Working Memory Load Increases Saccadic Eye Movements During Recall

Working memory has been shown to rely on theta oscillations for item representations, and the successful recall of items depends greatly on theta’s phase during both encoding and recall. At the same time, it has been observed that saccadic eye movements during visual exploration trigger theta phase-resets, raising the question of whether the neuronal substrates of mnemonic processing rely on motor-evoked responses. To quantify the relationship between eye-movements and working memory load, we tested human subjects performing an n-back Sternberg auditory task in combination with a colour-based catch detection task. We observed a task-specific interference in performance and an increase in microsaccades when both tasks were carried out simultaneously. Saccade rate increased concurrently with working memory load in the Sternberg task’s pre-response stage, reflecting its hypothesised role in memory recall. Our results suggest an interplay between eye movement activity and hippocampal theta during working memory retrieval.