Preprint: How workload and availability of spatial reference shape eye movement coupling in visuospatial working memory

Abstract

The eyes are active during memory recall and visual mental imagery. However, the current understanding of the qualities, and factors governing these internally coupled eye movements, particularly in unrestricted gaze conditions, remains limited. To address this knowledge gap, we conducted a study with 50 participants to investigate the factors contributing to internal coupling in imagined movements including workload, the availability of visual information, and the direction of imagined movement. We designed a visuospatial working memory task in which participants mentally shifted a black patch in a matrix based on auditory direction cues (up, down, left, right). We varied workload by adjusting matrix size, manipulated availability of visual information by presenting either a blank screen (requiring participants to rely solely on their mental representation of the matrix) or relevant visual information in the form of an empty matrix, and contrasted active task performance to two control conditions involving only active or passive listening. We found that eye movements consistently aligned with the imagined movement of the patch in the matrix and, importantly, this coupling effect was not merely the result of auditory or semantic processing of the direction cues. Intriguingly, while workload influenced pupil diameter, perceived demand, and performance, it had no observable impact on internal coupling. Notably, the availability of visual information, in the form of an empty matrix vs. a blank screen, strengthened the coupling of eye movements. This enhancement manifested through increased frequency, better precision, and reduced vulnerability to noise and horizontal bias in coupled saccades. In summary, our results suggest that eye movements naturally align with imagined movements during visuospatial working memory tasks. This coupling is more efficient when supported by relevant visual information and likely occurs intrinsically, and not just as a strategy to alleviate workload.