(d) Peak to peak distance in auto-correlation plots of de-trended NGN2::mScarlet-I spatial profile in motorneuron (MN) and interneuron (IN) domains as a measure of spatial period in NGN2 expression along dorsal-ventral axis of spinal cord; Grey data points represent mean peak to peak distance in a single slice, n=33, left and right ventricle analysed separately in 4 experiments; black line shows overall mean, error bars show SD; 2-tailed Mann-Whitney test with exact p-value *** p=0.0003. 