Fig. 6.

Territory refinement by CF and PF innervation in PCs. In the territory overlap phase (P9–P15), a winner CF (red) translocates to PC dendrites, weaker CFs (pink) remain on the soma, and newly differentiated PF synapses (blue) are added on to the growing tips of dendritic trees. All of these events fuel synaptic competitions among homologous and heterologous inputs, but their territories of innervation do not remain segregated. In the territory segregation phase (P15 onward), PF synapses are eliminated from overlapping dendritic portions, leading to the segregation of the CF and PF territories. Moreover, redundant CF synapses remaining on PC somata are eliminated, establishing CF monoinnervation. The mGluR1 signaling pathway promotes both the elimination of CF synapses from the soma (the late phase of CF synapse elimination, P12–P17) and the elimination of PF synapses from proximal dendrites. As a result, redundant innervations by homologous and heterologous inputs are refined into input-selective wiring in PCs (i.e., CF monoinnervation and segregated territories of CF and PF innervation).