EEG hyperscanning in intellectual disability: a scoping review with implications for cognitive stimulation therapy

Electroencephalography (EEG) hyperscanning has emerged as a valuable method for examining social dynamics during group-based activities and may serve as a promising outcome measure in group interventions. Cognitive stimulation therapy (CST) is one such interventions shown to improve cognition and quality of life in people with dementia and has recently been adapted for individuals with intellectual disability (ID). However, the potential for obtaining objective neural markers of CST benefit via EEG and hyperscanning is yet to be explored. This scoping review aims to identify existing evidence and gaps related to the use of EEG within CST research for adults with ID by examining three relevant areas: (1) the use of individual EEG and hyperscanning to evaluate cognitive and social outcomes in CST; (2) the evidence base for individual and group-based CST in people with ID; and (3) the use of EEG to evaluate cognitive and social outcomes for people with ID. Following the PRISMA-ScR guidelines, studies were searched in CINAHL, MEDLINE, PsychInfo, and EMBASE. Our search focused on adult participants with ID and studies that used EEG for the purpose of evaluating cognitive or social outcomes. Currently, there are no studies that use EEG to evaluate CST in adults with ID. Following screening and eligibility assessment, no studies met the inclusion criteria for EEG and CST. Five studies were included for CST and ID, and 14 articles met criteria for EEG and ID. In total, 19 articles were included in the final review. The evidence base suggests that EEG has been successfully used to investigate neural mechanism in ID and Down Syndrome related Alzheimer's disease. Existing CST research in ID remains largely feasibility-focused but some preliminary findings show cognitive benefits, enhanced enjoyment, and social connectedness. Our review shows that there is a large gap when it comes to any objective metrics for CST in general. Given that there is evidence of EEG studies including populations with ID, we propose that this gap can be filled by EEG hyperscanning which offers a non-invasive, objective approach to evaluate cognitive and social outcomes in people with ID in future CST research.