Figure 7. Distinct activation of different young neurons by different afferent fibre subpopulations.

(a) Synaptically evoked spiking in two simultaneously recorded mature GCs. The stimulation electrode was positioned at different locations Δs along a track parallel to the granule cell layer as indicated. The schematic diagram of the experimental configuration (left) shows the two recorded cells (red and blue) and the stimulation positions (dots in the ML). Δs represents the distance from the stimulation position to the mid-line between the two cells. (b) Synaptically evoked spiking in two simultaneously recorded young GCs 2–3 weeks post mitosis at various stimulation positions in the ML. Please note, that the locations to evoke successful firing in two young neurons do not overlap. (c, d) The firing probability of the two simultaneously recorded mature (c) and young neurons (d) shown in a and b, respectively, was plotted against the location Δs of the stimulation electrode. The data were fitted with a bell-shaped function (see Materials and methods for details). Note the small overlap of the area under the curves generated from the young cells (d). (e) Bar graph showing the normalized overlap of the area under the curve in pairs of mature (n = 8) and young neurons (n = 10, p<0.001, Mann Whitney).