Short-Term Memory to Long-Term Memory Transition in a Nanoscale Memristor

TLDR

Memory is essential for learning and decision‑making, yet unlike permanent semiconductor memory, human memory is not eternal; forgetfulness frees storage for important information and facilitates adaptation, with only significant memories transitioning from short‑term to long‑term through repeated stimulation. In this study, we show experimentally that the retention loss in a nanoscale memristor device bears striking resemblance to memory loss in biological systems. By repeatedly pulsing the memristor with voltage stimuli, we observe a transition analogous to biological memory, with improved retention and structural changes, and find that both the stimulus shape and the interval between pulses critically influence the effect, which can be explained by impurity redistribution following equations that also govern biological memories. The study demonstrates that a nanoscale memristor’s retention loss mirrors biological memory loss, and that repeated voltage stimulation can induce a transition to a long‑term‑like state with enhanced retention, driven by impurity redistribution governed by equations common to biological memory.

Abstract

"Memory" is an essential building block in learning and decision-making in biological systems. Unlike modern semiconductor memory devices, needless to say, human memory is by no means eternal. Yet, forgetfulness is not always a disadvantage since it releases memory storage for more important or more frequently accessed pieces of information and is thought to be necessary for individuals to adapt to new environments. Eventually, only memories that are of significance are transformed from short-term memory into long-term memory through repeated stimulation. In this study, we show experimentally that the retention loss in a nanoscale memristor device bears striking resemblance to memory loss in biological systems. By stimulating the memristor with repeated voltage pulses, we observe an effect analogous to memory transition in biological systems with much improved retention time accompanied by additional structural changes in the memristor. We verify that not only the shape or the total number of stimuli is influential, but also the time interval between stimulation pulses (i.e., the stimulation rate) plays a crucial role in determining the effectiveness of the transition. The memory enhancement and transition of the memristor device was explained from the microscopic picture of impurity redistribution and can be qualitatively described by the same equations governing biological memories.