The influence of very preterm birth on adolescent EEG connectivity, network organization and long-term outcome.

OBJECTIVE: The aim of this study was to explore differences in functional connectivity and network organization between very preterm born adolescents and term born controls and to investigate if these differences might explain the relation between preterm birth and adverse long-term outcome. METHODS: Forty-seven very preterm born adolescents (53% males) and 54 controls (54% males) with matching age, sex and parental educational levels underwent high-density electroencephalography (EEG) at 13 years of age. Long-term outcome was assessed by Intelligence Quotient (IQ), motor, attentional functioning and academic performance. Two minutes of EEG data were analysed within delta, theta, lower alpha, upper alpha and beta frequency bands. Within each frequency band, connectivity was assessed using the Phase Lag Index (PLI) and Amplitude Envelope Correlation, corrected for volume conduction (AEC-c). Brain networks were constructed using the minimum spanning tree method. RESULTS: Very preterm born adolescents had stronger beta PLI connectivity and less differentiated network organization. Beta AEC-c and differentiation of AEC-c based networks were negatively associated with long-term outcomes. EEG measures did not mediate the relation between preterm birth and outcomes. CONCLUSIONS: This study shows that very preterm born adolescents may have altered functional connectivity and brain network organization in the beta frequency band. Alterations in measures of functional connectivity and network topologies, especially its differentiating characteristics, were associated with neurodevelopmental functioning. SIGNIFICANCE: The findings indicate that EEG connectivity and network analysis is a promising tool for investigating underlying mechanisms of impaired functioning.

Heterogeneity of persisting symptoms after sport-related concussion (SRC): exploring symptom subtypes and patient subgroups.

This study aimed to explore the heterogeneity of persisting symptoms after sport-related concussion (SRC). We examined the structure of symptom subtypes within 163 patients with SRC (M = 16.7 weeks post-injury). Subsequently, we investigated the existence of subgroups of patients based on comparable configuration of co-occurring symptom subtypes. To explore factors that may contribute to the emergence of SRC patient subgroups, subgroups were compared on pre-injury (i.e., demographics and medical history), personality (Severity Indices of Personality Problems Short Form) and SRC characteristics (i.e., history of prior concussions, loss of consciousness and post-traumatic amnesia). To investigate the relevance of SRC subgrouping for clinical outcome, subgroups were compared on symptom severity (Sport Concussion Assessment Tool 5). The results provide empirical evidence for the existence of symptom subtypes, characterized as a: neurocognitive, fatigue, emotional, migraine and vestibular-ocular symptom subtype in patients with persisting SRC. Study results also showed evidence for the existence of SRC subgroups of patients with a comparable configuration of co-occurring prevailing symptom subtypes, including a neurocognitive-migraine, fatigue, migraine-emotional and neurocognitive-emotional subgroup. The subgroups differed on pre-injury, personality and SRC characteristics, suggesting that these factors may contribute to the emergence of specific SRC patient subgroups. The subgroups also differed in the severity of persisting symptoms, highlighting the clinical relevance of SRC subgrouping. These results support the idea that patient subgroups with persisting SRC with a comparable pattern of co-occurring symptom subtypes exists, which may require targeted prognosis, clinical management and treatment to optimize recovery.

Distress and post-traumatic stress in parents of patients with congenital gastrointestinal malformations: a cross-sectional cohort study.

BACKGROUND: Congenital gastrointestinal malformation (CGIM) require neonatal surgical treatment and may lead to disease-specific sequelae, which have a potential psychological impact on parents. The aim of this study is to assess distress and symptoms of post-traumatic stress disorder (PTSD) in parents of patients with CGIM. In this cross-sectional study, seventy-nine parents (47 mothers and 32 fathers) of 53 patients with CGIM completed the Distress Thermometer for Parents (DT-P) and the Self Rating Scale for Posttraumatic Stress Disorders (SRS-PTSD) as part of the multidisciplinary follow-up of their children (aged 5-35 months). Group differences were tested between parents and representative Dutch reference groups with regard to rates of (clinical) distress and PTSD, and severity of overall distress and PTSD, for mothers and fathers separately. Mixed model regression models were used to study factors associated with the risk of (clinical) distress, PTSD and with severity of symptoms of PTSD (intrusion, avoidance and hyperarousal). RESULTS: Prevalence of clinical distress was comparable to reference groups for mothers (46%) and fathers (34%). There was no difference in severity of overall distress between both mothers as well as fathers and reference groups. Prevalence of PTSD was significantly higher in mothers (23%) compared to the reference group (5.3%) (OR = 5.51, p < 0.001), not in fathers (6.3% vs 2.2.%). Symptoms of intrusion were commonly reported by all the parents (75%). Longer total length of child's hospital stay was associated with more severe symptoms of intrusion, avoidance and hyperarousal. Child's length of follow-up was negatively associated with severity of intrusion. CONCLUSIONS: Having a child with CGIM has a huge impact on parents, demonstrated by a higher prevalence of PTSD in mothers, but not fathers, compared to parents in the general population. Monitoring of symptoms of PTSD of parents in follow-up is necessary.

