Henry Gustave Molaison was a man who couldn't make memories. Better known to neuroscientists as "HM", the late Molaison suffered from seizures as a young man and struggled to lead a normal life, but things took a dramatic shift after he received a lobotomy in August 1953. Doctors removed large chunks of HM's temporal lobes and most of his hippocampus, on the assumption that these regions were responsible for the patient's neurological problems. The operation did cure HM's seizures, but it left him in a unique case of anterograde amnesia; he could remember his childhood and his personality remained unchanged, but he could not form new memories.

As Steven Shapin writes in a piece for the New Yorker this week, the operation left HM in a constant state of discovery and confusion, but it also gave scientists remarkable new insight into how the brain processes and stores memory.

"The operation could not have been better designed if the intent had been to create a new kind of experimental object that showed where in the brain memory lived," Shapin writes. "Molaison gave scientists a way to map cognitive functions onto brain structures. It became possible to subdivide memory into different types and to locate their cerebral Zip Codes."