STUDY OF HM
TOPIC 2: COGNITIVE PSYCHOLOGY
2.2.13 CASE STUDY OF BRAIN-DAMAGED PATIENTS
Including Henry Molaison (HM) and the use of qualitative data, exploring the strengths and weaknesses of the case study approach.
ONE CONTEMPORARY STUDY FROM THE FOLLOWING:
2.3.2 Schmolck et al. (2002): Semantic knowledge in patient HM and other patients with bilateral medial and lateral temporal lobe lesions.
IN-DEPTH CASE STUDY OF HENRY MOLAISON (HM): QUALITATIVE DATA AND THE CASE STUDY APPROACH
Henry Molaison's (HM) case is one of the most significant contributions to our understanding of memory. HM underwent brain surgery in 1953 to treat severe epilepsy, during which his medial temporal lobes, including the hippocampus, were removed bilaterally. While the surgery successfully controlled his epilepsy, it left HM with profound anterograde amnesia, unable to form new long-term memories. However, his short-term memory and some procedural memories remained intact. His case has been studied extensively through the case study method, mainly using qualitative data.
SCOVILLE & MILNER (1957): THE CASE STUDY OF H.M.
The case of Henry Gustav Molaison (H.M.) remains one of the most influential studies in cognitive psychology. This research, conducted by William Beecher Scoville and Brenda Milner, revolutionised our understanding of memory by demonstrating the role of the hippocampus in different memory functions.
SIGNIFICANCE OF THE STUDY
Before this research, psychologists believed memory was a single, uniform process occurring throughout the brain. Scoville and Milner’s findings challenged this view, showing that memory comprises distinct functions linked to specific brain regions.
The study exemplifies:
Instrumental case studies: Investigating phenomena that cannot be manipulated in a lab.
Generalisability issues: Highlighting limitations due to the uniqueness of single-case studies.
WHO WAS H.M.?
Henry Molaison developed epilepsy after a head injury at age 7. His seizures worsened throughout his life, leaving brain surgery as his only option. In 1953, at age 27, Scoville performed a bilateral medial temporal lobe resection, removing parts of H.M.'s hippocampus and amygdala to control the seizures.
While the surgery reduced his epilepsy, it caused severe memory impairments:
Retrograde amnesia: Gaps in his memory of the 11 years preceding the surgery.
Anterograde amnesia: An inability to form new long-term memories, leaving him unable to remember events beyond 30 seconds.
Despite these deficits, H.M. retained procedural memory (e.g., learning to play tennis) and could recall childhood memories. H.M. described his experience as:
"Like waking from a dream… every day is alone."
THE EVOLUTION OF H.M.'S CASE STUDIES
Brenda Milner began studying H.M. in the 1950s, publishing her findings in 1957. Milner tested H.M.'s cognitive abilities, distinguishing between short-term and long-term memory deficits. Her tests included tasks like maze navigation and mirror-drawing.
In the 1960s, Milner demonstrated that H.M. could learn new procedural skills despite his amnesia. Later, Suzanne Corkin expanded on this research, using advanced technologies like MRI scans to map H.M.'s brain. H.M. remained a research subject until his death in 2008, after which his brain was meticulously preserved and studied.
THE H.M. CASE STUDIES
AIM
To investigate the nature and extent of H.M.'s memory deficits and their relation to brain structures, particularly the hippocampus.
SAMPLE
H.M. was the primary participant in this case study. Scoville & Milner initially described nine other patients, but H.M. was the only one with "clean" amnesia (memory loss without other mental disorders).
PROCEDURE
Milner’s tests included:
In the 1962 case study, Milner asked H.M. to replicate a five-pointed star by drawing between the lines of a template, but with a twist—he could only see the reflection of the star and his hand in a mirror. This added complexity made the task particularly challenging. Like the maze task, Milner had H.M. repeat the star-drawing task multiple times to observe whether his procedural skills improved, even though he could not remember performing the task before.
