Brain hemisphericity and developmental dyslexia

Assessing Beliefs About Intrinsic and Extrinsic Determinants of SLD: Evaluating the Factor Structure of a Novel Instrument

Schools conduct comprehensive psychoeducational evaluations to identify students with specific learning disabilities (SLDs) and determine whether they qualify for special education services. This decision-making process is complex and research has documented many factors influencing SLD identification decisions. One such factor may be decision-makers' beliefs about the underlying causes of SLD, including intrinsic and extrinsic factors. However, no studies to date have examined the underlying factor structure of the responses to prompts about the causes of SLD from intrinsic and extrinsic perspectives. This study was conducted with a sample of 521 school psychologists as part of a larger study examining decision-making during SLD identification. Using confirmatory factor analyses (CFA) to compare two theoretically plausible models, results suggested that a single latent factor best captured variability in responses to these prompts. Implications for assessing beliefs and how they impact the psychoeducational assessment process to identify SLDs are discussed, along with areas for future research.

Event-related Potential Patterns Reflect Reversed Hemispheric Activity during Visual Attention Processing in Children with Dyslexia: A Preliminary Study

Objective

Individuals with dyslexia experience reading difficulties, whereas their other cognitive abilities seem normal. The purpose of this study was to investigate the event-related potential (ERP) patterns of children with dyslexia during a target-detection task.

Methods

Seventeen children with dyslexia and 18 children without this disorder participated in this study. We evaluated their writing and reading ability, symptoms of attention-deficit/hyperactivity disorder, and intelligence quotient. ERPs were recorded while participants performed a target-detection task, and the peak amplitude and latency of P100 and P300 were analyzed. The lateral asymmetry index (LAI) was calculated for each ERP component.

Results

The dyslexic group exhibited longer reaction times and larger P100 amplitudes than the non-dyslexic group in the right hemisphere. The P100 latency was also significantly delayed in the right hemisphere of those in the dyslexic group compared with those in the non-dyslexic group. The P300 amplitude was larger in the right hemisphere compared with left hemisphere in the dyslexic group, whereas no interhemispheric differences were observed with respect to the P300 latency. The LAI for P100 showed a significant right hemispheric dominance, whereas the LAI for P100 was significantly correlated with the accuracy of target detection in children with dyslexia.

Conclusion

Our results suggest that right hemispheric dominance acts as an ancillary system that compensates for poor reading in children with dyslexia.