Brain Potentials from Dyslexic Children Recorded During Short-Term Memory Tasks

Abstract

Event Related Potentials (ERPs) from thirty children (9-13 years old); fourteen of whom were dyslexic and sixteen normal-reading controls, were recorded during the performance of a memory scanning task. Visually presented stimuli consisted of either digits (lexical) or unfamiliar (non-lexical) characters. The subjects had to indicate whether a probe stimulus was a member of a preceding memorized set, or not. The memorized sets included 1, 2 or 3 items. Performance accuracies were significantly lower and reaction times longer in the dyslexic group. The significant Group x Lexicality interaction demonstrated P3 amplitudes which were smaller to lexical compared to non-lexical stimuli in dyslexics compared to skilled readers. Brain activity in response to the probes was more prominent over the right scalp in dyslexics, in contrast to controls that had left side prominence. The results suggest that dyslexic children relate to the physical features of stimuli as opposed to skilled readers, who rely more on the linguistic features of the stimuli. We suggest that remembering visually presented items in dyslexics involves different cognitive strategies and brain structures compared to skilled readers.

The contribution of AERPs (MMN and LDN) to studying temporal vs. linguistic processing deficits in children with reading difficulties

“…In this case, Leppänen et al (1999) found an anomalous right lateralisation in infants at risk for dyslexia when faced with speech sounds which, according to the authors, is associated with poorer execution in subsequent linguistic measurements. In groups of older ages, other authors have also informed about greater right asymmetry with both linguistic and non-linguistic stimuli in subjects with reading problems (Barnea et al, 1994;Erez and Pratt, 1992;Landwehrmeyer et al, 1990).…”

Executive functions in children with dyslexia

“…With regard to working Executive Functions and Dyslexia memory which may be the most extensively studied aspect of executive functioning in children with dyslexia, a number of studies have demonstrated (Baddeley, 1982;Barnea et al, 1994;Brady et al, 1983;Brady et al, 1987;Breznitz, 1997;Chiappe et al, 2000;Hulme & Mackenzie, 1992;Jorm, 1979;Poblano et al, 2000;Swanson et al, 1989;Torgesen, 1977;Vargo et al, 1995;Willcutt et al, 2001) that verbal working memory in children with dyslexia is disturbed in comparison to non-dyslexic children. The results of the present study also indicate that children with dyslexia display impairments in tasks measuring verbal and figural working memory.…”

The effect of cognitive training on recall range and speed of information processing in the working memory of dyslexic and skilled readers

“…A few studies have made use of electrophysiological measures to examine working memory in dyslexics. One study (Barnea, Lamm, Epstein, & Pratt, 1994) found that the P300 amplitude was lower for lexical than non-lexical stimuli in dyslexic readers, and the opposite for skilled readers. Reaction time and accuracy were significantly longer and poorer among the dyslexics than the controls for both the lexical and non-lexical tasks.…”