Exploring the switching of the focus of attention within working memory: A combined event-related potential and behavioral study.

Working memory enables humans to maintain selected information for cognitive processes and ensures instant access to the memorized contents. Theories suggest that switching the focus of attention between items within working memory realizes the access. This is reflected in object-switching costs in response times when the item for the task processing is to be changed. Another correlate of attentional allocation in working memory is the P3a-component of the human event-related potential. The aim of this study was to demonstrate that switching of attention within working memory is a separable processing step. Participants completed a cued memory-updating task in which they were instructed to update one memory item at a time out of a memory list of four digits by applying a mathematical operation indicated by a target sign. The hypotheses predicted (1) prolonged updating times in switch (different item compared to previous trial) versus repetition trials (same item), (2) an influence of cues (valid/neutral) presented before the mathematical target on switching costs, and (3) that the P3a-component is more pronounced in the cue-target interval in the valid cue condition and more pronounced in the post-target interval in the neutral cue condition. A student's t-test verified the first hypothesis, repeated-measurement analyses of variance demonstrated that hypotheses 2 and 3 should be rejected. Results suggest that switching of attention within working memory could not be separated from further processing steps and retro-cue benefits are not due to a head start of retrieval as well as that switch costs represent internal processes.