Frontostriatal connectivity and its role in cognitive control in parent-child dyads with ADHD

Recovery of an injured prefronto-caudate tract in a patient with traumatic brain injury: A diffusion tensor tractography study

OBJECTIVES

We report on a patient with improvement of akinetic mutism (AM), who showed recovery of an injured prefronto-caudate tract following traumatic brain injury (TBI), which was demonstrated by follow-up diffusion tensor tractographies (DTTs).

CASE PRESENTATION

A 72-year-old female had suffered from head trauma resulting from falling down the stairs. She was diagnosed as subdural hematoma on the right frontal lobe and subarachnoid haemorrhage. At 5 weeks after head trauma, when starting rehabilitation, she showed no spontaneous movement or speech. She participated in a comprehensive rehabilitative management programme, including movement therapy and dopaminergic drugs, for improvement of AM. During 5 week's intensive rehabilitation, she showed gradual improvement of AM: she became able to perform some daily activities by herself including eating, dressing and walking.

RESULTS

On 5-week DTT, the neural connectivity of the caudate nucleus (CN) to the medial prefrontal cortex (PFC; Broadmann area [BA]: 10 and 12) and the orbitofrontal cortex (BA: 11 and 13) was decreased in both hemispheres; in contrast, the neural connectivity of the CN to the medial PFC was increased on the left side on 10-week and 6-month DTT.

CONCLUSIONS

Recovery of an injured prefronto-caudate tract concurrent with the improvement of AM was demonstrated in a patient with TBI, using follow-up DTTs.

Intra-regional and inter-regional abnormalities and cognitive control deficits in young adult smokers

Tobacco use during later adolescence and young adulthood may cause serious neurophysiological changes; rationally, it is extremely important to study the relationship between brain dysfunction and behavioral performances in young adult smokers. Previous resting state studies investigated the neural mechanisms in smokers. Unfortunately, few studies focused on spontaneous activity differences between young adult smokers and nonsmokers from both intra-regional and inter-regional levels, less is known about the association between resting state abnormalities and behavioral deficits. Therefore, we used fractional amplitude of low frequency fluctuation (fALFF) and resting state functional connectivity (RSFC) to investigate the resting state spontaneous activity differences between young adult smokers and nonsmokers. A correlation analysis was carried out to assess the relationship between neuroimaging findings and clinical information (pack-years, cigarette dependence, age of onset and craving score) as well as cognitive control deficits measured by the Stroop task. Consistent with previous addiction findings, our results revealed the resting state abnormalities within frontostriatal circuits, i.e., enhanced spontaneous activity of the caudate and reduced functional strength between the caudate and anterior cingulate cortex (ACC) in young adult smokers. Moreover, the fALFF values of the caudate were correlated with craving and RSFC strength between the caudate and ACC was associated with the cognitive control impairments in young adult smokers. Our findings could lead to a better understanding of intrinsic functional architecture of baseline brain activity in young smokers by providing regional and brain circuit spontaneous neuronal activity properties as well as their association with cognitive control impairments.

The left dorsolateral prefrontal cortex and caudate pathway: New evidence for cue-induced craving of smokers

Although the activation of the prefrontal cortex (PFC) and the striatum had been found in smoking cue induced craving task, whether and how the functional interactions and white matter integrity between these brain regions contribute to craving processing during smoking cue exposure remains unknown. Twenty-five young male smokers and 26 age- and gender-matched nonsmokers participated in the smoking cue-reactivity task. Craving related brain activation was extracted and psychophysiological interactions (PPI) analysis was used to specify the PFC-efferent pathways contributed to smoking cue-induced craving. Diffusion tensor imaging (DTI) and probabilistic tractography was used to explore whether the fiber connectivity strength facilitated functional coupling of the circuit with the smoking cue-induced craving. The PPI analysis revealed the negative functional coupling of the left dorsolateral prefrontal cortex (DLPFC) and the caudate during smoking cue induced craving task, which positively correlated with the craving score. Neither significant activation nor functional connectivity in smoking cue exposure task was detected in nonsmokers. DTI analyses revealed that fiber tract integrity negatively correlated with functional coupling in the DLPFC-caudate pathway and activation of the caudate induced by smoking cue in smokers. Moreover, the relationship between the fiber connectivity integrity of the left DLPFC-caudate and smoking cue induced caudate activation can be fully mediated by functional coupling strength of this circuit in smokers. The present study highlighted the left DLPFC-caudate pathway in smoking cue-induced craving in smokers, which may reflect top-down prefrontal modulation of striatal reward processing in smoking cue induced craving processing. Hum Brain Mapp 38:4644-4656, 2017. © 2017 Wiley Periodicals, Inc.

Apathy Due to Injury of the Prefrontocaudate Tract Following Mild Traumatic Brain Injury

In this study, we report on a patient who developed apathy resulting from injury to the prefrontocaudate tract following mild traumatic brain injury (TBI), which was observed on diffusion tensor tractography (DTT). A 46-year-old female patient was involved in a bus accident. Her history included intracerebral hemorrhage (ICH) in the left putamen 4 years ago before the head trauma, and her family reported that she had fully recovered. She developed apathy after the TBI, worsening over time. Decreased neural connectivity of the left caudate nucleus (CN) to the left upper medial prefrontal cortex (PFC) resulting from the ICH was observed on the pre-TBI-DTT, whereas on the post-TBI-DTT (28 months after TBI), the neural connectivity of the left CN to the left upper medial PFC was increased, whereas that to the left lower medial PFC and orbitofrontal cortex was decreased. In the right hemisphere, decreased neural connectivity of the CN to the medial PFC and orbitofrontal cortex was observed on the post-TBI-DTT compared with the pre-TBI-DTT. Injury of the prefrontocaudate tract was observed in a patient with old ICH who developed apathy following mild TBI, using DTT.

Female-specific association of NOS1 genotype with white matter microstructure in ADHD patients and controls

BACKGROUND

The nitric oxide synthase gene (NOS1) exon 1f (ex1f) VNTR is a known genetic risk factor for Attention-Deficit/Hyperactivity Disorder (ADHD), particularly in females. NOS1 plays an important role in neurite outgrowth and may thus influence brain development, specifically white matter (WM) microstructure, which is known to be altered in ADHD. The current study aimed to investigate whether NOS1 is associated with WM microstructure in (female) individuals with and without ADHD.

METHODS

Diffusion Tensor Imaging (DTI) scans were collected from 187 participants with ADHD (33% female) and 103 controls (50% female), aged 8-26 years, and NOS1-ex1f VNTR genotype was determined. Whole-brain analyses were conducted for fractional anisotropy (FA) and mean diffusivity (MD) to examine associations between NOS1 and WM microstructure, including possible interactions with gender and diagnosis.

RESULTS

Consistent with previous literature, NOS1-ex1f was associated with total ADHD and hyperactivity-impulsivity symptoms, but not inattention; this effect was independent of gender. NOS1-ex1f was also associated with MD values in several major WM tracts in females, but not males. In females, homozygosity for the short allele was linked to higher MD values than carriership of the long allele. MD values in these regions did not correlate with ADHD symptoms. Results were similar for participants with and without ADHD.

CONCLUSIONS

NOS1-ex1f VNTR is associated with WM microstructure in females in a large sample of participants with ADHD and healthy controls. Whether this association is part of a neurodevelopmental pathway from NOS1 to ADHD symptoms should be further investigated in future studies.

