Hypoactivation in right inferior frontal cortex is specifically associated with motor response inhibition in adult ADHD

The right inferior frontal gyrus as pivotal node and effective regulator of the basal ganglia-thalamocortical response inhibition circuit

Background

The involvement of specific basal ganglia-thalamocortical circuits in response inhibition has been extensively mapped in animal models. However, the pivotal nodes and directed causal regulation within this inhibitory circuit in humans remains controversial.

Objective

The main aim of the present study was to determine the causal information flow and critical nodes in the basal ganglia-thalamocortical inhibitory circuits and also to examine whether these are modulated by biological factors (i.e. sex) and behavioral performance.

Methods

Here, we capitalize on the recent progress in robust and biologically plausible directed causal modeling (DCM-PEB) and a large response inhibition dataset (n = 250) acquired with concomitant functional magnetic resonance imaging to determine key nodes, their causal regulation and modulation via biological variables (sex) and inhibitory performance in the inhibitory circuit encompassing the right inferior frontal gyrus (rIFG), caudate nucleus (rCau), globus pallidum (rGP), and thalamus (rThal).

Results

The entire neural circuit exhibited high intrinsic connectivity and response inhibition critically increased causal projections from the rIFG to both rCau and rThal. Direct comparison further demonstrated that response inhibition induced an increasing rIFG inflow and increased the causal regulation of this region over the rCau and rThal. In addition, sex and performance influenced the functional architecture of the regulatory circuits such that women displayed increased rThal self-inhibition and decreased rThal to GP modulation, while better inhibitory performance was associated with stronger rThal to rIFG communication. Furthermore, control analyses did not reveal a similar key communication in a left lateralized model.

Conclusions

Together, these findings indicate a pivotal role of the rIFG as input and causal regulator of subcortical response inhibition nodes.

Functional reorganization of brain activity in children with attention-deficit/hyperactivity disorder: Evidence from the modulatory effect of cognitive demand during visuospatial attention task

Previous studies reported that the inferior parietal lobule (IPL) had lower activation during visuospatial attention in children with attention-deficit/hyperactivity disorder (ADHD), while the functional connectivity (FC) between the IPL and other brain regions and how cognitive demand might modulate IPL's FC remain unclear. We performed a functional magnetic resonance imaging experiment recruiting two task conditions with relatively low and high cognitive demand of visuospatial attention. Forty-four children with ADHD and 36 age- and sex-matched healthy controls were included. IPL's regional activation and FC intensities were compared between groups and correlated with clinical measurements. We found that the IPL had significantly reduced activation in children with ADHD compared to healthy controls and this abnormal activation was not modulated by the cognitive demand of visuospatial attention. Importantly, further analysis revealed that the functional connectivity between IPL and inferior frontal gyrus was modulated by the cognitive demand of visuospatial attention in children with ADHD. These results revealed a modulatory effect of cognitive demand of visuospatial attention on IPL's functional connectivity but not IPL's activation in children with ADHD. More generally, these results highlight the functional reorganization of the brain activity as a possible compensatory strategy in response to the symptoms of ADHD.

Altered prefrontal activation during the inhibition of eating responses in women with bulimia nervosa

BACKGROUND

The sense of 'loss of control' (LOC), or a feeling of being unable to stop eating or control what or how much one is eating, is the most salient aspect of binge eating. However, the neural alterations that may contribute to this experience and eating behavior remain poorly understood.

METHODS

We used functional near-infrared spectroscopy (fNIRS) to measure activation in the prefrontal cortices of 23 women with bulimia nervosa (BN) and 23 healthy controls (HC) during two tasks: a novel go/no-go task requiring inhibition of eating responses, and a standard go/no-go task requiring inhibition of button-pressing responses.

RESULTS

Women with BN made more commission errors on both tasks. BN subgroups with the most severe LOC eating (n = 12) and those who felt most strongly that they binge ate during the task (n = 12) showed abnormally reduced bilateral ventromedial prefrontal cortex (vmPFC) and right ventrolateral prefrontal cortex (vlPFC) activation associated with eating-response inhibition. In the entire BN sample, lower eating-task activation in right vlPFC was related to more frequent and severe LOC eating, but no group differences in activation were detected on either task when this full sample was compared with HC. BN severity was unrelated to standard-task activation.

CONCLUSIONS

Results provide initial evidence that diminished PFC activation may directly contribute to more severe eating-specific control deficits in BN. Our findings support vmPFC and vlPFC dysfunction as promising treatment targets, and indicate that eating-specific tasks and fNIRS may be useful tools for identifying neural mechanisms underlying dysregulated eating.

Functional near-infrared spectroscopy in developmental psychiatry: a review of attention deficit hyperactivity disorder

Research has linked executive function (EF) deficits to many of the behavioral symptoms of attention deficit hyperactivity disorder (ADHD). Evidence of the involvement of EF impairment in ADHD is corroborated by accumulating neuroimaging studies, specifically functional magnetic resonance imaging (fMRI) studies. However, in recent years, functional near-infrared spectroscopy (fNIRS) has become increasingly popular in ADHD research due to its portability, high ecological validity, resistance to motion artifacts, and cost-effectiveness. While numerous studies throughout the past decade have used fNIRS to examine alterations in neural correlates of EF in ADHD, a qualitative review of the reliability of these findings compared with those reported using gold-standard fMRI measurements does not yet exist. The current review aims to fill this gap in the literature by comparing the results generated from a qualitative review of fNIRS studies (children and adolescents ages 6-16 years old) to a meta-analysis of comparable fMRI studies and examining the extent to which the results of these studies align in the context of EF impairment in ADHD. The qualitative analysis of fNIRS studies of ADHD shows a consistent hypoactivity in the right prefrontal cortex in multiple EF tasks. The meta-analysis of fMRI data corroborates altered activity in this region and surrounding areas during EF tasks in ADHD compared with typically developing controls. These findings indicate that fNIRS is a promising functional brain imaging technology for examining alterations in cortical activity in ADHD. We also address the disadvantages of fNIRS, including limited spatial resolution compared with fMRI.

Meta-analysis of structural and functional alterations of brain in patients with attention-deficit/hyperactivity disorder

BACKGROUND

A large and growing body of neuroimaging research has concentrated on patients with attention-deficit/hyperactivity disorder (ADHD), but with inconsistent conclusions. This article was intended to investigate the common and certain neural alterations in the structure and function of the brain in patients with ADHD and further explore the differences in brain alterations between adults and children with ADHD.

METHODS

We conducted an extensive literature search of whole-brain voxel-based morphometry (VBM) and functional magnetic resonance imaging (fMRI) studies associated with ADHD. Two separate meta-analyses with the seed-based d mapping software package for functional neural activation and gray matter volume (GMV) were carried out, followed by a joint analysis and a subgroup analysis.

RESULTS

This analysis included 29 VBM studies and 36 fMRI studies. Structurally, VBM analysis showed that the largest GMV diminutions in patients with ADHD were in several frontal-parietal brain regions, the limbic system, and the corpus callosum. Functionally, fMRI analysis discovered significant hypoactivation in several frontal-temporal brain regions, the right postcentral gyrus, the left insula, and the corpus callosum.

CONCLUSION

This study showed that abnormal alterations in the structure and function of the left superior frontal gyrus and the corpus callosum may be the key brain regions involved in the pathogenesis of ADHD in patients and may be employed as an imaging metric for patients with ADHD pending future research. In addition, this meta-analysis discovered neuroanatomical or functional abnormalities in other brain regions in patients with ADHD as well as findings that can be utilized to guide future research.

