Visual-spatial working memory in ADHD: new evidence for a storage rather than a processing deficit

The ability to voluntarily control eye movements is part of the "executive function" domain, which includes working memory and is impaired in neuro-developmental disorders such as ADHD. The present study aimed to investigate two types of "executive" saccades - anti-saccades (AS) and memory-guided saccades (MGS) - as well as their relationships in samples of children and adolescents with ADHD and neurotypical controls. To that end, anti-saccades and memory-guided saccades were recorded in n = 65 participants with ADHD (age 9.2-17.1 years) and n = 74 neurotypical controls (aged 9.1-17.3 years) as part of a larger ocular-motor test battery, using the EyeLink 1000 + eye tracker (SR-Research). Results reveal less correct MGS with lower spatial accuracy as well as a trend for less correct AS with normal spatial accuracy in participants with ADHD, compared to neurotypical controls. Furthermore, the spatial accuracies of AS and MGS were significantly correlated in the control (r=.35) and ADHD (r=.26) groups, corresponding to medium effect sizes (eta2: control: 0.12, ADHD: 0.07). These findings suggest that the storage of spatial information in working memory, as required in the MGS task, is impaired in ADHD, while the processing of this information, as required in the AS task, remains largely intact. The correlations between the two task parameters in both groups confirm that storage and processing are related abilities in working memory and that this relationship is basically intact in ADHD.