Spike-rate dependent plasticity, one of the conventional learning protocols in neuroscience, has been achieved in semiconducting polymer/electrolyte cells. The frequency threshold theta(m) of spike-rate dependent plasticity is sliding in requirement of stability. In this work, various prior signal inputs are applied to poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]/polyethylene oxide-Nd3+ cells to explore their effects on theta(m). The study find that a prior inhibitory input, i.e., a weak stimulation, moves theta(m) in the low frequency direction, while a prior excitatory input, i.e., an intensive stimulation, moves theta(m) in the high frequency direction. Our results demonstrate the adaptivity of ionic kinetics in macromolecules systems for signal handling and learning. We suggest that a sliding threshold is due to the variable active ionic domains depending on stimulation strength and history. (C) 2016 Wiley Periodicals, Inc.