Alteration of Behavioral Inhibitory Control in High-Altitude Immigrants

Behavioral inhibitory control (BIC) acts as a key cognitive ability, which is essential for humans to withhold inappropriate behaviors. Meanwhile, many studies reported that long-term exposure to high altitude (HA) may affect cognitive ability. However, it is not clear whether long-term exposure to HAs may affect the BIC of an individual. To clarify the role of altitude in the behavioral control of adults and the underlying neural mechanism, we explored the BIC neural activity profiles of healthy immigrants from low-altitude (LA) regions to HA regions. Combining a two-choice oddball paradigm and electrophysiological techniques, this study monitored the N2 and P3 event-related components and neural oscillations across LA and HA groups. Results showed longer reaction times (RTs) for the HA group than the LA group. Relative to the LA group, lower N2 and P3 amplitudes were observed for the HA group. Significant positive correlations were also found between P3 amplitude and theta/delta band power across both groups. Importantly, lower theta/delta band powers were only observed for the HA group under the deviant condition. Collectively, these findings suggest that long-term exposure to HAs may attenuate BIC during the response inhibition stage and provide valuable insights into the neurocognitive implications of environmental altitude on BIC.

Self-regulation in the pre-adolescent brain

Self-regulation refers to the ability to monitor and modulate emotions, behavior, and cognition, which in turn allows us to achieve goals and adapt to ever changing circumstances. This trait develops from early infancy well into adulthood, and features both low-level executive functions such as reactive inhibition, as well as higher level executive functions such as proactive inhibition. Development of self-regulation is linked to brain maturation in adolescence and adulthood. However, how self-regulation in daily life relates to brain functioning in pre-adolescent children is not known. To this aim, we have analyzed data from 640 children aged 8–11, who performed a stop-signal anticipation task combined with functional magnetic resonance imaging, in addition to questionnaire data on self-regulation. We find that pre-adolescent boys and girls who display higher levels of self-regulation, are better able to employ proactive inhibitory control strategies, exhibit stronger frontal activation and more functional coupling between cortical and subcortical areas of the brain. Furthermore, we demonstrate that pre-adolescent children show significant activation in areas of the brain that were previously only associated with reactive and proactive inhibition in adults and adolescents. Thus, already in pre-adolescent children, frontal-striatal brain areas are active during self-regulatory behavior.

•

Children with higher levels of self-regulation employ more proactive inhibition.

•

During proactive inhibition, children aged 8–11 show activation in frontal-cortical areas.

•

Children higher in self-regulation exhibit more cortical-subcortical coupling.

•

Children aged 8–11 show similar brain activation as adults during inhibition.

Impulsive and Omission Errors: Potential Temporal Processing Endophenotypes in ADHD

Temporal processing (TP) is associated with functions such as perception, verbal skills, temporal perspective, and future planning, and is intercorrelated with working memory, attention, and inhibitory control, which are highly impaired in individuals with attention deficit hyperactivity disorder (ADHD). Here we evaluate TP measures as potential endophenotypes in Caribbean families ascertained from probands affected by ADHD. A total of 232 individuals were recruited and clinically evaluated using an extensive battery of neuropsychological tasks and reaction time (RT)-based task paradigms. Further, the heritability (genetic variance underpinning phenotype) was estimated as a measure of the genetics apportionment. A predictive framework for ADHD diagnosis was derived using these tasks. We found that individuals with ADHD differed from controls in neuropsychological tasks assessing mental control, visual-verbal memory, verbal fluency, verbal, and semantic fluency. In addition, TP measures such as RT, errors, and variability were also affected in individuals with ADHD. Moreover, we determined that only omission and commission errors had significant heritability. In conclusion, we have disentangled omission and commission errors as possible TP endophenotypes in ADHD, which can be suitable to assess the neurobiological and genetic basis of ADHD. A predictive model using these endophenotypes led to remarkable sensitivity, specificity, precision and classification rate for ADHD diagnosis, and may be a useful tool for patients' diagnosis, follow-up, and longitudinal assessment in the clinical setting.

A randomized-controlled neurofeedback trial in adult attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is a childhood onset disorder persisting into adulthood for a large proportion of cases. Neurofeedback (NF) has shown promising results in children with ADHD, but randomized controlled trials in adults with ADHD are scarce. We aimed to compare slow cortical potential (SCP)- and functional near-infrared spectroscopy (fNIRS) NF to a semi-active electromyography biofeedback (EMG-BF) control condition regarding changes in symptoms and the impact of learning success, as well as changes in neurophysiological parameters in an adult ADHD population. Patients were randomly assigned to SCP-NF (n = 26), fNIRS-NF (n = 21) or EMG-BF (n = 20). Outcome parameters were assessed over 30 training sessions (pre, intermediate, post) and at 6-months follow-up (FU) including 3 booster sessions. EEG was recorded during two auditory Go/NoGo paradigms assessing the P300 and contingent negative variation (CNV). fNIRS measurements were conducted during an n-back- as well as a Go/NoGo task. All three groups showed equally significant symptom improvements suggesting placebo- or non-specific effects on the primary outcome measure. Only when differentiating between learners and non-learners, fNIRS learners displayed stronger reduction of ADHD global scores compared to SCP non-learners at FU, and fNIRS learners showed specifically low impulsivity ratings. 30.8% in the SCP-NF and 61.9% of participants in the fNIRS-NF learned to regulate the respective NF target parameter. We conclude that some adults with ADHD learn to regulate SCP amplitudes and especially prefrontal hemodynamic activity during NF. We did not find any significant differences in outcome between groups when looking at the whole sample. When evaluating learners only, they demonstrate superior effects as compared to non-learners, which suggests specific effects in addition to non-specific effects of NF when learning occurs.

Opposed attentional hemi-bias on a visuoconstructive task in children with severe hyperactivity versus severe inattention

Twenty six empirical investigations have now established that children and adults with DSM-defined Attention deficit/Hyperactivity disorder (ADHD) of the Hyperactive type (ADHD-H) or, more commonly, Combined Hyperactive/Inattentive types (ADHD-C) manifest a small but significant visual attentional bias to the right side (left subclinical neglect), consistently suggesting the existence of a subtle right hemisphere dysfunction or hemispheric imbalance in hyperactive people. Only one research team has investigated and compared the DSM-defined Inattentive subtype (ADHD-I) to the Hyperactive subtype (ADHD-H), confirming that line bisection is biased to the right in ADHD-H and discovering that it is biased to the left in ADHD-I. We aimed to test whether a similar crossed double dissociation would extend to Rey's Complex Figure Copy Task (RCF-CT), a simple visuospatial-constructive task. Clinical files of 205 juvenile clients from 6 to 16 years of age from a neuropsychological private clinic specialized in ADHD were analysed. Extreme scores on the Connors-3 Hyperactivity vs Inattention Parent Rating scales associated, respectively, with significant rightward and significant leftward emplacement of the drawing on the page on the RCF-CT. These results replicate previous findings and extend the "energetics" model of hemispheric specialization.

Cortical and subcortical contributions to interference resolution and inhibition - An fMRI ALE meta-analysis

Interacting with our environment requires the selection of appropriate responses and the inhibition of others. Such effortful inhibition is achieved by a number of interference resolution and global inhibition processes. This meta-analysis including 57 studies and 73 contrasts revisits the overlap and differences in brain areas supporting interference resolution and global inhibition in cortical and subcortical brain areas. Activation likelihood estimation was used to discern the brain regions subserving each type of cognitive control. Individual contrast analysis revealed a common activation of the bilateral insula and supplementary motor areas. Subtraction analyses demonstrated the voxel-wise differences in recruitment in a number of areas including the precuneus in the interference tasks and the frontal pole and dorsal striatum in the inhibition tasks. Our results display a surprising lack of subcortical involvement within these types of cognitive control, a finding that is likely to reflect a systematic gap in the field of functional neuroimaging.

