Investigation of the Influence of Phonological Awareness Intervention and Transcranial Direct Current Stimulation on the Enhancement of Rapid Automatized Naming and Verbal Short Term Memory in Developmental Dyslexia: A Randomized Controlled Trial

Abstract

Phonological deficits include phonological awareness (PA), rapid automatized naming (RAN) and verbal short term memory (VSTM). PA is defined as a conscious manipulation of the word subunits in word structure. Recently, transcranial direct current stimulation (tDCS) has been used as a complementary treatment with PA intervention in the dyslexia treatment. In this trial we had both a PA intervention group and a PA + tDCS group in which the tDCS is applied over the left parieto-temporal area. It was hypothesized that the PA + tDCS treatment can improve RAN and VSTM. A randomized, double-blind, sham-controlled clinical trial was conducted to evaluate the influence of PA + tDCS intervention in improving RAN and VSTM. Twenty-eight participants were randomly allocated to the active (PA + anodal tDCS) or sham (PA + sham tDCS) groups. Each dyslexic student participated in 15 intervention sessions. RAN and VSTM sub-tests were assessed at the baseline, at the end of the fifth, tenth, and final treatment sessions and finally 6 weeks after the treatment. In both groups, mean scores of RAN sub-tests significantly decreased and the mean scores of the VSTM sub-tests significantly increased during, immediately and also 6 weeks after intervention. There was no significant difference between the two groups in the mean scores of the outcome measures. PA intervention leads to improvement in RAN and VSTM abilities in dyslexic students for a longer period of time. Combined intervention (PA + tDCS) had no further effect on outcome measures than PA intervention alone.