Behaviorally irrelevant feature matching increases neural and behavioral working memory readout: Support for activity-silent working memory

Abstract

AbstractThe activity-silent framework of working memory (WM) posits that the neural activity during object perception and encoding leaves behind patterned, “activity-silent” neural traces that enable WM maintenance without the need for continuous, memory-specific neural activity. The presence of such traces in the memory network subsequently patterns its responses to external stimulation, which can be used to readout the contents of WM using an impulse perturbation or “pinging” approach. The extent to which the neural impulse response is patterned by the WM network should be modulated by the physical overlap between the initial memory item and the subsequent external perturbation stimulus, with higher overlap increasing WM readout. Here we tested this prediction in a delayed orientation match-to-sample task, by either matching or mismatching task-irrelevant spatial frequencies between memory items and impulse stimuli, and between memory items and probes. Matching frequencies resulted in faster behavioral response times, and increased the WM-specificity of the neural impulse response as measured from the EEG signal. We found no evidence that matching spatial frequencies resulted in globally stronger or different neural responses, but rather in distinct neural activation patterns. The beneficial effects of feature matching in our task support the tenets of the activity-silent framework of WM, and confirm that impulse perturbation interacts directly with the representations that are held in memory.