Jointly looking to the past and the future in visual working memory

Abstract

Working memory enables us to bridge past sensory information to upcoming future behaviour. Accordingly, by its very nature, working memory is concerned with two components: the past and the future. Yet, in conventional laboratory tasks, these two components are often conflated, such as when sensory information in working memory is encoded and tested at the same location. We developed a task in which we dissociated the past (encoded location) and future (to-be-tested location) attributes of visual contents in working memory. This enabled us to independently track the utilisation of past and future memory attributes through gaze, as observed during mnemonic selection. Our results reveal the joint consideration of past and future locations. This was prevalent even at the single-trial level of individual saccades that were jointly biased to the past and future. This uncovers the rich nature of working memory representations, whereby both past and future memory attributes are retained and can be accessed together when memory contents become relevant for behaviour.

Re-focusing visual working memory during expected and unexpected memory tests

“…In addition to our EEG-alpha marker of spatial orienting in visual working memory, we have recently uncovered and reported how attentional shifts to visual objects in working memory can also be tracked by reliable spatial biases in gaze (see 23,29–33 ; for complementary findings see also 40–45 ), driven predominantly by microsaccades (see: 29,30,46 ). To date, however, we have only ever shown this following retrocues that were 100% reliable.…”

“…Together, our two markers of spatial shifts of attention in visual working memory thus each show a graded modulation by cue reliability, with larger modulations following more reliable cues. While the two markers each had their own characteristic patterns, a direct comparison between the two markers is non-trivial (as they are two distinct dependent variables) and was beyond the scope of the current study (for studies targeting the inter-relation between these two markers, we refer the reader to 30,46 ). Signatures of attentional orienting also reveal attentional re-orienting after the memory test, but only when the test is not certain A unique feature of our task was that the two memory items were always left and right at encoding, while the working-memory test was always central.…”

Tracking how attentional focusing in working memory benefits long-term memory

“…We utilized a velocity-based approach for saccade detection (as in: 41,42,86 ) that was developed building on closely-related velocity-based methods for saccade detection (e.g., 48 ). Because the memory objects in our experiment were always presented horizontally at center-left and center-right positions, our saccade detection targeted the horizontal channel of the eye data.…”

“…Finally, to further characterize the the saccade bias, we computed the saccadic bias as a function of saccade size (as in: 41,42,86 ). For this, we quantified the saccade bias (toward vs. away) iteratively for saccades falling within specific saccade-size bins.…”

Microsaccades track location-based object rehearsal in visual working memory

“…To detect gaze shifts (saccades) we build on an existing velocity-based detection approach that has been successfully employed and validated in prior studies from our lab (de Vries et al, 2023;Liu et al, 2022Liu et al, , 2023. Saccade detection was achieved by calculating the euclidean distance between successive gaze points in the horizontal and vertical planes, smoothing the resulting velocity vector (using the built-in "smoothdata" function in MATLAB, with a 7 ms sliding window), and identifying the onset of a saccade as the instant that the velocity exceeds a predetermined threshold.…”