Microsaccade directions track spatial oculomotor-based rehearsal of non-spatial object features in visual working memory

Poster Presentation 43.450: Monday, May 22, 2023, 8:30 am – 12:30 pm, Pavilion
Session: Visual Working Memory: Space, features, objects

Eelke de Vries1 (), Freek van Ede1; 1Vrije Universiteit Amsterdam

Besides controlling eye movements, the brain's oculomotor system has also been linked to the control of covert spatial attention and the rehearsal of spatial information in working memory. Here we investigate whether the oculomotor system is even involved in maintaining object-specific features (colour and orientation) in visual working memory, when the location of the memoranda is never asked about. To address this, we tracked the ‘incidental use’ of space for mnemonic rehearsal via directional biases in microsaccades while participants maintained two objects in memory that were encoded on opposite points on an imaginary circle. By varying the stimulus configuration (e.g. horizontal, diagonal, and vertical) at encoding, we were able to count the number of microsaccades whose direction were more aligned with the configurational axes of the memory content, as opposed to the orthogonal axes. Experiment 1 revealed that microsaccades continued to be biased toward the axis of the memory content several seconds into the memory delay. In Experiment 2, we confirmed that this spatial bias in microsaccades was specific to memory demands, ruling out lingering effects from passive (passive-viewing condition) and even attentive (perceptual-judgement condition) encoding of the same visual objects in the same configurations. Thus, by studying microsaccade directions, we reveal an oculomotor-based rehearsal of relevant colour and orientation memory features through their associated (but task-irrelevant) spatial locations.