. Cocaine dependence has been particularly associated with low activation in the frontoparietal regions during conditions requiring decision making and cognitive control. This functional magnetic resonance imaging (fMRI) study aimed to examine differential brain-related activation to cocaine addiction during an inhibitory control paradigm, the "Counting" Stroop task, given the uncertainties of previous studies using positron emission tomography. Sixteen comparison men and 16 cocaine-dependent men performed a cognitive "Counting" Stroop task in a 1.5T Siemens Avanto. The cocaine-dependent patient group and the control group were matched for age, level of education and general intellectual functioning. Groups did not differ in terms of the interference measures deriving from the counting Stroop task. Moreover, the cocaine-dependent group showed lower activation in the right inferior frontal gyrus, the right inferior parietal gyrus and the right superior temporal gyrus than the control group. Cocaine patients did not show any brain area with increased activation when compared with controls. In short, Stroop-interference was accompanied by lower activation in the right frontoparietal network in cocaine-dependent patients, even in the absence of inter-group behavioral differences. Our study is the first application of a counting Stroop task using fMRI to study cocaine dependence and yields results that corroborate the involvement of a frontoparietal network in the neural changes associated with attentional interference deficits in cocaine-dependent men.

Distraction by Auditory Novelty

The unexpected occurrence of an oddball auditory stimulus (novel) among an otherwise repeated stream of sounds (standards) is known to impact negatively on participants’ performance in an unrelated visual task. The present study sought to test new predictions emerging from Parmentier’s (2008) model of distraction by auditory novelty. Participants categorized the direction of visual arrows preceded by a task-irrelevant sound. Two time intervals between distractor and target were tested in separate blocks of trials. Rare auditory novels consisted of the words “left” or “right”, which were either congruent or incongruent with the upcoming target. The data confirmed the slowing of response in the face of a novel (novelty distraction) as well as, on incongruent trials, a further delay due to cross-talk interference between distractor and target (semantic effect). More importantly, and in line with our predictions, the results further showed that (1) the semantic effect, but not novelty distraction, increased with the time interval between distractor and target; and that (2) the production of a response on the first standard trial following a novel trial was slowed if that response required the activation of a recently inhibited network (post-novelty semantic effect). Overall, the data lend support to the view that behavioral distraction by auditory novelty reflects a mosaic of contributors, the effects of which can ripple across trials.

Event-related potential correlates of performance-monitoring in a lateralized time-estimation task

Performance-monitoring as a key function of cognitive control covers a wide range of diverse processes to enable goal directed behavior and to avoid maladjustments. Several event-related brain potentials (ERP) are associated with performance-monitoring, but their conceptual background differs. For example, the feedback-related negativity (FRN) is associated with unexpected performance feedback and might serve as a teaching signal for adaptational processes, whereas the error-related negativity (ERN) is associated with error commission and subsequent behavioral adaptation. The N2 is visible in the EEG when the participant successfully inhibits a response following a cue and thereby adapts to a given stop-signal. Here, we present an innovative paradigm to concurrently study these different performance-monitoring-related ERPs. In 24 participants a tactile time-estimation task interspersed with infrequent stop-signal trials reliably elicited all three ERPs. Sensory input and motor output were completely lateralized, in order to estimate any hemispheric processing preferences for the different aspects of performance monitoring associated with these ERPs. In accordance with the literature our data suggest augmented inhibitory capabilities in the right hemisphere given that stop-trial performance was significantly better with left- as compared to right-hand stop-signals. In line with this, the N2 scalp distribution was generally shifted to the right in addition to an ipsilateral shift in relation to the response hand. Other than that, task lateralization affected neither behavior related to error and feedback processing nor ERN or FRN. Comparing the ERP topographies using the Global Map Dissimilarity index, a large topographic overlap was found between all considered components.With an evenly distributed set of trials and a split-half reliability for all ERP components ≥.85 the task is well suited to efficiently study N2, ERN, and FRN concurrently which might prove useful for group comparisons, especially in clinical populations.

