A midline crossing complex of 4 synaptic neuropil domains of the adult brain: the ellipsoid body, the fan-shaped body, the paired noduli, and the protocerebral bridge. It is closely associated with another paired synaptic neuropil domain, the lateral complex. It lies in the middle of the brain between the pedunculi of the mushroom bodies and is bounded ventrally by the esophagus, dorsally by the pars intercerebralis and laterally by the antenno-glomerular tracts. [ http://flybrain.neurobio.arizona.edu/Flybrain/html/terms/terms.html ]