Differential effects of long-term aerobic versus cognitively-engaging physical activity on children's visuospatial working memory related brain activation: A cluster RCT.

Different types of physical activity are thought to differentially affect children's brain activation, via physiological mechanisms, or by activating similar brain areas during physical and cognitive tasks. Despite many behavioral studies relying on these mechanisms, they have been rarely studied. This study looks at both mechanisms simultaneously, by examining effects of two physical activity interventions (aerobic vs. cognitively-engaging) on children's brain activation. Functional Magnetic Resonance Imaging (fMRI) data of 62 children (48.4% boys, mean age 9.2 years) was analyzed. Children's visuospatial working memory related brain activity patterns were tested using a Spatial Span Task before and after the 14-week interventions consisting of four physical education lessons per week. The control group followed their regular program of two lessons per week. Analyses of activation patterns in SPM 12.0 revealed no activation changes between pretest and posttest (p > .05), and no differences between the three conditions in pretest-posttest changes in brain activation (p > .05). Large inter-individual differences were found, suggesting that not every child benefited from the interventions in the same way. To get more insight into the assumed mechanisms, further research is needed to understand whether, when, for whom, and how physical activity results in changed brain activation patterns.

Relationships between gross motor skills, cardiovascular fitness, and visuospatial working memory-related brain activation in 8- to 10-year-old children.

Relationships between gross motor skills and cardiovascular fitness with visuospatial working memory (VSWM) in children are hypothesized to be mediated by underlying functional brain mechanisms. Because there is little experimental evidence to support this mechanism, the present study was designed to investigate the relationships of gross motor skills and cardiovascular fitness with VSWM-related brain activation in 8- to 10-year-old children. Functional magnetic resonance imaging data obtained during a VSWM-task were analyzed for 80 children from grades 3 (47.5%) and 4 of 21 primary schools in the Netherlands (51.3% girls). Gross motor skills (Korper Koordinationstest für Kinder and Bruininks-Oseretsky Test of Motor Proficiency - 2nd Edition) and cardiovascular fitness (20-meter Shuttle Run Test) were assessed. VSWM-related brain activation was found in a network involving the angular gyrus, the superior parietal cortex, and the thalamus; deactivation was found in the inferior and middle temporal gyri. Although behavioral results showed significant relations of gross motor skills and cardiovascular fitness with VSWM performance, gross motor skills and cardiovascular fitness were not related to VSWM-related brain activation. Therefore, we could not confirm the hypothesis that brain activation underlies the relationship of gross motor skills and cardiovascular fitness with VSWM performance. Our results suggest that either the effects of physical activity on cognition do not necessarily go via changes in gross motor skills and/or cardiovascular fitness, or that brain activation patterns as measured with the blood-oxygen-level dependent (BOLD) signal may not be the mechanism underlying the relationships of gross motor skills and cardiovascular fitness with VSWM.

Error and post-error processing in children with attention-deficit/hyperactivity disorder: An electrical neuroimaging study.

OBJECTIVE: Inaccurate and inconsistent response styles in attention-deficit/hyperactivity disorder (ADHD) have been observed in a wide variety of cognitive tasks, in line with regulatory deficit models of ADHD. Event-related potential (ERP) studies of error processing have provided evidence for these models, but are limited in specificity. We aimed to improve the isolation, localization and identification of error (self-monitoring and adaptive control) and post-error (implementation of cognitive control) processing in ADHD. METHODS: ERPs were obtained for 46 ADHD and 51 typically developing (TD) children using the stop-signal task. Response-locked error (Ne and Pe) and stimulus-locked post-error (N2) components were compared between groups. Ne/Pe were corrected for preceding stimulus overlap and group differences were localized. RESULTS: Ne was intact, while Pe amplitude was markedly reduced in children with ADHD (ηp2 = 0.14). Pe differences were localized in the dorsal posterior/midcingulate (BA31/24) cortex. While the TD group showed increased N2 amplitude in post-error trials (ηp2 = 0.24), localized in the left ventrolateral prefrontal cortex (VLPFC) and angular gyrus, the ADHD group did not. CONCLUSIONS: Self-regulation deficits in ADHD are associated with later stages of error processing and subsequent implementation of cognitive control. SIGNIFICANCE: We contribute to the literature by further specifying error processing deficits in ADHD.

