Patient H.M. and the Discovery of Memory Systems (1957)
1953-2008What Happened
Henry Molaison had his hippocampi surgically removed to treat severe epilepsy. Afterward, he could not form new memories of events but could still learn new motor skills. Brenda Milner's studies of him over 50 years demonstrated that the brain contains multiple memory systems.
Outcome
Established that the hippocampus is essential for forming new episodic memories but not for procedural learning.
Created the conceptual foundation for distinguishing memory types, leading directly to Tulving's 1972 theory.
Why It's Relevant Today
The 2026 study uses imaging to examine the same brain regions H.M. lost, but reaches a different conclusion: that episodic and semantic memory share the same neural networks.
