part of overlaps Homo sapiens cerebral subcortex midbrain telencephalon aggregate regional part of brain collection of basal ganglia it is necessary to introduce two classes, one representing an individual basal ganglion, another representing the aggregate structure, in order to have consistent classification amongst AOs (e.g. in MA the aygdala is part of the BG, in FMA and BTO it is a subclass). Apart from achieving this consistency, the value of having two distinct classes is questionable, since the BG-plural is trivially the collection of all BGs-singular. it would be better for all AOs to decide on one single way of doing this. Do not merge until this is done.