Fig 7. All αRGC types share a distinctive spike shape.

A: The spike waveforms of seven ganglion cells, each averaged over many hundreds of spikes. These are representatives of the four αRGC types and three other identified types marked in transgenic lines: J-RGCs (J [31]), upward-coding On-Off DS cells (Hb9 [32]), and W3-RGCs (W3 [33]). All waveforms are aligned on the point with maximum time derivative. B: Waveform analysis of spikes from 50 RGCs of the types introduced in panel A. We computed the time derivative of each waveform, then subjected this set to a principal components analysis, and plotted the coefficients along the first two components (which accounted for 67% of the variance). Each point is one RGC’s waveform. Dotted line separates the αRGCs from all other RGCs, with just one exception. Corners of the plot are marked with the spike waveforms (width 2 ms) corresponding to those points in principal components space. C: Spike width—defined as the time between points of minimum and maximum slope of the action potential—for cells of the different types. Bars indicate Mean ± SEM for each cell type (n = 16, 12, 8, 18, 8, 8, 3 left to right). Two outliers (marked with open symbols in panels B and C) were excluded from this spike width analysis.