Synaptic Facilitation: A Key Biological Mechanism for Resource Allocation in Computational Models of Working Memory

Abstract

Working memory (WM) is a crucial cognitive function required to maintain and manipulate information that is no longer present through the senses. Two key features of WM are its limited capacity and the emergence of serial order effects. This study investigates how synaptic facilitation and diverse display dynamics influence the encoding and retention of multiple items in WM. A biophysically inspired attractor model of WM, endowed with synaptic facilitation, is considered in this study. The investigation delves into the behaviour of the model under both sequential and simultaneous display protocols. Synaptic facilitation plays a crucial role in establishing the response of the WM system by regulating resource allocation during the encoding stage. It boosts WM capacity and is a key mechanism in the emergence of serial order effects. The synaptic facilitation time constant (τF\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ au _F$$\\end{document}) is critical in modulating these effects, and its heterogeneity in the prefrontal cortex (PFC) may contribute to the combination of primacy and recency effects observed experimentally. Additionally, we demonstrate that the WM capacity exhibited by the network is heavily influenced by factors such as the stimuli nature, and their display duration. Although the network connectivity determines the WM capacity by regulating the excitation-inhibition balance, the display protocol modulates its effective limit. Our findings shed light on how different stimulation protocol dynamics affect WM, underscoring the importance of synaptic facilitation and experimental protocol design in modulating WM capacity.