Publications by authors named "Gail Tripp"

34 Publications

Shared Predictors of Academic Achievement in Children with ADHD: A Multi-Sample Study.

J Atten Disord 2021 May 17:10870547211012039. Epub 2021 May 17.

Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan.

Objective: To identify common and shared predictors of academic achievement across samples of children with ADHD.

Method: Two clinically referred samples from New Zealand (1  = 88, 82% boys; 2  = 121, 79% boys) and two community samples from the United States (3  = 111, 65% boys; 4  = 114, 69% boys), completed similar diagnostic, cognitive and academic assessments. Hierarchical multiple regression analyses identified significant predictors of word reading, spelling, and math computation performance in each sample.

Results: Entered after IQ, semantic language, age at testing, and verbal working memory emerged as consistent predictors of achievement across academic subjects and samples. Visual-spatial working memory contributed to variance in math performance only. Symptom severity explained limited variance.

Conclusions: We recommend evaluations of children with ADHD incorporate assessments of working memory and language skills. Classroom/academic interventions should accommodate reduced working memory and address any identified language weaknesses.
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http://dx.doi.org/10.1177/10870547211012039DOI Listing
May 2021

The profile of pragmatic language impairments in children with ADHD: A systematic review.

Dev Psychopathol 2021 May 11:1-23. Epub 2021 May 11.

Okinawa Institute of Science and Technology, Graduate University, Okinawa, Japan.

This systematic review synthesizes the empirical literature examining pragmatic language in children diagnosed with attention-deficit/hyperactivity disorder (ADHD). Using a taxonomy of pragmatic language, we compared the pragmatic language profiles of children with ADHD to those of typically developing (TD) children and children with autism. Three databases were searched up to October 2019: PsychInfo; PubMed; and CSA Linguistics and Language Behavior Abstracts. We included 34 studies reporting on 2,845 children (ADHD = 1,407; TD = 1,058; autism = 380). Quality and risk of bias assessments included sample size and representativeness; measure reliability and validity; and missing data management. Children with ADHD were found to have higher rates of pragmatic difficulties than their TD peers. Specific difficulties were identified with inappropriate initiation, presupposition, social discourse, and narrative coherence. Children with ADHD appear to differ from those with autism in the degree of their pragmatic language impairments. General language skills contribute to, but do not explain, pragmatic difficulties in samples of children with ADHD. Though the extant evidence is limited, a preliminary profile of the pragmatic language impairments in children with ADHD is indicated. This supports a call for evidence-based interventions that include pragmatic language skills training.
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http://dx.doi.org/10.1017/S0954579421000328DOI Listing
May 2021

Development of a Classical Conditioning Task for Humans Examining Phasic Heart Rate Responses to Signaled Appetitive Stimuli: A Pilot Study.

Front Behav Neurosci 2021 1;15:639372. Epub 2021 Apr 1.

Lab of Electric Stimulation of the Nervous System Rio de Janeiro State University, Rio de Janeiro, Brazil.

Cardiac responses to appetitive stimuli have been studied as indices of motivational states and attentional processes, the former being associated with cardiac acceleration and latter deceleration. Very few studies have examined heart rate changes in appetitive classical conditioning in humans. The current study describes the development and pilot testing of a classical conditioning task to assess cardiac responses to appetitive stimuli and cues that reliably precede them. Data from 18 adults were examined. They were shown initially neutral visual stimuli (putative CS) on a computer screen followed by pictures of high-caloric food (US). Phasic cardiac deceleration to food images was observed, consistent with an orienting response to motivationally significant stimuli. Similar responses were observed to non-appetitive stimuli when they were preceded by the cue associated with the food images, suggesting that attentional processes were engaged by conditioned stimuli. These autonomic changes provide significant information about classical conditioning effects in humans.
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http://dx.doi.org/10.3389/fnbeh.2021.639372DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8052094PMC
April 2021

Systematic Review: Attention-Deficit/Hyperactivity Disorder and Instrumental Learning.

J Am Acad Child Adolesc Psychiatry 2021 Apr 13. Epub 2021 Apr 13.

Mrs. Hulsbosch, Dr. De Meyer, and Prof. Drs. Beckers, Danckaerts, and Van der Oord are with KU Leuven, Belgium; Prof. Dr. Van der Oord is with the University of Amsterdam, The Netherlands.

Objective: Although instrumental learning deficits are, among other deficits, assumed to contribute to attention-deficit/hyperactivity disorder (ADHD), no comprehensive systematic review of instrumental learning deficits in ADHD exists. This review examines differences between ADHD and typically developing (TD) children in basic instrumental learning and the effects of reinforcement form, magnitude, schedule, and complexity, as well as effects of medication, on instrumental learning in children with ADHD.

Method: A systematic search of PubMed, PsyINFO, CINAHL, EMBASE+EMBASE CLASSIC, ERIC, and Web of Science was conducted for articles up to March 16, 2020. Experimental studies comparing instrumental learning between groups (ADHD versus TD) or a manipulation of reinforcement/medication within an ADHD sample were included. Quality of studies was assessed with an adapted version of the Hombrados and Waddington criteria to assess risk of bias in (quasi-) experimental studies.

Results: A total of 19 studies from among 3,384 non-duplicate screened articles were included. No difference in basic instrumental learning was found between children with ADHD and TD children, nor effects of form or magnitude of reinforcement. Results regarding reinforcement schedule and reversal learning were mixed, but children with ADHD seemed to show deficits in conditional discrimination learning compared to TD children. Methylphenidate improved instrumental learning in children with ADHD. Quality assessment showed poor quality of studies with respect to sample sizes and outcome and missing data reporting.

