  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.
