11. Henry Molaison
Henry Molaison, widely known as H.M., became a pivotal figure in neuroscience after undergoing a radical brain surgery in the 1950s to treat his severe epilepsy. The procedure, which involved removing parts of his medial temporal lobes, resulted in profound amnesia, providing invaluable insights into the nature of memory. Researchers studied H.M. extensively, discovering that he could not form new memories while retaining memories from before the surgery. His case transformed our understanding of the brain’s memory systems, illustrating the critical role of specific brain regions in memory formation, and highlighting the ethical complexities of studying individuals with significant cognitive impairments.