Conclusion: The review identified very few and highly heterogenous studies, with inconsistent findings. No clear deficit was found in instrumental learning under laboratory conditions. Children with ADHD do show deficits in complex forms of learning, that is, conditional discrimination learning. Clearly more research is needed, using more similar task designs and manipulations.
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http://dx.doi.org/10.1016/j.jaac.2021.03.009DOI Listing
April 2021

Conditional Learning Deficits in Children with ADHD can be Reduced Through Reward Optimization and Response-Specific Reinforcement.

Res Child Adolesc Psychopathol 2021 Apr 1. Epub 2021 Apr 1.

Behaviour, Health and Psychopathology, KU Leuven, Tiensestraat 102, 3000, Leuven, Belgium.

When children with ADHD are presented with behavioral choices, they struggle more than Typically Developing [TD] children to take into account contextual information necessary for making adaptive choices. The challenge presented by this type of behavioral decision making can be operationalized as a Conditional Discrimination Learning [CDL] task. We previously showed that CDL is impaired in children with ADHD. The present study explores whether this impairment can be remediated by increasing reward for correct responding or by reinforcing correct conditional choice behavior with situationally specific outcomes (Differential Outcomes). An arbitrary Delayed Matching-To-Sample [aDMTS] procedure was used, in which children had to learn to select the correct response given the sample stimulus presented (CDL). We compared children with ADHD (N = 45) and TD children (N = 49) on a baseline aDMTS task and sequentially adapted the aDMTS task so that correct choice behavior was rewarded with a more potent reinforcer (reward manipulation) or with sample-specific (and hence response-specific) reinforcers (Differential Outcomes manipulation). At baseline, children with ADHD performed significantly worse than TD children. Both manipulations (reward optimization and Differential Outcomes) improved performance in the ADHD group, resulting in a similar level of performance to the TD group. Increasing the reward value or the response-specificity of reinforcement enhances Conditional Discrimination Learning in children with ADHD. These behavioral techniques may be effective in promoting the learning of adaptive behavioral choices in children with ADHD.
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http://dx.doi.org/10.1007/s10802-021-00781-5DOI Listing
April 2021

The World Federation of ADHD International Consensus Statement: 208 Evidence-based conclusions about the disorder.

Neurosci Biobehav Rev 2021 Feb 4. Epub 2021 Feb 4.

Department of Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, University Hospital Wuerzburg, Wuerzburg, Germany. Electronic address:

Background: Misconceptions about ADHD stigmatize affected people, reduce credibility of providers, and prevent/delay treatment. To challenge misconceptions, we curated findings with strong evidence base.

Methods: We reviewed studies with more than 2000 participants or meta-analyses from five or more studies or 2000 or more participants. We excluded meta-analyses that did not assess publication bias, except for meta-analyses of prevalence. For network meta-analyses we required comparison adjusted funnel plots. We excluded treatment studies with waiting-list or treatment as usual controls. From this literature, we extracted evidence-based assertions about the disorder.

Results: We generated 208 empirically supported statements about ADHD. The status of the included statements as empirically supported is approved by 80 authors from 27 countries and 6 continents. The contents of the manuscript are endorsed by 366 people who have read this document and agree with its contents.

Conclusions: Many findings in ADHD are supported by meta-analysis. These allow for firm statements about the nature, course, outcome causes, and treatments for disorders that are useful for reducing misconceptions and stigma.
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http://dx.doi.org/10.1016/j.neubiorev.2021.01.022DOI Listing
February 2021

How to Improve Behavioral Parent and Teacher Training for Children with ADHD: Integrating Empirical Research on Learning and Motivation into Treatment.

Clin Child Fam Psychol Rev 2020 12 24;23(4):577-604. Epub 2020 Sep 24.

Human Developmental Neurobiology Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Kunigami District, Okinawa Prefecture, 904-0495, Japan.

Attention deficit hyperactivity disorder [ADHD] is one of the most common psychiatric disorders of childhood with poor prognosis if not treated effectively. Recommended psychosocial evidence-based treatment for preschool and school-aged children is behavioral parent and teacher training [BPT]. The core elements of BPT are instrumental learning principles, i.e., reinforcement of adaptive and the ignoring or punishment of non-adaptive behaviors together with stimulus control techniques. BPT is moderately effective in reducing oppositional behavior and improving parenting practices; however, it does not reduce blinded ratings of ADHD symptoms. Also after training effects dissipate. This practitioner review proposes steps that can be taken to improve BPT outcomes for ADHD, based on purported causal processes underlying ADHD. The focus is on altered motivational processes (reward and punishment sensitivity), as they closely link to the instrumental processes used in BPT. Following a critical analysis of current behavioral treatments for ADHD, we selectively review motivational reinforcement-based theories of ADHD, including the empirical evidence for the behavioral predictions arising from these theories. This includes consideration of children's emotional reactions to expected and unexpected outcomes. Next we translate this evidence into potential ADHD-specific adjustments designed to enhance the immediate and long-term effectiveness of BPT programs in addressing the needs of children with ADHD. This includes the use of remediation strategies for proposed deficits in learning not commonly used in BPT programs and cautions regarding the use of punishment. Finally, we address how these recommendations can be effectively transferred to clinical practice.
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http://dx.doi.org/10.1007/s10567-020-00327-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7585566PMC
December 2020

An Adaptation of Pavlovian-to-Instrumental Transfer (PIT) Methodology to Examine the Energizing Effects of Reward-Predicting Cues on Behavior in Young Adults.

Front Psychol 2020 14;11:195. Epub 2020 Feb 14.

D'Or Institute for Research and Education (IDOR), Rio de Janeiro, Brazil.

