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Flashcards in HNS49 Learning And Memory Deck (19)
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1
Q

Learning vs Memory

A

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

2
Q

How to know which brain regions involved in learning and memory

A
  1. Measure neuronal activity while subject is performing a task
  2. Examine selective memory deficits in patients with different brain lesions
3
Q

Classification of memory

A

Immediate memory (seconds)
—(attention)—> Short term memory (seconds - minutes)
—(consolidation)—> Long term memory (days - years)

ALL can be forgotten

4
Q

Short-term memories vs Long-term memories

A

Short term memory (labile)

  1. —> selective memory —> consolidate —> Long-term memory (stable)
  2. —> 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
5
Q

Working memory

A
  • 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)

6
Q

2 types of Amnesia

A
  1. Retrograde amnesia: memory loss of events prior to trauma (more recent events lost first)
  2. Anterograde amnesia: failure to form new memory after trauma (prior memory is intact)
7
Q

Brain regions of HM removed

A
  1. 2/3 of anterior hippocampus
  2. Amygdala
  3. 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)

  1. 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)
8
Q

***2 types of Long-term memory

A
  1. Explicit (declarative)
    - Episodic (events)
    - Semantic (facts)
    —> **Prefrontal Cortex, **Hippocampus (medial temporal lobe), ***Cortex
  2. 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
9
Q

Explicit memory

A

“普通人講既memory”

Explicit memory:

  1. Requires ***conscious recall
  2. 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)
  3. ***Easier to be formed and forgotten than implicit memories
  4. Episodic memory (memory for events)
    - personal experience in a specific spatial and temporal context
    - e.g. remembering dinner last night
  5. Semantic memory (memory for facts)
    - general knowledge (word, objects, concepts)
    - not associated with context
    - e.g. knowledge about a subject
10
Q

4 distinct processes mediating Explicit memory

A
  1. 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
  2. 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
  3. Consolidation (transform newly-stored memory (labile and susceptible to disruption) to more stable one)
    - Cerebral cortex + ***Hippocampus
  4. Retrieval (bring back different kinds of information from different brain areas)
    - Cerebral cortex + ***Hippocampus
11
Q

***Storage pathway: Interconnections between Hippocampus and Cortex

A

Information from Visual cortex —>

  1. Dorsal: Parietal association cortex (spatial information: position, motion) —> sensory guidance of motor behaviour + spatial awareness
  2. 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)

12
Q

***Hippocampus and spatial memory

A

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:

  1. **Place cells in **Hippocampus (map of individual places)
  2. **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

13
Q

Summary of Explicit memory

A

3 brain areas involved:

  1. Prefrontal cortex (attention)
  2. ***Hippocampus (medial temporal lobe) (formation)
  3. Cortex (storage)

Interconnections between Cortex and Hippocampus:

  • Initial formation + storage
  • Consolidation into long-term memory (requires continuous retrieval from Cortex to Hippocampus)
14
Q

Implicit memory: Priming

A

Prior exposure to a stimulus
—> influence response to a subsequent stimulus unconsciously

Example: ***Word-stem completion task

15
Q

Implicit memory: Procedural learning

A
  1. Skill learning (Visuomotor skill)
    e. g. ***Riding a bicycle (but cannot remember that he had performed the task)
  2. 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)
  3. 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

16
Q

Implicit memory: Non-associative learning

A

Stimuli —> Response

  1. Habituation (嚇大)
    - ***decrease response to non-threatening stimulus (learning to ignore stimulus)
  2. Sensitisation (越黎越敏感)
    - ***increase response to different stimuli after intense / noxious event (startled by a tap on shoulder after watching horror movie)
17
Q

Implicit memory: Associative learning

A
  1. Classical conditioning (Relate 2 different stimuli —> Same response)
    - Association of ***2 stimuli (e.g. fear conditioning) —> Association of an involuntary response and a stimulus
  2. Operant conditioning (Action —> Outcome)
    - Association of an **voluntary action and the **outcome (behaviour controlled by consequence)
18
Q

Fear conditioning

A
  • Involves ***Amygdala
  • relays information from ***Thalamus to Amygdala

Pathway:
Fear stimulus (Shock + Sound)
—> Thalamus —>
1. Rapid Direct pathway —> Amygdala (lateral nucleus) —> Fear responses
OR
2. Slower Indirect pathway —> ***Cortex (Auditory cortex + Somatosensory cortex) —> Amygdala (lateral nucleus) (integrate 2 stimuli) —> Fear responses

19
Q

Engram

A

Physical representation of memory in the brain

Synaptic strength: efficacy of synaptic transmission
—> can change
—> Learning induces change in synaptic strength between specific neurons (e.g. more NT receptors inserted into membrane / structural change of synapse)
—> ***Synaptic plasticity (experience-dependent change in synaptic strength)
—> Stronger the synapse —> stronger the response of postsynaptic neurons
—> Synapses activated during memory acquisition are the Engram

Example:
Fear conditioning:
- Repetitive pairing of weak stimulus (tone) with a strong stimulus (shock)
—> increase strength of weak synapse
—> learning occurs (freeze in response to sound despite no shock)
—> explain associative nature of learning and memory

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