Subtypes of Sport-Related Concussion: a Systematic Review and Meta-cluster Analysis.

OBJECTIVE: Current clinical guidelines provide a unitary approach to manage sport-related concussion (SRC), while heterogeneity in the presentation of symptoms suggests that subtypes of SRC may exist. We systematically reviewed the available evidence on SRC subtypes and associated clinical outcomes. DATA SOURCES: Ovid Medline, Embase, PsycINFO, and SPORTDiscus ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Electronic databases were searched for studies: (i) identifying SRC symptom clusters using classification methodology; or (ii) associating symptom clusters to clinical outcome variables. A total of 6,146 unique studies were identified, of which 75 full texts were independently assessed by two authors for eligibility. A total of 22 articles were included for systematic review. DATA EXTRACTION: Two independent authors performed data extraction and risk of bias analysis using the Cochrane Collaboration tool. DATA SYNTHESIS: Six studies found evidence for existence of SRC symptom clusters. Combining the available literature through Multiple Correspondence Analysis (MCA) provided evidence for the existence of a migraine cluster, a cognitive-emotional cluster, a sleep-emotional cluster, a neurological cluster, and an undefined feelings cluster. Nineteen studies found meaningful associations between SRC symptom clusters and clinical outcomes. Clusters mapping to the migraine cluster were most frequently reported in the literature and were most strongly related to aspects of clinical outcome. CONCLUSIONS: The available literature provides evidence for the existence of at least five subtypes in SRC symptomatology, with clear relevance to clinical outcome. Systematically embedding the differentiation of SRC subtypes into prognosis, clinical management, and intervention strategies may optimize the recovery from SRC.

Long-term effects of theta/beta neurofeedback on EEG power spectra in children with attention deficit hyperactivity disorder.

OBJECTIVE: Neurofeedback has been proposed as an effective alternative for pharmacological treatment in children with attention-deficit/hyperactivity disorder (ADHD), with potentially long-term and delayed benefits. However, the specificity of such long-term behavioral improvements remains inconclusive and therefore additional research into the neurophysiological effects of neurofeedback is needed. We compared long-term effects of theta/beta neurofeedback (NFB) to methylphenidate (MPH) and physical activity (PA, semi-active control intervention) on electroencephalogram (EEG) power spectra. Based on the vigilance stabilization model, we hypothesized further reductions in theta and alpha power in the NFB compared to the control groups. METHOD: EEG power spectra (theta, alpha and beta) during resting and task conditions were recorded at pre-, post-intervention and 6-months follow-up in 67 children, aged 7-13 (NFB: n = 24, MPH: n = 23, or PA: n = 20). RESULTS: Analyses revealed no power spectra differences at follow-up between MPH and NFB (range p = .165-.905) and PA and NFB (range p = .172-.822). CONCLUSIONS: No evidence was found for the specificity of theta/beta NFB at follow-up. SIGNIFICANCE: This was the first study into long-term neurophysiological effects of theta/beta NFB. Future studies are encouraged to explore both specific and non-specific mechanisms of NFB. CLINICAL TRIALS REGISTRATION: Train Your Brain? Exercise and neurofeedback intervention for ADHD, https://clinicaltrials.gov/show/NCT01363544, Ref. No. NCT01363544.

Role of conduct problems in the relation between Attention-Deficit Hyperactivity disorder, substance use, and gaming.

