The brain that made the greatest contribution to neuroscience and to our understanding of memory has become a gift that keeps on giving. Patient H.M., or Henry Molaison, gave neuroscience a gift few could imagine: a living map of memory itself. After brain surgery in 1953 to treat epilepsy, he could no longer form new memories—but his cooperation turned his life into a decades-long experiment that revealed the hidden architecture of thought.

Surgery and Amnesia

At 27, Molaison underwent removal of parts of his medial temporal lobes, including the hippocampus. His seizures eased, but he could no longer remember new events, and his recall of past experiences became patchy. Researchers observed him for decades, discovering the precise regions of the brain responsible for forming and storing memory.

Memory dissected, literally: Henry Molaison taught us where our past goes when we forget. #neuroscience #memory #neurodope Share on X

The Gift of Science

Molaison’s generosity didn’t end with his cooperation. After his death in 2008, his brain was frozen and sliced into 2401 ultra-thin layers. Each slice was photographed, cataloged, and preserved, allowing scientists to reconstruct a digital 3D model of the brain and virtually revisit the surgery that changed neuroscience forever.

Even in death, Patient H.M. keeps schooling scientists on memory. #brainresearch #memorymapping #neurodope Share on X

A Legacy in Slices

The digital brain model and preserved slices give researchers an unprecedented tool: to trace memory pathways, study epilepsy effects, and test new hypotheses about cognition. Molaison’s brain, meticulously archived, continues to speak, decades later, revealing secrets about how we think, remember, and forget.

Henry Molaison’s brain slices keep whispering the secrets of memory, one virtual cut at a time. #memoryscience #neuroscience #neurodope Share on X

Science on Display

The dissection was streamed live, showing the public the painstaking process. Three days, 2401 slices, and infinite lessons. Molaison’s contribution exemplifies the strange intimacy between patient and science, mortality and discovery.

From life to virtual immortality: Patient H.M.’s brain shows that memory is a map we can explore forever. #brainmapping #neurodope #memoryscience Share on X

When Molaison died of respiratory failure in 2008, he donated his brain to science. That allowed Jacopo Annese at the Brain Observatory in San Diego, California, and his colleagues, to conclusively link his memory problems to specific areas of damaged brain. The dissection was streamed live online.

Molaison is probably the most studied patient in the history of neuroscience, says Annese, and this collection of slices and digital images will provide an unprecedented opportunity for his contribution to neuroscience to continue far beyond his death.