Surface-Related Features Figure 8. Robustness to noise. A square stimulus that has been corrupted with high amplitude Gaussian noise was used as model input (A). Initial complex cells responses are strongly influenced by the noise pattern (B). Recurrent feedforward-feedback processing significantly reduce activity of noise-induced responses of V1 bipole cells (C) and end-stop cells (D) (illustrated are responses after 0, 1, and 3 cycles of feedback). At the same time, surface contours and corners are enhanced over time. doi:10.1371/journal.pone.0005909.g008 PLoS ONE | www.plosone.org 10 June 2009 | Volume 4 | Issue 6 | e5909