We calculate the instantaneous firing rate of a stochastic integrate-and-fire neuron driven by an arbitrary time-dependent signal up to second order in the signal amplitude. For cosine signals. this weakly nonlinear theory reveals: (i) a frequency-dependent change of the time-averaged firing rate reminiscent of frequency locking in deterministic oscillators; (ii) higher harmonics in t... https://www.spidertattooz.com/Messerschmitt-Me262A-1A-Fighter-Aircraft-LT-Walter-Hagenah-III-Jagdeschwader-7-Larz-Airfield-Germany-1945-German-Luft/