protocerebral embryonic fiber tract founder cluster P5m fiber tract founder cluster VFB:FBbt_00001616 optic lobe pioneer neuron The P5m fiber tract founder cluster is located in the posterior-ventral region of the protocerebrum, adjacent to the optic lobes. Along with founder clusters P4l and P5l, fibers developing from the P5m fiber tract founder cluster pioneer a lateral component of the protocerebral connective. fly_anatomy.ontology See Nassif et al. (1998) for a schematic view of founder cluster location. Nassif et al. (1998) claim that double immunolabelling with Mab22C10 and Fas2 reveals that the P5m fiber tract founder cluster correspond to the 'optic lobe pioneers'. FBbt:00001616