There is growing recognition that much of human behavior is governed by the presence of classically conditioned cues. The Pavlovian-to-Instrumental Transfer (PIT) paradigm offers a way to measure the effects of classically conditioned stimuli on behavior. In the current study, a novel behavioral task, an adaptation of the PIT framework, was developed for use in conjunction with an fMRI classical conditioning task. Twenty-four healthy young adults completed (1) instrumental training, (2) Pavlovian conditioning, and (3) a Transfer test. During instrumental training, participants learned to apply force to a handgrip to win money from slot machines pictured on a computer screen. During Pavlovian conditioning, slot machines appeared with one of two abstract symbols (cues), one symbol was predictive of monetary reward. During the Transfer test, participants again applied force to a handgrip to win money. This time, the slot machines were presented with the Pavlovian cues, but with the outcomes hidden. The results indicated increased effort on the instrumental task, i.e. higher response frequency and greater force, in the presence of the reward-predicting cue. Our findings add to the growing number of studies demonstrating PIT effects in humans. This new paradigm is effective in measuring the effects of a conditioned stimulus on behavioral activation.
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http://dx.doi.org/10.3389/fpsyg.2020.00195DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7034436PMC
February 2020

Methylphenidate modifies reward cue responses in adults with ADHD: An fMRI study.

Neuropharmacology 2020 01 2;162:107833. Epub 2019 Nov 2.

D'Or Institute for Research and Education (IDOR), Rio de Janeiro, Brazil; Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.

Attention deficit hyperactivity disorder (ADHD) has been associated with neural hyposensitivity to reward-predicting cues. Methylphenidate is widely used in the management of the disorder's symptoms, but its effects on reward sensitivity in ADHD are unknown. The current study used fMRI to measure striatal responses to reward-predicting cues in adults with ADHD on and off methylphenidate and a control group, during a classical conditioning task. Responses to cued reward were also explored. Larger differences in the ventral striatum activation to reward cues versus non-reward cues were observed when the ADHD participants were on methylphenidate compared to placebo. In response to cued-reward outcome, an exploratory analysis showed methylphenidate reduced the BOLD time-series correlation between the dorsal striatum and dorsal medial prefrontal cortex. Methylphenidate's therapeutic effects may be mediated by altering reward processing in individuals with ADHD.
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http://dx.doi.org/10.1016/j.neuropharm.2019.107833DOI Listing
January 2020

Deficits in Conditional Discrimination Learning in Children with ADHD are Independent of Delay Aversion and Working Memory.

J Clin Med 2019 Sep 3;8(9). Epub 2019 Sep 3.

Research Unit Behavior, Health and Psychopathology, KU Leuven, Tiensestraat 102, 3000 Leuven, Belgium.

Adaptive behavior requires the adjustment of one's behavioral repertoire to situational demands. The learning of situationally appropriate choice behavior can be operationalized as a task of Conditional Discrimination Learning (CDL). CDL requires the acquisition of hierarchical reinforcement relations, which may pose a particular challenge for children with Attention Deficit Hyperactivity Disorder (ADHD), particularly in light of documented deficits in short-term/working memory and delay aversion in ADHD. Using an arbitrary Delayed Matching-To-Sample task, we investigated whether children with ADHD (N = 46), relative to Typically Developing children (TD, N = 55), show a deficit in CDL under different choice delays (0, 8, and 16 seconds) and whether these differences are mediated by short-term/working memory capacity and/or delay aversion. Children with ADHD demonstrated poorer CDL than TD children under 8 and 16-second delays. Non-delayed CDL performance did not differ between groups. CDL differences were not mediated by short-term/working memory performance or delay aversion. Moreover, CDL performance under an 8-second delay was a better predictor of clinical status than short-term/working memory performance or delay aversion. CDL, under conditions of delay, is impaired in children with ADHD. This may lead to difficulties discriminating between different situational demands and adapting behavior according to the prevailing reward contingencies or expectations.
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http://dx.doi.org/10.3390/jcm8091381DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6780856PMC
September 2019

Reinforcement Contingency Learning in Children with ADHD: Back to the Basics of Behavior Therapy.

J Abnorm Child Psychol 2019 12;47(12):1889-1902

Research Unit Behavior, Health and Psychopathology, KU Leuven, Tiensestraat 102 box 3720, 3000, Leuven, Belgium.

Reinforcement deficits in ADHD may affect basic operant learning processes relevant for Behavioral Treatment. Behavior acquired under partial reinforcement extinguishes less readily after the discontinuation of reinforcement than behavior acquired under continuous reinforcement, a phenomenon known as the Partial Reinforcement Extinction Effect [PREE], which has great relevance for the emergence of behavioral persistence. The present study examined acquisition and extinction of operant responding under partial and continuous reinforcement in children with and without ADHD. In addition, we evaluated the effectiveness of gradual stretching the reinforcement rate during acquisition for remedying potential acquisition or extinction deficits under partial reinforcement in ADHD. In an operant learning task designed to mimic the task confronted by an animal in a Skinner box, 62 typically developing and 49 children with ADHD (age: 8-12) were presented with a continuous, partial or gradually stretching reinforcement scheme followed by extinction. Both groups of children acquired the instrumental response more slowly and exhibited more behavioral persistence (reduced extinction) when responding was initially reinforced under partial relative to continuous reinforcement, with no differences between groups. Progressive ratio stretching resulted in faster acquisition than partial reinforcement yet promoted equal behavioral persistence, again without differences between ADHD and TD groups. Unlike suggested by previous research, children with ADHD exhibit neither an acquisition deficit under partial reinforcement nor a deficit in PREE. Of relevance for Behavioral Treatment, gradual reinforcement stretching can be used to facilitate response acquisition over purely partial reinforcement while maintaining equal behavioral persistence upon reward discontinuation.
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http://dx.doi.org/10.1007/s10802-019-00572-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6842356PMC
December 2019

Is increased sensitivity to punishment a common characteristic of attention deficit/hyperactivity disorder? An experimental study of response allocation in Japanese children.

