This may mean that H.M.'s amnesia had more to do with the entorhinal cortex being removed, than with the parts of the hippocampus being removed, Annese said, although more study is needed to know for sure. As this region connects the hippocampus to other brain regions, the surgery may have nearly isolated the hippocampus from the rest of the brain. Īlmost all connections from the hippocampus to the cortex go through a part of the temporal lobe called the entorhinal cortex, which Annese found had been removed from H.M.'s brain. The new findings shed light on what happened to H.M., but likely won't revolutionize what researchers know about memory, and are in fact in line with modern views of hippocampal function, Annese said. "The most beautiful finding I think was the fact that we realized … that Scoville missed the posterior hippocampus," Annese said. The posterior part of the hippocampus deals with memory, and the brain slices show this part wasn't removed, and in fact, was undamaged at the cellular level, the researchers said. In the new study, Annese and his colleagues measured the exact length of H.M.'s hippocampus, and found the spared portion was even larger than what brain scans had shown. But after the advent of neuroimaging, researchers scanned H.M.'s brain in 1992 and found that a portion of the hippocampus had been spared. Until the 1990s, the researchers had only sketches drawn by the surgeon, Dr.
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