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

Abstract

Noninvasive brain stimulation (NIBS) allows to actively and noninvasively modulate brain function. Aside from inhibiting specific processes, NIBS may also enhance cognitive functions, which might be used for the prevention and intervention of learning disabilities such as dyslexia. However, despite the growing interest in modulating learning abilities, a comprehensive, up-to-date review synthesizing NIBS studies with dyslexics is missing. Here, we fill this gap and elucidate the potential of NIBS as treatment option in dyslexia. The findings of the 15 included studies suggest that repeated sessions of reading training combined with different NIBS protocols may induce long-lasting improvements of reading performance in child and adult dyslexics, opening promising avenues for future research. In particular, the "classical" reading areas seem to be most successfully modulated through NIBS, and facilitatory protocols can improve various reading-related subprocesses. Moreover, we emphasize the need to further explore the potential to modulate auditory cortex function as a preintervention and intervention approach for affected children, for example, to avoid the development of auditory and phonological difficulties at the core of dyslexia. Finally, we outline how future studies may increase our understanding of the neurobiological basis of NIBS-induced improvements in dyslexia.

Adaptive plasticity in the healthy reading network investigated through combined neurostimulation and neuroimaging

“…) (see a discussion on the role of the left mid to posterior IFC for pseudoword processing inTurker & Hartwigsen, 2021b). No effects were observed for word processing, supporting our hypothesis that effective stimulation of the left TPC primarily influences pseudoword processing.…”

“…Specifically, we used a spherical 5-mm “searchlight” across the whole brain, and at each searchlight location, we trained a machine learning classifier to decode between effective and sham TMS across participants, separately for words and pseudowords. We found above-chance between-subject decoding in the left posterior IFC selectively for pseudowords ( Figure 5 ) (see a discussion on the role of the left mid to posterior IFC for pseudoword processing in Turker & Hartwigsen, 2021b). No effects were observed for word processing, supporting our hypothesis that effective stimulation of the left TPC primarily influences pseudoword processing.…”

“…Understanding the causal engagement and functional contribution of brain areas to reading, however, is vital to improve our understanding of the healthy reading network. Additionally, it can help uncover and alleviate potential deficits encountered by individuals with dyslexia (see Turker & Hartwigsen, 2021b). Existing NIBS studies with typical readers provide first evidence for causal roles of reading-related regions to different reading subprocesses (see summary in Turker & Hartwigsen, 2021a).…”

“…Likewise, NIBS studies with atypical readers support the causal role of the left TPC to reading, but neglect underlying neural changes and mechanisms (see review by Turker & Hartwigsen, 2021b). Behaviorally, several single- or multiple-session studies with individuals with dyslexia found NIBS-induced improvements in reading performance in low frequency word, pseudoword and text reading after facilitation of the left TPC, or simultaneous inhibition of the right TPC and facilitation of the left TPC (e.g., Costanzo et al, 2016, 2019; Lazzaro et al, 2020, 2021).…”

A systematic review of randomized controlled trials on efficacy and safety of transcranial direct current stimulation in major neurodevelopmental disorders: ADHD, autism, and dyslexia

“…In the last couple of years, however, tDCS has been increasingly used in children and adolescents [5][6][7][8] . In child psychiatric disorders, tDCS has been mostly applied in neurodevelopmental disorders specifically attention-deficit hyperactivity disorder (ADHD) [9][10][11] , autism spectrum disorder (ASD) 12,13 , and developmental dyslexia 5,14 .…”