Modulation of auditory temporal processing, speech in noise perception, auditory-verbal memory, and reading efficiency by anodal tDCS in children with dyslexia

Cognitive enhancement through technology: A review of transcranial electrical stimulation (TES) interventions in children and adolescents with specific learning disabilities

BACKGROUND

In recent years, the exploration of innovative interventions for addressing problems of children and adolescents with specific learning disabilities (SLD) has garnered significant attention within the realm of neurocognitive research. Transcranial electrical stimulation (TES) has emerged as a promising tool for enhancing cognitive skills in children, offering a non-invasive and safe method that may particularly benefit those with learning difficulties. We aimed to appraise the extent and the quality of studies about impact of TES on cognitive skills including academic skills in children and adolescents with SLD.

METHODS

A literature search was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Articles published between January 2000 and January 2024 were searched in PubMed, Embase, Scopus, Web of Science and Google Scholar. The study eligibility criteria were previously established according to the PICO model. The Physiotherapy Evidence Database (PEDro) scale and Cochrane Collaboration tool (ROB2) were used to assess the methodological quality and the risk of bias of the included studies, respectively.

RESULTS

The initial search yielded 1571 studies among which 30 studies were systematically reviewed. The total number of participants was 224 individuals (intervention: 114; control: 110). Findings showed significant improvements in reading skills such as text reading, high-frequency word reading speed and efficiency and mathematical skills. Conversely, other cognitive skills such as working memory were not improved in people with dyslexia and dyscalculia.

DISCUSSION

TES interventions can positively affect cognitive skills in children and adolescents with SLD; However, due to the small number of studies, medium methodological quality and high risk of bias, caution should be taken when interpreting the results.

Perceptual and cognitive effects of focal tDCS of auditory cortex in tinnitus

OBJECTIVES

Noninvasive brain stimulation continues to grow as an effective, low-risk way of improving the symptoms of brain conditions. Transcranial direct current stimulation (tDCS) is particularly well-tolerated, with benefits including low cost and potential portability. Nevertheless, continued study of perceptual and cognitive side effects is warranted, given the complexity of functional brain organization. This paper describes the results of a brief battery of tablet-based tasks used in a recent pilot study of auditory-cortex tDCS in people with chronic tinnitus.

METHODS

Volunteers with chronic tinnitus (n=20) completed two hearing tasks (pure-tone thresholds, Words In Noise) and two cognitive tasks (Flanker, Dimension Change Card Sort) from the NIH Toolbox. Volunteers were randomized to active or sham 4×1 Ag/AgCl tDCS of auditory cortex, and tasks were completed immediately before and after the first tDCS session, and after the fifth/final tDCS session. Statistics included linear mixed-effects models for change in task performance over time.

RESULTS

Before tDCS, performance on both auditory tasks was highly correlated with clinical audiometry, supporting the external validity of these measures (r2>0.89 for all). Although overall auditory task performance did not change after active or sham tDCS, detection of right-ear Words in Noise stimuli modestly improved after five active tDCS sessions (t(34)=-2.07, p=0.05). On cognitive tasks, reaction times were quicker after sham tDCS, reflecting expected practice effects (e.g., t(88)=3.22, p=0.002 after 5 sessions on Flanker task). However, reaction times did not improve over repeated sessions in the active group, suggesting that tDCS interfered with learning these practice effects.

CONCLUSIONS

Repeated sessions of auditory-cortex tDCS does not appear to adversely affect hearing or cognition, but may modestly improve hearing in noisy environments and interfere with some types of motor learning. Low-burden cognitive/perceptual test batteries could be a powerful way to identify adverse effects and new treatment targets in brain stimulation research.