We mentioned spike timing-dependent plasticity (STDP) in Section 33.2 already. Experimental evidence for STDP was presented in [68]: The connection from cell A to cell B was shown to be strengthened when A fired just before B (Hebbian learning), and weakened when B fired just before A (anti-Hebbian learning). To model STDP at a synapse, we make the maximum conductance \(\overline{g}_{\mathrm{syn}}\) associated with the synapse (see eq. (20.8)) time-dependent. In analogy with Sections 39.1 and 39.2, we first describe a model in which the value of \(\overline{g}_{\mathrm{syn}}\) jumps discontinuously, and then turn it into a differential equations model in which the change is rapid but continuous.