Article Archive for ‘May, 2016’

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

May 05th, 2016
  • Attention-deficit hyperactivity disorder;
  • response allocation;
  • reinforcement;
  • change

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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Similar but different: differences in comprehension diagnosis on the Neale Analysis of Reading Ability and the York Assessment of Reading for Comprehension

May 04th, 2016

Psychometric tests are behavioural tests. We use measures of behaviour (which we can see directly) to infer something about a latent variable (something that can’t be seen or measured directly). Take tests of reading ability as an example. Reading occurs in the brain and is therefore a latent variable. We can’t see or measure it directly. The consequence is that different tests will provide different results depending on a number of factors, including the skills/items that the test samples and the normative population. 

Danielle ColenbranderLyndsey Nickels and Saskia Kohnen have just published a study that investigated differences in the content and scores obtained from two commonly used reading tests: The NARA and the YARC. The whole can be found in the Journal of Research in Reading. 

The Abstract

Identifying reading comprehension difficulties is challenging. There are many comprehension tests to choose from, and a child’s diagnosis can be influenced by various factors such as a test’s format and content and the choice of diagnostic criteria. We investigate these issues with reference to the Neale Analysis of Reading Ability (NARA) and the York Assessment of Reading for Comprehension (YARC).

Methods

Ninety-five children were assessed on both tests. Test characteristics were compared using Principal Components and Regression analyses as well as an analysis of passage content.

Results

NARA comprehension scores were more dependent on decoding skills than YARC scores, but children answered more comprehension questions on the NARA and passages spanned a wider range of difficulty. Consequently, 15–34% of children received different diagnoses across tests, depending on diagnostic criteria.

Conclusion

Knowledge of the strengths and weaknesses of comprehension tests is essential when attempting to diagnose reading comprehension difficulties.

 

For help with dyslexia, ADHD, autism spectrum disorders and other developmental and learning disorders in the Gold Coast and Tweed regions contact the Understanding Minds Clinic.

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A randomized controlled trial into the effects of neurofeedback, methylphenidate, and physical activity on EEG power spectra in children with ADHD

May 04th, 2016
Journal of Child Psychology and Psychiatry

Journal of Child Psychology and Psychiatry

Background

The clinical and neurophysiological effects of neurofeedback (NF) as treatment for children with ADHD are still unclear. This randomized controlled trial (RCT) examined electroencephalogram (EEG) power spectra before and after NF compared to methylphenidate (MPH) treatment and physical activity (PA) – as semi-active control group – during resting and active (effortful) task conditions to determine whether NF can induce sustained alterations in brain function.

Methods

Using a multicentre three-way parallel group RCT design, 112 children with a DSM-IV diagnosis of ADHD, aged between 7 and 13 years, were initially included. NF training consisted of 30 sessions of theta/beta training at Cz over a 10-week period. PA training was a semi-active control group, matched in frequency and duration. Methylphenidate was titrated using a double-blind placebo controlled procedure in 6 weeks, followed by a stable dose for 4 weeks. EEG power spectra measures during eyes open (EO), eyes closed (EC) and task (effortful) conditions were available for 81 children at pre- and postintervention (n = 29 NF, n = 25 MPH, n = 27 PA). Clinical trials registration: Train Your Brain? Exercise and Neurofeedback Intervention for ADHD, https://clinicaltrials.gov/show/;NCT01363544, Ref. No. NCT01363544.

Results

Both NF and MPH resulted in comparable reductions in theta power from pre- to postintervention during the EO condition compared to PA (ηp2 = .08 and .12). For NF, greater reductions in theta were related to greater reductions in ADHD symptoms. During the task condition, only MPH showed reductions in theta and alpha power compared to PA (ηp2 = .10 and .12).

Conclusions

This study provides evidence for specific neurophysiological effects after theta/beta NF and MPH treatment in children with ADHD. However, for NF these effects did not generalize to an active task condition, potentially explaining reduced behavioural effects of NF in the classroom.

 

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Heritability of autism spectrum disorders: a meta-analysis of twin studies (Tick et al., 2016)

May 04th, 2016
Journal of Child Psychology and Psychiatry

Journal of Child Psychology and Psychiatry

Background

The etiology of Autism Spectrum Disorder (ASD) has been recently debated due to emerging findings on the importance of shared environmental influences. However, two recent twin studies do not support this and instead re-affirm strong genetic effects on the liability to ASD, a finding consistent with previous reports. This study conducts a systematic review and meta-analysis of all twin studies of ASD published to date and explores the etiology along the continuum of a quantitative measure of ASD.

Methods

A PubMed Central, Science Direct, Google Scholar, Web of Knowledge structured search conducted online, to identify all twin studies on ASD published to date. Thirteen primary twin studies were identified, seven were included in the meta-analysis by meeting Systematic Recruitment criterion; correction for selection and ascertainment strategies, and applied prevalences were assessed for these studies. In addition, a quantile DF extremes analysis was carried out on Childhood Autism Spectrum Test scores measured in a population sample of 6,413 twin pairs including affected twins.

Results

The meta-analysis correlations for monozygotic twins (MZ) were almost perfect at .98 (95% Confidence Interval, .96–.99). The dizygotic (DZ) correlation, however, was .53 (95% CI .44–.60) when ASD prevalence rate was set at 5% (in line with the Broad Phenotype of ASD) and increased to .67 (95% CI .61–.72) when applying a prevalence rate of 1%. The meta-analytic heritability estimates were substantial: 64–91%. Shared environmental effects became significant as the prevalence rate decreased from 5–1%: 07–35%. The DF analyses show that for the most part, there is no departure from linearity in heritability.

Conclusions

We demonstrate that: (a) ASD is due to strong genetic effects; (b) shared environmental effects become significant as a function of lower prevalence rate; (c) previously reported significant shared environmental influences are likely a statistical artefact of overinclusion of concordant DZ twins.

 

For help with dyslexia, ADHD, autism spectrum disorders and other developmental and learning disorders in the Gold Coast and Tweed regions contact the Understanding Minds Clinic .

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