Mechanistic description of spontaneous loss of memory persistent activity based on neuronal synaptic strength

TL;DR

This paper proposes a passive, synaptic strength-based mechanism for the spontaneous loss of persistent neural activity in working memory, supported by analytical models, simulations, and rat experiments.

Contribution

It introduces a novel passive memory-loss mechanism based on ionic-current plateau dynamics, complementing existing active inhibition theories.

Findings

Passive memory loss can result from ionic-current long-term plateau dynamics.

Memory decay can occur due to neuronal noise even above criticality.

Experimental rat data supports the proposed passive loss mechanism.

Abstract

Persistent neural activity associated with working memory (WM) lasts for a limited time duration. Current theories suggest that its termination is \textit{actively} obtained via inhibitory currents, and there is currently no theory regarding the possibility of a \textit{passive} memory-loss mechanism that terminates memory persistent activity. Here, we develop an analytical-framework, based on synaptic strength, and show via simulations and fitting to wet-lab experiments, that passive memory-loss might be a result of an ionic-current long-term plateau, i.e., very slow reduction of memory followed by abrupt loss. We describe analytically the plateau, when the memory state is just below criticality. These results, including the plateau, are supported by experiments performed on rats. Moreover, we show that even just above criticality, forgetfulness can occur due to neuronal noise with ionic-current fluctuations, yielding a plateau, representing memory with very slow decay, and eventually a fast memory decay. Our results could have implications for developing new medications, targeted against memory impairments, through modifying neuronal noise.