# 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).