Self-paced working memory: validation of verbal variations of the n-back paradigm.

Self-paced versions of many paradigms could have utility in probing cognitive systems. To validate several self-paced n-back paradigms, fourteen subjects performed four variations of the working memory task using visually presented letters as stimuli. Several areas in the frontal lobe, the anterior cingulate and a parietal network were consistently activated in the four variations: identity of black letters, location of black letters, color of colored letters and identity of colored letters. Since the n-back task is one of the more popular methods of investigating working memory, we validated the utility of several self-paced versions in normal subjects via quantitative, coordinate-based meta-analyses. The self-paced results agree well with meta-analyses and other published results, giving confidence that a self-paced n-back paradigm is robust in multiple variations. Behavioral results differ from other published reports, perhaps offering insight into true working memory strategy in normal subjects.