Combined multi-session transcranial alternating current stimulation (tACS) and language skills training improves individual gamma band activity and literacy skills in developmental dyslexia

Effects of transcranial electrical stimulation on academic and cognitive skills in individuals with specific learning disabilities: A systematic review

There has been a rising interest in utilizing transcranial electrical stimulation (TES) techniques to induce neuroplasticity and modulate cognition in children and adults. Despite the escalating interest in non-pharmacological interventions in people with specific learning disabilities (SLD), there is a noticeable absence of a thorough and up-to-date review that consolidates studies of TES in individuals with SLD.A systematic literature search, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, was conducted across PubMed, Scopus, Web of Science, Google Scholar, and Embase databases, covering the period from 2000 to September 2024. Study eligibility criteria were pre-established using the Population, Intervention, Comparison, and Outcome (PICO) model. The grade of recommendation (GOR) for each learning disability was determined based on the level of evidence (LOE). Out of 1571 initial references, the screening resulted in inclusion of nineteen studies (17 dyslexia, 2 dyscalculia). The total number of participants in the included studies was 470, of which 249 were female (52.97 %) and 221 were male (47.03 %). The mean age of participants ranged from 9.5 to 33 years. Fifteen studies employed tDCS, one study used tACS and tRNS, and one utilized tRNS exclusively. TES interventions, especially tDCS, enhanced phonological awareness, improved reading accuracy, and reduced reading time in individuals with dyslexia. In those with dyscalculia, TES improved mathematical performance but did not demonstrate significant effects on cognitive skills. Findings suggest TES interventions, particularly tDCS, are beneficial for improving cognitive skills and reading performance in individuals with dyslexia.

Examining tolerability, safety, and blinding in 1032 transcranial electrical stimulation sessions for children and adolescents with neuropsychiatric and neurodevelopmental disorders

The present study first extensively evaluated the tolerability, safety, and blinding of transcranial direct current stimulation (tDCS) and transcranial random noise stimulation (tRNS) in paediatric clinical populations, composed of 92 children and adolescents (54 females, age range: 8-17 years), involving 1032 sessions across neuropsychiatric (i.e., anorexia nervosa) and neurodevelopmental (i.e., attention deficit and hyperactivity disorder, developmental dyscalculia) conditions. It compared adverse events (AEs) occurrence between active and sham transcranial electrical stimulation (tES) conditions (i.e., 528 active vs. 504 sham sessions) as well as tDCS and tRNS (i.e., 772 tDCS sessions vs. 260 tRNS sessions), while considering demographic and emotional-behavioural factors. Results showed tES safety with no "moderate" or "severe" AEs reported; about 77% of sessions were AE-free, supporting tES use in these populations. Itching was the most common symptom, and active sessions were found to be more likely to induce AEs compared to sham sessions. Notably, tRNS had a higher AE likelihood than tDCS, possibly due to experimental differences. In the current study, demographic and emotional-behavioural variables did not significantly affect AEs. Blinding procedures were moderately effective, with about half of participants correctly identifying their condition. As indicated in prior studies, tRNS seems to better preserve blinding integrity. In conclusion, this study provides comprehensive insights into tES tolerability and safety in paediatric clinical populations, emphasizing the need for further AEs exploration in tES and blinding procedure refinement in future research.

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.

Individualized EEG-Based Neurofeedback Targeting Auditory Steady-State Responses: A Proof-of-Concept Study

Gamma-band (> 30 Hz) brain oscillatory activity is linked with sensory and cognitive processes and exhibits abnormalities in neuropsychiatric disorders. Therefore, neuromodulation techniques targeting gamma activity are being developed. One promising approach is neurofeedback (NFB) which is based on the alteration of brain responses via online feedback. However, the existing gamma-based NFB systems lack individualized approach. In the present work, we developed and tested an individualized EEG-NFB system. 46 healthy volunteers participated in three sessions on separate days. Before NFB training, individual gamma frequency (IGF) was estimated using chirp-modulated auditory stimulation (30-60 Hz). Participants were subjected to IGF-increase (if IGF was ≤ 45 Hz) or IGF-decrease conditions (if IGF was > 45 Hz). Gamma-band responses were targeted during NFB training, in which participants received auditory steady-state stimulation at frequency slightly above or below IGF and were instructed to try to increase their response while receiving real-time visual feedback. Each time a pre-defined response goal was reached, stimulation frequency was either increased or decreased. After training, IGF was reassessed. Experimental group participants were divided into equal groups based on the median success rate during NFB training. The results showed that high-responders had a significantly higher IGF modulation compared to control group, while low-responders did not differ from controls. No differences in IGF modulation were found between sessions and between NFB repetitions in all participant groups. The initial evaluation of the proposed EEG-NFB system showed potential to modulate IGF. Future studies could investigate longer-lasting electrophysiological and behavioural effects of the application of ASSR/IGF-based NFB system in clinical populations.