Antagonism between brain regions relevant for cognitive control and emotional memory facilitates the generation of humorous ideas

The ability to generate humor gives rise to positive emotions and thus facilitate the successful resolution of adversity. Although there is consensus that inhibitory processes might be related to broaden the way of thinking, the neural underpinnings of these mechanisms are largely unknown. Here, we use functional Magnetic Resonance Imaging, a humorous alternative uses task and a stroop task, to investigate the brain mechanisms underlying the emergence of humorous ideas in 24 subjects. Neuroimaging results indicate that greater cognitive control abilities are associated with increased activation in the amygdala, the hippocampus and the superior and medial frontal gyrus during the generation of humorous ideas. Examining the neural mechanisms more closely shows that the hypoactivation of frontal brain regions is associated with an hyperactivation in the amygdala and vice versa. This antagonistic connectivity is concurrently linked with an increased number of humorous ideas and enhanced amygdala responses during the task. Our data therefore suggests that a neural antagonism previously related to the emergence and regulation of negative affective responses, is linked with the generation of emotionally positive ideas and may represent an important neural pathway supporting mental health.

Identifying ADHD Individuals From Resting-State Functional Connectivity Using Subspace Clustering and Binary Hypothesis Testing

Objective: This study focused on the ADHD classification through functional connectivity (FC) analysis. Method: An ADHD classification method was proposed with subspace clustering and binary hypothesis testing, wherein partial information of test data was adopted for training. By hypothesizing the binary label (ADHD or control) for the test data, two feature sets of training FC data were generated during the feature selection procedure that employed both training and test data. Then, a multi-affinity subspace clustering approach was performed to obtain the corresponding subspace-projected feature sets. With the energy comparison of projected feature sets, we finally identified ADHD individuals for the test data. Results: Our method outperformed several state-of-the-art methods with the above 90% average identification accuracy. By the discriminative FC contribution analysis, it also proved the reliability of our method. Conclusion: Results demonstrate the remarkable classification performance of our method and reveal some useful brain circuits to identify ADHD.

Effects of a five-day HD-tDCS application to the right IFG depend on current intensity: A study in children and adolescents with ADHD

Impaired executive functions in ADHD are associated with hypoactivity of the right inferior frontal gyrus (IFG). This region was targeted via repetitive applications of anodal, high-definition transcranial direct current simulation (HD-tDCS) on five consecutive days in 33 ADHD patients (10-17years) and in a healthy control group (n=13, only sham). Patients received either sham (n=13) or verum tDCS with 0.5mA (n=9) or 0.25mA (n=11) depending on individual cutaneous sensitivity. During stimulation, participants performed a combined working memory and response inhibition paradigm (n-back/nogo). At baseline, post, and a 4-month follow up, electroencephalography was recorded during this task. Moreover, interference control (flanker task) and spatial working memory (spanboard task) were assessed to explore possible transfer effects. Omission errors and reaction time variability in all tasks served as measures of attention. In the 0.25mA group increased nogo commission errors indicated a detrimental tDCS effect on response inhibition. After the 5-day stimulation, attentional improvements in the 0.5mA group were indicated by reduced omission errors and reaction time variability. Variability improvements were still evident at follow up. In all groups, nogo P3 amplitudes were reduced post-stimulation, but in the 0.5mA group this reduction was smaller than in the 0.25mA group. Results of the current study suggest distinct effects of tDCS with different current intensities demonstrating the importance of a deeper understanding on the impact of stimulation parameters and repeated tDCS applications to develop effective tDCS-based therapy approaches in ADHD.

Normal executive attention but abnormal orienting attention in individuals with sluggish cognitive tempo

Background/objective: Sluggish Cognitive Tempo (SCT) is an attentional disorder characterized by the symptoms of slowness in behavior or thinking, a lack of en.ergy, difficulty initiating and sustaining effort, daydreaming, and drowsiness. The aim of the present study was to investigate the distinctive attentional characteristics of SCT as compared to Attention-Deficit/Hyperactivity Disorder (ADHD). Method: A total of 110 adults were recruited and divided into four groups: SCT+ADHD, SCT, ADHD, and healthy controls. The Revised version of Attention Networks Test was used to investigate each group’s attentional profile. Results: The results revealed that the two SCT groups (SCT+ADHD and SCT) showed a significantly weaker orienting network due to the problems of engaging and disengaging attention than the other two groups. Additionally, the two ADHD groups (SCT+ADHD and ADHD) showed a significantly weaker executive control network than the other two groups. Conclusions: The findings demonstrate an attentional distinction between the SCT and the ADHD groups with a greater dysfunction in the orienting network in the SCT group as compared to the ADHD group. Furthermore, a greater executive control dysfunction was observed in the ADHD group as compared to the SCT group.

Gender differences in adult ADHD: Cognitive function assessed by the test of attentional performance

Introduction

The aim of this study was to assess cognitive differences between male and female adults with Attention Deficit Hyperactivity Disorder (ADHD).

Methods

Patients with an ADHD diagnosis according to the DSM-IV guidelines were included in a cross-sectional study evaluating cognitive measures. 28 women and 41 men from ages 19 to 56 completed self-report questionnaires and performed a computer-based test of attentional performance (TAP). The TAP assesses cognitive functions highly affected in ADHD patients, including working memory, alertness and attention as well as behavioral control and response inhibition.

Results

There were no measurable differences in self-report scales assessing current symptomology between the sexes, however men scored higher on the scale for childhood symptoms. Performance measures for general wakefulness were comparable between men and women, while working memory and behavioral control test results differed. Females reacted significantly slower and more unstable for both the TAP Go/NoGo paradigm and working memory subtest, while also making more errors in the latter.

Conclusions

We found gender-specific effects regarding working memory and behavioral control in this sample of adult patients with ADHD. Further studies are warranted, examining whether these differences relate to differences in clinical presentation and comorbidity patterns between men and women.

Attention Networks in ADHD Adults after Working Memory Training with a Dual n-Back Task

Patients affected by Attention-Deficit/Hyperactivity Disorder (ADHD) are characterized by impaired executive functioning and/or attention deficits. Our study aim is to determine whether the outcomes measured by the Attention Network Task (ANT), i.e., the reaction times (RTs) to specific target and cue conditions and alerting, orienting, and conflict (or executive control) effects are affected by cognitive training with a Dual n-back task. We considered three groups of young adult participants: ADHD patients without medication (ADHD), ADHD with medication (MADHD), and age/education-matched controls. Working memory training consisted of a daily practice of 20 blocks of Dual n-back task (approximately 30 min per day) for 20 days within one month. Participants of each group were randomly assigned into two subgroups, the first one with an adaptive mode of difficulty (adaptive training), while the second was blocked at the level 1 during the whole training phase (1-back task, baseline training). Alerting and orienting effects were not modified by working memory training. The dimensional analysis showed that after baseline training, the lesser the severity of the hyperactive-impulsive symptoms, the larger the improvement of reaction times on trials with high executive control/conflict demand (i.e., what is called Conflict Effect), irrespective of the participants’ group. In the categorical analysis, we observed the improvement in such Conflict Effect after the adaptive training in adult ADHD patients irrespective of their medication, but not in controls. The ex-Gaussian analysis of RT and RT variability showed that the improvement in the Conflict Effect correlated with a decrease in the proportion of extreme slow responses. The Dual n-back task in the adaptive mode offers as a promising candidate for a cognitive remediation of adult ADHD patients without pharmaceutical medication.

