Spike-Timing Dependent Plasticity

CAUSAL ORDER DETERMINES SYNAPTIC FATE · LEARNING WINDOW FROM BI & POO (1998)

Δt = tpost − tpre+25 ms→ LTP
PREPOSTPRESYNAPSEPOST00Δt = +25 mstime (ms) →-75-50-250255075-0.50.00.51.0Δt = t_post − t_pre (ms)ΔW (normalized)POST before PRE → LTDPRE before POST → LTPτ− ≈ 34msτ+ ≈ 17msΔW = +0.226LTDWINDOWLTPSYNAPTIC WEIGHTDEPRESSEDBASELINEPOTENTIATED

STDP adds temporal precision to Hebb's rule: not just "neurons that fire together, wire together," but the order matters. Pre before post (Δt > 0) implements a causal detection rule, strengthening synapses that predictively drive the postsynaptic cell. Post before pre reverses this, weakening the synapse. Drag the slider, fire repeatedly, and watch the weight accumulate or decay.

References: Bi & Poo (1998) · Markram et al. (1997) · Dan & Poo (2004) · Song, Miller & Abbott (2000)