  Synaptic plasticity, the dynamic tuning of signal transmission strength
between neurons, serves as a fundamental basis for memory and learning in
biological organisms. This adaptive nature of synapses is considered one of the
key features contributing to the superior energy efficiency of the brain. In
this study, we utilize molecular dynamics simulations to demonstrate
synaptic-like plasticity in a subnanoporous 2D membrane. We show that a train
of voltage spikes dynamically modifies the membrane's ionic permeability in a
process involving competitive bicationic transport. This process is shown to be
repeatable after a given resting period. Due to a combination of sub-nm pore
size and the atomic thinness of the membrane, this system exhibits energy
dissipation of 0.1--100 aJ per voltage spike, which is several orders of
magnitude lower than 0.1--10 fJ per spike in the human synapse. We reveal the
underlying physical mechanisms at molecular detail and investigate the local
energetics underlying this apparent synaptic-like behavior.