Regional gray and white matter volume associated with Stroop interference: evidence from voxel-based morphometry

During Stroop tasks, subjects experience cognitive interference when they resolve interferences such as identifying the ink color of a printed word while ignoring the word's identity. Stroop paradigms are commonly used as an index of attention deficits and a tool for investigating the functions of the frontal lobes and other associated structures. Despite these uses and the vast amount of attention given to Stroop paradigms, the regional gray matter volume/regional white matter volume (rGMV/rWMV) correlates of Stroop interference have not yet been identified at the whole brain level in normal adults. We examined this issue using voxel-based morphometry in right-handed healthy young adults. We found significant negative relationships between the Stroop interference rate and rGMV in the anterior cingulate cortex (ACC), right inferior frontal gyrus, and cerebellum. Furthermore, we found relationships between the Stroop interference rate and rWMV in bilateral anatomical clusters that extended around extensive WM regions in the dorsal part of the frontal lobe. These findings are the first to reveal rGMV/rWMV that underlie the performance of the Stroop task, a widely used psychological paradigm at the whole brain level. Of note, our findings support the notion that ACC contributes to Stroop performance and show the involvement of regions that have been implicated in response inhibition and attention.

Mechanisms underlying flexible adaptation of cognitive control: behavioral and neuroimaging evidence in a flanker task

Cognitive control can be adapted flexibly according to the conflict level in a given situation. In the Eriksen flanker task, interference evoked by flankers is larger in conditions with a higher, rather than a lower proportion of compatible trials. Such compatibility ratio effects also occur for stimuli presented at two spatial locations suggesting that different cognitive control settings can be simultaneously maintained. However, the conditions and the neural correlates of this flexible adaptation of cognitive control are only poorly understood. In the present study, we further elucidated the mechanisms underlying the simultaneous maintenance of two cognitive control settings. In behavioral experiments, stimuli were presented centrally above and below fixation and hence processed by both hemispheres or lateralized to stimulate hemispheres differentially. The different compatibility ratio at two stimulus locations had a differential influence on the flanker effect in both experiments. In an fMRI experiment, blocks with an identical compatibility ratio at two central spatial locations elicited stronger activity in a network of prefrontal and parietal brain areas, which are known to be involved in conflict resolution and cognitive control, as compared with blocks with a different compatibility ratio at the same spatial locations. This demonstrates that the simultaneous maintenance of two conflicting control settings vs. one single setting does not recruit additional neural circuits suggesting the involvement of one single cognitive control system. Instead a crosstalk between multiple control settings renders adaptation of cognitive control more efficient when only one uniform rather than two different control settings has to be simultaneously maintained.

Structural correlates of cognitive domains in normal aging with diffusion tensor imaging

The involvement of brain structures in specific cognitive functions is not straightforward. In order to characterize the brain micro-structural correlates of cognitive domains, 52 healthy subjects, age 25-82 years, completed a computerized neuropsychological battery and were scanned using magnetic resonance diffusion tensor imaging. Factor analysis of 44 different cognitive scores was performed, isolating three cognitive domains-executive function, information processing speed and memory. Partial correlation was conducted between DTI parameters and each of the three cognitive domains controlling for age and motor function. Regions showing significant correlations with cognitive domains are domain-specific and are consistent with previous knowledge. While executive function was correlated with diffusion tensor imaging (DTI) parameters in frontal white matter and in the superior longitudinal fasciculus, information processing speed was correlated with DTI parameters in the cingulum, corona radiata, inferior longitudinal fasciculus, parietal white matter and in the thalamus. Memory performance was correlated with DTI measures in temporal and frontal gray matter and white matter regions, including the cingulate cortex and the parahippocampus. Thus, inter-subject variability in cognitive performance and tissue morphology, as expressed by diffusion tensor magnetic resonance imaging, can be used to relate tissue microstructure with cognitive performance and to provide information to corroborate other functional localization techniques.