In Quest of Pathognomonic/Endophenotypic Markers of Attention Deficit Hyperactivity Disorder (ADHD): Potential of EEG-Based Frequency Analysis and ERPs to Better Detect, Prevent and Manage ADHD

Attention deficit hyperactivity disorder (ADHD) is a chronic heritable developmental delay psychiatric disorder requiring chronic management, characterized by inattention, hyperactivity, hyperkinectivity and impulsivity. Subjective clinical evaluation still remains crucial in its diagnosis. Discussed are two key aspects in the “characterizing ADHD” and on the quest for objective “pathognomonic/endophenotypic diagnostic markers of ADHD”. The first aspect briefly revolves around issues related to identification of pathognomonic/endophenotypic diagnostic markers in ADHD. Issues discussed include changes in ADHD definition, remission/persistence and overlapping-symptoms cum shared-heritability with its co-morbid cross-border mental disorders. The second aspect discussed is neurobiological and EEG-based studies on ADHD. Given the neurobiological and temporal aspects of ADHD symptoms the electroencephalograph (EEG) like NeuralScan by Medeia appears as an appropriate tool. The EEGs appropriateness is further enhanced when coupled with suitable behavior/cognitive/motor/psychological tasks/paradigms yielding EEG-based markers like event-related-potential (ERPs like P3 amplitudes and latency), reaction time variability (RTV), Theta:Beta ratio (TBR) and sensorimotor rhythm (SMR). At present, these markers could potentially help in the neurobiological characterization of ADHD and either help in identifying or lay the groundwork for identifying pathognomonic and/or endophenotypic EEG-based markers enabling its diagnosis, treatment and management.

Transcranial Direct Current Stimulation in ADHD: A Systematic Review of Efficacy, Safety, and Protocol-induced Electrical Field Modeling Results

Transcranial direct current stimulation (tDCS) is a promising method for altering cortical excitability with clinical implications. It has been increasingly used in neurodevelopmental disorders, especially attention-deficit hyperactivity disorder (ADHD), but its efficacy (based on effect size calculations), safety, and stimulation parameters have not been systematically examined. In this systematic review, we aimed to (1) explore the effectiveness of tDCS on the clinical symptoms and neuropsychological deficits of ADHD patients, (2) evaluate the safety of tDCS application, especially in children with ADHD, (3) model the electrical field intensity in the target regions based on the commonly-applied and effective versus less-effective protocols, and (4) discuss and propose advanced tDCS parameters. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses approach, a literature search identified 14 empirical experiments investigating tDCS effects in ADHD. Partial improving effects of tDCS on cognitive deficits (response inhibition, working memory, attention, and cognitive flexibility) or clinical symptoms (e.g., impulsivity and inattention) are reported in 10 studies. No serious adverse effects are reported in 747 sessions of tDCS. The left and right dorsolateral prefrontal cortex are the regions most often targeted, and anodal tDCS the protocol most often applied. An intensity of 2 mA induced stronger electrical fields than 1 mA in adults with ADHD and was associated with significant behavioral changes. In ADHD children, however, the electrical field induced by 1 mA, which is likely larger than the electrical field induced by 1 mA in adults due to the smaller head size of children, was sufficient to result in significant behavioral change. Overall, tDCS seems to be a promising method for improving ADHD deficits. However, the clinical utility of tDCS in ADHD cannot yet be concluded and requires further systematic investigation in larger sample sizes. Cortical regions involved in ADHD pathophysiology, stimulation parameters (e.g. intensity, duration, polarity, and electrode size), and types of symptom/deficit are potential determinants of tDCS efficacy in ADHD. Developmental aspects of tDCS in childhood ADHD should be considered as well.

Resilience to trauma: Just a matter of control?

Deficits in memory control may facilitate posttraumatic stress disorder

Fronto-parietal engagement in response inhibition is inversely scaled with attention-deficit/hyperactivity disorder symptom severity

•

A novel Go/No-go task points to a critical role for the IPS in response inhibition.

•

IPS engagement in response inhibition is scaled back with ADHD symptom severity.

•

Fronto-parietal connectivity increases when response inhibition is challenging.

•

Connectivity modulation is also scaled back with ADHD symptom severity.

Background

Impaired response inhibition is one of the most consistent findings in attention deficit hyperactivity disorder (ADHD). However, the underlying brain mechanisms are not clear. This study aimed to underpin atypical inhibition-related brain activation and connectivity patterns in ADHD using a novel Go/No-go task design, and to determine its association with clinical symptoms of the disorder.

Methods

Forty-eight adults with ADHD performed a Go/No-go task in which target frequency was manipulated during functional MRI. Specific inhibition-related brain activation was correlated with ADHD symptom severity, to assess the relationship of individual differences in engagement of inhibition-related brain circuits with the magnitude of every-day functioning impairments. Finally, generalized psychophysical interaction analyses were carried out to examine whether not only engagement but also functional connectivity between regions implicated in response inhibition is related to symptom severity.

Results

We found no evidence for the expected parietal modulation by increased demand for inhibition at the group-level results. However, this lack of modulation was mediated by individual differences in ADHD symptom severity – increased engagement of the intraparietal sulcus (IPS) in inhibition-demanding events was evident in individuals with less severe symptoms but dissipated with increase in symptomatology. Similarly, functional connectivity between the IPS and the right inferior frontal gyrus (rIFG) was elevated under high inhibitory demand conditions, but this effect diminished with increased symptom severity.

Conclusions

The results highlight the importance of IPS engagement in response inhibition and suggest that IPS modulation may be driven by top-down control from the IFG. Moreover, the current findings force the point of treating ADHD as a continuum whereby brain correlates are scaled with severity of the disorder, and point to the potential use of individual differences in the modulation of IPS activation and connectivity as a neuromarker of ADHD.

Dorsolateral prefrontal cortex hyperactivity during inhibitory control in children with ADHD in the antisaccade task

Children with ADHD show significant deficits in response inhibition. A leading hypothesis suggests prefrontal hypoactivation as a possible cause, though, there is conflicting evidence. We tested the hypoactivation hypothesis by analyzing the response inhibition process within the oculomotor system. Twenty-two children diagnosed with ADHD and twenty control (CTRL) children performed the antisaccade task while undergoing an fMRI study with concurrent eye tracking. This task included a preparatory stage that cued a prosaccade (toward a stimuli) or an antisaccade (away from a stimuli) without an actual presentation of a peripheral target. This allowed testing inhibitory control without the confounding activation from an actual response. The ADHD group showed longer reaction times and more antisaccade direction errors. While both groups showed activations in saccade network areas, the ADHD showed significant hyperactivation in the dorsolateral prefrontal cortex during the preparatory stage. No other areas in the saccade network had significant activation differences between groups. Further ADHD group analysis OFF and ON stimulant medication did not show drug-related activation differences. However, they showed a significant correlation between the difference in OFF/ON preparatory activation in the precuneus, and a decrease in the number of antisaccade errors. These results do not support the hypoactivity hypothesis as an inhibitory control deficit general explanation, but instead suggest less efficiency during the inhibitory period of the antisaccade task in children. Our findings contrast with previous results in ADHD adults showing decreased preparatory antisaccade activity, suggesting a significant age-dependent maturation effect associated to the inhibitory response in the oculomotor system.

Between-hand coupling during response inhibition

Response inhibition reflects the process of terminating inappropriate preplanned or ongoing movements. When one hand is cued to stop after preparing a bimanual response (Partial trial), there is a substantial delay on the responding side. This delay is termed the interference effect and identifies a constraint that limits selective response inhibition. γ-Aminobutyric acid (GABA)-mediated networks within primary motor cortex (M1) may have distinct roles during response inhibition. In this study we examined whether the interference effect is the consequence of between-hand "coupling" into a unitary response and whether this is reflected in GABAergic intracortical inhibition within M1. Eighteen healthy right-handed participants performed a bimanual synchronous and asynchronous anticipatory response inhibition task. Electromyographic recordings were obtained from the first dorsal interosseous muscle bilaterally. Motor evoked potentials were elicited by single- and paired-pulse transcranial magnetic stimulation over right M1. As expected, Go trial performance was better with the synchronous compared with the asynchronous version of the task. Paradoxically, response delays during Partial trials were longer with the synchronous compared with the asynchronous task. Although task difficulty did not modulate GABAergic intracortical inhibition, there was a trend for between-hand coupling on asynchronous trials to be associated with greater GABA_B receptor-mediated inhibition and lesser recruitment of GABA_A receptor-mediated inhibition. The novel findings indicate that the interference effect is in part a consequence of between-hand coupling into a unitary response during movement preparation. The ability to respond independently with the two hands may rely on modulation of distinct inhibitory processes.NEW & NOTEWORTHY The temporal dynamics of an anticipated response task were manipulated to effect the difficulty of behavioral stopping and the underlying effects on motor neurophysiology. There were large response delays during trials where a subcomponent of an upcoming bimanual response was cued to stop in conditions where the anticipated action of the hands were synchronous, but not when asynchronous. Response delays reflected the integration of actions of both hands into a unitary response.

