The Oscillatory Basis of Working Memory Function and Dysfunction in Epilepsy

Abstract

Working memory (WM) deficits are pervasive co-morbidities of epilepsy. Although the pathophysiological mechanisms underpinning these impairments remain elusive, it is thought that WM depends on oscillatory interactions within and between nodes of large-scale functional networks. These include the hippocampus and default mode network as well as the prefrontal cortex and frontoparietal central executive network. Here, we review the functional roles of neural oscillations in subserving WM and the putative mechanisms by which epilepsy disrupts normative activity, leading to aberrant oscillatory signatures. We highlight the particular role of interictal epileptic activity, including interictal epileptiform discharges and high frequency oscillations (HFOs) in WM deficits. We also discuss the translational opportunities presented by greater understanding of the oscillatory basis of WM function and dysfunction in epilepsy, including potential targets for neuromodulation.

Keywords: epilepsy; high frequency oscillations; hippocampus; neural networks; working memory.

FIGURE 1

Schematic representation of the multi-component model of WM. The central executive supervises the two domain-specific subsystems, the phonological loop and the visuospatial sketchpad. Within these sub-systems, the phonological store and visual cache serve as limited-capacity stores and the articulatory control process and inner scribe rehearse information. The episodic buffer integrates information across domains and enables interactions between WM and long-term memory.

FIGURE 2

Anatomical mapping of the multi-component model of WM and hubs of WM-related networks.

FIGURE 3

Overview of specialized oscillatory functions in WM.