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

Abstract

Dyslexia is a neurodevelopmental disorder with an atypical activation of posterior left-hemisphere brain reading networks (i.e., temporo-occipital and temporo-parietal regions) and multiple neuropsychological deficits. Transcranial direct current stimulation (tDCS) is a tool for manipulating neural activity and, in turn, neurocognitive processes. While studies have demonstrated the significant effects of tDCS on reading, neurocognitive changes beyond reading modulation have been poorly investigated. The present study aimed at examining whether tDCS on temporo-parietal regions affected not only reading, but also phonological skills, visuo-spatial working memory, visuo-spatial attention, and motion perception in a polarity-dependent way. In a within-subjects design, ten children and adolescents with dyslexia performed reading and neuropsychological tasks after 20 min of exposure to Left Anodal/Right Cathodal (LA/RC) and Right Anodal/Left Cathodal (RA/LC) tDCS. LA/RC tDCS compared to RA/LC tDCS improved text accuracy, word recognition speed, motion perception, and modified attentional focusing in our group of children and adolescents with dyslexia. Changes in text reading accuracy and word recognition speed—after LA/RC tDCS compared to RA/LC—were related to changes in motion perception and in visuo-spatial working memory, respectively. Our findings demonstrated that reading and domain-general neurocognitive functions in a group of children and adolescents with dyslexia change following tDCS and that they are polarity-dependent.

The use of noninvasive brain stimulation techniques to improve reading difficulties in dyslexia: A systematic review

“…The results showed a significant improvement in text reading accuracy for a bilateral montage with left anodal/ right cathodal tDCS (i.e., facilitating the left and inhibiting the right TPC), as well as an increase in errors after left cathodal/right anodal TPC stimulation. This study served as basis for the earlier presented multiple session interventions.Most recently, Lazzaro et al further investigated a tDCS-induced modulation of reading performance, while at the same time assessing other reading-relevant processes, such as motion perception and visuo-spatial working memory(Lazzaro et al, 2021). Left anodal/right cathodal tDCS of the left TPC (as in previous studies) improved text reading accuracy, word recognition and motion perception.…”

Disrupted Spatial Organization of Cued Exogenous Attention Persists Into Adulthood in Developmental Dyslexia

“…Consistent with the hypothesis of a right posterior parietal dysfunction in dyslexia (e.g., Hari et al, 1999 ; Facoetti et al, 2001 ), some studies observed deficient activations in the right TPJ in dyslexics when performing phonological decoding tasks (e.g., Hoeft et al, 2006 ). Moreover, a very recent study ( Lazzaro et al, 2021 ) has shown significant effects of tDCS on temporo-parietal regions either on reading performance as on visuo-spatial skills of dyslexic children and adolescents. Overall, the findings of the present study endorse this hypothesis by showing that the mechanisms of rapid orienting of spatial attention are impaired in adults with DD.…”

Brain stimulation: a therapeutic approach for the treatment of neurological disorders

“…Studies in dyslexic children and adolescents have shown that a treatment with tDCS causes improvement in reading skills and reduction in word reading errors and wordless reading time gap 80–83 . A study in 10 dyslexic children further demonstrated that the application of anodal tDCS improved text accuracy, word recognition speed, motion perception, and attentional focusing 84 . In addition, tDCS stimulation combined with training for reading in children and adolescents with dyslexia produced long‐lasting improvement in reading 85 .…”