Synaptic mechanisms of interference in working memory

Zachary P Kilpatrick

doi:10.1038/s41598-018-25958-9

Abstract

Information from preceding trials of cognitive tasks can bias performance in the current trial, a phenomenon referred to as interference. Subjects performing visual working memory tasks exhibit interference in their responses: the recalled target location is biased in the direction of the target presented on the previous trial. We present modeling work that develops a probabilistic inference model of this history-dependent bias, and links our probabilistic model to computations of a recurrent network wherein short-term facilitation accounts for the observed bias. Network connectivity is reshaped dynamically during each trial, generating predictions from prior trial observations. Applying timescale separation methods, we obtain a low-dimensional description of the trial-to-trial bias based on the history of target locations. Furthermore, we demonstrate task protocols for which our model with facilitation performs better than a model with static connectivity: repetitively presented targets are better retained in working memory than targets drawn from uncorrelated sequences.

Highlights

Information from preceding trials of cognitive tasks can bias performance in the current trial, a phenomenon referred to as interference
We propose short-term facilitation (STF), which acts on the timescale of seconds[25,26], can account for the dynamics of the bias
Both models use information about the target location on the previous trial to bias the response on the current trial

Summary

Introduction

Information from preceding trials of cognitive tasks can bias performance in the current trial, a phenomenon referred to as interference. Subjects performing visual working memory tasks exhibit interference in their responses: the recalled target location is biased in the direction of the target presented on the previous trial. Several authors have identified behavioral biases that cause the previous trial’s visual target to interfere with the subject’s response on the subsequent trial[12,13]. Investigations of interference in visuospatial working memory reveal other effects: Increasing the delay-period of working memory trials increases the bias strength, and responses are biased in the direction of the stimulus from the previous trial[13]. In a recurrent network that sustains persistent activity during a delay-period in the form of an activity bump, facilitated synapses from neurons tuned to the previous target attract the activity bump in the subsequent trial. Our study proposes interference arises as a result of an irrelevant working memory remaining from the previous trial

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