Atten Defic Hyperact Disord 2019 Dec 16;11(4):433-443. Epub 2019 May 16.

Human Developmental Neurobiology Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Okinawa, 904-0495, Japan.

Research on motivational processes in attention deficit/hyperactivity disorder (ADHD) focuses on reward. Studies with punishment are limited and findings mixed. This study evaluated the effects of punishment on response allocation in Japanese children with and without ADHD. Thirty-four children meeting DSM-IV criteria for ADHD and 59 typically developing control-group children completed an operant task in which they choose between playing two simultaneously available games. Reward was arranged symmetrically across the games under concurrent variable interval schedules. Asymmetric punishment schedules were superimposed with responses on one game punished four times as often as responses on the other. Children with ADHD showed greater behavioral sensitivity to punishment than controls. They allocated significantly more responses to the less frequently punished alternative and were more likely to play this game on consecutive trials and responded more slowly to the more punished game. Control group children allocated their responses evenly across games. Punishment exerted greater control over the behavior of Japanese children with ADHD than controls, similar to findings with children from Western countries, suggesting this is a common characteristic of the disorder. The behavior of typically developing Japanese children, while demonstrating awareness of punishment, was not controlled by the frequency of its occurrence.
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http://dx.doi.org/10.1007/s12402-019-00307-6DOI Listing
December 2019

Behavioral adjustment to asymmetric reward availability among children with and without ADHD: effects of past and current reinforcement contingencies.

Atten Defic Hyperact Disord 2019 Jun 6;11(2):149-158. Epub 2018 Sep 6.

Human Developmental Neurobiology Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Kunigami, Okinawa, 904-0495, Japan.

Altered reinforcement sensitivity is hypothesized to underlie symptoms of attention deficit hyperactivity disorder (ADHD). Here we evaluate the behavioral sensitivity of Brazilian children with and without ADHD to a change in reward availability. Forty typically developing children and 32 diagnosed with DSM-IV ADHD completed a signal-detection task in which correct discriminations between two stimuli were associated with different frequencies of reinforcement. The response alternative associated with the higher rate of reinforcement switched, without warning, after 30 rewards were delivered. The task continued until another 30 rewards were delivered. Both groups of children developed a response bias toward the initially more frequently reinforced alternative. This effect was larger in the control group. The response allocation of the two groups changed following the shift in reward availability. Over time the ADHD group developed a significant response bias toward the now more frequently reinforced alternative. In contrast, the bias of the control group stayed near zero after an initial decline following the contingency change. The overall shift in bias was similar for the two groups. The behavior of both groups of children was sensitive to the asymmetric reward distribution and to the change in reward availability. Subtle group differences in response patterns emerged, possibly reflecting differences in the time frame of reward effects and sensitivity to reward exposure.
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http://dx.doi.org/10.1007/s12402-018-0265-xDOI Listing
June 2019

Behavioral sensitivity of Japanese children with and without ADHD to changing reinforcer availability: an experimental study using signal detection methodology.

Behav Brain Funct 2017 Sep 25;13(1):13. Epub 2017 Sep 25.

Human Developmental Neurobiology Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Okinawa, 904-0495, Japan.

Background: Most research on motivational processes in attention deficit hyperactivity disorder (ADHD) has been undertaken in Western Europe and North America. The extent to which these findings apply to other cultural groups is unclear. The current study evaluated the behavioral sensitivity of Japanese children with and without ADHD to changing reward availability. Forty-one school-aged children, 19 diagnosed with DSM-IV ADHD, completed a signal-detection task in which correct discriminations between two stimuli were associated with different reinforcement frequencies. The response alternative associated with the higher rate of reinforcement switched twice during the task without warning.

Findings: Both groups of children developed an initial bias toward the more frequently reinforced response alternative. When the reward contingencies switched the response allocation (bias) of the control group children followed suit. The response bias scores of the children with ADHD did not, suggesting impaired tracking of reward availability over time.

Conclusions: Japanese children with ADHD adjust their behavioral responses to changing reinforcer availability less than their typically developing peers. This is not explained by poor attention to task or a lack of sensitivity to reward. The current results are consistent with altered sensitivity to changing reward contingencies identified in non-Japanese samples of children with ADHD. Irrespective of their country of origin, children with ADHD will likely benefit from behavioral expectations and reinforcement contingencies being made explicit together with high rates of reinforcement for appropriate behaviors.
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http://dx.doi.org/10.1186/s12993-017-0131-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5613339PMC
September 2017

Neurocognitive and Symptom Trajectories of ADHD from Childhood to Early Adolescence.

J Dev Behav Pediatr 2017 Sep;38(7):465-475

*Human Developmental Neurobiology Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan; †Department of Psychology, University of Otago, Dunedin, New Zealand.

Objective: This longitudinal study investigated changes in neurocognitive functioning from childhood to early adolescence in a sample of children diagnosed with DSM-IV attention-deficit hyperactivity disorder (ADHD). It also compared the neurocognitive trajectories of children who continued to meet the diagnostic criteria for ADHD at follow-up and those in partial remission.

Methods: Children diagnosed with ADHD (N = 55) were tested at baseline (M = 7.7 years, SD = 1.5) and 4 years later (M = 11.7 years, SD = 1.5) on measures of intellectual, academic, and executive functioning. Group and individual analyses were used to examine neurocognitive functioning over this period.

Results: Intellectual function was stable over the 4-year interval. Reliable change analyses highlighted variability in academic performance. Approximately half the sample showed a reliable decline in at least 1 academic subject with almost a third showing reliable improvement. Executive functions generally followed a stable or improving course, with significant improvements on measures of information processing, attentional control, cognitive flexibility, and goal setting. There was some evidence of better neurocognitive performance in those with partial symptom remission at follow-up.