Emotion regulation as a transdiagnostic factor in the development of internalizing and externalizing psychopathology: Current and future directions

In response to rapidly growing rates of comorbidity among psychiatric disorders, clinical scientists have become interested in identifying transdiagnostic processes that can help explain dysfunction across diagnostic categories (e.g., Kring & Sloan, 2009). One factor that has received a great deal of attention is that of emotion regulation, namely, the ability to modulate the intensity and/or duration of emotional states (e.g., Cicchetti, Ackerman, & Izard, 1995; Gross, 1998). Recent theoretical and empirical work has begun to emphasize the role that emotion regulation plays in the temporal comorbidity between internalizing and externalizing conditions (e.g., Aldao & De Los Reyes, 2015; De Los Reyes & Aldao, 2015; Drabick & Kendall, 2010; Jarrett & Ollendick, 2008; Patrick & Hajcak, 2016). However, close inspection of this work reveals two very pertinent areas of growth: (a) this literature is characterized by mixed findings that are likely explained, in part, by methodological heterogeneity; and (b) emotion regulation tends to be studied in relatively narrow terms. To address these issues, we provide a series of recommendations for facilitating cross-study comparisons and leveraging multifaceted approaches to studying emotion regulation processes within a developmental psychopathology framework. We hope that our perspective can enhance the organization and growth of this very important area of inquiry, and ultimately result in more effective prevention and treatment programs.

Trait Impulsivity and the Externalizing Spectrum

This article reviews evidence that trait impulsivity-expressed early in life as the hyperactive-impulsive and combined presentations of attention-deficit/hyperactivity disorder (ADHD)-is a bottom-up, subcortically mediated vulnerability to all externalizing disorders. This vulnerability arises from deficient mesolimbic dopamine responding, which imbues psychological states (irritability, discontentment) that motivate excessive approach behavior (hyperactivity, impulsivity). Through complex interactions with (a) aversive motivational states that arise from largely independent subcortical systems, (b) emotion regulatory mechanisms that arise from top-down, cortical modulation of subcortical neural function, and (c) environmental risk factors that shape and maintain emotion dysregulation, trait impulsivity confers vulnerability to increasingly severe externalizing behaviors across development. This perspective highlights the importance of identifying transdiagnostic neural vulnerabilities to psychopathology; dovetails with the hierarchical, latent structure of psychopathology; and suggests that progression along the externalizing spectrum is an ontogenic process whereby a common, multifactorially inherited trait interacts with endogenous and exogenous influences to yield increasingly intractable externalizing behaviors across development.

Components of the folate metabolic pathway and ADHD core traits: an exploration in eastern Indian probands

We investigated role of the folate-homocysteine metabolic pathway in the etiology of attention-deficit hyperactivity disorder (ADHD) due to its importance in maintaining DNA integrity as well as neurotransmission. Functional gene variants in MTR (rs1805087), CBS (rs5742905), MTHFR (rs1801133 &rs1801131), MTHFD (rs2236225), RFC1 (rs1051266), plasma vitamin B12, folate and homocysteine were analyzed. rs1805087 'A' showed strong association with ADHD. Vitamin B12 deficiency of ADHD probands (P=0.01) correlated with rs1801133 'T' and rs1805087'GG'. Mild hyperhomocysteinemia (P=0.05) in the probands was associated with rs1805087 'AA'. Probands having rs1805087 'GG' and rs1051266 'G' was more inattentive. Hyperactivity-impulsivity score revealed association with rs5742905 'TT' and rs2236225 'CC', while rs1801133 'CC' showed association with inattentiveness and hyperactivity-impulsivity. rs1801131 exhibited strong synergistic interaction with rs1051266 and rs2236225. This indicated that the folate-homocysteine pathway gene variants may affect ADHD etiology through mild hyperhomocysteinemia and vitamin B12 deficiency, factors known to be associated with cognitive deficit.

Dissociable frontostriatal white matter connectivity underlies reward and motor impulsivity

Dysfunction of cognitive control often leads to impulsive decision-making in clinical and healthy populations. Some research suggests that a generalized cognitive control mechanism underlies the ability to modulate various types of impulsive behavior, while other evidence suggests different forms of impulsivity are dissociable, and rely on distinct neural circuitry. Past research consistently implicates several brain regions, such as the striatum and portions of the prefrontal cortex, in impulsive behavior. However the ventral and dorsal striatum are distinct in regards to function and connectivity. Nascent evidence points to the importance of frontostriatal white matter connectivity in impulsivity, yet it remains unclear whether particular tracts relate to different control behaviors. Here we used probabilistic tractography of diffusion imaging data to relate ventral and dorsal frontostriatal connectivity to reward and motor impulsivity measures. We found a double dissociation such that individual differences in white matter connectivity between the ventral striatum and the ventromedial prefrontal cortex and dorsolateral prefrontal cortex was associated with reward impulsivity, as measured by delay discounting, whereas connectivity between dorsal striatum and supplementary motor area was associated with motor impulsivity, but not vice versa. Our findings suggest that (a) structural connectivity can is associated with a large amount of behavioral variation; (b) different types of impulsivity are driven by dissociable frontostriatal neural circuitry.

White Matter Microstructural Alterations in Children with ADHD: Categorical and Dimensional Perspectives

Studies of brain alterations in children with attention-deficit/hyperactivity disorder (ADHD) have shown heterogeneous results. The aims of the current study were to investigate white matter microstructure in children using both categorical and dimensional definitions of ADHD and to determine the functional consequences of observed alterations. In a large single-site sample of children (aged 8-15 years) with ADHD (n=83) and healthy controls (n=122), we used tract-based spatial statistics on diffusion tensor imaging data to investigate whole-skeleton differences of fractional anisotropy (FA), mean, axial, and radial diffusivity (MD, AD, RD), and mode of anisotropy related to ADHD status (categorical) and symptom severity (dimensional). For categorical differences observed, we analyzed their association with cognitive functioning in working memory and inhibition. Compared with healthy controls, children with ADHD showed decreased FA and increased RD in widespread, overlapping brain regions, mainly in corpus callosum (CC) and major tracts in the left hemisphere. Decreased FA was associated with inhibition performance in the participants with ADHD. Using dimensional definitions, greater hyperactivity/impulsivity symptom severity was associated with higher FA also in widespread regions, mainly in CC and major tracts in the right hemisphere. Our study showed white matter alterations to be related to ADHD status and symptom severity in patients. The coexistence of decreased FA and increased RD in the absence of alterations in MD or AD might indicate altered myelination as a pathophysiological factor in ADHD.

Prenatal Alcohol Exposure in Rodents As a Promising Model for the Study of ADHD Molecular Basis

A physiological parallelism, or even a causal effect relationship, can be deducted from the analysis of the main characteristics of the “Alcohol Related Neurodevelopmental Disorders” (ARND), derived from prenatal alcohol exposure (PAE), and the behavioral performance in the Attention-deficit/hyperactivity disorder (ADHD). These two clinically distinct disease entities, exhibits many common features. They affect neurological shared pathways, and also related neurotransmitter systems. We briefly review here these parallelisms, with their common and uncommon characteristics, and with an emphasis in the subjacent molecular mechanisms of the behavioral manifestations, that lead us to propose that PAE in rats can be considered as a suitable model for the study of ADHD.

Is the Relationship Between ADHD Symptoms and Binge Eating Mediated by Impulsivity?

OBJECTIVE

Individuals with ADHD may be at risk of developing binge eating disorder (BED). Impulsivity correlates with both BED and ADHD; however, more research is needed to explore whether impulsivity plays an underlying role in the observed relationship between ADHD and BED.

METHOD

Questionnaires were used to assess ADHD and BED symptoms. Multiple questionnaires and a behavioral task were used to assess impulsivity in undiagnosed undergraduate participants (n = 50).

RESULTS

Expected correlations were found among ADHD symptoms, BED tendencies, and measures of impulsivity with the exception of impulsivity on the behavioral task and BED symptoms; however, none of the measures of impulsivity were found to be significant mediators between ADHD and BED symptoms.

CONCLUSION

Although impulsivity may play an important role in the interrelationship of ADHD and binge eating, other factors may also be critical in the development of this comorbidity. Investigation of this research question in clinical samples is needed.

