Figure 6.

MF filopodia enhance both combinatorial diversity and redundancy produced by GCL. A, Representative image of an MFR bearing filopodia. B, A reconstruction of MFR in A that illustrates the MFR in green and putative filopodial boutons in red. C, Reconstructions of 70 MFRs from 9 mice that bore filopodia, illustrating morphological diversity. D, Box plots of median and interquartile ranges of distances of filopodial boutons to the MFR and the number of boutons/MFR for pontine fibers, nucleocortical fibers, and both sources (n = 84 MFRs, 9 mice). E, Cumulative distribution plot of nearest neighbors between filopodia bearing and nonfilopodia bearing MFR, showing that filopodia-bearing rosettes are more sparsely positioned (n = 874 boutons, 4 mice, 8 injections). F, Total number of unique combinations of inputs plotted as a function of MFR diversity when 20% MFRs bore between 1 and 5 filopodial boutons, contacting GrCs within 22 μm in the spatially constrained model. Filopodia enhance the total number of all sizes of combinations, such that the total unique quartets outnumber GrCs. G, Percentage increase in MFR combination redundancy seen when filopodia are added to 20% of MFRs (see Materials and Methods).