An asymmetric stroop/reverse-stroop interference phenomenon in ADHD

OBJECTIVE

To examine whether participants with ADHD showed a deficit in Stroop/reverse-Stroop interference by comparing them to non-ADHD participants.

METHOD

A group with ADHD, primarily inattentive type (n = 15), and a paired non-ADHD group (n = 15) completed the group version of the Stroop/reverse-Stroop test.

RESULTS

Asymmetric interference was observed between the Stroop test and the reverse-Stroop test in ADHD participants, presenting evidence contrary to Barkley's behavioral inhibition model of ADHD in which response inhibition deficits pertained only to the ADHD-C subtype.

CONCLUSION

Participants with ADHD showed a control deficit in reverse-Stroop interference but not in Stroop interference.

Local and global inhibition in bilingual word production: fMRI evidence from Chinese-English bilinguals

The current study examined the neural correlates associated with local and global inhibitory processes used by bilinguals to resolve interference between competing responses. Two groups of participants completed both blocked and mixed picture naming tasks while undergoing functional magnetic resonance imaging (fMRI). One group first named a set of pictures in L1, and then named the same pictures in L2. The other group first named pictures in L2, and then in L1. After the blocked naming tasks, both groups performed a mixed language naming task (i.e., naming pictures in either language according to a cue). The comparison between the blocked and mixed naming tasks, collapsed across groups, was defined as the local switching effect, while the comparison between blocked naming in each language was defined as the global switching effect. Distinct patterns of neural activation were found for local inhibition as compared to global inhibition in bilingual word production. Specifically, the results suggest that the dorsal anterior cingulate cortex (ACC) and the supplementary motor area (SMA) play important roles in local inhibition, while the dorsal left frontal gyrus and parietal cortex are important for global inhibition.

A Candidate for the Attentional Bottleneck: Set-size Specific Modulation of the Right TPJ during Attentive Enumeration

Several recent behavioral studies have shown that the enumeration of a small number of items (a process termed subitizing) depends on the availability of attentional resources and is not a preattentive process as previously thought. Here we studied the neural correlates of visual enumeration under different attentional loads in a dual-task paradigm using fMRI. Relatively intact subitizing under low attentional load compared to impaired subitizing under high attentional load was associated with an increase in BOLD signal in the right temporo-parietal junction (rTPJ). Crucially, attentionally modulated response in the rTPJ was specific to small set sizes (up to 3 items) and did not occur at larger set sizes (5–7 items). This result has two implications: (1) Subitizing involves part of the fronto-parietal network for stimulus-driven attention providing neural evidence against preattentive subitizing. (2) Activity in rTPJ is set-size modulated. Together with similar evidence from studies probing visual short-term memory, this result suggests that rTPJ modulation might reflect the brain's ability to attentively handle small set sizes. Thus, the rTPJ may play an important role for the emergence of a capacity limit in both enumeration and visual short-term memory.

Modulatory effects of levodopa on cognitive control in young but not in older subjects: a pharmacological fMRI study

Older individuals show decline of prefrontal cortex (PFC) functions which may be related to altered dopaminergic neurotransmission. We investigated the effects of aging and dopaminergic stimulation in 15 young and 13 older healthy subjects on the neural correlates of interference control using fMRI. In a double-blind, placebo-controlled within-subject design, subjects were measured after levodopa (100 mg) or placebo administration. In each session, subjects performed a visual-spatial interference task based on a Stroop/Simon-like paradigm. Across age groups, interference (incongruent relative to congruent trials) was associated with activations in the presupplementary motor area, ACC, and intraparietal cortex. Increased interference was found behaviorally in older volunteers. Differential activation in left dorsolateral PFC in young subjects and bilateral PFC activity in older subjects was observed to be associated with interference control. Performance deteriorated under levodopa only in young subjects. This was accompanied by an increase of neural activity in ACC (p < .05; small-volume correction for multiple comparisons). Worsening of performance under levodopa in young subjects and the associated effect on ACC may indicate that overstimulation of the dopaminergic system compromises interference control. This supports the inverted-U-shaped model of neurotransmitter action.