Known comorbidities for Attention-Deficit Hyperactivity Disorder (ADHD) include conduct problems, substance use disorder and gaming. Comorbidity with conduct problems may increase the risk for substance use disorder and gaming in individuals with ADHD. The aim of the study was to build a causal model of the relationships between ADHD and comorbid conduct problems, and alcohol, nicotine, and other substance use, and gaming habits, while accounting for age and sex. We used a state-of-the-art causal discovery algorithm to analyze a case-only sample of 362 ADHD-diagnosed individuals in the ages 12-24 years. We found that conduct problem severity mediates between ADHD severity and nicotine use, but not with more severe alcohol or substance use. More severe ADHD-inattentive symptoms lead to more severe gaming habits. Furthermore, our model suggests that ADHD severity has no influence on severity of alcohol or other drug use. Our findings suggest that ADHD severity is a risk factor for nicotine use, and that this effect is fully mediated by conduct problem severity. Finally, ADHD-inattentive severity was a risk factor for gaming, suggesting that gaming dependence has a different causal pathway than substance dependence and should be treated differently. By identifying these intervention points, our model can aid both researchers and clinicians.

Multilingualism was associated with lower cognitive outcomes in children who were born very and extremely preterm.

AIM: This study determined whether cognitive outcomes differed between very preterm (VPT) and extremely preterm (EPT) children who were monolingual or multilingual when they reached the corrected ages of two and five years. METHODS: The data were collected at the Emma Children's Hospital, Amsterdam, The Netherlands, as part of our national neonatal follow-up programme and comprised 325 VPT/EPT children born between January 1, 2007 and January 1, 2012. The study used the Third Editions of the Bayley Scales of Infant and Toddler Development and the Wechsler Preschool and Primary Scale of Intelligence. RESULTS: We compared 234 monolingual children, 65 multilingual children who spoke Dutch and at least one foreign language at home and 26 multilingual children who didn't speak Dutch at home. The best performers on the cognitive scale at two years of age and the verbal subscales at five years of age were the monolingual children, followed by the children who spoke Dutch and at least one foreign language at home, then the children who only spoke foreign languages at home. CONCLUSION: In our study cohort from The Netherlands, multilingualism lowered the cognitive and verbal outcomes of VPT/EPT children at the corrected ages of two and five years.

The Course of Neurocognitive Functioning and Prediction of Behavioral Outcome of ADHD Affected and Unaffected Siblings.

Longitudinal studies on the course of neurocognitive functioning of children with ADHD and their unaffected siblings are scarce. Also, it is unclear to what extent that course is related to ADHD outcomes. A carefully phenotyped large sample of 838 Caucasian participants (ADHD-combined type: n = 339, unaffected siblings: n = 271, controls: n = 228; mean age at baseline = 11.4 years, mean age at follow-up = 17.3 years, SD = 3.2) was used to investigate differences in the course of neurocognitive functioning of ADHD affected and unaffected siblings versus controls, and to investigate the relationship between neurocognitive change and ADHD outcomes. At baseline, an aggregated measure of overall neurocognitive functioning and eight neurocognitive measures of working memory, timing (speed/variability), motor control, and intelligence were investigated. Outcomes at follow-up were dimensional measures of ADHD symptom severity and the Kiddie-Global Assessment Scale (K-GAS) for overall functioning. At follow up, affected and unaffected siblings trended to, or fully caught up with performance levels of controls on four (44.4%) and five (55.6%) of the nine dependent variables, respectively. In contrast, performance in remaining key neurocognitive measures (i.e. verbal working memory, variability in responding) remained impaired at follow-up. Change in neurocognitive functioning was not related to ADHD outcomes. Our results question the etiological link between neurocognitive deficits and ADHD outcomes in adolescents and young adults.

Long-term outcome and quality of life in patients with total colonic aganglionosis in the Netherlands.

AIM: Total colonic aganglionosis (TCA) is a severe form of Hirschsprung's disease (HD) associated with a high morbidity. This study assessed long-term functional outcome and quality of life (QoL) of patients with TCA in a national consecutive cohort. METHODS: Surgical and demographic characteristics in the medical records of all patients (n = 53) diagnosed with TCA between 1995 and 2015 were reviewed. Functional outcome of all nonsyndromal patients, aged ≥ 4 years (n = 35), was assessed using a questionnaire and in medical records. Generic and disease-specific QoL were assessed using standardized validated questionnaires. RESULTS: Of 35 patients eligible for follow-up, 18 (51%) responded to the questionnaires. They were aged 4-19 years. A Duhamel procedure was performed in 67% of these patients and a Rehbein procedure was performed in 33%. In the questionnaire, 65% of the patients reported constipation, 47% faecal incontinence and 53% soiling. Moreover, 18% of patients used bowel management (flushing or laxatives) and 29% had an adapted diet only. Children and adolescents with TCA had worse perception of their general health and were more limited by bodily pain and discomfort compared with healthy peers. Their quality of life is influenced most by frequent complaints of diarrhoea and other physical symptoms. CONCLUSION: Children and adolescents with TCA report lower health-related QoL compared with healthy peers, especially in the physical domain. We suggest standardized follow-up and prospective longitudinal future research on functionality and QoL of these patients.