White matter and cognition: making the connection

Whereas the cerebral cortex has long been regarded by neuroscientists as the major locus of cognitive function, the white matter of the brain is increasingly recognized as equally critical for cognition. White matter comprises half of the brain, has expanded more than gray matter in evolution, and forms an indispensable component of distributed neural networks that subserve neurobehavioral operations. White matter tracts mediate the essential connectivity by which human behavior is organized, working in concert with gray matter to enable the extraordinary repertoire of human cognitive capacities. In this review, we present evidence from behavioral neurology that white matter lesions regularly disturb cognition, consider the role of white matter in the physiology of distributed neural networks, develop the hypothesis that white matter dysfunction is relevant to neurodegenerative disorders, including Alzheimer's disease and the newly described entity chronic traumatic encephalopathy, and discuss emerging concepts regarding the prevention and treatment of cognitive dysfunction associated with white matter disorders. Investigation of the role of white matter in cognition has yielded many valuable insights and promises to expand understanding of normal brain structure and function, improve the treatment of many neurobehavioral disorders, and disclose new opportunities for research on many challenging problems facing medicine and society.

Polymorphism of the 3'-UTR of the dopamine transporter gene (DAT) in New World monkeys

Genetic polymorphism in the 3'-untranslated region (3'-UTR) of the dopamine transporter (DAT) gene has been reported in both human and nonhuman primates, and the variable number of tandem repeats (VNTR) polymorphism has been related to several neurological and psychiatric disorders. As New World primates have been employed as models in biomedical research in these fields, in the present study we assessed genetic variation in the DAT gene in 25 robust capuchin monkeys (Sapajus spp.) and 39 common marmosets (Callithrix jacchus). Using enzymatic amplification followed by sequencing of amplified fragments, a VNTR polymorphism in the 3'-UTR region of the DAT gene was identified in both robust capuchins and common marmosets. The polymorphic tandem repeat of 40-bp basic units is similar to the human VNTR consensus sequence, with size variants composed of 9, 10, and 11 units in marmosets and 8, 9, 13, and 17 basic units in capuchins. We found behavioral evidence that carrying the 10-repeat DAT allele promotes flexible choice and maximization of foraging in marmosets tested in an operant choice paradigm. Moreover, in an intertemporal choice task, capuchins with longer repeat variants show less self-controlled choices than capuchins with at least one short repeat variant. Future research should focus on the relationship between these DAT polymorphisms, dopamine reuptake via the dopamine transporter, and behavioral and cognitive variation across New World monkey individuals.

The Broad Autism (Endo)Phenotype: Neurostructural and Neurofunctional Correlates in Parents of Individuals with Autism Spectrum Disorders

Autism Spectrum Disorders (ASD) are a set of neurodevelopmental disorders with an early-onset and a strong genetic component in their pathogenesis. According to genetic and epidemiological data, ASD relatives present personality traits similar to, but not as severe as the defining features of ASD, which have been indicated as the "Broader Autism Phenotype" (BAP). BAP features seem to be more prevalent in first-degree relatives of individuals with ASD than in the general population. Characterizing brain profiles of relatives of autistic probands may help to understand ASD endophenotype. The aim of this review was to provide an up-to-date overview of research findings on the neurostructural and neurofunctional substrates in parents of individuals with ASD (pASD). The primary hypothesis was that, like for the behavioral profile, the pASD express an intermediate neurobiological pattern between ASD individuals and healthy controls. The 13 reviewed studies evaluated structural magnetic resonance imaging (MRI) brain volumes, chemical signals using magnetic resonance spectroscopy (MRS), task-related functional activation by functional magnetic resonance imaging (fMRI), electroencephalography (EEG), or magnetoencephalography (MEG) in pASD.The studies showed that pASD are generally different from healthy controls at a structural and functional level despite often not behaviorally impaired. More atypicalities in neural patterns of pASD seem to be associated with higher scores at BAP assessment. Some of the observed atypicalities are the same of the ASD probands. In addition, the pattern of neural correlates in pASD resembles that of adult individuals with ASD, or it is specific, possibly due to a compensatory mechanism. Future studies should ideally include a group of pASD and HC with their ASD and non-ASD probands respectively. They should subgrouping the pASD according to the BAP scores, considering gender as a possible confounding factor, and correlating these scores to underlying brain structure and function. These types of studies may help to understand the genetic mechanisms involved in the various clinical dimension of ASD.

Longitudinal effects of prenatal exposure to air pollutants on self-regulatory capacities and social competence

BACKGROUND

We evaluated the influence of prenatal exposure to widespread urban air pollutants on the development of self-regulation and social competence in a longitudinal prospective cohort of children born to nonsmoking minority women in New York City.

METHODS

Air pollutant exposure was estimated categorically by level of polycyclic aromatic hydrocarbon (PAH)-DNA adducts in maternal blood collected at delivery, providing a biomarker of maternal exposure to PAH over a 2- to 3-month period. Deficient emotional self-regulation (DESR) was defined as moderate elevations on three specific scales of the child behavior checklist (anxious/depressed, aggressive behavior, and attention problems). We used generalized estimating equations to assess the influence of prenatal exposure to PAH on DESR in children at 3-5, 7, 9, and 11 years of age, adjusted for gender and race/ethnicity. Next, we assessed the association of prenatal exposure to PAH with social competence, as measured by the social responsiveness scale (SRS), the association of impaired self-regulation with social competence, and whether impairment in self-regulation mediated the association of prenatal exposure to PAH with social competence.

RESULTS

We detected a significant interaction (at p = .05) of exposure with time, in which the developmental trajectory of self-regulatory capacity was delayed in the exposed children. Multiple linear regression revealed a positive association between presence of PAH-DNA adducts and problems with social competence (p < .04), level of dysregulation and problems with social competence (p < .0001), and evidence that self-regulation mediates the association of prenatal exposure to PAH with social competence (p < .0007).

CONCLUSIONS

These data suggest that prenatal exposure to PAH produces long-lasting effects on self-regulatory capacities across early and middle childhood, and that these deficits point to emerging social problems with real-world consequences for high-risk adolescent behaviors in this minority urban cohort.

Hemispheric Coherence in ASD with and without Comorbid ADHD and Anxiety

There is a growing body of evidence suggesting that altered brain connectivity may be a defining feature of disorders such as autism spectrum disorder (ASD), anxiety, and ADHD. This study investigated whether resting state functional connectivity, measured by 128-channel EEG oscillation coherence, differs between developmental disorders. Analyses were conducted separately on groups with and without comorbid conditions. Analyses revealed increased coherence across central electrodes over the primary motor cortex and decreased coherence in the frontal lobe networks in those with ASD compared to neurotypical controls. There was increased coherence in occipital lobe networks in the ADHD group compared to other groups. Symptoms of generalised anxiety were positively correlated with both frontal-occipital intrahemispheric (alpha only) coherence and occipital interhemispheric coherence (alpha, approaching theta band). The patterns of coherence in the ASD pure group were different when comorbid conditions were included in the analyses, suggesting that aberrant coherence in the frontal and central areas of the brain is specifically associated with ASD. Our findings support the idea that comorbid conditions are additive, rather than being symptoms of the same disorder.

Social Networking Site Use While Driving: ADHD and the Mediating Roles of Stress, Self-Esteem and Craving

BACKGROUND

Adults who present ADHD symptoms have an increased risk for vehicle accidents. One conceivable overlooked account for this association is the possibility that people with ADHD symptoms use rewarding technologies such as social networking sites (SNS) while driving, more than others. The objective of this study was to understand if and how ADHD symptoms can promote SNS use while driving and specifically to conceptualize and examine mechanisms which may underlie this association. To do so, ADHD is viewed in this study as an underlying syndrome that promotes SNS use while driving in a manner similar to how addictive syndromes promote compulsive seeking of drug rewards.

METHODS

Time-lagged survey data regarding ADHD, stress, self-esteem, SNS craving experience, SNS use while driving, and control variables were collected from a sample of 457 participants who use a popular SNS (Facebook) and drive, after face-validity examination with a panel of five users and pretest with a sample of 47. These data were subjected to structural equation modeling (SEM) analyses using the frequency of ADHD symptoms measured with ASRS v1.1 Part A as a continuous variable, as well as multivariate analysis of variance using ADHD classification based on ASRS v1.1 scoring guidelines.

