Fig 2. Image preprocessing.

(A) The raw, unaligned, kymograph shown in Fig 1a (scale bar is 2 μm, 20 seconds of imaging). (B) The kymograph after Gaussian smoothing, and (C) The Laplacian response image, which we refer to as K, that results from applying the Laplacian of Gaussian filter (with σ = 10 pixels) to our smoothed kymograph. In K, dark regions represent positive values and light regions represent negative values.