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Authors & Affiliations
Deepak Raya, Sridharan Devarajan
Abstract
When walking down a trail, the location and identity of a fleetingly perceived object (e.g., a bird on a branch) can be remembered robustly, even if our gaze shifts away from it. How visual working memory (VWM) remains stable across gaze shifts and, specifically, the type of reference frame in which VWM content is stored, are poorly understood. VWM is typically maintained in the brain hemisphere contralateral to the memorandum [1,2,3,4], indicating a retinotopic (“gaze-centered”) reference frame. Yet, recent work [5] shows that VWM is transferred across hemispheres following a gaze shift, suggesting a spatiotopic (“world-centered”) reference frame.
Here, we asked whether VWM is stored in spatiotopic coordinates invariably or can be reconfigured flexibly based on task context. Participants (n=24) performed a VWM-based orientation discrimination task while also making horizontal eye-movements (in either direction) during the retention period (Fig. 1a). Electroencephalography (EEG) recordings were acquired concurrently. We tested: i) a “spatiotopic” context in which the test probe appeared at the same world-centered location as the memorandum and ii) a “retinotopic” context in which the test probe appeared at the same gaze-centered location.
Inter-hemispheric transfer of VWM – a shift in memorandum decoding from contralateral to ipsilateral electrodes – occurred in more robustly the spatiotopic relative to the retinotopic contexts (p=0.022) (Fig. 1b). In addition, closely mimicking literature [5], inter-hemispheric transfer evoked strong theta (3-6 Hz) and low-beta (12-15 Hz) coherence in the spatiotopic context (Fig. 2a). Finally, VWM precision – the slope of the psychometric curve [6] (Fig. 2b, left) – was higher on trials with a higher transfer magnitude, in the spatiotopic context alone (Fig. 2b, right).
Our findings show that VWM representations can be flexibly reconfigured either spatiotopically or retinotopically, contingent on task demands. More broadly, we uncover neural mechanisms by which gaze shifts interact with VWM in the brain.