Spike-timing-dependent plasticity window (in paired stimulation)

Spike-timing-dependent plasticity (STDP) makes the sign and magnitude of a synaptic change depend on the relative timing of pre- and postsynaptic spikes on a millisecond scale: pre-before-post within roughly tens of milliseconds tends to potentiate, the reverse tends to depress, and outside the window little happens. For plasticity-driven BCIs this timing rule is the design constraint — it sets how precisely a triggered stimulus, an FES pulse, or a paired TMS pulse must follow the decoded neural event to push the synapse in the desired direction rather than the wrong one.

Honesty: the clean, antisymmetric STDP curve from reduced preparations is an idealization. In vivo the effective timing rule depends on neuron type, dendritic location, neuromodulatory state, and network activity, and windows measured non-invasively (for example via TMS-evoked responses) are broader and noisier. This is a central reason paired protocols show high inter-subject variability, and why fixed latencies often underperform state-informed ones.