it is an "averaged brain" - brain scans are taken then databased (there is talk of creating a truely national datababnk) and then averaged for size (perimiter and internal modules) also scans for funtions. such as the left hemishpere is "usually" modularised for language. when there is evidence for language utilising the right hemishphere due to liesion (damage) or gentics (autism) it is refered to as atypical