macroscopic views of the brain. Macroscopic appearance of the brain of the PMG monkey Mk-PM (A, C, E) and of a normal monkey Mk-IU (B, D, F) in lateral (A and B), dorsal (C and D) and ventral (E and F) views. Comparison of panels A and C with B and D shows a clear excessive number of small gyri in Mk-PM, and a loss of the normal topography of the brain, such as the disappearance of the normally well defined arcuate (AS), central (CS) or principal (PS) sulci. Nevertheless, the topographical organization of the ventral part of the PMG brain (E) is closer to that of the normal brain (F), as the superior temporal (STS), the anterior middle temporal (AMTS) or the rhinal sulci (RHS) are clearly identifiable. The extent of the cortical malformation in Mk-PM was projected over the healthy brain of Mk-IU (dashed line).