Effects of a short and intensive transcranial direct current stimulation treatment in children and adolescents with developmental dyslexia: A crossover clinical trial

Abstract

Developmental Dyslexia (DD) significantly interferes with children’s academic, personal, social, and emotional functioning. Nevertheless, therapeutic options need to be further validated and tested in randomized controlled clinical trials. The use of transcranial direct current stimulation (tDCS) has been gaining ground in recent years as a new intervention option for DD. However, there are still open questions regarding the most suitable tDCS protocol for young people with DD. The current crossover study tested the effectiveness of a short and intensive tDCS protocol, including the long-term effects, as well as the influence of age and neuropsychological processes at baseline on reading improvements. Twenty-four children and adolescents with DD were randomly assigned to receive active tDCS during the first slot and sham tDCS during the second slot or vice versa. Five consecutive daily sessions of left anodal/right cathodal tDCS set at 1 mA for 20 min were administered over the parieto-occipital regions. Reading measures (text, high frequency word, low frequency word, and non-word lists) and neuropsychological measures (visual-spatial and verbal working memory, phoneme blending, and rapid automatized naming tasks) were collected before, immediately after, 1 week and 1 month later the treatment. Our results showed that only the active tDCS condition improved non-word reading speed immediately after and 1 month later the end of the treatment compared with baseline. In addition, the improvement in non-word reading speed was significantly correlated with age and with neuropsychological measures (verbal working memory and phoneme blending) at baseline but only in the active tDCS condition. The current crossover study contributed to enforce previous effects of tDCS, including long-term effects, on non-word reading speed and to understand the effect of age and neuropsychological processes on reading outcomes. Our findings showed that tDCS could be a low-cost and easy-to-implement treatment option with long-term effects for children and adolescents with DD.

Effects of online tDCS and hf-tRNS on reading performance in children and adolescents with developmental dyslexia: a study protocol for a within-subject, randomized, double-blind, and sham-controlled trial

“…According to the International 10-20 System, the anodal electrode will be placed over the left temporo-parietal region (TP7/P7), while the cathodal electrode will be placed over the contralateral temporo-parietal region (TP8/P8). Consistent with our previous tDCS protocols in developmental age (16)(17)(18)(19)(20)(21)(22), in the active condition a constant current at 1 mA intensity will be delivered for 20 min, with a density of 0.04 mA/cm 2 , preceded by 30 s of rump up (0 mA to 1 mA) and succeeded by 30 s of rump down (1mA to 0 mA). Direct current will be delivered by a battery driven, direct current stimulator (BrainStim stimulation by E.M.S.…”

“…Our selection of tES parameters, including intensity, density, duration, and frequency, will be based on previous research demonstrating the safety and beneficial effects of these parameters on reading performance (16)(17)(18)(19)(20)(21)(22) and cognitive tasks (23,57,60,67,68).…”

“…If accuracy will achieve 80%, the difficulty will increase and participants will be asked to remember not the last letter spoken or the last position shown, but the second-to-last (2-back), and so on (3-back, 4-back, etc.). An n-back performance index will be calculated and considered for each task (22,53).…”

“…Several studies have demonstrated the effects of tDCS, either alone or in combination with reading training, on reading abilities in children and adolescents with DD (16)(17)(18)(19)(20)(21)(22). While overall positive outcomes have been observed, the results still show heterogeneity in terms of specific reading aspects improved (e.g., non-word speed vs text reading accuracy).…”

Dysfunction of the Visual Sensory Thalamus in Developmental Dyslexia

“…The findings suggest that (i) sex differences in the brain basis of DD extend beyond the cerebral cortex to the sensory thalamus, and (ii) that an understanding of sensory thalamus alterations in DD would benefit from a thorough understanding of sex-related developmental determinants of thalamic maturation. The findings are also relevant for clinical studies as they suggest that targeting the thalamo-cortical system for example with complementary neurostimulation might be particularly effective in male individuals with DD (29,30).…”