Dissociation of spatial and feature-based attention in visual working memory: a TMS study

摘要

Attention can be deployed to representations in visual working memory (VWM), ensuring that only the most relevant information is maintained. We investigated whether the attentional selection of VWM representations can operate on features just as well as on spatial information, and we used transcranial magnetic stimulation (TMS) to test whether these attentional mechanisms can be dissociated based on the site of cortical stimulation. During the retention interval of a VWM task, a so-called retrocue was presented, which was either uninformative or indicated the item that would be tested at the end of the trial. The test item was cued by its location (spatial attention) or by its shape (feature-based attention). During cue presentation, TMS was applied to the supramarginal gyrus (SMG), which has been implicated in spatial attention, or to the lateral occipital cortex (LO), which is involved in representing object shape. We observed improved memory for objects cued by location and shape, confirming that both spatial as well as featural information can be used for selecting representations in VWM. Importantly, stimulation of SMG selectively facilitated spatial attention and stimulation of LO selectively facilitated feature-based attention. These results show that spatial and feature-based attentional mechanisms in VWM recruit distinct cortical regions. The same regions have been shown to be involved in attention to external events, indicating that attention in the mnemonic and in the perceptual domain are similarly implemented at the neural level. In general, these findings extend our understanding of how attentional mechanisms operating on different types of information optimize the use of the highly limited VWM system, allowing for an efficient and flexible updating of its contents.