Very preterm born children at early school age: Healthcare therapies and educational provisions.

AIM: To explore changes in motor and cognitive outcomes in very preterm (VP; gestational age<30weeks) born children between ages five and six years, and to determine whether changes in these outcomes were associated with the use of healthcare therapies and educational provisions. STUDY DESIGN: Single-center observational cohort study. Five-year-old VP born children of a one-year-cohort of our neonatal follow-up program (N=90) were invited for re-assessments at age six. Use of healthcare therapies and educational provisions was registered at ages five and six years. Motor function (Movement Assessment Battery for Children-2 [M-ABC-2]; higher scores indicate better functioning) and IQ (Wechsler Preschool and Primary Scale for Intelligence [WPPSI-III-NL]) were assessed at both ages. RESULTS: Sixty-four VP born children were seen at ages five and at six years. In this year, 61% received healthcare therapies and/or educational provisions. M-ABC-2 scores of VP born children who received healthcare therapy and/or educational provisions were significantly higher (M=8.9 [SD=3.2]) at age six years than at age five years (M=7.5 [SD=3.3]); p<0.00). M-ABC-2 scores remained stable in the average range in VP born children without any support. IQ scores remained stable irrespective of received support. CONCLUSIONS: Improvements in motor outcomes are associated with the use of healthcare therapies and/or educational support between ages five and six years in VP born children. Future studies need to determine the efficacy of existing interventions, and to develop tailored interventions to support VP born children in the transfer period from preschool to primary education.

The association between the behavior rating inventory of executive functioning and cognitive testing in children diagnosed with a brain tumor.

Pediatric brain tumor survivors (PBTS) suffer from cognitive late effects, such as deteriorating executive functioning (EF). We explored the suitability of the Behavior Rating Inventory of Executive Function (BRIEF) to screen for these late effects. We assessed the relationship between the BRIEF and EF tasks, and between the BRIEF-Parent and BRIEF-Teacher, and we explored the clinical utility. Eighty-two PBTS (8-18 years) were assessed with EF tasks measuring attention, cognitive flexibility, inhibition, visual-, and working memory (WM), and with the BRIEF-Parent and BRIEF-Teacher. Pearson's correlations between the BRIEF and EF tasks, and between the BRIEF-Parent and BRIEF-Teacher were calculated. The BRIEF-Parent related poorly to EF tasks (rs < .26, ps > .01), but of the BRIEF-Teacher the WM-scale, Monitor-scale, Behavioral-Regulation-Index, and Meta-cognition-Index, and Total-score (rs > .31, ps < .01) related significantly to some EF tasks. When controlling for age, only the WM scale and Total score related significantly to the attention task (ps < .01). The inhibit scales of the BRIEF-Parent and BRIEF-Teacher correlated significantly (r = .33, p < .01). Children with clinically elevated scores on BRIEF scales that correlated with EF tasks performed worse on all EF tasks (ds 0.56-1.23, ps < .05). The BRIEF-Teacher Total and Index scores might better screen general EF in PBTS than the BRIEF-Parent. However, the BRIEF-Teacher is also not specific enough to capture separate EFs. Solely relying on the BRIEF as a screening measure of EFs in BPTS is insufficient. Questionnaires and tasks give distinctive, valuable information.

Neural network topology in ADHD; evidence for maturational delay and default-mode network alterations.

