Partial canceling of fluctuations in a linear system by inhibitory feedback.
Response of a linear system with impulse response (1st-order low-pass, cutoff frequency ) to Gaussian white noise input with amplitude for three local-input scenarios. A (light gray): No feedback (local input ). B (black): Negative feedback () with strength . The fluctuations of the weighted local input (B) are anticorrelated to the external drive (B). C (dark gray): Feedback in B is replaced by uncorrelated feedforward input with the same auto-statistics as the response in B. The local input is constructed by assigning a random phase to each Fourier component of the response in B. Fluctuations in C and C are uncorrelated. A, B, C: Network sketches. A, B, C: External input . A, B, C: Weighted local input . A, B, C: Responses . D, E: Response auto-correlation functions (D) and power-spectra (E) for the three cases shown in A,B,C (same gray coding as in A,B,C; inset in D: normalized auto-correlations).