An adaptive spike-timing-dependent plasticity rule

We examine the conditions under which spike-timing-dependent plasticity (STDP) normalizes post-synaptic firing rates. Our simulations show that the rate normalization property of STDP is fragile and small changes in the LTD/LTP ratio or pre-synaptic input rates can lead to high firing rates. We propose an adaptive scheme to dynamically control the LTP/LTD ratio. The biophysics of synapses lead us to suggest a control mechanism using action potential-induced calcium influx, a known mediator of synaptic plasticity. This adaptive STDP rule is shown to stabilize the post-synaptic firing rates under a variety of perturbations.