RESULTS

ADHD symptoms promoted increased stress and reduced self-esteem, which in turn, together with ADHD symptoms, increased one's cravings to use the SNS. These cravings ultimately translated into increased SNS use while driving. Using the ASRS v1.1 classification, people having symptoms highly consistent with ADHD presented elevated levels of stress, cravings to use the SNS, and SNS use while driving, as well as decreased levels of self-esteem. Cravings to use the SNS among men were more potent than among women.

CONCLUSION

SNS use while driving may be more prevalent than previously assumed and may be indirectly associated with ADHD symptoms. It is a new form of impulsive and risky behavior which is more common among people with symptoms compatible with ADHD than among others. Consistent with addiction and decision making models, SNS use while driving can be viewed as a form of a compensatory reward seeking behavior. As such, prevention and reduction interventions that target the mediating perceptions and states should be devised.

The implication of frontostriatal circuits in young smokers: A resting-state study

The critical roles of frontostriatal circuits had been revealed in addiction. With regard to young smokers, the implication of frontostriatal circuits resting-state functional connectivity (RSFC) in smoking behaviors and cognitive control deficits remains unclear. In this study, the volume of striatum subsets, i.e., caudate, putamen, and nucleus accumbens, and corresponding RSFC differences were investigated between young smokers (n1  = 60) and nonsmokers (n2  = 60), which were then correlated with cigarette smoking measures, such as pack_years-cumulative effect of smoking, Fagerström Test for Nicotine Dependence (FTND)-severity of nicotine addiction, Questionnaire on Smoking Urges (QSU)-craving state, and Stroop task performances. Additionally, mediation analysis was carried out to test whether the frontostriatal RSFC mediates the relationship between striatum morphometry and cognitive control behaviors in young smokers when applicable. We revealed increased volume of right caudate and reduced RSFC between caudate and dorsolateral prefrontal cortex (DLPFC), orbitofrontal cortex in young smokers. Significant positive correlation between right caudate volume and QSU as well as negative correlation between anterior cingulate cortex-right caudate RSFC and FTND were detected in young smokers. More importantly, DLPFC-caudate RSFC strength mediated the relationship between caudate volume and incongruent errors during Stroop task in young smokers. Our results demonstrated that young smokers showed abnormal interactions within frontostriatal circuits, which were associated with smoking behaviors and cognitive control impairments. It is hoped that our study focusing on frontostriatal circuits could provide new insights into the neural correlates and potential novel therapeutic targets for treatment of young smokers. Hum Brain Mapp 37:2013-2026, 2016. © 2016 Wiley Periodicals, Inc.

Mode of Anisotropy Reveals Global Diffusion Alterations in Attention-Deficit/Hyperactivity Disorder

OBJECTIVE

Diffusion tensor imaging (DTI) can identify structural connectivity alterations in attention-deficit/hyperactivity disorder (ADHD). Most ADHD DTI studies have concentrated on regional differences in fractional anisotropy (FA) despite its limited sensitivity to complex white matter architecture and increasing evidence of global brain differences in ADHD. Here, we examine multiple DTI metrics in separate samples of children and adults with and without ADHD with a principal focus on global between-group differences.

METHOD

Two samples: adults with ADHD (n = 42) and without (n = 65) and children with ADHD (n = 82) and without (n = 80) were separately group matched for age, sex, and head motion. Five DTI metrics (FA, axial diffusivity, radial diffusivity, mean diffusivity, and mode of anisotropy) were analyzed via tract-based spatial statistics. Group analyses tested for diagnostic differences at the global (averaged across the entire white matter skeleton) and regional level for each metric.

RESULTS

Robust global group differences in diffusion indices were found in adults, with the largest effect size for mode of anisotropy (MA; Cohen's d = 1.45). Global MA also differed significantly between groups in the pediatric sample (d = 0.68). In both samples, global MA increased classification accuracy compared to the model with clinical Conners' ADHD ratings alone. Regional diagnostic differences did not survive familywise correction for multiple comparisons.

CONCLUSION

Global DTI metrics, particularly the mode of anisotropy, which is sensitive to crossing fibers, capture connectivity abnormalities in ADHD across both pediatric and adult samples. These findings highlight potential diffuse white matter microarchitecture differences in ADHD.

Computational Psychiatry of ADHD: Neural Gain Impairments across Marrian Levels of Analysis

Attention-deficit hyperactivity disorder (ADHD), one of the most common psychiatric disorders, is characterised by unstable response patterns across multiple cognitive domains. However, the neural mechanisms that explain these characteristic features remain unclear. Using a computational multilevel approach, we propose that ADHD is caused by impaired gain modulation in systems that generate this phenotypic increased behavioural variability. Using Marr's three levels of analysis as a heuristic framework, we focus on this variable behaviour, detail how it can be explained algorithmically, and how it might be implemented at a neural level through catecholamine influences on corticostriatal loops. This computational, multilevel, approach to ADHD provides a framework for bridging gaps between descriptions of neuronal activity and behaviour, and provides testable predictions about impaired mechanisms.

White matter microstructure and developmental improvement of hyperactive/impulsive symptoms in attention-deficit/hyperactivity disorder

BACKGROUND

A developmental improvement of symptoms in attention-deficit/hyperactivity disorder (ADHD) is frequently reported, but the underlying neurobiological substrate has not been identified. The aim of this study was to determine whether white matter microstructure is related to developmental improvement of ADHD symptoms.

METHODS

A cross-sectional magnetic resonance imaging (MRI) analysis was embedded in a prospective follow-up of an adolescent cohort of ADHD and control subjects (NeuroIMAGE). Mean age at baseline was 11.9 years, mean interval of follow-up was 5.9 years. About 75.3% of the original cohort was retained successfully. Data of 101 participants with ADHD combined type at baseline and 40 healthy controls were analysed. ADHD symptoms were measured with semistructured, investigator-based interviews and Conners' questionnaires, on the basis of DSM-IV criteria. Fractional anisotropy (FA) and mean diffusivity (MD) indices of white matter microstructure were measured using whole brain diffusion tensor imaging at follow-up only. In a dimensional analysis FA and MD were related to change in ADHD symptoms. To link this analysis to DSM-IV diagnoses, a post hoc categorical group analysis was conducted comparing participants with persistent (n = 59) versus remittent (n = 42) ADHD and controls.

RESULTS

Over time, participants with ADHD showed improvement mainly in hyperactive/impulsive symptoms. This improvement was associated with lower FA and higher MD values in the left corticospinal tract at follow-up. Findings of the dimensional and the categorical analysis strongly converged. Changes in inattentive symptoms over time were minimal and not related to white matter microstructure.

CONCLUSIONS

The corticospinal tract is important in the control of voluntary movements, suggesting the importance of the motor system in the persistence of hyperactive/impulsive symptoms.

Neurobiology of ADHD From Childhood to Adulthood: Findings of Imaging Methods

OBJECTIVE

To review the pattern of morphological and functional brain changes in both children and adults with ADHD that emerges from the recent literature. In addition, the task of the present review is to explore how to understand the nature of the brain changes.

METHODS

Literature review.

RESULTS

Neuroimaging studies provide a multitude of information that currently allows us to expand the notions of ADHD neurobiology beyond its traditional understanding as a manifestation of frontostriatal dysfunction. They point to disorders of several other areas of the brain, particularly the anterior cingulum, the dorsolateral as well as ventrolateral prefrontal cortex, the orbitofrontal cortex, the superior parietal regions, the caudate nucleus, the thalamus, the amygdala and the cerebellum. Imaging studies point to the persistence of changes in both brain structure and function into adulthood, although there might be a tendency for improvement of caudate nucleus pathology. Changes in neuronal (dendritic) plasticity, which are under the modulatory influence of the dopaminergic system, may be in the background of disorders of brain morphology and anatomical connectivity with subsequent brain dysfunction. Growing evidence suggest that methylphenidate treatment can lead to improvement of brain changes seen in neuroimaging by its positive effect on neuroplasticity.

