HNS49 Learning And Memory Flashcards
Learning vs Memory
Learning: Acquisition of new information and can be observed as a change in behaviour
Memory: Retention of learned information, categorised based on duration of retention
There are different types of learning and memory
How to know which brain regions involved in learning and memory
- Measure neuronal activity while subject is performing a task
- Examine selective memory deficits in patients with different brain lesions
Classification of memory
Immediate memory (seconds)
—(attention)—> Short term memory (seconds - minutes)
—(consolidation)—> Long term memory (days - years)
ALL can be forgotten
Short-term memories vs Long-term memories
Short term memory (labile)
- —> selective memory —> consolidate —> Long-term memory (stable)
- —> trivial —> forgotten
- NOT all short-term memories are converted to long-term memories
- meaningless information needs to be discarded —> forgotten
- ***Motivation, Reward, Association with pre-existing information (give memory a meaning) plays a role in consolidation of memories
Working memory
- A type of short-term memory
- used to achieve a behavioural goal (e.g. remember phone number, keep up conversation)
- ***Limited capacity
- Need repetition
- ***Very short duration
- may be used in planning (e.g. planning route when driving)
Test:
- ***Wisconsin card-sorting test (cognitive task to test working memory)
Location:
- ***Prefrontal cortex (damaged patients perform poorly)
2 types of Amnesia
- Retrograde amnesia: memory loss of events prior to trauma (more recent events lost first)
- Anterograde amnesia: failure to form new memory after trauma (prior memory is intact)
Brain regions of HM removed
- 2/3 of anterior hippocampus
- Amygdala
- Part of temporal cortex (Entorhinal cortex)
Memory of HM
- Severe anterograde amnesia (but only in certain kinds of memory)
- Less severe retrograde amnesia (temporally graded: memory formed a few years prior lost, remote memory intact)
- Normal working memory
Significance:
1. Formation and Storage of memory are 2 distinct processes (i.e. 2 separate regions) (Anterograde amnesia more severe in HM)
- Anterograde Long-term memory are divided into 2 types (based on whether it requires conscious awareness) (HM can still form certain types of long-term memory)
- Explicit (impaired in HM)
- Implicit (spared)
***2 types of Long-term memory
- Explicit (declarative)
- Episodic (events)
- Semantic (facts)
—> **Prefrontal Cortex, **Hippocampus (medial temporal lobe), ***Cortex - Implicit (non-declarative, does not require conscious recall)
- Priming —> **Cortex
- Procedural (skills, habit) —> **Striatum
- Non-associative learning (habituation and sensitisation) —> Reflex pathways
- Associative learning (classical and operant conditioning)
—> Emotional responses —> **Amygdala
—> Skeletal musculature —> **Cerebellum
Explicit memory
“普通人講既memory”
Explicit memory:
- Requires ***conscious recall
- More ***flexible than implicit memories (different information can be associated under different circumstances) (e.g. good memory of a restaurant, bad memory of the same restaurant after poor experience later)
- ***Easier to be formed and forgotten than implicit memories
- Episodic memory (memory for events)
- personal experience in a specific spatial and temporal context
- e.g. remembering dinner last night - Semantic memory (memory for facts)
- general knowledge (word, objects, concepts)
- not associated with context
- e.g. knowledge about a subject
4 distinct processes mediating Explicit memory
- Encoding (acquire new information and link to existing one)
- **Prefrontal cortex + **Medial temporal lobe (esp. ***Hippocampus)
—> higher activity of these regions —> more attention to subject —> better memory - Storage (retain information in specific cortical areas, different specialised areas where the specific aspect of a concept is processed e.g. image, sound)
- ***Cerebral cortex - Consolidation (transform newly-stored memory (labile and susceptible to disruption) to more stable one)
- Cerebral cortex + ***Hippocampus - Retrieval (bring back different kinds of information from different brain areas)
- Cerebral cortex + ***Hippocampus
***Storage pathway: Interconnections between Hippocampus and Cortex
Information from Visual cortex —>
- Dorsal: Parietal association cortex (spatial information: position, motion) —> sensory guidance of motor behaviour + spatial awareness
- Ventral: Temporal association cortex (form: colour shape) —> **storage of **semantic memory
**Storage pathway:
Association cortices
(—> Parahippocampal and Entorhinal cortex)
—> widespread projections to Hippocampal area in Medial temporal lobe
—> Hippocampus **integrates various sensory information to form memory
—> Hippocampal output —> **Association cortices —> Storage
AND
—> Hippocampus —(Fornix)—> **Thalamus + ***Hypothalamus
Conclusion:
Interaction between Association cortices and Medial temporal lobe is important for:
1. Initial memory formation + storage (unstable)
2. Memory consolidation + retrieval (來回好多次)
***Hippocampus and spatial memory
Hippocampus is activated during ***spatial navigation in a virtual environment
—> constitutes a cognitive map for surround environment
Cells involved in navigation and formation of spatial map:
- **Place cells in **Hippocampus (map of individual places)
- **Grid cells in **Entorhinal cortex (input to hippocampus) (map of overall area)
Clinical relevance:
Alzheimer’s disease: Entorhinal cortex affected in early stage —> get lost easily
Summary of Explicit memory
3 brain areas involved:
- Prefrontal cortex (attention)
- ***Hippocampus (medial temporal lobe) (formation)
- Cortex (storage)
Interconnections between Cortex and Hippocampus:
- Initial formation + storage
- Consolidation into long-term memory (requires continuous retrieval from Cortex to Hippocampus)
Implicit memory: Priming
Prior exposure to a stimulus
—> influence response to a subsequent stimulus unconsciously
Example: ***Word-stem completion task
Implicit memory: Procedural learning
- Skill learning (Visuomotor skill)
e. g. ***Riding a bicycle (but cannot remember that he had performed the task) - Skill learning (Perceptual learning)
e. g. ***Reading mirror-reversed text
- after training: shift from Parietal cortex (visuospatial transformation) —> Inferior temporal cortex (direct recognition of transformed letters)
- Amnesia patients with damage to medial temporal lobe can learn to read mirror-reversed text, but this learning is impaired in Parkinson’s (injured Striatum) - Habit learning
- depends on Striatum rather than Medial temporal lobe
- Probabilistic classification learning: PD cannot learn this task but Amnesic patients can
- ***Radial arms maze:
—> explicit learning (Spatial memory): performance impaired if lesion in Hippocampus but not impaired by Striatum lesion
—> implicit learning (go to arm with light): performance impaired if Striatum is lesioned
Conclusion: Procedural learning by Striatum