Conclusion: Study findings emphasize the importance of monitoring academic performance in children with ADHD, including examination of change at the individual level. Declines in academic performance were observed, despite stable intellectual and improving executive function. Early cognitive functioning did not predict symptom remission; however, reduced symptoms at follow-up were associated with better executive function.
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http://dx.doi.org/10.1097/DBP.0000000000000476DOI Listing
September 2017

Adapting an attention-deficit hyperactivity disorder parent training intervention to different cultural contexts: The experience of implementing the New Forest Parenting Programme in China, Denmark, Hong Kong, Japan, and the United Kingdom.

Psych J 2017 Mar;6(1):83-97

Academic Unit of Psychology, University of Southampton, Southampton, UK.

The New Forest Parenting Programme (NFPP) is a parenting program developed for parents who have a child with attention-deficit hyperactivity disorder (ADHD). It is a manualized program that is delivered in a parent's home over 8 weeks, or in a group format, or through a self-help manual. Three randomized controlled trials have been carried out in the United Kingdom. The NFPP group has adapted the program according to feedback from parents and therapists, and for use with different populations, both within the United Kingdom and internationally. The first international trial took place in New York, United States. Trials in Denmark, Hong Kong, and Japan followed. More recently, a trial of the self-help manual has been carried out in mainland China. This paper will outline the adaptions that were needed in order to be able to deliver the program in different countries with their own expectations of parenting, culture, and language. Training had to be differently focused; manuals and handouts had to be revised, translated and back-translated; and supervision had to be delivered at a distance to maintain the fidelity of the program. The international group will outline their experience of running trials in their own countries with the NFPP in a face-to-face format (Denmark), a group format (Hong Kong and Japan), and a self-help format (mainland China).
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http://dx.doi.org/10.1002/pchj.159DOI Listing
March 2017

Evidence for increased behavioral control by punishment in children with attention-deficit hyperactivity disorder.

J Child Psychol Psychiatry 2017 03 9;58(3):248-257. Epub 2016 Sep 9.

Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan.

Background: The behavioral sensitivity of children with ADHD to punishment has received limited theoretical and experimental attention. This study evaluated the effects of punishment on the response allocation of children with ADHD and typically developing children.

Method: Two hundred and ten children, 145 diagnosed with ADHD, completed an operant task in which they chose between playing two simultaneously available games. Reward was arranged symmetrically across the games under concurrent variable interval schedules. Asymmetric punishment schedules were superimposed; responses on one game were punished four times as often as responses on the other.

Results: Both groups allocated more of their responses to the less frequently punished alternative. Response bias increased significantly in the ADHD group during later trials, resulting in missed reward trials and reduced earnings.

Conclusions: Punishment exerted greater control over the response allocation of children with ADHD with increased time on task. Children with ADHD appear more sensitive to the cumulative effects of punishment than typically developing children.
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http://dx.doi.org/10.1111/jcpp.12635DOI Listing
March 2017

Behavioral sensitivity to changing reinforcement contingencies in attention-deficit hyperactivity disorder.

J Child Psychol Psychiatry 2016 08 15;57(8):947-56. Epub 2016 Apr 15.

Okinawa Institute of Science and Technology Graduate University, Onna, Japan.

Background: Altered sensitivity to positive reinforcement has been hypothesized to contribute to the symptoms of attention-deficit hyperactivity disorder (ADHD). In this study, we evaluated the ability of children with and without ADHD to adapt their behavior to changing reinforcer availability.

Method: Of one hundred sixty-seven children, 97 diagnosed with ADHD completed a signal-detection task in which correct discriminations between two stimuli were associated with different frequencies of reinforcement. The response alternative associated with the higher rate of reinforcement switched twice during the task without warning. For a subset of participants, this was followed by trials for which no reinforcement was delivered, irrespective of performance.

Results: Children in both groups developed an initial bias toward the more frequently reinforced response alternative. When the response alternative associated with the higher rate of reinforcement switched, the children's response allocation (bias) followed suit, but this effect was significantly smaller for children with ADHD. When reinforcement was discontinued, only children in the control group modified their response pattern.

Conclusions: Children with ADHD adjust their behavioral responses to changing reinforcer availability less than typically developing children, when reinforcement is intermittent and the association between an action and its consequences is uncertain. This may explain the difficulty children with ADHD have adapting their behavior to new situations, with different reinforcement contingencies, in daily life.
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http://dx.doi.org/10.1111/jcpp.12561DOI Listing
August 2016

Abnormal striatal BOLD responses to reward anticipation and reward delivery in ADHD.

PLoS One 2014 26;9(2):e89129. Epub 2014 Feb 26.

D'Or Institute for Research and Education (IDOR), Rio de Janeiro, Brazil.

Altered reward processing has been proposed to contribute to the symptoms of attention deficit hyperactivity disorder (ADHD). The neurobiological mechanism underlying this alteration remains unclear. We hypothesize that the transfer of dopamine release from reward to reward-predicting cues, as normally observed in animal studies, may be deficient in ADHD. Functional magnetic resonance imaging (fMRI) was used to investigate striatal responses to reward-predicting cues and reward delivery in a classical conditioning paradigm. Data from 14 high-functioning and stimulant-naïve young adults with elevated lifetime symptoms of ADHD (8 males, 6 females) and 15 well-matched controls (8 males, 7 females) were included in the analyses. During reward anticipation, increased blood-oxygen-level-dependent (BOLD) responses in the right ventral and left dorsal striatum were observed in controls, but not in the ADHD group. The opposite pattern was observed in response to reward delivery; the ADHD group demonstrated significantly greater BOLD responses in the ventral striatum bilaterally and the left dorsal striatum relative to controls. In the ADHD group, the number of current hyperactivity/impulsivity symptoms was inversely related to ventral striatal responses during reward anticipation and positively associated with responses to reward. The BOLD response patterns observed in the striatum are consistent with impaired predictive dopamine signaling in ADHD, which may explain altered reward-contingent behaviors and symptoms of ADHD.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0089129PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3935853PMC
January 2015

Altered functional brain connectivity in a non-clinical sample of young adults with attention-deficit/hyperactivity disorder.

