Systematic Review and Meta-analysis of STM and WM in Long-Term CI Users

Short-term memory (STM) and working memory (WM) capacity, which are at the centre of information processing, are significant predictors of learning in both children with typical hearing (TH) and hearing loss. We compared the performance of long-term cochlear implant (CI) users with their typical hearing (TH) peers on verbal short-term memory (STM), verbal working memory (WM), visuospatial STM, and visuospatial WM. Through a database search, we identified relevant articles published up to 14 February 2021. Twenty articles met the inclusion criteria for a systematic analysis. Meta-analysis was performed on both verbal STM and WM. Limitation in verbal STM was found to have a large effect size, and limitation in verbal WM was found to have a medium to large effect size in long-term CI users in a WM task. There was no significant difference between long-term CI users and their TH peers in two verbal WM (reading span and visual digit span) tasks. Results revealed that the long-term CI users have more difficulty in storing than processing information. The outcomes of this meta-analysis have clinical and educational implications for CI users. The visual representation of verbal items compensated for the limitation in verbal WM in long-term CI users. The opposite was observed for verbal STM tasks. A significant difference between TH and long-term CI users was observed for the visuospatial STM with a small to medium effect size in individual studies. However, our findings should be interpreted very cautiously in this preliminary systematic review and meta-analysis because of small samples. All interpretations have been made according to current findings. There is a need for more studies about verbal and visuospatial STM and WM in long-term CI users.