LTP-only curves for a small number of pairings under the triplet protocol at 5 Hz.

(A) Data reproduced from [19], fit with a Gaussian function (lease squares fit). (B) LTP ‘fatigue’ produces an LTP-only curve for 25 pairings under the triplet protocol. Fatigue of the processes initiating LTP was simulated with an LTP-dependent LTP threshold , where was given an initial value equal to the LTD threshold , to which it decayed with a time constant of 1 s. For all positive values of , was incremented by . All other parameters are identical to the simulations above. refers to the change in synaptic strength relative to initial strength ( defined as in Figure 4).