Electroencephalography Functional Networks Reveal Global Effects of Methylphenidate in Youth with Attention Deficit/Hyperactivity Disorder

Methylphenidate (MPH) is the leading drug for treatment of attention deficit/hyperactivity disorder (ADHD), yet its underlying neuronal mechanisms are still unclear. Here, we use a dynamical brain networks approach to explore the effects of cognitive effort and MPH on ADHD subjects. Electroencephalography data were recorded from 19 ADHD subjects and 18 controls during a Go/No-Go Task. ADHD subjects completed the task twice a day over 2 days. The second session was administered post-ingestion of placebo/MPH (alternately). Controls performed two tasks in 1 day. The data were divided into 300 ms windows from -300 pre-stimulus until 1200 ms post-stimulus. Brain networks were constructed per subject and window, from which network metrics were extracted and compared across the experimental conditions. We identified an immediate shift of global connectivity and of network segregation after the stimulus for both groups, followed by a gradual return to baseline. Decreased global connectivity was found to be 400-700 ms post-stimulus in ADHD compared with controls, and it was normalized post-MPH. An increase of the networks' segregation occurred post-placebo at 100-400 and 400-700 ms post-stimulus, yet it was inhibited post-MPH. These global alterations resulted mainly from changes in task-relevant frontal and parietal regions. The networks of medicated ADHD subjects and controls exhibited a more significant and lasting change, relative to baseline, compared with those of nonmedicated ADHD. These results suggest impaired network flexibility in ADHD, corrected by MPH.

Using subjective expectations to model the neural underpinnings of proactive inhibition

Proactive inhibition – the anticipation of having to stop a response – relies on objective information contained in cue‐related contingencies in the environment, as well as on the subjective interpretation derived from these cues. To date, most studies of brain areas underlying proactive inhibition have exclusively considered the objective predictive value of environmental cues, by varying the probability of stop‐signals. However, by only taking into account the effect of different cues on brain activation, the subjective component of how cues affect behavior is ignored. We used a modified stop‐signal response task that includes a measurement for subjective expectation, to investigate the effect of this subjective interpretation. After presenting a cue indicating the probability that a stop‐signal will occur, subjects were asked whether they expected a stop‐signal to occur. Furthermore, response time was used to retrospectively model brain activation related to stop‐expectation. We found more activation during the cue period for 50% stop‐signal probability, when contrasting with 0%, in the mid and inferior frontal gyrus, inferior parietal lobe and putamen. When contrasting expected vs. unexpected trials, we found modest effects in the mid frontal gyrus, parietal, and occipital areas. With our third contrast, we modeled brain activation during the cue with trial‐by‐trial variances in response times. This yielded activation in the putamen, inferior parietal lobe, and mid frontal gyrus. Our study is the first to use the behavioral effects of proactive inhibition to identify the underlying brain regions, by employing an unbiased task‐design that temporally separates cue and response.

Identification of neurophysiological biotypes in attention deficit hyperactivity disorder

AIM

Findings on neurophysiological alterations in attention deficit hyperactivity disorder (ADHD) have been proposed to underlie ADHD symptoms, with different etiological pathways for different patient biotypes. We aimed at determining whether neurophysiological deviations confirm distinct neurophysiological profiles in ADHD, thus providing direct evidence for the endophenotype concept.

METHODS

Neurophysiological biotypes were investigated in 87 adult patients with ADHD using cluster analysis. Parameters fed into the analysis comprised both hemodynamic and electrophysiological data. To validate results, the independent variables of the clusters were compared with healthy controls.

RESULTS

Cluster analysis yielded three neurophysiologically based ADHD biotypes showing: (i) above-average functioning in attention allocation; (ii) difficulties in attention allocation and inhibitory control but elevated frontal activation during a working memory task; and (iii) functional impairments in state regulation.

CONCLUSION

Classifying patients with ADHD into neurophysiological biotypes sheds light on etiological pathways, with implications for diagnostics and (individualized) treatment options.

Motor dysfunction as research domain across bipolar, obsessive-compulsive and neurodevelopmental disorders

Although genuine motor abnormalities (GMA) are frequently found in schizophrenia, they are also considered as an intrinsic feature of bipolar, obsessive-compulsive, and neurodevelopmental disorders with early onset such as autism, ADHD, and Tourette syndrome. Such transnosological observations strongly suggest a common neural pathophysiology. This systematic review highlights the evidence on GMA and their neuroanatomical substrates in bipolar, obsessive-compulsive, and neurodevelopmental disorders. The data lends support for a common pattern contributing to GMA expression in these diseases that seems to be related to cerebello-thalamo-cortical, fronto-parietal, and cortico-subcortical motor circuit dysfunction. The identified studies provide first evidence for a motor network dysfunction as a correlate of early neurodevelopmental deviance prior to clinical symptom expression. There are also first hints for a developmental risk factor model of these mental disorders. An in-depth analysis of motor networks and related patho-(physiological) mechanisms will not only help promoting Research Domain Criteria (RDoC) Motor System construct, but also facilitate the development of novel psychopharmacological models, as well as the identification of neurobiologically plausible target sites for non-invasive brain stimulation.

Individual differences in stop-related activity are inflated by the adaptive algorithm in the stop signal task

Research using the Stop Signal Task employing an adaptive algorithm to accommodate individual differences often report inferior performance on the task in individuals with ADHD, OCD, and substance use disorders compared to non-clinical controls. Furthermore, individuals with deficits in inhibitory control tend to show reduced neural activity in key inhibitory regions during successful stopping. However, the adaptive algorithm systematically introduces performance-related differences in objective task difficulty that may influence the estimation of individual differences in stop-related neural activity. This report examines the effect that these algorithm-related differences have on the measurement of neural activity during the stop signal task. We compared two groups of subjects (n = 210) who differed in inhibitory ability using both a standard fMRI analysis and an analysis that resampled trials to remove the objective task difficulty confound. The results show that objective task difficulty influences the magnitude of between-group differences and that controlling for difficulty attenuates stop-related activity differences between superior and poor inhibitors. Specifically, group differences in the right inferior frontal gyrus, right middle occipital gyrus, and left inferior frontal gyrus are diminished when differences in objective task difficulty are controlled for. Also, when objective task difficulty effects are exaggerated, group differences in stop related activity emerge in other regions of the stopping network. The implications of these effects for how we interpret individual differences in activity levels are discussed.

Neural Basis of the Emotional Conflict Processing in Major Depression: ERPs and Source Localization Analysis on the N450 and P300 Components

Objects: Effective psychological function requires that cognition is not affected by task-irrelevant emotional stimuli in emotional conflict. Depression is mainly characterized as an emotional disorder. The object of this study is to reveal the behavioral and electrophysiological signature of emotional conflict processing in major depressive disorder (MDD) using event-related potentials (ERPs) and standardized low-resolution brain electromagnetic tomography (sLORETA) analysis.

Method: We used a face–word Stroop task involving emotional faces while recording EEG (electroencephalography) in 20 patients with MDD and 20 healthy controls (HCs). And then ERPs were extracted and the corresponding brain sources were reconstructed using sLORETA.

