Featural and spatial interference with functionally active and passive items in working memory

We hypothesised that functionally active and passive states in working memory might be related to different neural mechanisms. Memoranda in active states might be maintained by persistent neural firing, whereas memoranda in passive states might be maintained through short-term synaptic plasticity. We reasoned that this might make these items differentially susceptible to interference during maintenance, and that passive items in particular might be more robust. To test this hypothesis, we gave our participants a working memory task in which one item was prioritised (active) by always probing it first, while the other item was deprioritised (passive) by always probing it second. In three experiments, we presented an interfering task during memory maintenance, in which the stimuli matched either the feature dimension of the memory items (colour or orientation), their spatial location, or both. We found that both active and passive memory items were affected by interference, to a similar extent, with overall performance being closely matched. However, we observed a qualitative difference in the nature of their representations. Specifically, featural interference seemed to produce reduced precision for active items, whereas it resulted in higher guess rates for passive items. The existence of this qualitative difference suggests that functionally active and passive working memory states may indeed map onto different neural mechanisms, even though on average they seem to be equally robust to interference. ### Competing Interest Statement The authors have declared no competing interest.