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.

Outlines

00:00

🧠 The Story of Patient HM and His Groundbreaking Surgery

In 1953, Henry Molaison, suffering from severe seizures since a childhood bicycle accident, underwent a radical brain surgery performed by Dr. William Scoville. Scoville removed significant portions of Henry's medial temporal lobes, including the hippocampus, amygdala, and entorhinal cortex, in an attempt to control his seizures. While the procedure partially succeeded in reducing the seizures, it also left Henry with profound anterograde amnesia, unable to form new memories but retaining his intellectual abilities and long-term memories from before the surgery. This case would later revolutionize our understanding of memory, highlighting the critical role of the medial temporal lobe.

05:04

🔬 The Research Legacy of Henry Molaison

Two years post-surgery, Henry Molaison became a pivotal figure in memory research, extensively studied by Brenda Milner and later by her student, Suzanne Corkin. Milner's early work with Henry revealed that memory is not uniformly distributed across the brain but localized to specific structures in the medial temporal lobe. Henry’s unique condition allowed researchers to discover the distinct nature of declarative and non-declarative memory systems. Despite his inability to form new declarative memories, Henry could still learn and retain new motor skills, pointing to the involvement of different brain regions in skill learning and memory retention.

Keywords

💡Henry Molaison

Henry Molaison, known as Patient HM in medical literature, is a central figure in the video. He underwent a lobotomy in 1953 to alleviate severe seizures, which resulted in a unique case study for understanding memory. His case is pivotal to the video's theme as it provides insight into the effects of brain surgery on memory formation and the discovery of specific brain regions responsible for memory.

💡Lobotomy

Lobotomy is a surgical procedure that involves the removal of part of the brain's frontal lobes. In the context of the video, Henry Molaison's lobotomy was performed by William Scoville to treat his uncontrollable seizures. The procedure inadvertently led to the discovery of memory's localization in the brain, making 'lobotomy' a key term in understanding the historical approach to psychiatric treatment and its unintended consequences on memory.

💡Seizures

Seizures are sudden, uncontrolled electrical disturbances in the brain that can cause changes in behavior, movements, feelings, and consciousness. In the video, Henry's seizures began after a childhood accident and worsened to the point where they affected his ability to lead a normal life, leading to his participation in the experimental procedure. Seizures are a critical element of the narrative, as they are the reason for the lobotomy and subsequent memory issues.

💡Medial Temporal Lobe

The medial temporal lobe is a region of the brain involved in memory consolidation. In the script, it is mentioned that the majority of this area, including the hippocampus, amygdala, and entorrhinal cortex, was removed during Henry's surgery. This removal is directly related to the video's theme as it resulted in Henry's inability to form new memories, highlighting the importance of this brain region in memory processes.

💡Hippocampus

The hippocampus is a part of the brain crucial for learning and memory. In the video, its removal during Henry's surgery led to his anterograde amnesia, the inability to form new memories. The hippocampus is a key concept in the video as it exemplifies the specific brain structures responsible for memory formation.

💡Anterograde Amnesia

Anterograde amnesia refers to the inability to create new memories after a certain event, while retaining old memories. Henry's case of anterograde amnesia is central to the video's exploration of memory, as it demonstrates the impact of the medial temporal lobe's damage on memory formation without affecting pre-existing long-term memories.

💡Memory Researcher

Memory researchers, such as Brenda Milner and Suzanne Corkin mentioned in the video, are scientists who study the cognitive process of memory. Their work with Henry Molaison has been instrumental in advancing our understanding of memory systems in the brain. The role of memory researchers is integral to the video's theme, as they are the ones who conducted the studies that led to the discovery of different memory systems.

💡Declarative Memory

Declarative memory is the type of memory that involves the conscious recollection of facts and events. The video explains that Henry was unable to form new declarative memories after his surgery, but could recall old ones. This concept is essential to the video's narrative as it distinguishes between the types of memory affected by Henry's condition.

💡Non-Declarative Memory

Non-declarative memory encompasses skills, habits, and emotional memories that are not consciously recalled but are expressed through behavior. The video mentions that Henry could still acquire new motor skills, indicating that non-declarative memory was not affected by his surgery. This term is key to understanding the different memory systems and their localization in the brain.

💡Motor Skills

Motor skills refer to the abilities required to perform deliberate actions with muscles, often involving complex movements. In the script, it is noted that Henry could learn and retain new motor skills like mirror drawing despite his memory impairment. Motor skills are an example used in the video to illustrate the separation of memory systems and their impact on different cognitive functions.

💡Ethical Considerations

Ethical considerations pertain to moral principles that guide actions and decisions, especially in scientific research. The video raises ethical issues regarding Henry's treatment and the control over his life and posthumous brain by researchers. This concept is crucial as it adds a layer of reflection on the responsibilities of scientists and the rights of research subjects.

Highlights

In 1953, Henry Molaison underwent a brain surgery to cure his severe seizures, which led to the discovery of the brain's role in memory formation.

The surgery removed the medial temporal lobe, including the hippocampus, amygdala, and entorrhinal cortex, which resulted in Henry's inability to form new memories.

Despite memory loss, Henry's perception, intellect, language, and motor skills remained unaffected post-surgery.

Henry's case, known as Patient HM, revolutionized the understanding of memory, showing it is localized to specific brain structures.

Brenda Milner's research on Henry revealed that memory is not uniformly distributed throughout the brain but is confined to certain areas.

Henry demonstrated that long-term memories formed before the surgery were intact, indicating a distinction between short-term and long-term memory storage.

