Dissociable neural mechanisms underlie currently-relevant, future-relevant, and discarded working memory representations

Mark D'Esposito,Annelinde R E Vandenbroucke,Derek E Nee,Elizabeth S Lorenc,Floris P De Lange

doi:10.1038/s41598-020-67634-x

Abstract

In daily life, we use visual working memory (WM) to guide our actions. While attending to currently-relevant information, we must simultaneously maintain future-relevant information, and discard information that is no longer relevant. However, the neural mechanisms by which unattended, but future-relevant, information is maintained in working memory, and future-irrelevant information is discarded, are not well understood. Here, we investigated representations of these different information types, using functional magnetic resonance imaging in combination with multivoxel pattern analysis and computational modeling based on inverted encoding model simulations. We found that currently-relevant WM information in the focus of attention was maintained through representations in visual, parietal and posterior frontal brain regions,whereas deliberate forgetting led to suppression of the discarded representations in early visual cortex. In contrast, future-relevant information was neither inhibited nor actively maintained in these areas. These findings suggest that different neural mechanisms underlie the WM representation of currently- and future-relevant information, as compared to information that is discarded from WM.

Highlights

In daily life, we use visual working memory (WM) to guide our actions
The results of the current study are congruent with previous findings demonstrating that early visual cortex maintains a representation of cued WM items[1,2,3,4]
Both bilateral intraparietal sulcus (IPS) and the right pre- and postcentral sulci exhibited above-chance decoding of orientations maintained in WM

Summary

Introduction

We use visual working memory (WM) to guide our actions. While attending to currentlyrelevant information, we must simultaneously maintain future-relevant information, and discard information that is no longer relevant. These studies have lent support to the ‘sensory recruitment’ hypothesis[1,5,6], which proposes that the same brain regions that process information during perception are involved in the maintenance of task-relevant mnemonic representations Consistent with this hypothesis, stimulus-specific activity has been observed in early visual cortex during the delay period in visual WM tasks[1,2,3,4]. When the system is activated by a non-specific visual stimulus or a single pulse of transcranial magnetic stimulation (TMS) during a memory delay, category information about an un-cued WM item can be transiently decoded with electroencephalography (EEG)[14,15,16] This implies that this information may be represented in perceptual regions in a silent code that can only be decoded when it is activated, either through a shift in internal attention or an external perturbation like TMS. Such a transformation was not observed for future-irrelevant (discarded) information

Methods

Results

Conclusion