Additional experiments were conducted on H.M. to explore the effects of reinforcement and punishment. For instance, researchers investigated whether mild electric shocks could help H.M. retain correct answers. Later, under Suzanne Corkin's supervision, advancements in brain scanning technology were employed to gain deeper insights into H.M.'s condition and the neural mechanisms underlying his memory deficits.
Memory recall tasks: Testing H.M.’s ability to recall events from childhood, adulthood, and after the surgery.
Maze navigation: Tracing routes repeatedly to see if H.M. could learn without remembering the task.
Mirror-drawing: Copying a star shape while only seeing its reflection, testing procedural memory.
Milner conducted maze tests with H.M., where he was asked to trace the correct route through a maze using his finger. She repeated the test multiple times with the same maze to determine whether H.M. could retain the route despite being unable to recall having performed the task previously.
Later studies investigated reinforcement and punishment (e.g., mild electric shocks) and used MRI scans to analyse H.M.’s brain.
RESULTS
H.M. retained clear childhood memories but forgot experiences after ~30 seconds.
He had everyday language skills, an above-average IQ, and consistent personality traits.
Procedural memory remained intact: in the mirror-drawing task, H.M. improved despite forgetting each attempt, starting with 30 errors and dropping to fewer than five by Day 3.
H.M. remembered some general knowledge after the surgery (e.g., the moon landing) but forgot the events.
CONCLUSIONS
The study provided critical insights into the structure of memory:
The hippocampus is vital for transferring short-term to long-term memory.
Procedural and semantic memory rely on different brain regions, remaining intact in H.M. despite his hippocampal damage.
H.M.'s calm demeanour and impaired pain perception may be linked to his damaged amygdala.
EVALUATING H.M.'S CASE STUDIES (AO3)
GENERALISABILITY
H.M.’s case is both unique and representative. His "clean" amnesia provides rare insight into hippocampal function, but his specific surgery and epilepsy history make generalising to other populations difficult.
RELIABILITY
Milner’s use of standardised memory tasks ensures test-retest reliability. However, H.M.'s condition makes replication impossible, as no similar cases have occurred since.
APPLICATIONS
H.M.'s case transformed memory research:
It contributed to models like the Multi Store Model and Tulving’s memory distinctions.
It advanced surgical techniques, ensuring a better understanding of the hippocampus's role in memory.
It influenced neuropsychological approaches to treating memory disorders.
Critics argue that the case has overshadowed the importance of other brain regions, such as the base of the brain (e.g., B.J.’s case of amnesia caused by a snooker cue accident).
VALIDITY
H.M.'s condition provided a "pure" study of amnesia, unaffected by other mental health issues. However, the artificial nature of some tasks (e.g., mirror drawing) raises concerns about ecological validity.
ETHICS
H.M. consented to the surgery without a full understanding of the consequences, as the hippocampus’s role was unknown at the time. Researchers explained the studies to H.M. throughout his life, and he willingly participated.
However, H.M. depended on researchers, and critics argue he could not withhold consent. Given its profound scientific contributions, researchers maintained anonymity during his life and justified their work as a cost-benefit trade-off.
EXEMPLAR 8-MARK ESSAY
Assess how H.M.’s case studies have contributed to our understanding of memory. (8 marks)
Description (AO1):
H.M. underwent surgery in 1953 to control epilepsy, which involved removing his hippocampus. This caused severe anterograde amnesia, preventing him from forming new long-term memories. Brenda Milner’s case studies showed that H.M. retained procedural memory (e.g., improving at mirror drawing) and semantic knowledge despite his episodic memory deficits.
Evaluation (AO3):
H.M.’s case transformed our understanding of memory, revealing its division into different types and brain regions. Milner’s work led to influential models like the Multi Store Model. However, H.M.’s uniqueness limits generalisability and some tasks' artificial nature reduces ecological validity. Despite ethical concerns, the research has had invaluable applications, from surgical techniques to memory models.
Conclusion:
H.M.’s case provides unparalleled insights into memory’s structure, but its uniqueness limits broader applicability. Nevertheless, its contributions to psychology and neuroscience remain foundational.