Results: Behaviorally, subjects with MDDs manifested significantly increased Stroop effect when examining the RT difference between happy incongruent trials and happy congruent trials, compared with HC subjects. ERP results exhibited that MDDs were characterized by the attenuated difference between P300 amplitude to sad congruent stimuli and sad incongruent stimuli, as electrophysiological evidence of impaired conflict processing in subjects with MDD. The sLORETA results showed that MDD patients had a higher current density in rostral anterior cingulate cortex (rostral ACC) within N450 time window in response to happy incongruent trials than happy congruent stimuli. Moreover, HC subjects had stronger activity in right inferior frontal gyrus (rIFG) region in response to incongruent stimuli than congruent stimuli, revealing successful inhibition of emotional distraction in HCs, which was absent in MDDs.

Conclusion: Our results indicated that rostral ACC was implicated in the processing of negative emotional distraction in MDDs, as well as impaired inhibition of task-irrelevant emotional stimuli, relative to HCs. This work furnishes novel behavioral and neurophysiological evidence that are closely related to emotional conflict among MDD patients.

Regional Gray Matter Volume Differences Between Adolescents With ADHD and Typically Developing Controls: Further Evidence for Anterior Cingulate Involvement

OBJECTIVE

The present study investigated structural brain differences between adolescents with ADHD and matched control participants.

METHOD

Voxel-based morphometry (VBM) using the DARTEL approach was performed to assess regional gray matter (GM) volumes. Additionally, individual performance on tests of attention was recorded to correlate ADHD related cognitive impairments with regional gray matter abnormalities.

RESULTS

We found significantly smaller GM volume in subjects with ADHD compared to their matched controls within the anterior cingulate cortex (ACC), the occipital cortex, bilateral hippocampus/amygdala and in widespread cerebellar regions. Further, reductions of the ACC gray matter volume were found to correlate with scores of selective inattention.

CONCLUSION

These findings underline that structural alterations in a widespread cortico-subcortical network seem to underlie the observable attention problems in patients with ADHD.

The Correlation Between Cognitive and Movement Shifting and Brain Activity in Children With ADHD

OBJECTIVE

We assessed the correlation between the deficits of cognition, movement, and brain activity in children with Attention Deficit Hyperactvity Disorder (ADHD).

METHOD

We recruited 15 children with ADHD and 15 age- and sex-matched healthy control participants. Clinical symptoms, cognitive shifting, movement shifting, and brain activity were assessed using the Korean ADHD Rating Scale, the Wisconsin Card Sorting Test (WCST), the 7- and 14-ring drill test with hop jumps (7 HJ and 14 HJ), and 3.0 Tesla functional magnetic resonance imaging scanner, respectively.

RESULTS

ADHD children showed an increased distance traveled and decreased speed on the 14 HJ task. In response to the WCST task, ADHD children showed decreased activation within right gyrus. Total distance on the 14 HJ task was negatively correlated with the mean β value of Cluster 2 in ADHD children.

CONCLUSION

These results suggested that children with ADHD showed difficulty with attention shifting as well as with movement shifting.

Cue-dependent inhibition in posttraumatic stress disorder and attention-deficit/hyperactivity disorder

OBJECTIVE

Attention-deficit/hyperactivity disorder (ADHD) and posttraumatic stress disorder (PTSD) are common among military veterans, but the comorbidity of these two psychiatric disorders remains largely unstudied. Evaluating response inhibition and cue-dependent learning as behavioral and neurocognitive mechanisms underlying ADHD/PTSD can inform etiological models and development of tailored interventions.

METHOD

A cued go/no-go task evaluated response inhibition in 160 adult males. Participants were recruited from the community and a Veterans Administration medical center. Four diagnostic groups were identified: ADHD-only, PTSD-only, ADHD+PTSD, controls.

RESULTS

Group differences were observed across most indices of inhibitory functioning, reaction time, and reaction time variability, whereby PTSD-only and ADHD+PTSD participants demonstrated deficits relative to controls. No cue dependency effects were observed.

CONCLUSION

Finding complement prior work on neurocognitive mechanisms underlying ADHD, PTSD, and ADHD+PTSD. Lack of expected group differences for the ADHD-only group may be due to limited power. Additional work is needed to better characterize distinctions among clinical groups, as well as to test effects among women and youth.

Centrality of prefrontal and motor preparation cortices to Tourette Syndrome revealed by meta-analysis of task-based neuroimaging studies

Tourette Syndrome (TS) is a neurodevelopmental condition characterized by chronic multiple tics, which are experienced as compulsive and 'unwilled'. Patients with TS can differ markedly in the frequency, severity, and bodily distribution of tics. Moreover, there are high comorbidity rates with attention deficit hyperactivity disorder (ADHD), obsessive compulsive disorder (OCD), anxiety disorders, and depression. This complex clinical profile may account for apparent variability of findings across neuroimaging studies that connect neural function to cognitive and motor behavior in TS. Here we crystalized information from neuroimaging regarding the functional circuitry of TS, and furthermore, tested specifically for neural determinants of tic severity, by applying activation likelihood estimation (ALE) meta-analyses to neuroimaging (activation) studies of TS. Fourteen task-based studies (13 fMRI and one H2O-PET) met rigorous inclusion criteria. These studies, encompassing 25 experiments and 651 participants, tested for differences between TS participants and healthy controls across cognitive, motor, perceptual and somatosensory domains. Relative to controls, TS participants showed distributed differences in the activation of prefrontal (inferior, middle, and superior frontal gyri), anterior cingulate, and motor preparation cortices (lateral premotor cortex and supplementary motor area; SMA). Differences also extended into sensory (somatosensory cortex and the lingual gyrus; V4); and temporo-parietal association cortices (posterior superior temporal sulcus, supramarginal gyrus, and retrosplenial cortex). Within TS participants, tic severity (reported using the Yale Global Tic Severity Scale; YGTSS) selectively correlated with engagement of SMA, precentral gyrus, and middle frontal gyrus across tasks. The dispersed involvement of multiple cortical regions with differences in functional reactivity may account for heterogeneity in the symptomatic expression of TS and its comorbidities. More specifically for tics and tic severity, the findings reinforce previously proposed contributions of premotor and lateral prefrontal cortices to tic expression.

Psychoradiology: The Frontier of Neuroimaging in Psychiatry

Unlike neurologic conditions, such as brain tumors, dementia, and stroke, the neural mechanisms for all psychiatric disorders remain unclear. A large body of research obtained with structural and functional magnetic resonance imaging, positron emission tomography/single photon emission computed tomography, and optical imaging has demonstrated regional and illness-specific brain changes at the onset of psychiatric disorders and in individuals at risk for such disorders. Many studies have shown that psychiatric medications induce specific measurable changes in brain anatomy and function that are related to clinical outcomes. As a result, a new field of radiology, termed psychoradiology, seems primed to play a major clinical role in guiding diagnostic and treatment planning decisions in patients with psychiatric disorders. This article will present the state of the art in this area, as well as perspectives regarding preparations in the field of radiology for its evolution. Furthermore, this article will (a) give an overview of the imaging and analysis methods for psychoradiology; (b) review the most robust and important radiologic findings and their potential clinical value from studies of major psychiatric disorders, such as depression and schizophrenia; and (c) describe the main challenges and future directions in this field. An ongoing and iterative process of developing biologically based nomenclatures with which to delineate psychiatric disorders and translational research to predict and track response to different therapeutic drugs is laying the foundation for a shift in diagnostic practice in psychiatry from a psychologic symptom-based approach to an imaging-based approach over the next generation. This shift will require considerable innovations for the acquisition, analysis, and interpretation of brain images, all of which will undoubtedly require the active involvement of radiologists. ^© RSNA, 2016 Online supplemental material is available for this article.

Trait impulsivity components correlate differently with proactive and reactive control

The relationship between impulsivity and cognitive control is still unknown. We hypothesized that trait impulsivity would differentially correlate with specific cognitive control processes. Trait impulsivity was measured by the Barratt Impulsiveness Scale, which assesses motor, attention, and non-planning impulsiveness components. Cognitive control was measured by a hybrid-designed Stroop task, which distinguishes proactive and reactive control. Thirty-three participants performed the Stroop task while they were scanned by functional magnetic resonance imaging. Proactive and reactive control involved increased activity in the fronto-parietal network, and brain activity was associated with impulsivity scores. Specifically, higher motor impulsiveness was associated with a larger proactive control effect in the inferior parietal lobule and a smaller reactive control effect in the right dorsolateral prefrontal cortex (DLPFC) and anterior cingulate contex. Higher attention impulsivity was associated with a smaller proactive control effect in the right DLPFC. Such a correlation pattern suggests that impulsivity trait components are attributable to different cognitive control subsystems.

