Learning rules for two different time scales.

For short-time scale, instantaneous change of postsynaptic [Ca2+]i is α and its average over a long time is β. The difference (α−β) integrated over a short time (∫(α−β)dt) indicates whether the CF activity has increased (>0), decreased (<0) or remained the same ( = 0). For long-time scale, α and β are the instantaneous CF signal and its average over a long time, respectively. The terms increment or decrement of excitability are used for long-time scale plastic changes to discriminate these from the well known LTP, LTD phenomena, which primarily refer to the changes in AMPAR pathways.