STRENGTHS OF THE CASE STUDY APPROACH IN HM'S CASE
Rich, Detailed Data The case study of HM provided in-depth insights into the nature of memory, particularly its division into distinct components such as short-term memory, long-term memory, and procedural memory. Researchers like Brenda Milner and Suzanne Corkin conducted detailed assessments, including interviews, memory tests, and observations, which allowed for a comprehensive understanding of his cognitive impairments.
Example: HM could recall procedural tasks, such as learning to trace a star in a mirror, but had no recollection of performing the task, demonstrating that procedural memory relies on different brain structures than declarative memory.
Qualitative Data for Unique Cases HM's unique condition provided an opportunity to collect qualitative data that could not be obtained through experimental methods. His rare brain surgery and the resulting amnesia offered insights into memory functions that are not ethically or practically replicable in controlled studies.
Foundation for Theories HM's case led to groundbreaking discoveries in memory research, such as the understanding that the hippocampus is critical for forming declarative memories but not procedural or implicit ones. These findings have had profound implications for memory models, including the Multi-Store Model and the distinction between explicit and implicit memory.
Real-World Application The qualitative data collected from HM has informed clinical practices, particularly in treating memory-related conditions such as Alzheimer’s disease, traumatic brain injury, and epilepsy. For instance, his case highlighted the importance of careful surgical planning to minimise cognitive side effects.
WEAKNESSES OF THE CASE STUDY APPROACH IN HM'S CASE
Lack of Generalisability Case studies focus on a single individual, making it difficult to generalise findings to the broader population. HM's specific condition, including the extent and location of his brain damage, is unique and may not fully represent other cases of amnesia or brain injury.
Example: While HM demonstrated severe anterograde amnesia, other amnesic patients with less extensive hippocampal damage have shown different memory profiles, indicating variability in-memory processing.
Subjectivity in Data Collection Qualitative data, such as interviews and observations, can be influenced by researcher bias or interpretation. Although researchers like Milner and Corkin employed rigorous methods, subjective interpretations of HM’s behaviour and responses could have influenced conclusions.
Reliance on Retrospective Reports Much of the data collected from HM depended on his ability to report his experiences, which was inherently limited by his memory impairments. For example, HM could not recall events immediately after they occurred, potentially leading to incomplete or inaccurate data.
Ethical Concerns HM participated in decades of research, sometimes without fully understanding or recalling his consent. Although researchers acted within the ethical norms of the time, modern ethical standards emphasise informed consent, raising questions about the prolonged use of HM in studies.
Limited Scope of Quantitative Analysis While qualitative data provided rich insights, the lack of controlled experimental data limits the ability to quantify HM’s impairments and compare them systematically with other cases. The reliance on qualitative methods may miss opportunities for statistical validation.
CONTRIBUTION OF QUALITATIVE DATA IN HM'S CASE
Using qualitative data, such as interviews, direct observation, and narrative descriptions, was crucial in understanding HM's condition. These methods allowed researchers to:
Identify specific deficits (e.g., anterograde amnesia).
Explore his preserved abilities (e.g., procedural memory).
Formulate hypotheses about the role of the hippocampus in memory.
CONTRIBUTION OF QUALITATIVE DATA
Qualitative data played a central role in understanding HM’s condition. It enabled researchers to identify the specific nature of his memory deficits and preserved abilities. For instance, using interviews and observations allowed a detailed exploration of his inability to form new episodic memories while maintaining procedural learning. This nuanced data contributed to key hypotheses about the hippocampus and its function in declarative memory.
However, qualitative data also posed challenges. The subjective nature of interpretation and the inability to quantify some aspects of his condition made it difficult to compare HM’s case systematically with others. This reliance on qualitative data meant some findings lacked the statistical validation of controlled experimental designs.
CONCLUDING REMARKS
The study of Henry Molaison demonstrates the unique value of the case study approach and qualitative data in uncovering complex cognitive phenomena. While the findings from his case were rich and transformative, they were also limited by generalisability, subjectivity, and ethical considerations. Despite these challenges, HM’s case remains a cornerstone of memory research, offering unparalleled insights into the workings of the human brain and laying the foundation for future explorations into memory and cognition.
