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Video abstract for the article 'The defect effects on the signal transport of an excitable soft cable' by Tang-Yu Liu and Cheng-Hung Chang (Tang-Yu Liu and Cheng-Hung Chang 2013 New J. Phys. 15 035018). Read the full article in New Journal of http://iopscience.iop.org/1367-2630/15/3/035018/article. Part of Focus on Soft Mesoscopics Physics for Biology at a Mesoscopic Scale GENERAL SCIENTIFIC SUMMARY Introduction and background. The defect effect is a general problem in physics and material science. Intuitively, a local defect would be expected to suppress the mass and energy flow and to monotonically reduce the conductance or information transfer through a quasi one-dimensional system. This is indeed true for normal non-excitable materials, such as carbon nanotubes, nanowires and DNA double helixes. However, for an excitable cable such as a neuron, the dynamics caused by defects can be highly non-trivial, which is beyond standard neural behaviours and lacks systematic analysis. Main results. By using the Hodgkin--Huxley model, we analyze the complex dynamics generated by locally non-uniform ion channel densities. Such channel density defects could induce several exotic behaviours, in contrast with the normal destructive role of defects in solid-state materials. They may behave as an electric signal generator exhibiting spontaneous or stimulated emissions, as well as trap, reflect, rectify, delay or extinguish propagating signals or be switched to different functions by a signal. Nonlinear analysis and phase diagrams were employed to quantify and classify this complex dynamical system. Wider implications. The results may (i) serve as a simple example illustrating the typical defect dynamics in general excitable cables, (ii) give hints on how to utilize defects to manipulate neuronal signals for biotechnological applications, (iii) quantitatively elucidate disease-related irregular firings at the subcellular level and (iv) enrich our understanding of the contemporary challenging issue of channel density heterogeneity-induced neural behaviours.