Brain structures in memory formation: WACE Year 12 Psychology Unit 3
“Memory formation and structures of the brain: the role of the hippocampus in the formation and storage of memory (Henry Molaison case study); the role of the cerebellum in the formation and storage of implicit memories; the role of the amygdala in the formation of memories”
The hippocampus forms and consolidates new explicit (declarative) memories and helps transfer them to long-term storage; the Henry Molaison case showed that without it, new explicit long-term memories cannot be formed. The cerebellum forms and stores implicit memories, especially procedural (motor skill) memories and simple conditioned movements. The amygdala is involved in forming emotional memories, particularly fear, and strengthens the consolidation of emotionally significant events.
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What this dot point is asking
The syllabus names three structures and one case study. You should be able to identify each structure on a diagram, state its role, match it to a type of memory from the multi-store model, and use the Henry Molaison case study as evidence.
The hippocampus
The hippocampus is a curved structure deep in the medial temporal lobe, one in each hemisphere, and is part of the limbic system.
- It is essential for forming new explicit (declarative) memories, both semantic and episodic.
- It consolidates memories: it strengthens and stabilises new memories and helps transfer them from short-term to long-term storage.
- It is involved in spatial memory (remembering locations and routes).
- Long-term memories are not stored permanently in the hippocampus: over time they are stored across areas of the cerebral cortex.
Case study: Henry Molaison (H.M.)
- Background. Henry Molaison had severe epilepsy that did not respond to medication.
- Surgery. In 1953, aged 27, he had surgery that removed large parts of the medial temporal lobe on both sides, including most of the hippocampus and the amygdala. His seizures were greatly reduced.
- Effects on memory.
- Severe anterograde amnesia: he could not form new explicit long-term memories. He could meet the same researcher many times and not recognise them.
- Some retrograde amnesia: he lost memories from the years just before the surgery, but kept many older memories from childhood.
- Short-term memory was intact: he could hold information for a short time and follow a conversation.
- Procedural memory was intact: in a mirror-drawing task, he improved over several days even though he did not remember doing the task before.
- Contribution. Studied for more than 50 years until his death in 2008, the case showed that memory is not one single system, that the hippocampus is needed to form new explicit memories, and that short-term, procedural and explicit long-term memory depend on different brain structures.
- Limitation. A single case cannot be generalised with certainty, and his brain damage was not limited to the hippocampus, so not every effect can be attributed to it alone.
Could not: form new explicit (declarative) long-term memories. Could: use short-term memory, recall many older memories, and learn new motor skills (implicit procedural memory). This pattern is the evidence for the hippocampus's role.
The cerebellum
The cerebellum sits at the back of the brain, under the cerebral hemispheres.
- It is involved in forming and storing implicit memories, especially procedural memories for motor skills and sequences of movement (typing, riding a bike, a dance routine).
- It is involved in timing and coordinating movements, and in classically conditioned motor responses, such as learning to blink when a tone predicts a puff of air.
- Damage to the cerebellum can make it hard to learn new motor skills, even when explicit memory is normal.
The amygdala
The amygdala is an almond-shaped structure in the medial temporal lobe, next to the hippocampus.
- It is involved in forming emotional memories, especially memories of fear and threat.
- It attaches emotional significance to experiences and strengthens the consolidation of emotionally arousing memories (with the hippocampus), which is why emotional events are often remembered vividly.
- It is involved in classically conditioned fear: learning that a neutral stimulus predicts something frightening, as in the Little Albert experiment.
Matching structures to memory types
| Structure | Main type of memory | Example |
|---|---|---|
| Hippocampus | Explicit (declarative): semantic and episodic; consolidation | Remembering what you did last weekend |
| Cerebellum | Implicit: procedural skills and conditioned movements | Knowing how to kick a football |
| Amygdala | Emotional memories, especially fear | Feeling anxious near a dog that once bit you |
A learner driver
Ava is learning to drive.
- Remembering the road rules from her learner's test is semantic memory, formed with the help of the hippocampus.
- Remembering her first lesson, when she stalled at a busy intersection, is episodic memory, also formed via the hippocampus. Because she felt embarrassed and frightened, the amygdala strengthened the memory, so she recalls it vividly.
- Over many lessons, changing gears becomes automatic. This is procedural (implicit) memory, formed and stored with the help of the cerebellum.
Marker's note: name the structure, name the type of memory, and point to the part of the scenario that shows it.
- Saying memories are stored in the hippocampus permanently
- It forms and consolidates explicit memories, but long-term memories are stored across the cortex.
- Saying H.M. lost all memory
- His short-term memory, many older memories and his procedural learning were intact.
- Linking the cerebellum to explicit memory
- The cerebellum is for implicit procedural and conditioned motor memories.
- Describing the amygdala only as "emotion"
- Link it to memory: forming and strengthening emotional memories and conditioned fear.
Exam-style questions
Questions in the style of SCSA exam questions on this dot point, each with a worked answer. They are written by ExamExplained unless tagged "Past paper"; the year shows the paper a question is modelled on.
Original6 marksDescribe what happened to Henry Molaison's memory after his 1953 surgery and explain what his case shows about the role of the hippocampus.Show worked answer →
Three marks for the effects on memory and three marks for what the case shows.
Effects. After most of his hippocampus (and surrounding medial temporal lobe) was removed on both sides, Henry Molaison could no longer form new explicit long-term memories (severe anterograde amnesia): he could not remember people he met or events that happened after the surgery. His short-term memory was intact, so he could hold a conversation. He could still learn new motor skills, such as mirror drawing, even though he did not remember practising.
Role of the hippocampus. The hippocampus is needed to form and consolidate new explicit (declarative) memories and transfer them into long-term storage. It is not needed for short-term memory or for implicit procedural memory, and because many older memories survived, long-term memories are not stored only in the hippocampus.
Original3 marksState three roles of the amygdala in memory formation.Show worked answer →
One mark each for any three accurate roles.
- It is involved in forming memories of emotionally significant events, especially frightening ones.
- It attaches emotional significance to memories and strengthens (enhances) their consolidation, which is why emotional events are often remembered vividly.
- It is involved in classically conditioned fear responses (learning that a stimulus predicts danger).
- It interacts with the hippocampus, which stores the explicit details of the emotional event.
Practise this
Sources & how we know this
- Psychology ATAR course Year 12 syllabus (effective from 1 January 2024) — School Curriculum and Standards Authority (SCSA)
- Psychology ATAR course: syllabus and support materials — SCSA
- Past ATAR course examinations — SCSA