Revisit once more the sensory storage account of visual working memory

Abstract

Recent work has highlighted the role of early visual areas in visual working memory (VWM) storage and put forward a sensory storage account of VWM. Using a distractor interference paradigm, however, we previolsy showed that the contribution of early visual areas to VWM storage may not be essential. Instead, higher cortical regions such as the posterior parietal cortex may play a more significant role in VWM storage. This is consistent with reviews of other available behavioral, neuroimaging and neurophysiology results. Recently, a number of studies brought forward new evidence regarding this debate. Here I review these new pieces of evidence in detail and show that there is still no strong and definitive evidence supporting an essential role of the early visual areas in VWM storage. Instead, converging evidence suggests that early visual areas may contribute to the decision stage of a VWM task by facilitating target and probe comparison. Aside from further clarifying this debate, it is also important to note that whether or not VWM storage uses a sensory code depends on how it is defined, and that behavioral interactions between VWM and perception tasks do not necessarily support the involvement of sensory regions in VWM storage.

Keywords: attention; early visual areas; fMRI; posterior parietal cortex; visual working memory.

Figure 1.

Trial structures and timings of the studies conducted by Bettencourt and Xu (2016a), Christophel et al. (2018), Lorenc et al. (2018) and Rademaker et al. (2019). The delay period in each study in which VWM decoding was examined is marked by a box with a bold outline.

Figure 2.

To examine the cross-decoding between VWM and perceptual representations in superior IPS, we asked seven participants (six females) to perform a VWM task and a perceptual task (Bettencourt & Xu, 2015). The VWM task adopted the same paradigm we used before (see Betterncourt & Xu, 2016a) but always with an unfilled delay period (i.e., no distractors) and with either a face or a gazebo image as the target instead of oriented gratings. In the perceptual task, participants viewed a sequential presentation of either faces or gazebos and performed a 1-back repetition detection task on the letter string shown at fixation. For within-task decoding, we performed training and testing on data within the same task; and for cross-task decoding, we trained the decoder on the data from the perception task and then tested it on the data from the VWM task. Error bars indicate s.e.m. * p < .05; *** p < .001; n.s., not significant. Stats reported here are corrected for multiple comparisons using the Benjamini-Hochberg method (Benjamini & Hochberg, 1995).