J Neurosci 2012 Dec;32(49):17753-61

Queensland Brain Institute, The University of Queensland, St Lucia, Queensland 4072, Australia.

Attention-deficit/hyperactivity disorder (ADHD) is characterized by symptoms of inattention and hyperactivity/impulsivity that often persist in adulthood. There is a growing consensus that ADHD is associated with abnormal function of diffuse brain networks, but such alterations remain poorly characterized. Using resting-state functional magnetic resonance imaging, we characterized multivariate (complex network measures), bivariate (network-based statistic), and univariate (regional homogeneity) properties of brain networks in a non-clinical, drug-naive sample of high-functioning young men and women with ADHD (nine males, seven females) and a group of matched healthy controls. Data from our sample allowed the isolation of intrinsic functional connectivity alterations specific to ADHD diagnosis and symptoms that are not related to developmental delays, general cognitive dysfunction, or history of medication use. Multivariate results suggested that frontal, temporal, and occipital cortices were abnormally connected locally as well as with the rest of the brain in individuals with ADHD. Results from the network-based statistic support and extend multivariate results by isolating two brain networks comprising regions between which inter-regional connectivity was significantly altered in the ADHD group; namely, a frontal amygdala-occipital network and a frontal temporal-occipital network. Brain behavior correlations further highlighted the key role of altered orbitofrontal-temporal and frontal-amygdala connectivity for symptoms of inattention and hyperactivity/impulsivity. All univariate properties were similar between groups. Taken together, results from this study show that the diagnosis and the two main symptom dimensions of ADHD are related to altered intrinsic connectivity in orbitofrontal-temporal-occipital and fronto-amygdala-occipital networks. Accordingly, our findings highlight the importance of extending the conceptualization of ADHD beyond segregated fronto-striatal alterations.
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http://dx.doi.org/10.1523/JNEUROSCI.3272-12.2012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6621678PMC
December 2012

Reinforcement, dopamine and rodent models in drug development for ADHD.

Neurotherapeutics 2012 Jul;9(3):622-34

Human Developmental Neurobiology Unit, Okinawa Institute of Science and Technology Graduate University, Kunigami, Okinawa 904-0412, Japan.

Attention deficit hyperactivity disorder (ADHD) presents special challenges for drug development. Current treatment with psychostimulants and nonstimulants is effective, but their mechanism of action beyond the cellular level is incompletely understood. We review evidence suggesting that altered reinforcement mechanisms are a fundamental characteristic of ADHD. We show that a deficit in the transfer of dopamine signals from established positive reinforcers to cues that predict such reinforcers may underlie these altered reinforcement mechanisms, and in turn explain key symptoms of ADHD. We argue that the neural substrates controlling the excitation and inhibition of dopamine neurons during the transfer process are a promising target for future drug development. There is a need to develop animal models and behavioral paradigms that can be used to experimentally investigate these mechanisms and their effects on sensitivity to reinforcement. More specific and selective targeting of drug development may be possible through this approach.
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http://dx.doi.org/10.1007/s13311-012-0132-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3441939PMC
July 2012

Animal models to guide clinical drug development in ADHD: lost in translation?

Br J Pharmacol 2011 Oct;164(4):1107-28

Okinawa Institute of Science and Technology, Okinawa, Japan.

We review strategies for developing animal models for examining and selecting compounds with potential therapeutic benefit in attention-deficit hyperactivity disorder (ADHD). ADHD is a behavioural disorder of unknown aetiology and pathophysiology. Current understanding suggests that genetic factors play an important role in the aetiology of ADHD. The involvement of dopaminergic and noradrenergic systems in the pathophysiology of ADHD is probable. We review the clinical features of ADHD including inattention, hyperactivity and impulsivity and how these are operationalized for laboratory study. Measures of temporal discounting (but not premature responding) appear to predict known drug effects well (treatment validity). Open-field measures of overactivity commonly used do not have treatment validity in human populations. A number of animal models have been proposed that simulate the symptoms of ADHD. The most commonly used are the spontaneously hypertensive rat (SHR) and the 6-hydroxydopamine-lesioned (6-OHDA) animals. To date, however, the SHR lacks treatment validity, and the effects of drugs on symptoms of impulsivity and inattention have not been studied extensively in 6-OHDA-lesioned animals. At the present stage of development, there are no in vivo models of proven effectiveness for examining and selecting compounds with potential therapeutic benefit in ADHD. However, temporal discounting is an emerging theme in theories of ADHD, and there is good evidence of increased value of delayed reward following treatment with stimulant drugs. Therefore, operant behaviour paradigms that measure the effects of drugs in situations of delayed reinforcement, whether in normal rats or selected models, show promise for the future.
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http://dx.doi.org/10.1111/j.1476-5381.2011.01412.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3229754PMC
October 2011

Working memory deficits in ADHD: the contribution of age, learning/language difficulties, and task parameters.

J Atten Disord 2011 Aug 23;15(6):461-72. Epub 2010 Jun 23.

Department of Psychology, University of Otago, Dunedin, New Zealand.

Objective: To further define the nature of working memory (WM) impairments in children with combined-type ADHD.

