Beyond the dual pathway model : evidence for the dissociation of timing, inhibitory, and delay-related impairments in attention-deficit/hyperactivity disorder

Objective: The dual pathway model explains neuro-psychological heterogeneity in Attention Deficit/Hyperactivity Disorder (ADHD) in terms of dissociable cognitive and motivational deficits each affecting some but not other patients. We explore whether deficits in temporal processing might constitute a third dissociable neuropsychological component of ADHD. Method: Nine tasks designed to tap three domains (inhibitory control, delay aversion and temporal processing) were administered to ADHD probands (n=71; ages 6 to 17 years), their siblings (n=71; 65 unaffected by ADHD) and a group of non-ADHD controls (n=50). IQ and working memory were measured. Results: Temporal processing, inhibitory control and delay-related deficits represented independent neuropsychological components. ADHD children differed from controls on all factors. For ADHD patients, the co-occurrence of inhibitory, temporal processing and delay-related deficits was no greater than expected by chance with substantial groups of patients showing only one problem. Domain-specific patterns of familial co-segregation provided evidence for the validity of neuropsychological subgroupings. Conclusion: The current results illustrate the neuropsychological heterogeneity in ADHD and initial support for a triple pathway model. The findings need to be replicated in larger samples

Dissecting the neuropsychological structure of ADHD : inhibitory control and delay aversion

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Dissecting the neuropsychological structure of ADHD : inhibitory control and delay aversion

Attention deficit/hyperactivity disorder (ADHD) has been characterised as a clinically and genetically heterogenous disorder.  Over the past decades, researchers have studied the neuropsychological causal factors associated with this heterogeneity.  Neuropsychological deficits such as inhibitory control (Barkley, 1997) and delay aversion (Sonuga-Barke et al., 1992) have been associated with ADHD.  However, none of these unitary causal models can fully explain the aetiology of the disorder.  In fact, there is a theoretical and empirical focus on identifying multiple causal pathways (Sonuga-Barke, 2002).  Up to date, very few studies have been conducted to distinguish these different causal pathways to ADHD by using multiple indicators of these neuropsychological domains.  In the present thesis 71 pairs of children with ADHD and their unaffected siblings and 50 children were examined on inhibitory control and delay aversion tasks as part of the Southampton site of the International Multicentre ADHD Genetics Study (IMAGE project).  First, these two neuropsychological deficit domains were found to be two separate latent constructs.  Secondly these latent factors of inhibitory control and delay aversion deficits were found to be associated with ADHD.  Third, a comparison of probands and their siblings found little evidence of familial effects on either construct.  Confounding effects such as age, gender, non-executive processes, IQ, and comorbid ODD were also investigated in a secondary analysis.  The current thesis provides strong support for the dual pathway model of ADHD – but leaves open the question of whether these effects are familial or genetic in nature.  Based on the present results, clinical and research implications on using neuropsychological subtypes, as part of the clinical diagnosis, are discussed.</p

Probing the limits of delay intolerance: preliminary young adult data from the Delay Frustration Task (DeFT)

Delay intolerance/aversion is one amongst a number of candidate neuropsychological endophenotypes for ADHD. Pilot data suggest that, because of potential ceiling effects, simple choice measures of delay tolerance used for children are probably not appropriate for adolescents and adults. The Delay Frustration Task (DeFT) is a new measure of delay intolerance, designed to be used in a similar form with adolescents and adults as well as children. In it delay frustration is indexed as the number and duration of responses made on a response key during a series of unpredictable and unsignalled delay periods, which interrupt the completion of a simple computer-based tests. The aim of this study was to provide preliminary data on the applicability of the task in a sample of young adults. The DeFT was administered to 49 male and female undergraduate students selected from a normal population-base. Their mean age was 23.14 (S.D. = 1.54). Three measures of delay frustration were recorded across time intervals during the response window; the number of responses, their duration and their combined product (total time button was pressed) was calculated for each second interval bin during the post-response delay period. The AARS and HADS were used as screening questionnaires for ADHD and anxiety behaviour, respectively. The results indicated that young adults with high-ADHD symptoms scores pressed the button more than those with low ADHD scores during the post-response delay condition. While both groups increased responding across time within intervals this was significantly more marked in the high-ADHD symptom group. These effects became more pronounced when anxiety was controlled. Young adults with high-ADHD symptoms appear to be more sensitive to the imposition of unscheduled and unsignalled delay during a simple maths test. DeFT may provide a useful index of delay tolerance in young adults with ADHD. Future research needs to examine DeFT performance in different age groups and in clinical and non-clinical populations. <br/

