I read Wikipedia claiming 52. I heard that this can be extended to 54. I see there is no limit of having more areas - just better understanding of the neuroblast migration and fibroblast too, probably. How is this newer classification of Brodmann map done?
I am no expert on the topic, but according to an article published on the centenary of his study, it states that the microscopical structure and classification of these areas are in parallel to the evolutionary distinction between old and new cortical subdivisions. So as and when new subdivisions are deduced (based on its function, cytoarchitecture or the structure and organisation of cells) the map can be extended to include them. There was no upper limit to the number of divisions set in any article I read so it would be nice if you could provide some reference to where it says that the extension can be done to 54. If you are interested, you could have a look at the map published by Constantin von Economo in 1925.