ADHD symptoms in non-treatment seeking young adults: relationship with other forms of impulsivity

OBJECTIVE

Attention-deficit hyperactivity disorder (ADHD) has been associated with various manifestations of impulsivity in adults, including elevated rates of other impulsive disorders, substance use, questionnaire-based impulsivity scores, and inhibitory dysregulation on neurocognitive tests. The relationship between ADHD and all these other forms of impulsivity has yet to be explored within the context of a single comprehensive study.

METHODS

A total of 423 young adults, who gambled ≥5 times in the preceding year, were recruited using media advertisements and undertook detailed assessment including structured psychiatric interview, questionnaires, and neurocognitive tests. Participants with ADHD symptoms were identified using the Adult ADHD Self-Report Scale Screener (ASRS-V1.1) and were compared to controls using multivariate analysis of variance (MANOVA).

RESULTS

ADHD symptoms were found in 20.3% of the sample, but only 7.3% of these subjects had ever received a formal diagnosis. ADHD symptoms were associated with significantly lower quality of life, lower self-esteem, higher emotional dysregulation, higher impulsivity questionnaire scores, more problematic Internet use, greater occurrence of psychiatric disorders, and impaired stop-signal reaction times. Of these variables, stop-signal reaction times and Barratt attentional impulsiveness were the strongest predictors of group classification.

CONCLUSIONS

ADHD symptoms are common and under-diagnosed in young adults who gamble, and are most strongly linked with certain other types of impulsivity (questionnaire- and cognitive-based measures) and with emotional dysregulation, suggesting that these are each important considerations in understanding the pathophysiology of the disorder, but also potential treatment targets. It is necessary to question whether treatment for adult ADHD could be enhanced by considering self-esteem, emotional reactivity, and impaired inhibitory control as specific treatment targets, in addition to the core diagnostic symptoms of the disorder.

Differential Recruitment of Brain Regions During Response Inhibition in Children Prenatally Exposed to Alcohol

BACKGROUND

Response inhibition is a distinct aspect of executive function that is frequently impaired in children with fetal alcohol spectrum disorders (FASD). We used a Go/NoGo (GNG) task in a functional MRI protocol to investigate differential activation of brain regions in the response inhibition network in children diagnosed with full or partial fetal alcohol syndrome (FAS/PFAS), compared with healthy controls.

METHODS

A rapid, event-related task with 120 Go and 60 NoGo trials was used to study children aged 8 to 12 years-8 with FAS/PFAS, 17 controls. Letters were projected sequentially, with Go and NoGo trials randomly interspersed across the task. BOLD signal in the whole brain was contrasted for the correct NoGo minus correct Go trials between the FAS/PFAS and control groups.

RESULTS

Compared to the FAS/PFAS group, controls showed greater activation of the inferior frontal and anterior cingulate network linked to response inhibition in typically developing children. By contrast, the FAS/PFAS group showed greater BOLD response in dorsolateral prefrontal cortex and other middle prefrontal regions, suggesting compensation for inefficient function of pathways that normally mediate inhibitory processing. All group differences were significant after control for potential confounding variables. None of the effects of prenatal alcohol exposure on activation of the regions associated with response inhibition were attributable to the effects of this exposure on IQ.

CONCLUSIONS

This is the first FASD GNG study in which all participants in the exposed group met criteria for a diagnosis of full FAS or PFAS. Although FASD is frequently comorbid with attention deficit hyperactivity disorder, the pattern of brain activation seen in these disorders differs, suggesting that different neural pathways mediate response inhibition in FASD and that different interventions for FASD are, therefore, warranted.

Functional Decoding and Meta-analytic Connectivity Modeling in Adult Attention-Deficit/Hyperactivity Disorder

BACKGROUND

Task-based functional magnetic resonance imaging (fMRI) studies of adult attention-deficit/hyperactivity disorder (ADHD) have revealed various ADHD-related dysfunctional brain regions, with heterogeneous findings across studies. Here, we used novel meta-analytic data-driven approaches to characterize the function and connectivity profile of ADHD-related dysfunctional regions consistently detected across studies.

METHODS

We first conducted an activation likelihood estimation meta-analysis of 24 task-based fMRI studies in adults with ADHD. Each ADHD-related dysfunctional region resulting from the activation likelihood estimation meta-analysis was then analyzed using functional decoding based on ~7500 fMRI experiments in the BrainMap database. This approach allows mapping brain regions to functions not necessarily tested in individual studies, thus suggesting possible novel functions for those regions. Additionally, ADHD-related dysfunctional regions were clustered based on their functional coactivation profiles across all the experiments stored in BrainMap (meta-analytic connectivity modeling).

RESULTS

ADHD-related hypoactivation was found in the left putamen, left inferior frontal gyrus (pars opercularis), left temporal pole, and right caudate. Functional decoding mapped the left putamen to cognitive aspects of music perception/reproduction and the left temporal lobe to language semantics; both these regions clustered together on the basis of their meta-analytic functional connectivity. Left inferior gyrus mapped to executive function tasks; right caudate mapped to both executive function tasks and music-related processes.

CONCLUSIONS

Our study provides meta-analytic support to the hypothesis that, in addition to well-known deficits in typical executive functions, impairment in processes related to music perception/reproduction and language semantics may be involved in the pathophysiology of adult ADHD.

Divergent subcortical activity for distinct executive functions: stopping and shifting in obsessive compulsive disorder

BACKGROUND

There is evidence of executive function impairment in obsessive compulsive disorder (OCD) that potentially contributes to symptom development and maintenance. Nevertheless, the precise nature of these executive impairments and their neural basis remains to be defined.

METHOD

We compared stopping and shifting, two key executive functions previously implicated in OCD, in the same task using functional magnetic resonance imaging, in patients with virtually no co-morbidities and age-, verbal IQ- and gender-matched healthy volunteers. The combined task allowed direct comparison of neural activity in stopping and shifting independent of patient sample characteristics and state variables such as arousal, learning, or current symptom expression.

RESULTS

Both OCD patients and controls exhibited right inferior frontal cortex activation during stopping, and left inferior parietal cortex activation during shifting. However, widespread under-activation across frontal-parietal areas was found in OCD patients compared to controls for shifting but not stopping. Conservative, whole-brain analyses also indicated marked divergent abnormal activation in OCD in the caudate and thalamus for these two cognitive functions, with stopping-related over-activation contrasting with shift-related under-activation.

CONCLUSIONS

OCD is associated with selective components of executive function, which engage similar common elements of cortico-striatal regions in different abnormal ways. The results implicate altered neural activation of subcortical origin in executive function abnormalities in OCD that are dependent on the precise cognitive and contextual requirements, informing current theories of symptom expression.

Fronto-striatal circuits in response-inhibition: Relevance to addiction

Disruptions to inhibitory control are believed to contribute to multiple aspects of drug abuse, from preexisting vulnerability in at-risk individuals, through escalation to dependence, to promotion of relapse in chronic users. Paradigms investigating the suppression of actions have been investigated in animal and human research on drug addiction. Rodent research has focused largely on impulsive behaviors, often gauged by premature responding, as a viable model highlighting the relevant role of dopamine and other neurotransmitters primarily in the striatum. Human research on action inhibition in stimulant dependence has highlighted impaired performance and largely prefrontal cortical abnormalities as part of a broader pattern of cognitive abnormalities. Animal and human research implicate inhibitory difficulties mediated by fronto-striatal circuitry both preceding and as a result of excessive stimulus use. In this regard, response-inhibition has proven a useful cognitive function to gauge the integrity of fronto-striatal systems and their role in contributing to impulsive and compulsive features of drug dependence.