Brain dynamics of upstream perceptual processes leading to visual object recognition: a high density ERP topographic mapping study

Recent studies suggest that visual object recognition is a proactive process through which perceptual evidence accumulates over time before a decision can be made about the object. However, the exact electrophysiological correlates and time-course of this complex process remain unclear. In addition, the potential influence of emotion on this process has not been investigated yet. We recorded high density EEG in healthy adult participants performing a novel perceptual recognition task. For each trial, an initial blurred visual scene was first shown, before the actual content of the stimulus was gradually revealed by progressively adding diagnostic high spatial frequency information. Participants were asked to stop this stimulus sequence as soon as they could correctly perform an animacy judgment task. Behavioral results showed that participants reliably gathered perceptual evidence before recognition. Furthermore, prolonged exploration times were observed for pleasant, relative to either neutral or unpleasant scenes. ERP results showed distinct effects starting at 280 ms post-stimulus onset in distant brain regions during stimulus processing, mainly characterized by: (i) a monotonic accumulation of evidence, involving regions of the posterior cingulate cortex/parahippocampal gyrus, and (ii) true categorical recognition effects in medial frontal regions, including the dorsal anterior cingulate cortex. These findings provide evidence for the early involvement, following stimulus onset, of non-overlapping brain networks during proactive processes eventually leading to visual object recognition.

The effects of APOE on brain activity do not simply reflect the risk of Alzheimer's disease

Possession of the APOE-ε4 allele is the best established genetic risk factor for sporadic Alzheimer's disease (AD), while the ε2 allele may confer protection against the disease. Previous functional magnetic resonance imaging (fMRI) studies have shown an effect of APOE genotype on brain function, typically by comparing only ε4 carriers with noncarriers. Here we included a wide range of genotype groups to determine how closely the effects of APOE on brain function are related to differences in relative risk for AD. We used functional magnetic resonance imaging (fMRI) to compare the pattern of activation during an episodic encoding task and during a counting Stroop task in 76 adults, aged 32 to 55, with different APOE genotypes (23 ε2/ε3, 20 ε3/ε3, 26 ε3/ε4, and 7 ε4/ε4). Strikingly, participants with an increased risk (ε4 carriers) and with a decreased risk (ε2 carriers) for AD both showed increased activation, relative to ε3 homozygotes, during both tasks. The increased activation was due to decreased deactivation or paradoxical activation of nontask-related regions of the brain, which suggests an intrinsic effect of APOE on the differentiation of functional cortical networks. These results question the often assumed link between APOE, the blood oxygenation level dependent (BOLD) response, and AD risk.

Lying about the valence of affective pictures: an fMRI study

The neural correlates of lying about affective information were studied using a functional magnetic resonance imaging (fMRI) methodology. Specifically, 13 healthy right-handed Chinese men were instructed to lie about the valence, positive or negative, of pictures selected from the International Affective Picture System (IAPS) while their brain activity was scanned by a 3T Philip Achieva scanner. The key finding is that the neural activity associated with deception is valence-related. Comparing to telling the truth, deception about the valence of the affectively positive pictures was associated with activity in the inferior frontal, cingulate, inferior parietal, precuneus, and middle temporal regions. Lying about the valence of the affectively negative pictures, on the other hand, was associated with activity in the orbital and medial frontal regions. While a clear valence-related effect on deception was observed, common neural regions were also recruited for the process of deception about the valence of the affective pictures. These regions included the lateral prefrontal and inferior parietal regions. Activity in these regions has been widely reported in fMRI studies on deception using affectively-neutral stimuli. The findings of this study reveal the effect of valence on the neural activity associated with deception. Furthermore, the data also help to illustrate the complexity of the neural mechanisms underlying deception.