OBJECTIVE: Attention-deficit/hyperactivity disorder (ADHD) has been associated with widespread brain abnormalities in white and grey matter, affecting not only local, but global functional networks as well. In this study, we explored these functional networks using source-reconstructed electroencephalography in ADHD and typically developing (TD) children. We expected evidence for maturational delay, with underlying abnormalities in the default mode network. METHODS: Electroencephalograms were recorded in ADHD (n=42) and TD (n=43) during rest, and functional connectivity (phase lag index) and graph (minimum spanning tree) parameters were derived. Dependent variables were global and local network metrics in theta, alpha and beta bands. RESULTS: We found evidence for a more centralized functional network in ADHD compared to TD children, with decreased diameter in the alpha band (ηp2=0.06) and increased leaf fraction (ηp2=0.11 and 0.08) in the alpha and beta bands, with underlying abnormalities in hub regions of the brain, including default mode network. CONCLUSIONS: The finding of a more centralized network is in line with maturational delay models of ADHD and should be replicated in longitudinal designs. SIGNIFICANCE: This study contributes to the literature by combining high temporal and spatial resolution to construct EEG network topology, and associates maturational-delay and default-mode interference hypotheses of ADHD.

Predicting attention-deficit/hyperactivity disorder severity from psychosocial stress and stress-response genes: a random forest regression approach.

Identifying genetic variants contributing to attention-deficit/hyperactivity disorder (ADHD) is complicated by the involvement of numerous common genetic variants with small effects, interacting with each other as well as with environmental factors, such as stress exposure. Random forest regression is well suited to explore this complexity, as it allows for the analysis of many predictors simultaneously, taking into account any higher-order interactions among them. Using random forest regression, we predicted ADHD severity, measured by Conners' Parent Rating Scales, from 686 adolescents and young adults (of which 281 were diagnosed with ADHD). The analysis included 17 374 single-nucleotide polymorphisms (SNPs) across 29 genes previously linked to hypothalamic-pituitary-adrenal (HPA) axis activity, together with information on exposure to 24 individual long-term difficulties or stressful life events. The model explained 12.5% of variance in ADHD severity. The most important SNP, which also showed the strongest interaction with stress exposure, was located in a region regulating the expression of telomerase reverse transcriptase (TERT). Other high-ranking SNPs were found in or near NPSR1, ESR1, GABRA6, PER3, NR3C2 and DRD4. Chronic stressors were more influential than single, severe, life events. Top hits were partly shared with conduct problems. We conclude that random forest regression may be used to investigate how multiple genetic and environmental factors jointly contribute to ADHD. It is able to implicate novel SNPs of interest, interacting with stress exposure, and may explain inconsistent findings in ADHD genetics. This exploratory approach may be best combined with more hypothesis-driven research; top predictors and their interactions with one another should be replicated in independent samples.

Interplay between stress response genes associated with attention-deficit hyperactivity disorder and brain volume.

The glucocorticoid receptor plays a pivotal role in the brain's response to stress; a haplotype of functional polymorphisms in the NR3C1 gene encoding this receptor has been associated with attention-deficit hyperactivity disorder (ADHD). The serotonin transporter (5-HTT) gene polymorphism 5-HTTLPR is known to influence the relation between stress exposure and ADHD severity, which may be partly because of its reported effects on glucocorticoid levels. We therefore investigated if NR3C1 moderates the relation of stress exposure with ADHD severity and brain structure, and the potential role of 5-HTTLPR. Neuroimaging, genetic and stress exposure questionnaire data were available for 539 adolescents and young adults participating in the multicenter ADHD cohort study NeuroIMAGE (average age: 17.2 years). We estimated the effects of genetic variation in NR3C1 and 5-HTT, stress exposure and their interactions on ADHD symptom count and gray matter volume. We found that individuals carrying the ADHD risk haplotype of NR3C1 showed significantly more positive relation between stress exposure and ADHD severity than non-carriers. This gene-environment interaction was significantly stronger for 5-HTTLPR L-allele homozygotes than for S-allele carriers. These two- and three-way interactions were reflected in the gray matter volume of the cerebellum, parahippocampal gyrus, intracalcarine cortex and angular gyrus. Our findings illustrate how genetic variation in the stress response pathway may influence the effects of stress exposure on ADHD severity and brain structure. The reported interplay between NR3C1 and 5-HTT may further explain some of the heterogeneity between studies regarding the role of these genes and hypothalamic-pituitary-adrenal axis activity in ADHD.

Adolescent behavioral and neural reward sensitivity: a test of the differential susceptibility theory.

