Editorial Volume 10, Issue 8 pp 1793—1794

Figure 1. Distribution of dividing stem cells may reflect pre-existing bias in their spacing, and aging tends to randomize the distribution. Neural stem cells - grey dots; dividing stem cells at timepoints t1, t2, and t3 – pink, red, and carmine dots. Stem cells deplete with age, a process driven by the activation of their asymmetric divisions, with eventual production of neurons. At each timepoint a subset of stem cells is dividing and some of these are found in adjacent positions which can be perceived as symmetric divisions. However, the rate of division and geometry of cell positioning within each subset is random (symbolized by dice) and the bias of the spacing of the dividing population of stem cells reflects a similar bias in the spacing of all cells. Gradual disappearance of pairs of closely positioned cells evens out the original spacing bias.