Henry Molaison: How Patient HM Changed What We Know About Memory

Summary

Henry Molaison, known as Patient HM, underwent a brain procedure in 1953 to cure his severe seizures, which inadvertently left him with anterograde amnesia. The surgery, performed by William Scoville, removed parts of his medial temporal lobe, including the hippocampus, revealing the brain's memory centers. Despite his inability to form new memories, Henry retained his intellect and motor skills. His case became pivotal in understanding the distinction between declarative and non-declarative memory systems, with researchers like Brenda Milner and Suzanne Corkin studying his unique condition. The narrative also touches on the ethical considerations of treating human subjects in scientific research.

Takeaways

• 🧠 Henry Molaison underwent a brain surgery in 1953 to cure severe seizures, which resulted in the removal of parts of his medial temporal lobe, including the hippocampus.
• 🔍 The surgery was performed by William Scoville, a lobotomist who noted that lobotomy could relieve seizures in some patients.
• 💡 The procedure successfully reduced Henry's seizures but left him with anterograde amnesia, unable to form new memories while preserving his intellect and other cognitive functions.
• 🧐 Memory researcher Brenda Milner studied Henry extensively, revealing that memory is localized to specific brain structures rather than distributed throughout the brain.
• 📚 Henry's case helped to establish the concept of the medial temporal lobe memory system, which includes the hippocampus and surrounding cortices.
• 🕵️‍♂️ Henry's memory loss was selective; he could recall long-term memories from before his surgery but could not form new ones.
• 🤹‍♂️ Despite his memory issues, Henry was able to learn and retain new motor skills, demonstrating the existence of multiple memory systems in the brain.
• 🔑 The distinction between declarative memory (factual information) and non-declarative memory (skills, habits, emotional memory) was clarified through Henry's case.
• 🧬 Non-declarative memory relies on brain structures like the basal ganglia, amygdala, cerebellum, and neocortex, which were unaffected by Henry's surgery.
• 🏛️ The academic community's relationship with Henry was complex, with some researchers treating him more as a subject than a person, impacting his personal life and legacy.
• 📖 The story of Henry Molaison, known as Patient HM, has been a significant contribution to our understanding of the human brain and memory.

Q & A

What was the reason Henry Molaison underwent a brain surgery in 1953?

Henry Molaison underwent brain surgery in 1953 to cure his severe and uncontrollable seizures, which had begun after a childhood bicycle accident.

Who was the surgeon that performed the experimental procedure on Henry Molaison?

The surgeon who performed the procedure on Henry Molaison was William Scoville, a well-known lobotomist at the time.

What part of Henry's brain was removed during the surgery?

During the surgery, a thumb-sized section of the medial temporal lobe, including the hippocampus, amygdala, and entorrhinal cortex, was removed from both sides of Henry's brain.

What was the immediate effect of the surgery on Henry's seizures?

The surgery alleviated some of Henry's seizures but left him unable to form any new memories.

How did the surgery affect Henry's intellectual abilities?

The surgery did not affect Henry's perception or intellect; in fact, he scored higher on IQ tests following the surgery.

Who was the memory researcher from McGill University that studied Henry Molaison?

Brenda Milner was the memory researcher from McGill University who studied Henry Molaison.

What did Brenda Milner's observations on Henry contribute to our understanding of memory?

Brenda Milner's observations helped to conclude that memory is not distributed throughout the entire brain but is limited to specific structures, now known as the medial temporal lobe memory system.

What type of memory loss did Henry Molaison experience?

Henry Molaison experienced anterograde amnesia, meaning he was unable to create new memories while still being able to recall long-term memories from before the surgery.

How did Henry's ability to acquire new motor skills demonstrate the existence of multiple memory systems?

Henry's ability to learn and retain new complex motor skills, such as mirror drawing, showed that there are multiple memory systems housed in different parts of the brain.

What are the two main types of memory as understood from Henry's case?

The two main types of memory are declarative memory, which is the ability to recall factual information, and non-declarative memory, which includes skill learning, habit learning, and emotional memory.

Why is Henry Molaison referred to as 'Patient HM' in academic literature?

Henry Molaison is referred to as 'Patient HM' in academic literature to maintain his anonymity and protect his identity, despite his significant contributions to the study of memory.

What ethical concerns arose from the treatment and posthumous handling of Henry Molaison?

Ethical concerns include the control over access to Henry by Susanne Corkins, the arrangement of his brain donation, and the perceived lack of empathy shown towards Henry as a person, treating him more as a scientific subject than a human being.