CONCLUSION

Changes in neuronal plasticity may be behind persisting brain changes in ADHD. Current treatment approaches seem to improve these neuroplastic processes, and, therefore, may have a positive effect on the neuropathology of ADHD.

Altered white matter tract property related to impaired focused attention, sustained attention, cognitive impulsivity and vigilance in attention-deficit/ hyperactivity disorder

BACKGROUND

The neural substrate for clinical symptoms and neuropsychological performance in individuals with attention-deficit/hyperactivity disorder (ADHD) has rarely been studied and has yielded inconsistent results. We sought to compare the microstructural property of fibre tracts associated with the prefrontal cortex and its association with ADHD symptoms and a wide range of attention performance in youth with ADHD and healthy controls.

METHODS

We assessed youths with ADHD and age-, sex-, handedness-, coil- and intelligence-matched controls using the Conners' Continuous Performance Test (CCPT) for attention performance and MRI. The 10 target tracts, including the bilateral frontostriatal tracts (caudate to dorsolateral prefrontal cortex, ventrolateral prefrontal cortex and orbitofrontal cortex), superior longitudinal fasciculus (SLF) and cingulum bundle were reconstructed using diffusion spectrum imaging tractography. We computed generalized fractional anisotropy (GFA) values to indicate tract-specific microstructural property.

RESULTS

We included 50 youths with ADHD and 50 healthy controls in our study. Youths with ADHD had lower GFA in the left frontostriatal tracts, bilateral SLF and right cingulum bundle and performed worse in the CCPT than controls. Furthermore, alteration of the right SLF GFA was most significantly associated with the clinical symptom of inattention in youths with ADHD. Finally, youths with ADHD had differential association patterns of the 10 fibre tract GFA values with attention performance compared with controls.

LIMITATIONS

Ten of the youths with ADHD were treated with methylphenidate, which may have long-term effects on microstructural property.

CONCLUSION

Our study highlights the importance of the SLF, cingulum bundle and frontostriatal tracts for clinical symptoms and attention performance in youths with ADHD and demonstrates the involvement of different fibre tracts in attention performance in these individuals.

Low serum sphingolipids in children with attention deficit-hyperactivity disorder

Background: Attention deficit-hyperactivity disorder (ADHD) is the most prevalent neuropsychiatric condition in childhood. ADHD is a multifactorial trait with a strong genetic component. One neurodevelopmental hypothesis is that ADHD is associated with a lag in brain maturation. Sphingolipids are essential for brain development and neuronal functioning, but their role in ADHD pathogenesis is unexplored. We hypothesized that serum sphingolipid levels distinguish ADHD patients from unaffected subjects.

Methods: We characterized serum sphingolipid profiles of ADHD patients and two control groups: non-affected relatives and non-affected subjects without a family history of ADHD. Sphingolipids were measured by LC-MS/MS in 77 participants (28 ADHD patients, 28 related controls, and 21 unrelated controls). ADHD diagnosis was based on the Diagnostic and Statistical Manual of Mental Disorders (DSM IV-TR). Diagnostic criteria were assessed by two independent observers. Groups were compared by parametrical statistics.

Results: Serum sphingomyelins C16:0, C18:0, C18:1, C24:1, ceramide C24:0, and deoxy-ceramide C24:1 were significantly decreased in ADHD patients at 20–30% relative reductions. In our sample, decreased serum sphingomyelin levels distinguished ADHD patients with 79% sensitivity and 78% specificity.

Conclusions: Our results showed lower levels of all major serum sphingomyelins in ADHD. These findings may reflect brain maturation and affect neuro-functional pathways characteristic for ADHD.

White matter microstructure predicts autistic traits in attention-deficit/hyperactivity disorder

Traits of autism spectrum disorder (ASD) in children with attention-deficit/hyperactivity disorder (ADHD) have previously been found to index clinical severity. This study examined the association of ASD traits with diffusion parameters in adolescent males with ADHD (n = 17), and also compared WM microstructure relative to controls (n = 17). Significant associations (p < 0.05, corrected) were found between fractional anisotropy/radial diffusivity and ASD trait severity (positive and negative correlations respectively), mostly in the right posterior limb of the internal capsule/corticospinal tract, right cerebellar peduncle and the midbrain. No case-control differences were found for the diffusion parameters investigated. This is the first report of a WM microstructural signature of autistic traits in ADHD. Thus, even in the absence of full disorder, ASD traits may index a distinctive underlying neurobiology in ADHD.

The cognition-enhancing effects of psychostimulants involve direct action in the prefrontal cortex

Psychostimulants are highly effective in the treatment of attention-deficit/hyperactivity disorder. The clinical efficacy of these drugs is strongly linked to their ability to improve cognition dependent on the prefrontal cortex (PFC) and extended frontostriatal circuit. The procognitive actions of psychostimulants are only associated with low doses. Surprisingly, despite nearly 80 years of clinical use, the neurobiology of the procognitive actions of psychostimulants has only recently been systematically investigated. Findings from this research unambiguously demonstrate that the cognition-enhancing effects of psychostimulants involve the preferential elevation of catecholamines in the PFC and the subsequent activation of norepinephrine α2 and dopamine D1 receptors. In contrast, while the striatum is a critical participant in PFC-dependent cognition, where examined, psychostimulant action within the striatum is not sufficient to enhance cognition. At doses that moderately exceed the clinical range, psychostimulants appear to improve PFC-dependent attentional processes at the expense of other PFC-dependent processes (e.g., working memory, response inhibition). This differential modulation of PFC-dependent processes across dose appears to be associated with the differential involvement of noradrenergic α2 versus α1 receptors. Collectively, this evidence indicates that at low, clinically relevant doses, psychostimulants are devoid of the behavioral and neurochemical actions that define this class of drugs and instead act largely as cognitive enhancers (improving PFC-dependent function). This information has potentially important clinical implications as well as relevance for public health policy regarding the widespread clinical use of psychostimulants and for the development of novel pharmacologic treatments for attention-deficit/hyperactivity disorder and other conditions associated with PFC dysregulation.

Fractional anisotropy shows differential reduction in frontal-subcortical fiber bundles-A longitudinal MRI study of 76 middle-aged and older adults

Motivated by the frontal- and white matter (WM) retrogenesis hypotheses and the assumptions that fronto-striatal circuits are especially vulnerable in normal aging, the goal of the present study was to identify fiber bundles connecting subcortical nuclei and frontal areas and obtain site-specific information about age related fractional anisotropy (FA) changes. Multimodal magnetic resonance image acquisitions [3D T1-weighted and diffusion weighted imaging (DWI)] were obtained from healthy older adults (N = 76, range 49-80 years at inclusion) at two time points, 3 years apart. A subset of the participants (N = 24) was included at a third time-point. In addition to the frontal-subcortical fibers, the anterior callosal fiber (ACF) and the corticospinal tract (CST) was investigated by its mean FA together with tract parameterization analysis. Our results demonstrated fronto-striatal structural connectivity decline (reduced FA) in normal aging with substantial inter-individual differences. The tract parameterization analysis showed that the along tract FA profiles were characterized by piece-wise differential changes along their extension rather than being uniformly affected. To the best of our knowledge, this is the first longitudinal study detecting age-related changes in frontal-subcortical WM connections in normal aging.