Little is known about the causes of individual differences in reward sensitivity. We investigated gene-environment interactions (GxE) on behavioral and neural measures of reward sensitivity, in light of the differential susceptibility theory. This theory states that individuals carrying plasticity gene variants will be more disadvantaged in negative, but more advantaged in positive environments. Reward responses were assessed during a monetary incentive delay task in 178 participants with and 265 without attention-deficit/hyperactivity disorder (ADHD), from N=261 families. We examined interactions between variants in candidate plasticity genes (DAT1, 5-HTT and DRD4) and social environments (maternal expressed emotion and peer affiliation). HTTLPR short allele carriers showed the least reward speeding when exposed to high positive peer affiliation, but the most when faced with low positive peer affiliation or low maternal warmth. DAT1 10-repeat homozygotes displayed similar GxE patterns toward maternal warmth on general task performance. At the neural level, DRD4 7-repeat carriers showed the least striatal activation during reward anticipation when exposed to high maternal warmth, but the most when exposed to low warmth. Findings were independent of ADHD severity. Our results partially confirm the differential susceptibility theory and indicate the importance of positive social environments in reward sensitivity and general task performance for persons with specific genotypes.

Feedback learning and behavior problems after pediatric traumatic brain injury.

BACKGROUND: Feedback learning is essential for behavioral development. We investigated feedback learning in relation to behavior problems after pediatric traumatic brain injury (TBI). METHOD: Children aged 6-13 years diagnosed with TBI (n = 112; 1.7 years post-injury) were compared with children with traumatic control (TC) injury (n = 52). TBI severity was defined as mild TBI without risk factors for complicated TBI (mildRF- TBI, n = 24), mild TBI with ⩾1 risk factor for complicated TBI (mildRF+ TBI, n = 51) and moderate/severe TBI (n = 37). The Probabilistic Learning Test was used to measure feedback learning, assessing the effects of inconsistent feedback on learning and generalization of learning from the learning context to novel contexts. The relation between feedback learning and behavioral functioning rated by parents and teachers was explored. RESULTS: No evidence was found for an effect of TBI on learning from inconsistent feedback, while the moderate/severe TBI group showed impaired generalization of learning from the learning context to novel contexts (p = 0.03, d = -0.51). Furthermore, the mildRF+ TBI and moderate/severe TBI groups had higher parent and teacher ratings of internalizing problems (p's ⩽ 0.04, d's ⩾ 0.47) than the TC group, while the moderate/severe TBI group also had higher parent ratings of externalizing problems (p = 0.006, d = 0.58). Importantly, poorer generalization of learning predicted higher parent ratings of externalizing problems in children with TBI (p = 0.03, ß = -0.21) and had diagnostic utility for the identification of children with TBI and clinically significant externalizing behavior problems (area under the curve = 0.77, p = 0.001). CONCLUSIONS: Moderate/severe pediatric TBI has a negative impact on generalization of learning, which may contribute to post-injury externalizing problems.

Stimulant treatment history predicts frontal-striatal structural connectivity in adolescents with attention-deficit/hyperactivity disorder.

Diffusion tensor imaging (DTI) has revealed white matter abnormalities in individuals with attention-deficit/hyperactivity disorder (ADHD). Stimulant treatment may affect such abnormalities. The current study investigated associations between long-term stimulant treatment and white matter integrity within the frontal-striatal and mesolimbic pathways, in a large sample of children, adolescents and young adults with ADHD. Participants with ADHD (N=172; mean age 17, range 9-26) underwent diffusion-weighted MRI scanning, along with an age- and gendermatched group of 96 control participants. Five study-specific white matter tract masks (orbitofrontal-striatal, orbitofrontal-amygdalar, amygdalar-striatal, dorsolateral-prefrontal-striatal and medialprefrontal-striatal) were created. First we analyzed case-control differences in fractional anisotropy (FA) and mean diffusivity (MD) within each tract. Second, FA and MD in each tract was predicted from cumulative stimulant intake within the ADHD group. After correction for multiple testing, participants with ADHD showed reduced FA in the orbitofrontal-striatal pathway (p=0.010, effect size=0.269). Within the ADHD group, higher cumulative stimulant intake was associated with lower MD in the same pathway (p=0.011, effect size=-0.164), but not with FA. The association between stimulant treatment and orbitofrontal-striatal MD was of modest effect size. It fell short of significance after adding ADHD severity or ADHD type to the model (p=0.036 and p=0.094, respectively), while the effect size changed little. Our findings are compatible with stimulant treatment enhancing orbitofrontal-striatal white matter connectivity, and emphasize the importance of the orbitofrontal cortex and its connections in ADHD. Longitudinal studies including a drug-naïve baseline assessment are needed to distinguish between-subject variability in ADHD severity from treatment effects.