Retinotopic Spatial Working Memory Representations Are Not Affected by Task-irrelevant Visual Stimuli.

Abstract

Visual working memory (WM) enables the maintenance and manipulation of information no longer accessible in the world. Previous research has identified spatial WM representations in sustained activation patterns in visual, parietal, and frontal cortex, while MEG/EEG studies have additionally supported a role for "activity-silent" mechanisms revealed by transient reactivation or amplification of an existing representation by a task-irrelevant "ping" stimulus. In natural vision, the delay period between encoding information into WM and its use to guide behavior is rarely "empty," as is the case in many laboratory experiments. Instead, eye movements, movement of the individual, and events in the environment result in visual inputs that may overwrite or impair the fidelity of WM representations, especially in early sensory cortices. Here, we evaluated the extent to which a brief, irrelevant interrupting visual stimulus presented during a spatial WM delay period impaired behavioral performance and retinotopic WM representation fidelity assayed using an inverted encoding model. On each trial, participants (both sexes) viewed two target dots and were immediately postcued to remember the precise spatial position of one dot. On 50% of trials, a brief interrupter stimulus appeared. While we observed strong transient univariate visual responses to the interrupter stimulus, we saw no change in reconstructed neural WM representations due to this interruption, nor a change in behavioral performance on a continuous recall task. This suggests that spatial WM representations can be robust to interference from incoming task-irrelevant visual information, perhaps related to their role in guiding movements.