Patient H.M. had his hippocampus removed and could not form any new episodic memories — he had no recollection of conversations from minutes earlier. Yet across multiple sessions of mirror-drawing practice, his performance improved at the normal rate. What does this demonstrate?
AThe hippocampus stores both episodic memories and procedural skills, but procedural learning is more resilient
BDeclarative and procedural memory are neurologically dissociable systems — one can be destroyed while the other remains intact
CMotor improvement does not require memory — it is driven by real-time feedback only
DEpisodic memory is stored in working memory, which was intact in H.M.
H.M.'s case is the canonical demonstration of a double dissociation: profound destruction of declarative (episodic) memory with fully intact procedural learning. This shows the two systems are not just different in degree — they rely on different neural structures (hippocampus for declarative; basal ganglia and cerebellum for procedural). Option A mischaracterizes the case; the hippocampus is not involved in procedural memory at all.
Question 2 Multiple Choice
After reading the word 'doctor' in a word list, you process the word 'nurse' faster when it appears later — even without any conscious recognition that you saw 'doctor.' This best exemplifies:
AEpisodic memory, since you were personally exposed to the word at a specific time and place
BSemantic memory, since 'doctor' and 'nurse' are conceptually related categories
CPriming — a form of non-declarative memory expressed through facilitated processing performance
DProcedural memory, since reading words is a learned skill
Priming is the facilitation of processing by prior exposure, expressed through performance (faster reaction times, easier recognition) without deliberate recollection. It is a non-declarative memory phenomenon. Semantic memory (B) is the long-term store of conceptual knowledge — it explains *why* doctor and nurse are related, but it does not describe the facilitation effect itself. Priming uses that structure but is the memory phenomenon of interest here.
Question 3 True / False
Implicit memory is called 'implicit' because its contents are stored below the level of consciousness and cannot be consciously accessed or described.
TTrue
FFalse
Answer: False
Implicit does not mean unconscious or inaccessible — it means memory is expressed through performance rather than through deliberate recollection. You can often become conscious of implicitly learned patterns; the key point is that retrieval does not *require* conscious effort. For example, you can describe how to ride a bike after the fact, even though your procedural memory expresses itself automatically during the act. The implicit/explicit distinction is about retrieval mode, not a wall between conscious and unconscious.
Question 4 True / False
A patient with severe hippocampal damage who cannot form new episodic memories could still show normal improvement across sessions of a newly learned motor task.
TTrue
FFalse
Answer: True
This is exactly what H.M. demonstrated. Procedural memory is supported by the basal ganglia and cerebellum, not the hippocampus. H.M. improved at mirror-drawing at a normal rate across sessions despite having no recollection of ever having practiced. Episodic amnesia does not impair procedural learning — the two systems are independent.
Question 5 Short Answer
Why is the distinction between declarative and non-declarative memory considered a difference in *kind* rather than just a difference in degree or content?
Think about your answer, then reveal below.
Model answer: The systems differ in neural substrate, retrieval mode, and content type — and they are doubly dissociable. Declarative memory requires conscious recollection and depends on the hippocampus; non-declarative memory is expressed through performance without deliberate retrieval and depends on different structures (basal ganglia, cerebellum, amygdala). H.M.'s case shows one can be completely destroyed while the other remains fully functional — this bidirectional independence is the hallmark of a genuine dissociation between systems, not just a quantitative difference.
A double dissociation — finding patients where A is impaired and B is intact, and other patients where B is impaired and A is intact — is the gold standard for establishing that A and B are truly separate systems. This architecture matters for understanding memory disorders, designing rehabilitation strategies, and explaining why expertise in one domain doesn't automatically transfer to others.