Attention deficit/hyperactivity disorder and medication with stimulants in young children: a DTI study

The relationship between attention deficit/hyperactivity disorder (ADHD) and white matter connectivity has not been well established yet, specially for children under 10 years of age. In addition, the effects of treatment on brain structure have not been sufficiently explored from a Diffusion Tensor Imaging (DTI) perspective. In this study, the influence of treatment with methylphenidate in the white matter of children with ADHD was investigated using two different and complementary DTI analysis methods: Tract-Based Spatial Statistics (TBSS) and a robust tractography selection method. No significant differences were found in Fractional Anisotropy (FA) between medicated, drug-naïve patients and healthy controls, but a reduced Mean Diffusivity (MD) was found in ADHD patients under treatment with respect to both healthy controls and drug-naïve ADHD patients. Also, correlations were found between MD increases and performance indicators of ADHD. These findings may help elucidate the nature of white matter alterations in ADHD, their relationship with symptoms and the effects of treatment with psychostimulants.

ADHD severity is associated with white matter microstructure in the subgenual cingulum

Aims

This analysis examined hypothesised associations between microstructural attributes in specific white matter (WM) tracts selected a priori and measures of clinical variability in adolescents with a diagnosis of attention deficit hyperactivity disorder (ADHD). Firstly, associations were explored between WM microstructure and ADHD severity in the subgenual cingulum. Secondly, to ensure that tract-specific approaches afforded enhanced rather than differential sensitivity, associations were measured between WM microstructure and autistic traits in the right corticospinal tract based on results of a previously-published voxelwise analysis.

Methods

40 right-handed males aged 14–18 years (19 with DSM-IV combined type ADHD and 21 healthy controls) underwent a 60 direction diffusion MRI scan. Clinical ADHD and autism variation were assessed by validated questionnaires. Deterministic tractography based on spherical deconvolution methods was used to map the subgenual cingulum and corticospinal tract.

Results

Fractional anisotropy was positively correlated and radial diffusivity was negatively correlated with a) ADHD severity in the left subgenual cingulum and b) autistic traits in the inferior segment of the right corticospinal tract. No case–control differences were found.

Conclusions

Results shed light on possible anatomical correlates of ADHD severity and autistic symptoms in pathways which may be involved in the ADHD phenotype. They provide further evidence that tract-specific approaches may a) reveal associations between microstructural metrics and indices of phenotypic variability which would not be detected using voxelwise approaches, and b) provide improved rather than differential sensitivity compared to voxelwise approaches.

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Adolescents with ADHD and controls underwent a diffusion MRI scan.

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ADHD severity was associated with microstructure in the left subgenual cingulum.

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Autistic traits in were associated with microstructure in the right corticospinal tract.

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No case–control differences were found.

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Use of tract-specific approaches may improve sensitivity to detect associations.

Multisensory integration and child neurodevelopment

A considerable number of cognitive processes depend on the integration of multisensory information. The brain integrates this information, providing a complete representation of our surrounding world and giving us the ability to react optimally to the environment. Infancy is a period of great changes in brain structure and function that are reflected by the increase of processing capacities of the developing child. However, it is unclear if the optimal use of multisensory information is present early in childhood or develops only later, with experience. The first part of this review has focused on the typical development of multisensory integration (MSI). We have described the two hypotheses on the developmental process of MSI in neurotypical infants and children, and have introduced MSI and its neuroanatomic correlates. The second section has discussed the neurodevelopmental trajectory of MSI in cognitively-challenged infants and children. A few studies have brought to light various difficulties to integrate sensory information in children with a neurodevelopmental disorder. Consequently, we have exposed certain possible neurophysiological relationships between MSI deficits and neurodevelopmental disorders, especially dyslexia and attention deficit disorder with/without hyperactivity.

White matter microstructure and the variable adult outcome of childhood attention deficit hyperactivity disorder

Changes in cerebral cortical anatomy have been tied to the clinical course of attention deficit hyperactivity disorder (ADHD). We now ask if alterations in white matter tract microstructure are likewise linked with the adult outcome of childhood ADHD. Seventy-five young adults, 32 with ADHD persisting from childhood and 43 with symptom remission were contrasted against 74 never-affected comparison subjects. Using diffusion tensor imaging, we defined fractional anisotropy, a metric related to white matter microstructure, along with measures of diffusion perpendicular (radial) and parallel (axial) to the axon. Analyses were adjusted for head motion, age and sex, and controlled for multiple comparisons and medication history. Tract-based analyses showed that greater adult inattention, but not hyperactivity-impulsivity, was associated with significantly lower fractional anisotropy in the left uncinate (standardized β=-0.37, t=3.28, p=0.002) and inferior fronto-occipital fasciculi (standardized β=-0.37, t=3.29, p=0.002). The ADHD group with symptoms persisting into adulthood had significantly lower fractional anisotropy than the never-affected controls in these tracts, differences associated with medium to large effect sizes. By contrast, the ADHD group that remitted by adulthood did not differ significantly from controls. The anomalies were found in tracts that connect components of neural systems pertinent to ADHD, such as attention control (inferior fronto-occipital fasciculus) and emotion regulation and the processing of reward (the uncinate fasciculus). Change in radial rather than axial diffusivity was the primary driver of this effect, suggesting pathophysiological processes including altered myelination as future targets for pharmacological and behavioral interventions.

Association between microstructural integrity of frontostriatal tracts and school functioning: ADHD symptoms and executive function as mediators

BACKGROUND

Deficits in executive function (EF), impaired school functioning and altered white matter integrity in frontostriatal networks have been associated with attention-deficit/hyperactivity disorder (ADHD). However, relationships between impairments in these areas are unclear. Using a sample of youths with and without ADHD, this study examined the association between microstructural integrity of frontostriatal tracts and school dysfunction and the mediating roles of EF and ADHD symptoms in this association.

METHOD

The sample included 32 Taiwanese youths with ADHD and 32 age-, sex-, handedness- and IQ-matched typically-developing (TD) youths. Participants were assessed using psychiatric interviews, parent reports on ADHD symptoms and school functioning, and EF measures from the Cambridge Neuropsychological Test Automated Battery (CANTAB). The frontostriatal tracts were reconstructed by diffusion spectrum imaging (DSI) tractography and were subdivided into four functionally distinct segments: caudate-dorsolateral, caudate-medial prefrontal, caudate-orbitofrontal and caudate-ventrolateral tracts.

RESULTS

Youths with ADHD, relative to TD youths, showed altered white matter integrity in all four bilateral pairs of frontostriatal tracts (decreased general fractional anisotropy, GFA), had poor attention, vigilance and response inhibition, and showed impaired school functioning. Altered microstructural integrity in frontostriatal tracts was significantly associated with school dysfunction, which was mediated by EF measures of attention/vigilance and response inhibition in addition to inattention and hyperactivity symptoms.

CONCLUSIONS

Our findings demonstrate an association between white matter integrity in the frontostriatal networks and school functioning and suggest that EF deficits and ADHD symptoms may be the mediating mechanisms for this association. Future research is needed to test the directionality and specificity of this finding.

A parietal biomarker for ADHD liability: as predicted by the distributed effects perspective model of ADHD

BACKGROUND

We previously hypothesized that poor task-directed sensory information processing should be indexed by increased weighting of right hemisphere (RH) biased attention and visuo-perceptual brain functions during task operations and have demonstrated this phenotype in ADHD across multiple studies, using multiple methodologies. However, in our recent distributed effects model of ADHD, we surmised that this phenotype is not ADHD specific, but rather more broadly reflective of any circumstance that disrupts the induction and maintenance of an emergent task-directed neural architecture. Under this view, increased weighting of RH-biased attention and visuo-perceptual brain functions is expected to generally index neurocognitive sets that are not optimized for task-directed thought and action, and when durable expressed, liability for ADHD.

METHOD

The current study tested this view by examining whether previously identified rightward parietal EEG asymmetry in ADHD was associated with common ADHD characteristics and comorbidities [i.e., ADHD risk factors (RFs)].

RESULTS

Barring one exception (non-right handedness), we found that it was. Rightward parietal asymmetry (RPA) was associated with carrying the DRD4-7R risk allele, being male, having mood disorder, and having anxiety disorder. However, differences in the specific expression of RPA were observed, which are discussed in relation to possible unique mechanisms underlying ADHD liability in different ADHD RFs.

