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

Giulia Lazzaro,Andrea Battisti,Sara Bertoni,Sandro Franceschini,Cristiana Varuzza,Stefano Vicari,Simone Gori,Luca Ronconi,Andrea Facoetti,Floriana Costanzo,Deny Menghini

doi:10.3390/brainsci11020263

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.

Highlights

IntroductionReplicated structural/functional neuroimaging studies have demonstrated specific neural signatures for dyslexia
These results demonstrate that motion sensitivity was higher in Left Anodal/Right Cathodal (LA/RC) in comparison to Right Anodal/Left Cathodal (RA/LC) Transcranial direct current stimulation (tDCS) stimulation and that the shape of the respective curves differed significantly, which implies that in LA/RC, the stimuli were processed significantly different than in RA/LC tDCS stimulation
In the attentional zooming task, the results showed a significant effect of Eccentricities (F(2,18) = 6.77, p < 0.006, ηp2 = 0.43), a Cue × Eccentricities interaction (F(2,18) = 5.58, p < 0.013, ηp2 = 0.38), and, importantly, a Stimulation condition × Cue × Soa interaction (F(1,9) = 11.29, p < 0.008, ηp2 = 0.55)

Summary

Introduction

Replicated structural/functional neuroimaging studies have demonstrated specific neural signatures for dyslexia. Neuroimaging findings have converged on atypical activation in a distributed left-hemisphere network in children and adults with dyslexia [4]. Evidence showed that children with dyslexia exhibit hypoactivation in the bilateral temporo-parietal regions, compared to chronological age-matched groups, and to reading-matched children [7], excluding, the contribution of reading experience to these hypoactivations. The reduced activation of the bilateral temporo-parietal regions—including the left inferior parietal cortex close to the intraparietal sulcus [5]—could indicate a possible role of the dorsal attentional network dysfunction [8] in dyslexia and highlights the contribution of domain-general neurocognitive functions in reading acquisition [9]

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