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

Functionally active and passive states in working memory have been 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, in particular that passively maintained items 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 two experiments, on half the trials, we presented an interfering task during memory maintenance, in which the stimuli matched either the feature dimension of the memory items (colour or orientation), or their spatial location. Whether the interfering task appeared on a given trial was unpredictable. In a third experiment where participants were given prior knowledge of the interference condition, and finally in a fourth experiment we used a reward-based prioritisation cue. Across experiments, we found that both active and passive memory items were affected by interference to a similar extent, with overall performance being closely matched in all experiments. We further investigated precision and probability of target response parameters from the standard mixture model, which also showed no differences between states. We conclude that active and passive items, although potentially stored in different neuronal states, do not show differential susceptibility to interference. Public significance statementThe ability to briefly remember information is critical to human cognition. Our so-called working memory is nevertheless rather limited, able to hold only a few items at any one time, and prone to forgetting when we are briefly distracted. Yet, there is reason to believe that not all information in working memory is equally vulnerable. Items that are more passively stored, because they will only be required after some time, might be more resilient to interference. Items that are stored actively, for more immediate recall, might be more easily disrupted. Here, we investigated the effect of an interference task on the retention of both active and passive items in working memory. Our results showed that active and passive items are equally affected by interference, suggesting that resilience in working memory does not depend on the functional state of the items therein.