CONCLUSION

Rightward parietal asymmetry appears to be a durable feature of ADHD liability, as predicted by the Distributed Effects Perspective Model of ADHD. Moreover, variability in the expression of this phenotype may shed light on different sources of ADHD liability.

Intergenerational transmission of fronto-parietal dysfunction during forethought in attention deficit/hyperactivity disorder: a pilot study

There are only a few published reports of neural abnormalities within the families of children with attention deficit/hyperactivity disorder (ADHD). Functional magnetic resonance imaging was used to compare cerebral activation of ADHD and control biological parent-child dyads during forethought, a prospective function of working memory. Reduced activations in ADHD dyads were found in the inferior frontal gyrus, right superior parietal lobule and left inferior parietal lobule. This suggests that fronto-parietal abnormalities are shared within ADHD families.

Widespread reductions in cortical thickness following severe early-life deprivation: a neurodevelopmental pathway to attention-deficit/hyperactivity disorder

BACKGROUND

Children exposed to early-life psychosocial deprivation associated with institutional rearing are at markedly elevated risk of developing attention-deficit/hyperactivity disorder (ADHD). Neurodevelopmental mechanisms that explain the high prevalence of ADHD in children exposed to institutionalization are unknown. We examined whether abnormalities in cortical thickness and subcortical volume were mechanisms explaining elevations in ADHD among children raised in institutional settings.

METHODS

Data were drawn from the Bucharest Early Intervention Project, a cohort of children raised from early infancy in institutions in Romania (n = 58) and age-matched community control subjects (n = 22). Magnetic resonance imaging data were acquired when children were aged 8 to 10 years, and ADHD symptoms were assessed using the Health and Behavior Questionnaire.

RESULTS

Children reared in institutions exhibited widespread reductions in cortical thickness across prefrontal, parietal, and temporal regions relative to community control subjects. No group differences were found in the volume of subcortical structures. Reduced thickness across numerous cortical areas was associated with higher levels of ADHD symptoms. Cortical thickness in lateral orbitofrontal cortex, insula, inferior parietal cortex, precuneus, superior temporal cortex, and lingual gyrus mediated the association of institutionalization with inattention and impulsivity; additionally, supramarginal gyrus thickness mediated the association with inattention and fusiform gyrus thickness mediated the association with impulsivity.

CONCLUSIONS

Severe early-life deprivation disrupts cortical development resulting in reduced thickness in regions with atypical function during attention tasks in children with ADHD, including the inferior parietal cortex, precuneus, and superior temporal cortex. These reductions in thickness are a neurodevelopmental mechanism explaining elevated ADHD symptoms in children exposed to institutional rearing.

Connectomic disturbances in attention-deficit/hyperactivity disorder: a whole-brain tractography analysis

BACKGROUND

Few studies have sought to identify, in a regionally unbiased way, the precise cortical and subcortical regions that are affected by white matter abnormalities in attention-deficit/hyperactivity disorder (ADHD). This study aimed to derive a comprehensive, whole-brain characterization of connectomic disturbances in ADHD.

METHODS

Using diffusion tensor imaging, whole-brain tractography, and an imaging connectomics approach, we characterized altered white matter connectivity in 71 children and adolescents with ADHD compared with 26 healthy control subjects. White matter differences were further delineated between patients with (n = 40) and without (n = 26) the predominantly hyperactive/impulsive subtype of ADHD.

RESULTS

A significant network comprising 25 distinct fiber bundles linking 23 different brain regions spanning frontal, striatal, and cerebellar brain regions showed altered white matter structure in ADHD patients (p < .05, family-wise error-corrected). Moreover, fractional anisotropy in some of these fiber bundles correlated with attentional disturbances. Attention-deficit/hyperactivity disorder subtypes were differentiated by a right-lateralized network (p < .05, family-wise error-corrected) predominantly linking frontal, cingulate, and supplementary motor areas. Fractional anisotropy in this network was also correlated with continuous performance test scores.

CONCLUSIONS

Using an unbiased, whole-brain, data-driven approach, we demonstrated abnormal white matter connectivity in ADHD. The correlations observed with measures of attentional performance underscore the functional importance of these connectomic disturbances for the clinical phenotype of ADHD. A distributed pattern of white matter microstructural integrity separately involving frontal, striatal, and cerebellar brain regions, rather than direct frontostriatal connectivity, appears to be disrupted in children and adolescents with ADHD.

Multimodal magnetic resonance imaging study of treatment-naïve adults with attention-deficit/hyperactivity disorder

Background

Attention-Deficit/Hiperactivity Disorder (ADHD) is a prevalent disorder, but its neuroanatomical circuitry is still relatively understudied, especially in the adult population. The few morphometric magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) studies available to date have found heterogeneous results. This may be at least partly attributable to some well-known technical limitations of the conventional voxel-based methods usually employed to analyze such neuroimaging data. Moreover, there is a great paucity of imaging studies of adult ADHD to date that have excluded patients with history of use of stimulant medication.

Methods

A newly validated method named optimally-discriminative voxel-based analysis (ODVBA) was applied to multimodal (structural and DTI) MRI data acquired from 22 treatment-naïve ADHD adults and 19 age- and gender-matched healthy controls (HC).

Results

Regarding DTI data, we found higher fractional anisotropy in ADHD relative to HC encompassing the white matter (WM) of the bilateral superior frontal gyrus, right middle frontal left gyrus, left postcentral gyrus, bilateral cingulate gyrus, bilateral middle temporal gyrus and right superior temporal gyrus; reductions in trace (a measure of diffusivity) in ADHD relative to HC were also found in fronto-striatal-parieto-occipital circuits, including the right superior frontal gyrus and bilateral middle frontal gyrus, right precentral gyrus, left middle occipital gyrus and bilateral cingulate gyrus, as well as the left body and right splenium of the corpus callosum, right superior corona radiata, and right superior longitudinal and fronto-occipital fasciculi. Volumetric abnormalities in ADHD subjects were found only at a trend level of significance, including reduced gray matter (GM) in the right angular gyrus, and increased GM in the right supplementary motor area and superior frontal gyrus.

Conclusions

Our results suggest that adult ADHD is associated with neuroanatomical abnormalities mainly affecting the WM microstructure in fronto-parieto-temporal circuits that have been implicated in cognitive, emotional and visuomotor processes.

Probing behavioral responses to food: development of a food-specific go/no-go task

The ability to exert self-control in the face of appetitive, alluring cues is a critical component of healthy development. The development of behavioral measures that use disease-relevant stimuli can greatly improve our understanding of cue-specific impairments in self-control. To produce such a tool relevant to the study of eating and weight disorders, we modified the traditional go/no-go task to include food and non-food targets. To confirm that performance on this new task was consistent with other go/no-go tasks, it was given to 147 healthy, normal weight volunteers between the ages of 5 and 30. High-resolution photos of food or toys were used as the target and nontarget stimuli. Consistent with expectations, overall improvements in accuracy were seen from childhood to adulthood. Participants responded more quickly and made more commission errors to food cues compared to nonfood cues (F(1,140)=21.76, P<0.001), although no behavioral differences were seen between low- and high-calorie food cues for this non-obese, healthy developmental sample. This novel food-specific go/no-go task may be used to track the development of self-control in the context of food cues and to evaluate deviations or deficits in the development of this ability in individuals at risk for eating problem behaviors and disorders.

Abnormal Parietal Brain Function in ADHD: Replication and Extension of Previous EEG Beta Asymmetry Findings

BACKGROUND

Abundant work indicates ADHD abnormal posterior brain structure and function, including abnormal structural and functional asymmetries and reduced corpus callosum size. However, this literature has attracted considerably less research interest than fronto-striatal findings.

OBJECTIVE

To help address this imbalance, the current study replicates and extends our previous work showing abnormal parietal brain function in ADHD adults during the Conner's Continuous Performance Test (CPT).

