Memory
High-Yield Summary
- Memory has three stages: encoding (getting information in), storage (maintaining it), retrieval (accessing it later).
- Encoding types: visual, acoustic, semantic (best retention, tied to the self-reference effect). Maintenance rehearsal keeps info active short-term; mnemonics (method of loci, peg-word, chunking) aid durable encoding.
- Storage: sensory memory (iconic/echoic, <1 sec) → short-term memory (stores, limited capacity/duration) → working memory (actively manipulates) → long-term memory, split into explicit/declarative (episodic + semantic) and implicit (procedural).
- Retrieval: recall (generate, no options) vs. recognition (identify among options, easier) vs. relearning (faster the second time). Semantic networks + spreading activation explain how one cue unlocks a memory; context-dependent (external environment) and state-dependent (internal state) memory both improve retrieval via matching conditions.
- Forgetting: Alzheimer's (acetylcholine dysfunction, amyloid plaques, tau tangles), Korsakoff syndrome (thiamine deficiency, anterograde + retrograde amnesia), agnosia (can't recognize despite normal senses), decay, and interference (proactive/retroactive).
- Memory is reconstructive, not a recording — producing false memories, the misinformation effect (Loftus), intrusion errors, and source monitoring errors.
- Neurobiology: neuroplasticity, synaptic pruning, AMPA receptor changes, and long-term potentiation (LTP) strengthen synapses; the hippocampus stabilizes new declarative memories during consolidation, which continues during sleep.
Key Terms
- Self-reference effect
- Information related to oneself is easier to encode and retrieve.
- Chunking
- Organizing many small pieces of information into larger, more meaningful units to ease encoding.
- Working memory
- Actively manipulates information being held in mind (vs. short-term memory, which just stores it).
- Semantic network
- A model of memory where related concepts are linked, so activating one can spread activation to others.
- Retrieval cue
- Anything that helps trigger access to a stored memory.
- Neuroplasticity
- The brain's capacity to strengthen, weaken, form, or reorganize neural connections based on experience.
- Long-term potentiation (LTP)
- A long-lasting increase in synaptic strength after repeated neuron activation; the cellular basis of learning/memory.
- Memory consolidation
- Stabilizing a new memory into a stable long-term form, centrally aided by the hippocampus and continuing during sleep.
Long-Term Memory: Explicit vs. Implicit
| Explicit (declarative) — conscious | Implicit — no conscious access needed |
|---|---|
| Episodic: personal experiences tied to time/place | Procedural: learned skills and tasks (riding a bike, typing) |
| Semantic: facts and general knowledge, not tied to a personal event | Influences thought/behavior without requiring awareness of the stored information |
Classic Memory Contrasts
| Term A | Term B |
|---|---|
| Anterograde amnesia: can't form new long-term memories after onset | Retrograde amnesia: can't access memories formed before onset |
| Proactive interference: old memories interfere with new | Retroactive interference: new memories interfere with old |
| Context-dependent memory: matches the external environment | State-dependent memory: matches the internal state |
| Recall: generate the answer with no options given | Recognition: identify the answer among options (generally easier) |
Memory Consolidation at the Cellular Level
- 1Repeated neuron activation strengthens a synapse: the presynaptic neuron releases more neurotransmitter, and the postsynaptic neuron inserts more AMPA receptors, becoming more responsive.
- 2This produces long-term potentiation (LTP) — a lasting increase in communication strength between the two neurons.
- 3The hippocampus helps stabilize new declarative information, gradually establishing it as long-term memory (memory consolidation).
- 4Consolidation continues during sleep, as the brain keeps processing and strengthening recently learned pathways.
- 5Over time, long-term declarative memories become supported by distributed cortical networks, relying less on the hippocampus.
Common MCAT Trap
- Anterograde amnesia blocks new memory formation going forward; retrograde amnesia blocks access to memories from before onset — picture a point on a timeline.
- Proactive interference is old interfering with new; retroactive interference is new interfering with old.
- Recognition is easier than recall because the correct answer is already present as a retrieval cue.
- Short-term memory passively stores; working memory actively manipulates what's held.
- A vivid, confidently held memory is not necessarily an accurate one — memory is reconstructive, not a recording.
Quick Recall
A patient with chronic alcohol use disorder develops severe memory impairment. What's the underlying deficiency, and what syndrome?
Which mnemonic technique organizes information into larger, more meaningful units?
A witness is asked how fast a car was going when it 'smashed into' vs. 'hit' another car, changing their memory of the accident's severity. What effect is this?
What's the difference between an intrusion error and a source monitoring error?
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