Method: A total of 40 Children with ADHD and an age and gender-matched control group (n = 40) completed two measures of visuo-spatial WM and two measures of verbal WM. The effects of age and learning/language difficulties on performance were evaluated.

Results: Children with ADHD obtained significantly lower scores than controls on measures of both visuo-spatial and verbal WM. The impairments in verbal WM were age related.

Conclusion: Children with ADHD exhibit impaired visuo-spatial WM performance. Younger (less than 8 years), but not older, children with ADHD demonstrate impairments in verbal WM. This latter result may explain the previously reported inconsistent performance of children with ADHD on verbal WM tasks. The importance of taking a developmental perspective in WM research is stressed.
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http://dx.doi.org/10.1177/1087054710370674DOI Listing
August 2011

Apnea-hypopnea indices and snoring in children diagnosed with ADHD: a matched case-control study.

Sleep Breath 2011 Sep 4;15(3):455-62. Epub 2010 May 4.

Department of Women's and Children's Health, University of Otago, Dunedin, New Zealand.

Objectives: To measure apnea-hypopnea indices and snoring in children diagnosed with attention-deficit hyperactivity disorder (ADHD) in a case-control design. Additionally, the study design allowed us to investigate whether or not methylphenidate had any effect on breathing variables.

Methods: Twenty-eight children (22 boys) aged 6-12 years meeting diagnostic criteria for Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV ADHD were studied together with matched controls. Two nights of polysomnography (PSG) were conducted that included recordings of snoring waveforms. A randomly assigned 48-h on-off medication protocol was used for ADHD children. Control children's recordings were matched for PSG night, but medication was not used. A low apnea-hypopnea index (AHI) threshold of >1 event per hour was used to define sleep-disordered breathing (SDB) because of a clinical relevance in ADHD.

Results: Categorical analyses for paired binary data showed no significant differences between control and ADHD children for presence of an AHI >1 or snoring. Variables were extracted from a significantly shorter total sleep time (67 min) on the medication night in children with ADHD. Eight (28%) control and 11 (40%) ADHD children snored >60 dB some time during the night. Methylphenidate had no effect on central apneas, AHI, desaturation events, or any snoring data.

Conclusions: Our PSG findings show no strong link between ADHD and SDB although our findings could be limited by a small sample size. Findings from PSG studies in the literature argue both for and against an association between ADHD and SDB. Our results suggest medication is not a factor in the debate.
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http://dx.doi.org/10.1007/s11325-010-0357-0DOI Listing
September 2011

The sleep of children with attention deficit hyperactivity disorder on and off methylphenidate: a matched case-control study.

J Sleep Res 2010 Jun 28;19(2):366-73. Epub 2009 Dec 28.

Department of Women's and Children's Health, University of Otago, Dunedin, New Zealand.

In the present study, we assessed the effects of regular use of methylphenidate medication in children diagnosed with attention deficit hyperactivity disorder (ADHD) on sleep timing, duration and sleep architecture. Twenty-seven children aged 6-12 years meeting diagnostic criteria for Diagnostic and Statistical Manual version IV ADHD and 27 control children matched for age (+/-3 months) and gender. Two nights of standard polysomnographic (PSG) recordings were conducted. ADHD children were allocated randomly to an on- or 48 h off-methylphenidate protocol for first or second recordings. Control children's recordings were matched for night, but no medication was used. Mixed modelling was employed in the analyses so that the full data set was used to determine the degree of medication effects. Methylphenidate in ADHD children prolonged sleep onset by an average of 29 min [confidence interval (CI) 11.6, 46.7], reduced sleep efficiency by 6.5% (CI 2.6, 10.3) and shortened sleep by 1.2 h (CI 0.65, 1.9). Arousal indices were preserved. Relative amounts of stages 1, 2 and slow wave sleep were unchanged by medication. Rapid eye movement sleep was reduced (-2.4%) on the medication night, an effect that became non-significant when control data were incorporated in the analyses. PSG data from ADHD children off-medication were similar to control data. Our findings suggest that methylphenidate reduces sleep quantity but does not alter sleep architecture in children diagnosed with ADHD. An adequate amount of sleep is integral to good daytime functioning, thus the sleep side effects of methylphenidate may affect adversely the daytime symptoms the drug is targeted to control.
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http://dx.doi.org/10.1111/j.1365-2869.2009.00795.xDOI Listing
June 2010

Identifying the neurobiology of altered reinforcement sensitivity in ADHD: a review and research agenda.

Neurosci Biobehav Rev 2010 Apr 26;34(5):744-54. Epub 2009 Nov 26.

Department of Clinical Neurpsychology, Vrije Universiteit Amsterdam, Van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands.

ADHD is associated with altered reinforcement sensitivity, despite a number of inconsistent findings. This review focuses on the overlap and differences between seven neurobiologically valid models and lists 15 predictions assessing reinforcement sensitivity in ADHD. When comparing the models it becomes clear that there are great differences in the level of explanation. For example, some models try to explain a single core deficit in terms lower-level reinforcement systems, such as the dopamine transfer to reward back in time. Other models explain multiple deficits, by describing higher-level systems, such as impaired bottom-up prefrontal activation. When reviewing the available experimental evidence in support of the predictions, most experimental studies have been focusing on behavioral changes in the face of reward and response cost over no-reward, and on delay discounting. There is currently a lack in studies that focus on explaining underlying cognitive or neural mechanisms of altered reinforcement sensitivity in ADHD. Additionally, there is a lack in studies that try to understand what subgroup of children with ADHD shows alterations in reinforcement sensitivity. The scarcity in studies testing the neurobiological predictions is explained partly by a lack in knowledge how to test some of these predictions in humans. Nevertheless, we believe that these predictions can serve as a useful guide to the systematic evaluation of altered reinforcement sensitivity in ADHD.
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http://dx.doi.org/10.1016/j.neubiorev.2009.11.021DOI Listing
April 2010

Neurobiology of ADHD.