Henry's ability to learn new motor skills post-surgery showed the existence of multiple memory systems in the brain.

Memory was categorized into declarative and non-declarative types, with non-declarative memory being linked to structures like the basal ganglia and cerebellum.

Henry's case study highlighted the importance of the medial temporal lobe in creating new memories and the process of memory consolidation.

The preservation of Henry's non-declarative memory after surgery underscored the different neural pathways for various types of memory.

Susanne Corkin continued Brenda Milner's research, further exploring the complexities of Henry's memory and its implications for neuroscience.

The ethical considerations surrounding Henry's case raised questions about the treatment of research subjects and the balance between scientific discovery and personal autonomy.

The controversy over Henry's brain donation and the actions of his conservator and researchers reflect the ongoing debate about ownership and exploitation in scientific research.

Henry's story emphasizes the human side of scientific research and the need to recognize the individual behind the research subject.

The video concludes with a reflection on the legacy of Henry Molaison and the ethical implications of his treatment by the scientific community.

Transcripts

In 1953 a desperate young man agreed to undergo an experimental procedure to

remove a part of his brain in an attempt to cure his seizures Henry Molaison had

begun experiencing seizures as a child following a bicycle accident where he

cracked his skull. At 27 years old his seizures were so severe and

uncontrollable that he was unable to lead a normal life. His surgeon William

Scoville was a well-known lobotomist at the time. He had spent his career

performing lobotomy on psychotic patients and noted that in some of those

patients the lobotomy had the unintended consequence of relieving their seizures.

And so on September 1st 1953 William Scoville removed a thumb-sized section

from both sides of Henry's brain. The majority of the medial temporal lobe was

removed including the hippocampus, amygdala and entorrhinal cortex. The

surgery did alleviate some of Henry's seizures but they also left him unable to

form any new memories, eventually becoming known in the medical literature

as patient HM. Our understanding of memory at the time was rudimentary.

Memory was thought to be distributed throughout the entire brain and tied to

other brain functions such as perception and intellect. But the surgery didn't

affect Henry's perception nor did it dim his intellect, in fact he scored

higher on IQ tests following the surgery. Similarly his language and motor

skills were entirely preserved. It seemed the only thing he had lost was the

ability to form new memories. Two years later in 1955 Henry Molaison was visited

by a memory researcher from McGill University Brenda Milner, who then spent

the next three decades of her career testing and studying Henry's brain -

eventually passing him on to her former student Susanne Corkins.

Though Henry was studied extensively by both Brenda Milner and Suzanne Corkins,

it was Brenda Milner's early observations that taught us most of what

we know about memory. Milner found Henry to be the ideal study subject. He was

highly intelligent well-mannered and could sit through hours and hours of

testing without ever getting bored or complaining, always eager to cooperate. It

was in those early years that we were able to conclude that memory far from

being distributed throughout the entire brain was limited to specific brain

structures, namely the hippocampus and adjacent perirhinal, entorhinal and

parahippocampal cortices; together they are now referred to as the medial

temporal lobe memory system. But Henry's memory loss was an anterograde amnesia

meaning that he was unable to create any new memories while still

being able to recall long-term memories from before the surgery. This is because

while the medial temporal lobe is responsible for creating new memories,

once these memories have been consolidated over time becoming

long-term memories they are then moved to be stored outside the medial temporal

lobe in other parts of the brain. While Henry was able to recall personal events

from his childhood with remarkable clarity and able to recognize the faces

of famous people who were in the news before his surgery, Brenda Milner found

herself having to introduce herself for the very first time every single time

she met him. Milner observed that despite Henry's inability to create any new

memories or remember things he was still able to acquire new motor skills. He was

able to learn new complex skills such as mirror drawing and was able to retain

those skills. This was the earliest demonstration that there existed

multiple memory systems that were housed in different parts of the brain.

Eventually we came to understand memory as being either declarative (the ability

to recall factual information) or non declarative (an umbrella term that

describes skill learning, habit learning and emotional memory - things like walking,

cycling and nail-biting). We now know that non-declarative memory

depends on the basal ganglia, amygdala, cerebellum and neocortex. These

structures were all preserved during Henry's brain surgery in 1953 thus

allowing him to acquire new skills and habits. You probably noticed that

throughout this video I referred to Henry as simply Henry or as Henry

Molaison despite him being known in most of the academic literature as

Patient HM. There are several reasons why I insisted on this. Henry was able to

provide scientists with tremendous insight on the inner workings of the

human brain. Throughout his life scientists like Brenda Milner and

Susanne Corkins built their careers on the back of Henry's mind, but despite the

great debt owed to him Susanne Corkins effectively became Henry's gatekeeper

controlling who was allowed and denied access to him. Eventually she arranged

for a distant third cousin, Thomas Mooney, to become Henry's conservator in 1992.

Soon afterwards, Mooney signed a brain donation form donating Henry's brain to

Susanne Corkins and her team. When Henry died on a cold winter afternoon in 2008

Corkins arranged to have his brain removed from his skull. She claimed

ownership over his brain, his family pictures and all of his belongings. When

she saw his brain through the glass after it had been removed

she later wrote in her diary that she felt absolutely nothing at all except,

"ecstatic." It's clear that to Corkins Henry was not a real person; he was

merely a new discovery, a scientific paper to be published -- Patient HM; an object to

be owned and something to build your career on. Perhaps she forgot the

desperate young man who trusted his life in the hands of an overly enthusiastic

lobotomist, who looked in a mirror many years later

surprised to see his own elderly eyes "I'm not a boy," he'd remark bewildered.

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