Neural mechanisms underlying the flexible and continuous allocation of visual short-term memory resources.

Abstract

It has long been debated whether objects stored in visual short-term memory (VSTM) are maintained as discrete items or as a continuous resource. While much recent behavioral evidence has supported a continuous resource model, neurological support has lagged behind. In the current study, participants underwent fMRI while they completed a delayed-estimation task with probabilistic cues directing flexible allocation of resources across four items. Behavioural evidence replicated the finding that participants could flexibly allocate memory resources between items, contrary to discrete models of VSTM. Neural activity demonstrated that participants were maintaining multiple items on trials in which one item had a high probability of being cued, consistent with continuous resource models. Whole brain analysis revealed frontal areas play a role in controlling the flexible allocation of memory resources in response to probabilistic cues. The results suggest a mechanism of frontal top-down attentional control over the flexible allocation of memory resources.