tDCS Modulatory Effect on Reading Processes: A Review of Studies on Typical Readers and Individuals With Dyslexia

Abstract

The possibility to use non-invasive brain stimulation to modulate reading performance in individuals with developmental dyslexia (DD) has been recently explored by few empirical investigations. The present systematic review includes nine studies which have employed transcranial direct current stimulation (tDCS) aiming at improving reading abilities in both typical readers and individuals with DD. Anodal tDCS over the left temporo-parietal cortex—a region which is typically involved in phonological and orthographic processing during reading tasks and underactive in individuals with DD—was the most frequently used montage. The majority of studies employing such stimulation protocol showed significant improvement in differential reading subprocesses. More precisely, word decoding was improved in adult readers, whereas non-word and low-frequency word reading in younger individuals. Furthermore, tDCS was found to be specifically effective in poor readers and individuals with DD rather than typical readers, in spite of the specific brain region targeted by the stimulation; Left frontal, left temporo-parietal, and right cerebellar tDCS failed to modulate reading in already proficient readers. Overall, tDCS appears to be a promising remedial tool for reading difficulties, even when applied to younger populations with reading problems. Further empirical evidence is needed to confirm the potential of neuromodulation as a successful intervention method for DD.

Beyond Reading Modulation: Temporo-Parietal tDCS Alters Visuo-Spatial Attention and Motion Perception in Dyslexia

“…These results supported previous evidence that anodal stimulation (increased excitability) in the left temporo-parietal areas combined with concomitant cathodal stimulation (decreased excitability) of contralateral areas can modulate reading, as already showed in typically reading adults and in children and adolescents with dyslexia [ 62 , 80 ].…”

Non-invasive Brain Stimulation for the Rehabilitation of Children and Adolescents With Neurodevelopmental Disorders: A Systematic Review

“…A possible progress in the treatment of this disorder could be achieved by the integration of these cognitive trainings with NIBS techniques (Vicario and Nitsche, 2013b), to foster the activation of the areas that are involved in compensatory processes in dyslexia. In this vein, the use of tDCS has been proposed (Vicario and Nitsche, 2013b; Cancer and Antonietti, 2018) and three recent double-blind, sham controlled studies assessed the effects of enhancing left parieto-temporal activation with anodal tDCS. No studies for the treatment of dyslexia with other NIBS techniques have been conducted so far.…”

The Effectiveness of Interventions for Developmental Dyslexia: Rhythmic Reading Training Compared With Hemisphere-Specific Stimulation and Action Video Games

“…A test-training-retest study showed the efficacy of RRT intervention on reading abilities of 14 junior high school students with DD, compared to a matched control group that received no intervention (Bonacina et al, 2015). Other test-training-retest small scale studies supported RRT efficacy in primary and junior high-school Italian students with DD, under different conditions (Cancer and Antonietti, 2017;Cancer et al, 2019).…”

“…This lively search for DD brain basis is fostering a new wave of innovative treatments aiming at enhancing reading skills in an indirect way, by training the cognitive and perceptual skills potentially involved in the reading process (e.g., Thomson et al, 2012;Bhide et al, 2013;Flaugnacco et al, 2015;Cancer and Antonietti, 2018;Frey et al, 2019;Pecini et al, 2019). However, there remains a strong need to identify among old and new interventions the ones that are, first of all, effective in improving reading skills (Lorusso et al, 2006) and, secondly, use resources efficiently (Franceschini et al, 2013).…”