A subthreshold signal is undetectable alone. Adding the right amount of noise enables the leaky integrate-and-fire neuron to fire in sync with the signal — noise helps!
Leaky integrate-and-fire: τ dV/dt = −V + I_signal + η(t). Fires when V reaches threshold (1.0), resets to 0. The signal alone is subthreshold. Stochastic resonance: SNR peaks at optimal noise — neither too quiet nor too loud.