Functional heterogeneity of conflict, error, task-switching, and unexpectedness effects within medial prefrontal cortex

The last decade has seen considerable discussion regarding a theoretical account of medial prefrontal cortex (mPFC) function with particular focus on the anterior cingulate cortex. The proposed theories have included conflict detection, error likelihood prediction, volatility monitoring, and several distinct theories of error detection. Arguments for and against particular theories often treat mPFC as functionally homogeneous, or at least nearly so, despite some evidence for distinct functional subregions. Here we used functional magnetic resonance imaging (fMRI) to simultaneously contrast multiple effects of error, conflict, and task-switching that have been individually construed in support of various theories. We found overlapping yet functionally distinct subregions of mPFC, with activations related to dominant error, conflict, and task-switching effects successively found along a rostral-ventral to caudal-dorsal gradient within medial prefrontal cortex. Activations in the rostral cingulate zone (RCZ) were strongly correlated with the unexpectedness of outcomes suggesting a role in outcome prediction and preparing control systems to deal with anticipated outcomes. The results as a whole support a resolution of some ongoing debates in that distinct theories may each pertain to corresponding distinct yet overlapping subregions of mPFC.

Emotion triggers executive attention: anterior cingulate cortex and amygdala responses to emotional words in a conflict task

Coherent behavior depends on attentional control that detects and resolves conflict between opposing actions. The current functional magnetic resonance imaging study tested the hypothesis that emotion triggers attentional control to speed up conflict processing in particularly salient situations. Therefore, we presented emotionally negative and neutral words in a version of the flanker task. In response to conflict, we found activation of the dorsal anterior cingulate cortex (ACC) and of the amygdala for emotional stimuli. When emotion and conflict coincided, a region in the ventral ACC was activated, which resulted in faster conflict processing in reaction times. Emotion also increased functional connectivity between the ventral ACC and activation of the dorsal ACC and the amygdala in conflict trials. These data suggest that the ventral ACC integrates emotion and conflict and prioritizes the processing of conflict in emotional trials. This adaptive mechanism ensures rapid detection and resolution of conflict in potentially threatening situations signaled by emotional stimuli.

Reduced cognitive control of response inhibition by the anterior cingulate cortex in autism spectrum disorders

Response inhibition, or the suppression of prepotent, but contextually inappropriate behaviors, is essential to adaptive, flexible responding. In autism spectrum disorders (ASD), difficulty inhibiting prepotent behaviors may contribute to restricted, repetitive behavior (RRB). Individuals with ASD consistently show deficient response inhibition while performing antisaccades, which require one to inhibit the prepotent response of looking towards a suddenly appearing stimulus (i.e., a prosaccade), and to substitute a gaze in the opposite direction. Here, we used fMRI to identify the neural correlates of this deficit. We focused on two regions that are critical for saccadic inhibition: the frontal eye field (FEF), the key cortical region for generating volitional saccades, and the dorsal anterior cingulate cortex (dACC), which is thought to exert top-down control on the FEF. We also compared ASD and control groups on the functional connectivity of the dACC and FEF during saccadic performance. In the context of an increased antisaccade error rate, ASD participants showed decreased functional connectivity of the FEF and dACC and decreased inhibition-related activation (based on the contrast of antisaccades and prosaccades) in both regions. Decreased dACC activation correlated with a higher error rate in both groups, consistent with a role in top-down control. Within the ASD group, increased FEF activation and dACC/FEF functional connectivity were associated with more severe RRB. These findings demonstrate functional abnormalities in a circuit critical for volitional ocular motor control in ASD that may contribute to deficient response inhibition and to RRB. More generally, our findings suggest reduced cognitive control over behavior by the dACC in ASD.

