Science, sophistry and 'commercial sensitivity': comments on 'Evaluation of an exercise-based treatment for children with reading difficulties', by Reynolds, Nicolson and Hambly

An fMRI study of finger movements in children with and without dyslexia

Introduction

Developmental dyslexia is a language-based reading disability, yet some have reported motor impairments, usually attributed to cerebellar dysfunction.

Methods

Using fMRI, we compared children with and without dyslexia during irregularly paced, left or right-hand finger tapping. Next, we examined seed-to-voxel intrinsic functional connectivity (iFC) using six seed regions of the motor system (left and right anterior lobe of the cerebellum, SM1 and SMA).

Results

A whole-brain task-evoked analysis revealed relatively less activation in the group with dyslexia in right anterior cerebellum during right hand tapping. For iFC, we found the group with dyslexia to have greater iFC between the right SM1 seed and a medial aspect of right postcentral gyrus for left hand tapping; and greater iFC between the left SM1 seed and left thalamus, as well as weaker local iFC around the left SM1 seed region for right hand tapping. Lastly, extracted activity and connectivity values that had been identified in these between-group comparisons were not correlated with measures of reading.

Discussion

We conclude that there are some aberrations in motor system function in children with dyslexia, but these are not tied to reading ability.

Cerebellar function in developmental dyslexia

Developmental dyslexia is a genetically based neurobiological syndrome, which is characterized by reading difficulty despite normal or high general intelligence. Even remediated dyslexic readers rarely achieve fast, fluent reading. Some dyslexics also have impairments in attention, short-term memory, sequencing (letters, word sounds, and motor acts), eye movements, poor balance, and general clumsiness. The presence of "cerebellar" motor and fluency symptoms led to the proposal that cerebellar dysfunction contributes to the etiology of dyslexia. Supporting this, functional imaging studies suggest that the cerebellum is part of the neural network supporting reading in typically developing readers, and reading difficulties have been reported in patients with cerebellar damage. Differences in both cerebellar asymmetry and gray matter volume are some of the most consistent structural brain findings in dyslexics compared with good readers. Furthermore, cerebellar functional activation patterns during reading and motor learning can differ in dyslexic readers. Behaviorally, some children and adults with dyslexia show poorer performance on cerebellar motor tasks, including eye movement control, postural stability, and implicit motor learning. However, many dyslexics do not have cerebellar signs, many cerebellar patients do not have reading problems, and differences in dyslexic brains are found throughout the whole reading network, and not isolated to the cerebellum. Therefore, impaired cerebellar function is probably not the primary cause of dyslexia, but rather a more fundamental neurodevelopmental abnormality leads to differences throughout the reading network.

Follow-up of an exercise-based treatment for children with reading difficulties

This study reports the results of a long-term follow-up of an exercise-based approach to dyslexia-related disorders (Reynolds, Nicolson, & Hambly, Dyslexia, 2003; 9(1): 48-71). In the initial study, children at risk of dyslexia were identified in 3 years of a junior school. One half then undertook a 6 month, home-based exercise programme. Evaluation after 6 months indicated that the exercise group improved significantly more than the controls on a range of cognitive and motor skills. Critics had suggested that the improvement might be attributable to artifactual issues including Hawthorne effects; an initial literacy imbalance between the groups; and inclusion of non-dyslexic participants. The present study evaluated the issue of whether the gains were maintained over the following 18 months, and whether they were in some sense artifactual as postulated by critics of the original study. Comparison of (age-adjusted) initial and follow-up performance indicated significant gains in motor skill, speech/language fluency, phonology, and working memory. Both dyslexic and non-dyslexic low achieving children benefited. There was also a highly significant reduction in the incidence of symptoms of inattention. Interestingly there were no significant changes in speeded tests of reading and spelling, but there was a significant improvement in (age-adjusted) reading (NFER). It is concluded that the gains were indeed long-lasting, and that the alternative hypotheses based on potential artifacts were untenable, and that the exercise treatment therefore achieved its applied purpose. Further research is needed to determine the underlying reasons for the benefits. Possible (and potentially synergistic) explanations include: improved cerebellar function (neural level); improved learning ability and/or attentional ability (cognitive level); improved self-esteem and self-efficacy (affective level); and improved parental/familial support (social level).