Functional neuroimaging of visuospatial working memory tasks enables accurate detection of attention deficit and hyperactivity disorder

Finding neurobiological markers for neurodevelopmental disorders, such as attention deficit and hyperactivity disorder (ADHD), is a major objective of clinicians and neuroscientists. We examined if functional Magnetic Resonance Imaging (fMRI) data from a few distinct visuospatial working memory (VSWM) tasks enables accurately detecting cases with ADHD. We tested 20 boys with ADHD combined type and 20 typically developed (TD) boys in four VSWM tasks that differed in feedback availability (feedback, no-feedback) and reward size (large, small). We used a multimodal analysis based on brain activity in 16 regions of interest, significantly activated or deactivated in the four VSWM tasks (based on the entire participants' sample). Dimensionality of the data was reduced into 10 principal components that were used as the input variables to a logistic regression classifier. fMRI data from the four VSWM tasks enabled a classification accuracy of 92.5%, with high predicted ADHD probability values for most clinical cases, and low predicted ADHD probabilities for most TDs. This accuracy level was higher than those achieved by using the fMRI data of any single task, or the respective behavioral data. This indicates that task-based fMRI data acquired while participants perform a few distinct VSWM tasks enables improved detection of clinical cases.

Dissociating Two Stages of Preparation in the Stop Signal Task Using fMRI

Often we must balance being prepared to act quickly with being prepared to suddenly stop. The stop signal task (SST) is widely used to study inhibitory control, and provides a measure of the speed of the stop process that is robust to changes in subjects' response strategy. Previous studies have shown that preparation affects inhibition. We used fMRI to separate activity that occurs after a brief (500 ms) warning stimulus (warning-phase) from activity that occurs during responses that follow (response-phase). Both of these phases could contribute to the preparedness to stop because they both precede stop signals. Warning stimuli activated posterior networks that signal the need for top-down control, whereas response phases engaged prefrontal and subcortical networks that implement top-down control. Regression analyses revealed that both of these phases affect inhibitory control in different ways. Warning-phase activity in the cerebellum and posterior cingulate predicted stop latency and accuracy, respectively. By contrast, response-phase activity in fronto-temporal areas and left striatum predicted go speed and stop accuracy, in pre-supplementary motor area affected stop accuracy, and in right striatum predicted stop latency and accuracy. The ability to separate hidden contributions to inhibitory control during warning-phases from those during response-phases can aid in the study of models of preparation and inhibitory control, and of disorders marked by poor top-down control.

Feedback associated with expectation for larger-reward improves visuospatial working memory performances in children with ADHD

•

Children with ADHD and normal controls were tested in working memory tasks.

•

Availability of feedback and expectation for monetary reward were manipulated.

•

ADHDs showed improved working memory when feedback was associated with larger-reward.

•

Performance improvement in ADHD was associated with brain activity normalization.

We tested the interactive effect of feedback and reward on visuospatial working memory in children with ADHD. Seventeen boys with ADHD and 17 Normal Control (NC) boys underwent functional magnetic resonance imaging (fMRI) while performing four visuospatial 2-back tasks that required monitoring the spatial location of letters presented on a display. Tasks varied in reward size (large; small) and feedback availability (no-feedback; feedback). While the performance of NC boys was high in all conditions, boys with ADHD exhibited higher performance (similar to those of NC boys) only when they received feedback associated with large-reward. Performance pattern in both groups was mirrored by neural activity in an executive function neural network comprised of few distinct frontal brain regions. Specifically, neural activity in the left and right middle frontal gyri of boys with ADHD became normal-like only when feedback was available, mainly when feedback was associated with large-reward. When feedback was associated with small-reward, or when large-reward was expected but feedback was not available, boys with ADHD exhibited altered neural activity in the medial orbitofrontal cortex and anterior insula. This suggests that contextual support normalizes activity in executive brain regions in children with ADHD, which results in improved working memory.

Differentiating SCT and inattentive symptoms in ADHD using fMRI measures of cognitive control

Attention Deficit/Hyperactivity Disorder (ADHD) is associated with different impairment profiles in the symptom domains of hyperactivity/impulsivity and/or inattention. An additional symptom domain of sluggish cognitive tempo (SCT) has also been proposed. Although there is a degree of correlation between the SCT symptom domain and inattention, it has been proposed as a distinct disorder independent of ADHD. The objective of this study was to examine the neural substrates of cue-related preparatory processes associated with SCT symptoms versus inattentive symptoms in a group of adolescents with ADHD. We also compared cue-related effects in the entire ADHD group compared with a group of typically developing (TD) peers. A modified cued flanker paradigm and fMRI examined brain activity associated with attention preparation and motor response preparation. Between group contrasts between the ADHD and TD group revealed significant hypoactivity in the ADHD group during general attention preparation in the supplementary motor area (SMA) and in the right superior parietal lobe (SPL) during response preparation. In the ADHD group, greater numbers of SCT symptoms were associated with hypoactivity in the left SPL to cues in general whereas greater numbers of inattentive symptoms were associated with greater activity in the SMA to cues that provided no information and less activity in the thalamus during response preparation. Hypoactivity in the SPL with increasing SCT symptoms may be associated with impaired reorienting or shifting of attention. Altered activity in the SMA and thalamus with increasing inattention may be associated with a general problem with response preparation, which may also reflect inefficient processing of the response preparation cue. Our results support a degree of differentiation between SCT and inattentive symptom profiles within adolescents with ADHD.

•

We examine cognitive control activity in ADHD SCT versus inattentive symptomatology.

•

An increase in SCT symptoms was associated with impaired attention orienting.

•

More inattentive symptoms were associated with impaired response preparation.

•

SCT activity differed from inattentive activity in adolescents with ADHD.

The influence of levetiracetam in cognitive performance in healthy individuals: neuropsychological, behavioral and electrophysiological approach

OBJECTIVE

The present study sought to analyze the influence of Levetiracetam (LEV) in cognitive performance by identifying the changes produced by LEV in reaction time, in neuropsychological assessment of attention and memory and in absolute theta power in frontal activity.

METHODS

Twelve healthy subjects (5 men and 7 women; mean age, 30.08 years, standard deviation, 4.71) were recruited for this study. The neuropsychological tests: Trail Making Test (A and B), Digit Span (direct and indirect numerical orders/working memory); Stroop test (inhibitory control of attention); Tower of London (planning and decision-making) and a quantitative electroencephalography were applied in 2 different days after and before the participants ingested the capsule of placebo or 500 mg LEV.

RESULTS

A two-way-ANOVA was implemented to observe the interaction between conditions (placebo or LEV 500 mg) and moments (pre- and post-ingestion of LEV or placebo). The data were analyzed by the SPSS statistical package (p<0.05). For the neuropsychological parameter, the Trail Making Test (A) was the only test that showed significant difference for condition in the task execution time (p=0.026). Regarding the reaction time in the behavioral parameter, an interaction between both factors (p=0.034) was identified through a two-way-ANOVA (condition versus moment). Electrophysiological measures showed a significant interaction for electrodes: F7, F3, and FZ.

CONCLUSIONS

The findings showed that LEV promotes an important cognitive enhancement in the executive functions.

Traditional and alert hypnotic phenomena: development through anteriorization

Modern research techniques show that hypnotic induction involves behavioral and cognitive inhibition as components of many hypnotic phenomena. One standard laboratory technique for measuring cognitive inhibition is the Go/NoGo procedure. The procedure moves the average, or centroid, of electroencephalography signals toward the frontal, or anterior, part of the brain. This process, called anteriorization, produces a shift in the emotional and cognitive signals from the anterior cingulate cortex. This has implications for both the scientific understanding and clinical use of hypnosis.