Impairment of fronto-striatal and parietal cerebral networks correlates with attention deficit hyperactivity disorder (ADHD) psychopathology in adults - a functional magnetic resonance imaging (fMRI) study

Attention deficit hyperactivity disorder (ADHD) is a common, genetically transmitted common childhood-onset disorder with a high rate of persistence in adulthood. Although many studies have shown anatomical and functional abnormalities in children and adolescents, studies with adult patients are rare. Nineteen adults with ADHD (11 ADHD, combined type; 8 ADHD, partially remitted) and 17 controls were included in this functional magnetic resonance imaging (fMRI) study. Brain activation was investigated with a continuous performance test (CPT). Impaired activation of a fronto-striatal and a parietal attentional network was observed during the NoGo condition in ADHD subjects. Correlations of reduced activity of the caudate nuclei, the anterior cingulate cortex, and parietal cortical structures, as well as increased activity in the insular cortex, with inattention and impulsivity symptom scores were found. The activation patterns were similar to those known from children and adolescents with ADHD. In conclusion we found not only a widespread dysfunction of brain regions that are involved in cognitive processing in adults with ADHD compared with controls, but also correlations between symptom severity and dysfunction of neuronal systems across adult subjects with a history of ADHD in childhood but whose symptoms did (persistent ADHD) and did not (not persistent ADHD) qualify for a full diagnosis of ADHD in adulthood.

Developmental change in the neurophysiological correlates of self-regulation in high- and low-emotion conditions

One of the most important tasks of childhood is learning to self-regulate in the presence of negative emotions. Until recently, almost no research has examined the neurophysiological correlates of emotional self-regulation as it develops over childhood and adolescence. We were interested in plotting a fine-grained developmental profile of the neural underpinnings of self-regulation, in the context of negative emotion, for 7- to 14-year-old children. We predicted that children would recruit less cortical activation with age in the service of self-regulation, reflecting increased neural efficiency with development. We also predicted that children would recruit more cortical activation with increased negative emotion, possibly reflecting greater demand on cortical resources. We administered a Go No-Go task with an emotion induction block and we measured the amplitude of the N2, an event related potential associated with inhibitory control, as it varied with block and with age. Furthermore, we estimated activation for a ventral prefrontal region of interest (ROI; suggestive of orbital frontal, ventromedial prefrontal, or rostral anterior cingulate activation) and a dorsomedial prefrontal ROI (suggestive of dorsal anterior cingulate activation) frequently modeled as cortical generators underlying the N2. Results revealed a marginal decrease in mediofrontal scalp activation, but a more pronounced decrease in activation of the ventromedial prefrontal ROI, with age. There were no age-related changes in dorsomedial prefrontal ROI activation. Lastly, as predicted, we found increased ventral prefrontal ROI activation during the negative emotion induction, possibly reflecting greater recruitment of frontocortical resources underlying emotion regulation, but developmental change in this activation was no different than for the other conditions. Thus, both self-regulation in general and emotion regulation in particular recruited less cortical activation with age, suggesting more efficient cortical mechanisms of response inhibition.

Age-related differences in brain activity underlying identification of emotional expressions in faces

We used fMRI to explore brain activity in young and old adults, while they viewed and labeled faces expressing different emotions as well as neutral expressions. Older adults had significantly greater difficulty identifying expressions of sadness, anger and disgust than young adults. Both groups performed at ceiling for happy expressions. The functional neuroimaging data revealed that both young and old adults recruited a pattern of activity that distinguished happy expressions from all other expressions, but the patterns were age-specific. Older adults showed increased activity in ventromedial prefrontal cortex, lingual gyrus and premotor cortex for happy expressions, whereas younger adults recruited a more widely distributed set of regions including the amgydala, ventromedial prefrontal cortex, lateral prefrontal regions and bilateral inferior parietal and superior temporal areas. Conversely, younger adults showed more activity in the dorsal anterior cingulate for other types of expressions, and older adults had more activity in dorsal cingulate, as well as middle and inferior frontal gyri, somatosensory cortex, insula and middle temporal regions. These results support previous research demonstrating age differences in brain activity during emotional processing, and suggest possible age-related differences in cognitive strategy during identification of happy faces, despite no effect of age on this ability.

