This paper presents a rate coded synaptic plasticity rule that has temporal characteristics of spike-timing dependent plasticity: Activity-variation-timing dependent plasticity (AVTDP). In AVTDP, the synaptic plasticity depends on the timings when the neuronal activities change as the spike timings are important in spike-timing dependent plasticity (STDP). The proposed equation has a simple form derived from a plain physical meaning. Detailed plasticity mechanisms can be interpreted through a graphical method. A series of simulations are conducted to show that AVTDP has the timing dependent characteristics of STDP. (C) 2008 Elsevier B.V. All rights reserved.