METHOD

Our previous study found that ADHD adults had increased rightward EEG beta (16-21 Hz) asymmetry in inferior parietal brain regions during the CPT (p = 0.00001), and that this metric exhibited a lack of normal correlation (i.e., observed in controls) with beta asymmetry at temporal-parietal regions. We re-tested these effects in a new ADHD sample and with both new and old samples combined. We additionally examined: (a) EEG asymmetry in multiple frequency bands, (b) unilateral effects for all asymmetry findings, and (c) the association between EEG asymmetry and a battery of cognitive tests.

RESULTS

We replicated our original findings by demonstrating abnormal rightward inferior parietal beta asymmetry in adults with ADHD during the CPT, and again this metric exhibited abnormal reduced correlation to temporal-parietal beta asymmetry. Novel analyses also demonstrated a broader pattern of rightward beta and theta asymmetry across inferior, superior, and temporal-parietal brain regions, and showed that rightward parietal asymmetry in ADHD was atypically associated with multiple cognitive tests.

CONCLUSION

Abnormal increased rightward parietal EEG beta asymmetry is an important feature of ADHD. We speculate that this phenotype may occur with any form of impaired capacity for top-down task-directed control over sensory encoding functions, and that it may reflect associated increase of attentional shifting and compensatory sustained/selective attention.

Altered white matter microstructure underlies listening difficulties in children suspected of auditory processing disorders: a DTI study

INTRODUCTION

The purpose of the present study was to identify biomarkers of listening difficulties by investigating white matter microstructure in children suspected of auditory processing disorder (APD) using diffusion tensor imaging (DTI). Behavioral studies have suggested that impaired cognitive and/or attention abilities rather than a pure sensory processing deficit underlie listening difficulties and auditory processing disorder (APD) in children. However, the neural signature of listening difficulties has not been investigated.

METHODS

Twelve children with listening difficulties and atypical left ear advantage (LEA) in dichotic listening and twelve age- and gender-matched typically developing children with typical right ear advantage (REA) were tested. Using voxel-based analysis, fractional anisotropy (FA), and mean, axial and radial diffusivity (MD, AD, RD) maps were computed and contrasted between the groups.

RESULTS

Listening difficulties were associated with altered white matter microstructure, reflected by decreased FA in frontal multifocal white matter regions centered in prefrontal cortex bilaterally and left anterior cingulate. Increased RD and decreased AD accounted for the decreased FA, suggesting delayed myelination in frontal white matter tracts and disrupted fiber organization in the LEA group. Furthermore, listening difficulties were associated with increased MD (with increase in both RD and AD) in the posterior limb of the internal capsule (sublenticular part) at the auditory radiations where auditory input is transmitted between the thalamus and the auditory cortex.

CONCLUSIONS

Our results provide direct evidence that listening difficulties in children are associated with altered white matter microstructure and that both sensory and supramodal deficits underlie the differences between the groups.

Neonatal brain pathology predicts adverse attention and processing speed outcomes in very preterm and/or very low birth weight children

OBJECTIVE

This study aimed to examine attention and processing speed outcomes in very preterm (VPT; < 32 weeks' gestational age) or very low birth weight (VLBW; < 1,500 g) children, and to determine whether brain abnormality measured by neonatal MRI can be used to predict outcome in these domains.

METHOD

A cohort of 198 children born < 30 weeks' gestational age and/or < 1,250 g and 70 term controls were examined. Neonatal MRI scans at term equivalent age were quantitatively assessed for white matter, cortical gray matter, deep gray matter, and cerebellar abnormalities. Attention and processing speed were assessed at 7 years using standardized neuropsychological tests. Group differences were tested in attention and processing speed, and the relationships between these cognitive domains and brain abnormalities at birth were investigated.

RESULTS

At 7 years of age, the VPT/VLBW group performed significantly poorer than term controls on all attention and processing speed outcomes. Associations between adverse attention and processing speed performances at 7 years and higher neonatal brain abnormality scores were found; in particular, white matter and deep gray matter abnormalities were reasonable predictors of long-term cognitive outcomes.

CONCLUSION

Attention and processing speed are significant areas of concern in VPT/VLBW children. This is the first study to show that adverse attention and processing speed outcomes at 7 years are associated with neonatal brain pathology.

Neural substrates of behavioral variability in attention deficit hyperactivity disorder: based on ex-Gaussian reaction time distribution and diffusion spectrum imaging tractography

BACKGROUND

Increased intra-individual variability (IIV) in reaction time (RT) across various tasks is one ubiquitous neuropsychological finding in attention deficit hyperactivity disorder (ADHD). However, neurobiological underpinnings of IIV in individuals with ADHD have not yet been fully delineated. The ex-Gaussian distribution has been proved to capture IIV in RT. The authors explored the three parameters [μ (mu), σ (sigma), τ (tau)] of an ex-Gaussian RT distribution derived from the Conners' continuous performance test (CCPT) and their correlations with the microstructural integrity of the frontostriatal-caudate tracts and the cingulum bundles.

METHOD

We assessed 28 youths with ADHD (8-17 years; 25 males) and 28 age-, sex-, IQ- and handedness-matched typically developing (TD) youths using the CCPT, Wechsler Intelligence Scale for Children, 3rd edition and magnetic resonance imaging (MRI). Microstructural integrity, indexed by generalized fractional anisotropy (GFA), was measured by diffusion spectrum imaging tractrography on a 3-T MRI system.

RESULTS

Youths with ADHD had larger σ (s.d. of Gaussian distribution) and τ (mean of exponential distribution) and reduced GFA in four bilateral frontostriatal tracts. With increased inter-stimulus intervals of CCPT, the magnitude of greater τ in ADHD than TD increased. In ADHD youths, the cingulum bundles and frontostriatal integrity were associated with three ex-Gaussian parameters and with μ (mean of Gaussian distribution) and τ, respectively; while only frontostriatal GFA was associated with μ and τ in TD youths.

CONCLUSIONS

Our findings suggest the crucial role of the integrity of the cingulum bundles in accounting for IIV in ADHD. Involvement of different brain systems in mediating IIV may relate to a distinctive pathophysiological processing and/or adaptive compensatory mechanism.

Abnormal amygdala functional connectivity associated with emotional lability in children with attention-deficit/hyperactivity disorder

OBJECTIVE

A substantial proportion of children with attention-deficit/hyperactivity disorder (ADHD) also display emotion regulation deficits manifesting as chronic irritability, severe temper outbursts, and aggression. The amygdala is implicated in emotion regulation, but its connectivity and relation to emotion regulation in ADHD has yet to be explored. The purpose of this study was to examine the relationship between intrinsic functional connectivity (iFC) of amygdala circuits and emotion regulation deficits in youth with ADHD.

METHOD

Bilateral amygdala iFC was examined using functional magnetic resonance imaging in 63 children with ADHD, aged 6 to 13 years. First, we examined the relationship between amygdala IFC and parent ratings of emotional lability (EL) in children with ADHD. Second, we compared amygdala iFC across subgroups of children with ADHD and high EL (n = 18), ADHD and low EL (n = 20), and typically developing children (TDC), all with low EL (n = 19).

RESULTS

Higher EL ratings were associated with greater positive iFC between the amygdala and rostral anterior cingulate cortex in youth with ADHD. EL scores were also negatively associated with iFC between bilateral amygdala and posterior insula/superior temporal gyrus. Patterns of amygdala-cortical iFC in ADHD participants with low EL were not different from the comparison group, and the effect sizes for these comparisons were smaller than those for the trend-level differences observed between the high-EL and TDC groups.

CONCLUSIONS

In children with ADHD and a range of EL, deficits in emotion regulation were associated with altered amygdala-cortical iFC. When comparing groups that differed on ADHD status but not EL, differences in amygdala iFC were small and nonsignificant, highlighting the specificity of this finding to emotional deficits, independent of other ADHD symptoms.