Altered processing of contextual information during fear extinction in PTSD: an fMRI study

Medial prefrontal cortical areas have been hypothesized to underlie altered contextual processing in posttraumatic stress disorder (PTSD). We investigated brain signaling of contextual information in this disorder. Eighteen PTSD subjects and 16 healthy trauma-exposed subjects underwent a two-day fear conditioning and extinction paradigm. On day 1, within visual context A, a conditioned stimulus (CS) was followed 60% of the time by an electric shock (conditioning). The conditioned response was then extinguished (extinction learning) in context B. On day 2, recall of the extinction memory was tested in context B. Skin conductance response (SCR) and functional magnetic resonance imaging (fMRI) data were collected during context presentations. There were no SCR group differences in any context presentation. Concerning fMRI data, during late conditioning, when context A signaled danger, PTSD subjects showed dorsal anterior cingulate cortical (dACC) hyperactivation. During early extinction, when context B had not yet fully acquired signal value for safety, PTSD subjects still showed dACC hyperactivation. During late extinction, when context B had come to signal safety, they showed ventromedial prefrontal cortex (vmPFC) hypoactivation. During early extinction recall, when context B signaled safety, they showed both vmPFC hypoactivation and dACC hyperactivation. These findings suggest that PTSD subjects show alterations in the processing of contextual information related to danger and safety. This impairment is manifest even prior to a physiologically-measured, cue-elicited fear response, and characterized by hypoactivation in vmPFC and hyperactivation in dACC.

Reduced functional connectivity in a right-hemisphere network for volitional ocular motor control in schizophrenia

Patients with schizophrenia consistently show deficient performance on tasks requiring volitional saccades. We previously reported reduced fractional anisotropy in the white matter underlying right dorsal anterior cingulate cortex in schizophrenia, which, along with lower fractional anisotropy in the right frontal eye field and posterior parietal cortex, predicted longer latencies of volitional saccades. This suggests that reduced microstructural integrity of dorsal anterior cingulate cortex white matter disrupts connectivity in the right hemisphere-dominant network for spatial attention and volitional ocular motor control. To test this hypothesis, we examined functional connectivity of the cingulate eye field component of this network, which is located in dorsal anterior cingulate cortex, during a task comprising volitional prosaccades and antisaccades. In patients with schizophrenia, we expected to find reduced functional connectivity, specifically in the right hemisphere, which predicted prolonged saccadic latency. Twenty-seven medicated schizophrenia outpatients and 21 demographically matched healthy controls performed volitional saccades during functional magnetic resonance imaging. Based on task-related activation, seed regions in the right and left cingulate eye field were defined. In both groups, the right and left cingulate eye field showed positive correlations with the ocular motor network and negative correlations with the default network. Patients showed reduced positive functional connectivity of the cingulate eye field, specifically in the right hemisphere. Negative functional connectivity of the right cingulate eye field predicted faster saccades, but these relations differed by group, and were only present in controls. This pattern of relations suggests that the coordination of activity between ocular motor and default networks is important for efficient task performance and is disrupted in schizophrenia. Along with prior observations of reduced white matter microstructural integrity (fractional anisotropy) in schizophrenia, the present finding of reduced functional connectivity suggests that functional and structural abnormalities of the right cingulate eye field disrupt connectivity in the network for spatial attention and volitional ocular motor control. These abnormalities may contribute to deficits in overcoming prepotency in the service of directing eye gaze and attention to the parts of the environment that are the most behaviourally relevant.

Attention-deficit/hyperactivity disorder and attention networks

Research attempting to elucidate the neuropathophysiology of attention-deficit/hyperactivity disorder (ADHD) has not only shed light on the disorder itself, it has simultaneously provided new insights into the mechanisms of normal cognition and attention. This review will highlight and integrate this bidirectional flow of information. Following a brief overview of ADHD clinical phenomenology, ADHD studies will be placed into a wider historical perspective by providing illustrative examples of how major models of attention have influenced the development of neurocircuitry models of ADHD. The review will then identify major components of neural systems potentially relevant to ADHD, including attention networks, reward/feedback-based processing systems, as well as a 'default mode' resting state network. Further, it will suggest ways in which these systems may interact and be influenced by neuromodulatory factors. Recent ADHD imaging data will be selectively provided to both illustrate the field's current level of knowledge and to show how such data can inform our understanding of normal brain functions. The review will conclude by suggesting possible avenues for future research.

