Sx-5CSRTT performance during a fixed ITI (fITI) and vITI sessions under simple task (top panels) and dual-task (bottom panels) conditions for NBD and BD. Mean (±SEM) of the percentage of (a, d) accuracy of responding, (b, e) percentage of omissions, and (c, f) premature responses. *p<0.05, **p<0.01 compared with NBD (independent sample t-test or non-parametric Mann–Whitney U-test).