What does research in cognitive neuroscience tell us about working memory?Brain mechanisms of proactive interference in working memory
Section snippets
Brain mechanisms of proactive interference in working memory revealed by the recent-probes task
One experimental paradigm has dominated brain studies of the resolution of proactive interference in working memory. We shall call this the “Recent-Probes” task. The paradigm is due originally to the work of Monsell (1978) and is schematized in Fig. 1. The task is based on the item-recognition task of Sternberg (1966). Participants are given a series of trials in which they are presented a target-set of items to commit to memory (e.g. letters), and they store these items for a retention
Content-specificity versus content-generality
Before turning to accounts of the function of left IFG, let us examine whether the activations in this task are specific to the content of the material (e.g. verbal) or are content-general. The results on this issue are mixed. Mecklinger et al. (2003) compared activations in the recent-negatives task using letters as stimuli versus abstract objects. Each target-set included just two memoranda, but otherwise the procedure for the experiment was largely the same as for other implementations of
Individual differences in the recent-probes task
One of the advantages we cite above for the focus on the Recent-Probes task is that the interference effect it causes is apparently unknown to participants and so cannot come under strategic control (Bunge et al., 2001). However, it is possible to alter the task so that strategic control is possible, and in that case individual differences in interference-resolution emerge. Part of the work on this issue comes from Braver et al. (in press). They varied the probability of recent-negatives in
Other proactive interference effects
Of course, the Recent-Probes task is not the only way of tapping into processes of proactive interference-resolution in working memory. Although the behavioral literature includes many other tasks (e.g. Wickens et al., 1963), there have not been investigations of most of these tasks using the tools of cognitive neuroscience. An exception is tasks that engage directed-forgetting operations. In such tasks, a subject is provided some material to hold in memory, after which a cue is presented
Mechanisms of proactive interference resolution
Let us begin our discussion of mechanisms by summarizing some facts that have been documented about the Recent-Probes task.
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Recent-negative probes yield longer response times and often worse accuracy than non-recent negative probes (Monsell 1978, Jonides et al 1998, Postle et al 2004, Badre and Wagner in press, Mecklinger et al 2003).
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Recent-positive probes often, but not always, yield shorter response times and better accuracy than non-recent positive probes (Badre and Wagner, in press, but
Acknowledgments
Preparation of this manuscript was supported by grant MH60655 from NIMH and grant AG18286, both to the University of Michigan.
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