A Study of Null Effects for the Use of Transcranial Direct Current Stimulation (tDCS) in Adults With and Without Reading Impairment

There is evidence to support the hypothesis that the delivery of anodal transcranial direct current stimulation (tDCS) to the left temporoparietal junction can enhance performance on reading speed and reading accuracy (Costanzo et al., 2016b; Heth & Lavidor, 2015). Here, we explored whether we could demonstrate similar effects in adults with and without reading impairments. Method: Adults with (N = 33) and without (N = 29) reading impairment were randomly assigned to anodal or sham stimulation conditions. All individuals underwent a battery of reading assessments pre and post stimulation. The stimulation session involved 15 min of anodal/sham stimulation over the left temporoparietal junction while concurrently completing a computerized nonword segmentation task known to activate the temporoparietal junction. Results: There were no conclusive findings that anodal stimulation impacted reading performance for skilled or impaired readers. Conclusions: While tDCS may provide useful gains on reading performance in the paediatric population, much more work is needed to establish the parameters under which such findings would transfer to adult populations. The documentation, reporting, and interpreting of null effects of tDCS are immensely important to a field that is growing exponentially with much uncertainty

Supplementary Material for: The Relationship between White Matter and Reading Acquisition, Refinement and Maintenance

Reading requires efficient communication between brain regions that are situated all over the cortex. These brain areas are structurally connected by white-matter pathways that develop over the period of reading acquisition. Here, we conducted a cross-sectional study to assess the relationship between white-matter tracts and reading performance across the lifespan. <b><i>Methods:</i></b> Behavioral (reading performance) and neuroimaging (diffusion tensor imaging [DTI]) data were collected from participants aged 3–21 years as a part of the multi-site project called the pediatric imaging neurocognition genetics study. DTI measures (fractional anisotropy [FA], mean diffusivity, radial diffusivity and axial diffusivity) of bilateral dorsal tracts (arcuate fasciculus, superior longitudinal fasciculus, and posterior superior longitudinal fasciculus) and ventral tracts (uncinate fasciculus, inferior fronto-occipital fasciculus, and inferior longitudinal fasciculus) were extracted. Reading performance was calculated as the number of items correctly read (words for older children and letters in the case of young children). Correlational and regression analyses were conducted between the DTI measures and reading scores. <b><i>Results:</i></b> During the early stages of reading acquisition (ages 3–6), the dorsal tracts were positively related to reading performance (as FA goes up, reading performance goes up). For ages 6–10, the dorsal tracts remain positively associated with reading performance and a relationship between ventral tracts and reading performance emerges. From the age of 10 onwards, the dorsal tracts no longer correlate with reading performance, and a brain-behavior relationship in the right ventral tracts begins to shift, whereby higher FA is associated with lower reading performance. In addition to the involvement of left hemispheric tracts, this study revealed the initial engagement of right hemispheric tracts during the early stages of reading acquisition. <b><i>Conclusion:</i></b> We discuss these different associations of white-matter tracts with reading during development in the context of the biological processes model of myelination and pruning

Supplementary Material for: Changes in White Matter Integrity following Intensive Voice Treatment (LSVT LOUD®) in Children with Cerebral Palsy and Motor Speech Disorders

<p>Preliminary evidence suggests that intensive voice and speech treatment based on activity-dependent neuroplasticity principles holds promise for affecting positive change in children with cerebral palsy (CP) and motor speech disorders. Diffusion tensor imaging (DTI) allows researchers to make inferences about the integrity of white matter tracks and provides a sensitive measure of neuroplasticity. Previous treatment studies looking at the effects of training on white matter integrity have shown positive results, but these studies have been limited to gross motor function. Eight children with motor speech disorders and CP (3 females; age 8-16 years) and an age- and sex-matched group of typically developing (TD) children participated. Each child with CP completed a full dose of LSVT LOUD® and a 12-week maintenance program. Participants attended 3 recording sessions: before and after treatment, and after the maintenance period. TD children were tested at the same 3 time points. Recording sessions for both groups of children included measures of white matter integrity using DTI and acoustic measures of voice and speech. Fractional anisotropy (FA) was measured for 2 motor tracts and 5 association tracts. In children with CP, we observed an increase in FA in several motor and association tracts immediately following treatment and 12 weeks after treatment. Acoustic data on untrained tasks were correlated with changes in FA detected immediately following treatment and after the 12-week maintenance program. These findings suggest that long-term practice of skills attained during the treatment phase enhances white matter tract integrity in speech production networks.</p