Maintaining information online in discrete time; rethinking working memory processes.

Linguistic operations occur with verbal information maintained online for a discrete time. It is posited that online maintenance of information is accomplished by verbal working memory (WM), a system that is: (a) independent from the linguistic operations carried out with the information (specialized), and (b) consists of a holding place where information is held in a phonological code (phonological loop) and a rehearsal mechanism that refreshes the phonological loop. This model does not account for the serial position effects associated with information maintenance and additional models are needed to explain the latter effects, which leaves us with a disjointed understanding of online maintenance of information. In this study, 36 middle-aged, healthy subjects (33 males and 3 females) were required to maintain linguistic information (letters) online. The letters called upon different cognitive operations (orthographic; orthographic and phonetic; or orthographic, phonetic and semantic). It was found that online maintenance capacity depends on the cognitive operations associated with the letters and on their serial position. Additionally, the cognitive operation effect on online maintenance was modulated by the serial position. These data favor a model for WM consisting of a simple holding place where verbal information maintenance depends on what the information is used for. We will discuss an integrated model for online information maintenance that accounts for the serial position effects.