Neuropharmacology 2009 Dec 21;57(7-8):579-89. Epub 2009 Jul 21.

Human Developmental Neurobiology Unit, Okinawa Institute of Science and Technology, 12-22 Suzaki, Uruma City, Okinawa 904-2234, Japan.

Attention-deficit hyperactivity disorder (ADHD) is a prevalent and debilitating disorder diagnosed on the basis of persistent and developmentally-inappropriate levels of overactivity, inattention and impulsivity. The etiology and pathophysiology of ADHD is incompletely understood. There is evidence of a genetic basis for ADHD but it is likely to involve many genes of small individual effect. Differences in the dimensions of the frontal lobes, caudate nucleus, and cerebellar vermis have been demonstrated. Neuropsychological testing has revealed a number of well documented differences between children with and without ADHD. These occur in two main domains: executive function and motivation although neither of these is specific to ADHD. In view of the recent advances in the neurobiology of reinforcement, we concentrate in this review on altered reinforcement mechanisms. Among the motivational differences, many pieces of evidence indicate that an altered response to reinforcement may play a central role in the symptoms of ADHD. In particular, sensitivity to delay of reinforcement appears to be a reliable finding. We review neurobiological mechanisms of reinforcement and discuss how these may be altered in ADHD, with particular focus on the neurotransmitter dopamine and its actions at the cellular and systems level. We describe how dopamine cell firing activity is normally associated with reinforcing events, and transfers to earlier time-points in the behavioural sequence as reinforcement becomes more predictable. We discuss how a failure of this transfer may give rise to many symptoms of ADHD, and propose that methylphenidate might act to compensate for the proposed dopamine transfer deficit.
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http://dx.doi.org/10.1016/j.neuropharm.2009.07.026DOI Listing
December 2009

Sensitivity to delay of reinforcement in two animal models of attention deficit hyperactivity disorder (ADHD).

Behav Brain Res 2009 Dec 16;205(2):372-6. Epub 2009 Jul 16.

Department of Psychology, University of Otago, Dunedin, New Zealand.

An altered response to reinforcement has been proposed as a mechanism underlying many of the symptoms of attention deficit hyperactivity disorder (ADHD). We measured sensitivity to delay of reinforcement in two animal models of ADHD, the spontaneously hypertensive rat (SHR) and a newly proposed model, the genetically hypertensive (GH) rat. A task previously used to measure effects of delay of reinforcement in children with ADHD was adapted for use in the present experiment. The SHR and GH rats were compared to their respective genetic control strains, Wistar-Kyoto (WKY), and Wistar (WI). The experimental task required pressing one of two available levers each trial. One lever delivered an immediate reinforcement, and the other lever a delayed reinforcement. Both the SHR and GH strains allocated significantly more responses to the immediately reinforced lever than their genetic control strains. Individual instances of reinforcement differentially affected response allocation in the GH but not the SHR. These findings support the use of the SHR and GH rat to model altered response to reinforcement, and demonstrate the additional value of the GH strain to model the effects of individual instances of reinforcement in children with ADHD.
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http://dx.doi.org/10.1016/j.bbr.2009.07.011DOI Listing
December 2009

Origins of altered reinforcement effects in ADHD.

Behav Brain Funct 2009 Feb 18;5. Epub 2009 Feb 18.

Centre for Advanced Study (CAS) at the Norwegian Academy for Science and Letters, Oslo, Norway.

Attention-deficit/hyperactivity disorder (ADHD), characterized by hyperactivity, impulsiveness and deficient sustained attention, is one of the most common and persistent behavioral disorders of childhood. ADHD is associated with catecholamine dysfunction. The catecholamines are important for response selection and memory formation, and dopamine in particular is important for reinforcement of successful behavior. The convergence of dopaminergic mesolimbic and glutamatergic corticostriatal synapses upon individual neostriatal neurons provides a favorable substrate for a three-factor synaptic modification rule underlying acquisition of associations between stimuli in a particular context, responses, and reinforcers. The change in associative strength as a function of delay between key stimuli or responses, and reinforcement, is known as the delay of reinforcement gradient. The gradient is altered by vicissitudes of attention, intrusions of irrelevant events, lapses of memory, and fluctuations in dopamine function. Theoretical and experimental analyses of these moderating factors will help to determine just how reinforcement processes are altered in ADHD. Such analyses can only help to improve treatment strategies for ADHD.
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http://dx.doi.org/10.1186/1744-9081-5-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2649942PMC
February 2009

Research review: dopamine transfer deficit: a neurobiological theory of altered reinforcement mechanisms in ADHD.

J Child Psychol Psychiatry 2008 Jul 1;49(7):691-704. Epub 2008 Jul 1.

Human Developmental Neurobiology Unit, Okinawa Institute of Science and Technology, Uruma, Okinawa, Japan.

This review considers the hypothesis that changes in dopamine signalling might account for altered sensitivity to positive reinforcement in children with ADHD. The existing evidence regarding dopamine cell activity in relation to positive reinforcement is reviewed. We focus on the anticipatory firing of dopamine cells brought about by a transfer of dopamine cell responses to cues that precede reinforcers. It is proposed that in children with ADHD there is diminished anticipatory dopamine cell firing, which we call the dopamine transfer deficit (DTD). The DTD theory leads to specific and testable predictions for human and animal research. The extent to which DTD explains symptoms of ADHD and effects of pharmacological interventions is discussed. We conclude by considering the neural changes underlying the etiology of DTD.
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http://dx.doi.org/10.1111/j.1469-7610.2007.01851.xDOI Listing
July 2008