Q as a function of noise intensity D and period Ts of input signal in FFNs with different connection probabilities. aP = 0.15, identical distribution; bP = 0.15, uniform distribution; cP = 0.15, exponential distribution; dP = 0.3, identical distribution; eP = 0.3, uniform distribution; fP = 0.3, exponential distribution. The input signal is set as A = 0.08