Postmortem examination of patient H.M.'s brain based on histological sectioning and digital 3D reconstruction.

Modern scientific knowledge of how memory functions are organized in the human brain originated from the case of Henry G. Molaison (H.M.), an epileptic patient whose amnesia ensued unexpectedly following a bilateral surgical ablation of medial temporal lobe structures, including the hippocampus. The neuroanatomical extent of the 1953 operation could not be assessed definitively during H.M.'s life. Here we describe the results of a procedure designed to reconstruct a microscopic anatomical model of the whole brain and conduct detailed 3D measurements in the medial temporal lobe region. This approach, combined with cellular-level imaging of stained histological slices, demonstrates a significant amount of residual hippocampal tissue with distinctive cytoarchitecture. Our study also reveals diffuse pathology in the deep white matter and a small, circumscribed lesion in the left orbitofrontal cortex. The findings constitute new evidence that may help elucidate the consequences of H.M.'s operation in the context of the brain's overall pathology.

Quantitative examination of the bottlenose dolphin cerebellum.

Neuroanatomical research into the brain of the bottlenose dolphin (Tursiops truncatus) has revealed striking similarities with the human brain in terms of size and complexity. However, the dolphin brain also contains unique allometric relationships. When compared to the human brain, the dolphin cerebellum is noticeably larger. Upon closer examination, the lobule composition of the cerebellum is distinct between the two species. In this study, we used magnetic resonance imaging to analyze cerebellar anatomy in the bottlenose dolphin and measure the volume of the separate cerebellar lobules in the bottlenose dolphin and human. Lobule identification was assisted by three-dimensional modeling. We find that lobules VI, VIIb, VIII, and IX are the largest lobules of the bottlenose dolphin cerebellum, while the anterior lobe (I-V), crus I, crus II, and the flocculonodular lobe are smaller. Different lobule sizes may have functional implications. Auditory-associated lobules VIIb, VIII, IX are likely large in the bottlenose dolphin due to echolocation abilities. Our study provides quantitative information on cerebellar anatomy that substantiates previous reports based on gross observation and subjective analysis. This study is part of a continuing effort toward providing explicit descriptions of cetacean neuroanatomy to support the interpretation of behavioral studies on cetacean cognition.