Prioritization in working memory reduces interference via a beta-linked transformation of the not-selected item

We studied the effects of prioritization in a two-step retrocuing task in which participants hold two items in working memory, and the item not cued by the first cue cannot be dropped because it may be prioritized by the second cue. In Experiment 1, using a dense sampling procedure, we observed that recall performance oscillated at 15 Hz in the prioritization task, in comparison to 20 Hz in a matched task employing a neutral cue. Furthermore, the prioritized item was shielded from bias exerted by the uncued item, as well as from items from the previous trial. In Experiment 2, we recorded the EEG while participants performed variants of the two tasks. The prioritization cue uniquely triggered a phase reset at 15 Hz and an increase in oscillatory peaks at this frequency. Burst analysis ruled out bursting as a possible underlying factor. Time-resolved representational similarity analysis (RSA) revealed that the prioritization cue triggered representational transformations that were larger for the uncued item. The shielding effects of prioritization may arise from the transformation of the not-prioritized item into an "unprioritized" state that is implemented and maintained by a mechanism that cycles at 15 Hz.