Identifying a distinctive familial frequency band in reaction time fluctuations in ADHD

Objective: Patients with ADHD are typically more variable in their reaction times (RT) than control children. Signal processing analyses have shown that time series RT data of children with ADHD have a distinctive low frequency periodic structure suggestive of a pattern of occasional spontaneous performance lapses. Here we use a fine-grained analysis of spectral power across a broader frequency range to differentiate the periodic qualities of ADHD time series RT data from (a) 1/frequency noise, and (b) control performance. We also assess the familiality of these frequencies by using a proband-sibling design. Method: Seventy-one children with ADHD, one of their siblings, and 50 control participants completed a simple RT task. Power across the RT frequency spectrum was calculated. The frequencies significantly differentiating the two groups were identified. Familiality was assessed in two ways: first, by comparing probands with their unaffected siblings and controls, and, second, by investigating the siblings of neuropsychologically impaired and unimpaired children with ADHD. Results: Analyses converged to highlight the potential importance of the .20–.26 Hz band in differentiating the periodic structure of ADHD RT time series data from both 1/frequency noise and control performance. This frequency band also showed the strongest evidence of familiality. Conclusions: RT performance of children with ADHD had a distinctive periodic structure. The band identified as most differentiating and familial was at a higher frequency than in most previous reports. This highlights the importance of employing tasks with faster interstimulus intervals that will allow a larger portion of the frequency spectrum to be examined

Delay Aversion in Attention Deficit/Hyperactivity Disorder: an empirical investigation of the broader phenotype

Background Delay-related motivational processes are impaired in children with Attention Deficit/Hyperactivity Disorder (ADHD). Here we explore the impact of ADHD on the performance of three putative indices of Delay Aversion (DAv): (i) the choice for immediate over delayed reward; (ii) slower reaction times following delay; and (iii) increased delay-related frustration—to see whether these tap into a common DAv construct that differentiates ADHD cases from controls and shows evidence of familiality.Method Seventy seven male and female individuals (age range 6–17) with a research diagnosis combined type ADHD, 65 of their siblings unaffected by ADHD and 50 non-ADHD controls completed three delay tasks.Results As predicted the size of the correlation between tasks was small but a common latent component was apparent. Children with ADHD differed from controls on all tasks (d = .4–.7) and on an overall DAv index (d = .9): The battery as a whole demonstrated moderate sensitivity and specificity. In general, deficits were equally marked in childhood and adolescence and were independent of comorbid ODD. IQ moderated the effect on the MIDA. Scores on the DAv factor co-segregated within ADHD families.Discussion There is value in exploring the broader DAv phenotype in ADHD. The results illustrate the power of multivariate approaches to endophenotypes. By highlighting the significant, but limited, role of DAv in ADHD these results are consistent with recent accounts that emphasize neuropsychological heterogeneity

Practical research-based guidance for motor imagery practice in neurorehabilitation

PURPOSE: The purpose of this appraisal is to offer guidance to clinicians on applying motor imagery in neurorehabilitation and provide guidance to support this process. METHOD: We used evidence from a variety of fields as well as clinical experience with motor imagery to develop guidance for employing motor imagery during neurorehabilitation. RESULTS: Motor imagery is a relatively new intervention for neurorehabilitation supported by evidence from areas such as cognitive neuroscience and sports psychology. Motor imagery has become a very popular intervention modality for clinicians but there is insufficient information available on how to administer it in clinical practice and make deliberate decisions during its application. CONCLUSIONS: We provide evidence-based guidance for employing motor imagery in neurorehabilitation and use the principles of motor learning as the framework for clinical application

Disentangling child and family influences on maternal expressed emotion toward children with attention-deficit/hyperactivity disorder

addresses: Institute for Disorders of Impulse and Attention, School of Psychology, University of Southampton, UK.types: Journal ArticleCopyright © 2011 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. NOTICE: This is the author’s version of a work accepted for publication by Elsevier. Changes resulting from the publishing process, including peer review, editing, corrections, structural formatting and other quality control mechanisms, may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of the American Academy of Child & Adolescent Psychiatry, 2011, Vol. 50, Issue 10, pp. 1042 – 1053 DOI: 10.1016/j.jaac.2011.07.006We used multi-level modelling of sibling-pair data to disentangle the influence of proband-specific and more general family influences on maternal expressed emotion (MEE) toward children and adolescents with attention-deficit/hyperactivity disorder (ADHD)