A neurofilament moving through a gap in the axonal neurofilament array. Axon of a cortical neuron expressing GFP-NFM, visualized by epifluorescence microscopy. The axons exhibit discontinuities in the axonal neurofilament array, which we call gaps. Filaments that move into the gaps can be tracked by time-lapse imaging to analyze the kinetics of movement. These images are excerpted from the movie named Additional file 3 in the Supplementary Data. Proximal is left and distal is right. Scale bar = 10 μm.