part of medulla layer M3 medulla layer medulla sublayer M3B 2015-11-10T14:00:27Z Proximal sublayer of the medulla layer M3, proximal to layer M3A. It is defined by the extent of the arborization of Dm12 and Dm20 neurons. FBbt:00111268 VFB:FBbt_00111268 fly_anatomy.ontology In the literature there are two methods for describing spatial location of neurons in the visual system: distal-proximal (e.g. Fischbach and Dittrich, 1989), and medial-lateral (e.g. Ito et al., 2014), both meaning outer and inner, and refer to the distance of a structure along the visual pathway relative to the center of the brain. Currently we will adopt the classical 'distal-proximal'.