Localisation of function
HM Milner and Eugene Pauley
Definitions of key terms:
Localization of function: The theory that specific areas of the brain are responsible for specific cognitive processes and behaviors.
Declarative memory: Conscious memory of facts and events that can be explicitly recalled.
Procedural memory: Unconscious memory of skills and habits, often learned through repetition.
Hippocampus: A region of the medial temporal lobe involved in forming new declarative memories.
Basal ganglia: A group of subcortical structures involved in procedural memory and habit formation.
Context: Within the biological approach, localization of function is used to understand how damage to specific brain regions produces predictable patterns of cognitive deficits, particularly in memory.
Outline: This essay will evaluate localization of function using the case studies of Henry Molaison (HM) and Eugene Pauly (EP), showing how hippocampal damage affects declarative memory while leaving procedural memory relatively intact.
T – Theory
Localization of function proposes that cognitive processes are functionally specialized within specific brain regions. For memory, the hippocampus is critical for forming new declarative memories, whereas procedural memory is mainly supported by the basal ganglia. Damage to these areas should therefore result in selective impairments of the functions they control.
E – Evidence
Henry Molaison (HM)
HM underwent bilateral removal of the hippocampus and surrounding medial temporal lobe tissue to treat severe epilepsy. Following surgery, HM suffered anterograde amnesia, unable to form new declarative memories, although his pre-surgery memories remained intact. Despite this, HM could still learn procedural skills, such as mirror drawing, even though he had no conscious memory of practicing them. This dissociation supports the idea that different types of memory rely on distinct brain areas.
Eugene Pauly (EP)
EP developed severe amnesia after viral encephalitis, which damaged his medial temporal lobe, including the hippocampus and amygdala. Squire et al. conducted a case study using interviews, MRI scans, psychometric testing, and the Autobiographical Memory Interview (AMI). EP could not form new declarative memories, performing poorly on recent autobiographical memory tasks. However, his procedural memory remained intact: he could perform habitual tasks such as finding the kitchen or walking around the block and could learn object-pairing tasks through repetition without conscious recall. MRI scans confirmed that EP’s basal ganglia were undamaged.
A – Application
HM and EP illustrate localization of function. Damage to the hippocampus impaired declarative memory, while procedural memory was preserved due to intact basal ganglia. This explains why both could carry out skills or habits without conscious awareness, highlighting the functional specialization of brain structures.
C – Criticism
A strength of these studies is the in-depth longitudinal case study design, allowing detailed observation of brain–behavior relationships. However, both are single cases, limiting generalizability. HM’s damage was surgical, while EP’s was disease-related, making direct comparisons difficult. Additionally, neural plasticity may compensate over time, complicating strict conclusions about localization.
U – Unanswered questions
Although HM and EP support localization, they do not fully explain how memory systems interact or whether other brain regions can compensate for hippocampal damage. The studies also do not clarify how habits are initiated and controlled in the absence of declarative memory.
P – Practical use
Understanding localization informs rehabilitation strategies. For patients with hippocampal damage, procedural learning and habit-based approaches can allow skill acquisition despite declarative memory impairment. Knowledge of localization also guides neurological treatment and surgical planning.
3. Counterarguments
Some psychologists argue that memory is distributed across networks, not strictly localized. While HM and EP show specialization, their preserved abilities indicate that memory involves interacting systems, challenging overly rigid interpretations of localization.
4. Conclusion
The cases of HM and Eugene Pauly provide strong evidence for localization of function, demonstrating that hippocampal damage selectively impairs declarative memory while procedural memory remains intact via the basal ganglia. These findings support functional specialization but also highlight that memory is complex and involves multiple interacting systems, showing that localization is a useful but not complete explanation.