Postconcussion syndrome after minor head injury: brain activation of working memory and attention

After minor head injury (MHI) postconcussive symptoms (PCS) such as memory and attention deficits frequently occur. It has been hypothesised that PCS are caused by microstructural damage to the brain due to shearing injury, which is not detectable with conventional imaging, and may be responsible for a functional deficit. The purpose of this study was to correlate functional magnetic resonance imaging brain activation of working memory and selective attention with PCS. 21 MHI patients and 12 healthy controls were scanned at 3T. Stimulation paradigms were the n-back and Counting Stroop tasks to engage working memory and selective attention, respectively. Functional data analysis consisted of random effects group analyses, correlating brain activation patterns with the severity of PCS as evaluated with the Rivermead postconcussion symptoms questionnaire. At minimal working memory load, activation was seen in patients with greater severity of PCS in the working memory network. With an increase of working memory load, increase of activation was more pronounced in patients with greater severity of PCS. At high and increased working memory load, activation associated with the severity of PCS was seen in the posterior parietal area, parahippocampal gyrus, and posterior cingulate gyrus. Activation related to selective attention processing was increased with greater severity of PCS. The increased activity in relation to working memory and attention, and the recruitment of brain areas outside the working memory network at high working memory load, may be considered a reflection of the brain's compensatory response to microstructural injury in patients with PCS.

Developmental trajectories of magnitude processing and interference control: an FMRI study

Neurodevelopmental changes regarding interference and magnitude processing were assessed in 3 age groups (children, n = 10; young adults, n = 11; elderly participants, n = 9) by using an functional magnetic resonance imaging version of the numerical Stroop task. Behaviorally, comparable distance and size congruity effects were found in all 3 age groups. Distance effects were most pronounced in the more difficult numerical task, whereas size congruity effects were comparable across tasks. In response to interference, an age-linear trend in the pattern of activation in left and right prefrontal and left middle temporal regions of the brain was observed. This implicates that with increasing age interference control requires increasing effort (possible explanations for children's relatively lower interference effects are provided). In contrast, the distance effect produced a negative linear trend in right prefrontal, supplementary motor area, and intraparietal cortex. This suggests that relative to old adults, children and young adults had to recruit a larger network upon processing magnitude. The latter findings are even more remarkable considering that the behavioral effects were similar across groups. In summary, the developmental trajectories of interference control and magnitude processing differ, although these cognitive functions activate partially overlapping brain regions.

Structural disruption of the dorsal cingulum bundle is associated with impaired Stroop performance in patients with schizophrenia

Previous diffusion tensor imaging (DTI) studies have shown structural abnormalities of the cingulum bundle (CB) in patients with schizophrenia. However, regional specificity and functional relevance of the pregenual and dorsal CB subdivisions has not been fully studied. In the current study, 31 patients with schizophrenia and 65 age- and gender-matched healthy subjects underwent DTI to measure fractional anisotropy (FA) and mean diffusivity (MD) in cross sections of dorsal and pregenual CB tractography. To test the hypothesis of region-specific association with neurocognition, all of the patients and 31 controls performed the Stroop task, which is assumed to mainly involve dorsal cingulate function. The verbal memory subscale of Wechsler Memory Scale-Revised and premorbid IQs estimated from the Japanese version of the National Adult Reading Test, which were non-specific to dorsal cingulate function, were also employed as control neurocognitive indices. Significant bilateral FA reductions in the pregenual and dorsal CB, and bilateral MD increases in the dorsal CB were observed in the patients compared with the controls. As predicted, significant associations between DTI measures and neurocognition were found in the schizophrenia group only: double-dissociable correlation between higher MD in the dorsal, not in the pregenual CB, and a longer reaction time in the Stroop task, not verbal memory or premorbid IQs. The current DTI study suggests that structural disruption of the dorsal CB has region-specific functional relevance to selective attention deficits, although structural disruption also exists in the pregenual CB in patients with schizophrenia.