How similar can different species of primate be?
Do the New World monkey DM and V3 have clear-cut Old World monkey homologues and, if so, do they look exactly the same? These are not rhetorical questions, particularly if one assumes, as proposed above, that the formation and refinement of any given topographic map in development may be shaped by the configuration of adjacent maps. In this situation, it would be quite possible to have two distinct areas, originating from different evolutionary events yet in the same position relative to V2, sharing a similar general topographic organization. The argument for homology becomes stronger, however, if specific functional, connectional and neurochemical parallels can be traced between species, as it would be unlikely that all of these would have originated in parallel purely by chance. As outlined in more detail elsewhere (Rosa & Tweedale 2001), we feel that there is a strong case for homology between DM and the macaque’s sixth visual area (V6), as recently redefined by Galletti et al. (199
