Learning & Memory Flashcards
1
Q
What is dementia?
A
A general term to describe a group of conditions that affect memory, thinking and social abilities
Has different causes
Alzheimer’s is most common
2
Q
What are the health and social care costs of dementia in the UK?
A
Around £26.3bn per year.
Currently more than 850,000 people in the UK are diagnosed with dementia (more common in older people)
3
Q
Is dementia progressive?
A
Yes, symptoms get worse with time.
4
Q
What are the primary types of dementia?
A
Different types according to their cause.
5
Q
What role does PKA play in synaptic mechanisms?
A
PKA plays an important role in diverse signalling pathways involved.
6
Q
What does ERK stand for?
A
Extracellular signal-regulated protein kinases.
7
Q
What receptors are involved in long-term potentiation (LTP)?
A
AMPA and NMDA receptors.
8
Q
What occurs in the LTP mechanism?
A
- AMPA and NMDA receptors involved
- First, presynaptic changes occur —> increased NT vesicles and increased NT release
- Then, postsynaptic changes occur —> increased dendritic area and spines (increased sensitivity) and increased AMPA receptors
9
Q
What is the role of AMPA receptors?
A
Requires glutamate to open and allows Na+ influx = depolarisation
10
Q
What is required for NMDA receptors to open?
A
Glutamate + glycine + depolarisation
Can then allow Na+ and Ca2+ influx
11
Q
What is long-term potentiation (LTP)?
A
A persistent strengthening of synapses following high-frequency stimulation of a chemical synapse.
- Produces a long lasting increase in signal transmission between 2 neurons
- Is one mechanism of synaptic plasticity
- Is the principle model of mechanisms underlying learning & memory
12
Q
What is long-term depression (LTD)?
A
A long-lasting decrease in the efficiency of synaptic transmission.
13
Q
What is anterograde amnesia?
A
Difficulty learning new information.
14
Q
What is retrograde amnesia?
A
Difficulty remembering past information.
15
Q
What is amnesia?
A
Refers to loss of memories, often resulting from trauma.
Can be transient or permanent
16
Q
What characterizes Alzheimer’s disease (AD)?
A
Presence of intracellular neurofibrillary tangles and accumulation of extracellular Beta-amyloid plaques.
17
Q
What is the key symptom of AD?
A
Memory loss.
18
Q
What are the stages of memory?
A
- Sensory stimulus received by brain
- Encoding (brain stores information) = acoustically in STM and semantically in LTM
- Storage (brain retains information)
- Retrieval = sequentially in STM and by association in LTM
19
Q
What are the two types of memory?
A
- Declarative (explicit) = have to think about i.e. facts and events
- Non-Declarative (implicit) = unconscious recollection I.e. associative responses & procedural skills/habits
20
Q
What is the duration of short-term memory?
A
Lasts for seconds to hours.
21
Q
What is the capacity of long-term memory?
A
Unlimited capacity.
22
Q
What is required for long-term memory consolidation?
A
New RNA or protein synthesis.
23
Q
What are place cells?
A
Hippocampal neurons that fire at a high rate when an animal is in a specific location in the environment called the place field
These are the neuronal basis of cognitive maps
24
Q
Where is explicit memory stored in the brain?
A
Hippocampus.
25
Where is procedural memory stored in the brain?
Cerebellum and basal ganglia (striatum, putamen).
26
What is a cognitive map?
An internal neural representation of the landscape in which an animal travels (mental representation of the environment)
27
What is meant by learning?
The acquisition of new knowledge or skills
Learning is adaptive = adjusted according to life experiences
28
What is meant by memory?
Retention of learned information
Linked to storage and retrieval
29
What is stored in regions of the cortex?
Short & long term explicit memory
30
What types of memory are stored in the amygdala?
Emotional responses
31
How was the hippocampus studied in taxi drivers?
- London taxi drivers have greater grey matter in the hippocampus than bus drivers
- Grey matter is associated with years of navigation experience
- Spatial knowledge is associated with the pattern of hippocampal grey matter volume
32
Features of short-term memory
- lasts for seconds to hours
- repetition promotes retention
- limited capacity of up to 7 digits
- sensitive to disruption
- does not require new RNA or protein synthesis
33
Features of long-term memory
- consolidation of short-term memory
- lasts for days to years
- insensitive to disruption
- requires new RNA or protein synthesis
34
What is working memory?
Used to hold information ‘in mind’
Requires rehearsal
Only lasts a few seconds and has very limited capacity
35
What are the basic mechanisms of memory?
- Learning & memory involve changes in existing neural circuits
- Changes include altered synaptic strength and neuronal excitability
- Intracellular signalling pathways play a key role in effecting these changes
36
What is Hebbian plasticity?
Principle that Neurons that fire together ‘wire’ together
37
What’s important about the structure of dendrites in learning & memory?
Contain a large number of dendritic spines that form contacts (synapses) with other neurons
38
What are post synaptic mechanisms?
Key to stabilisation of synaptic strength
- diverse signalling pathways involves
- protein kinase A (PKA) plays an important role
- different pathways converge on common targets e.g. ERK
- requires protein synthesis
39
How does LTP induce changes in dendritic spines?
Dendritic spine head volume changes and there is a widening/shortening of the spine neck = increased number of receptors and presynaptic vesicles
Multiple spine bouton = synapse branches leading to increased transmission
40
What causes LTP?
Synaptic transmission occurring at the same time as a strong depolarisation of the postsynaptic neuron causes LTP of the active synapses
= increase in synaptic transmission
41
What causes LTD?
Synaptic transmission occurring at the same time as a weak/modest depolarisation of the postsynaptic neuron causes LTD of the active synapses
= decrease in synaptic transmission
42
What occurs in LTP and LTD?
- A rise in postsynaptic Ca2+ can trigger both LTP and LTD
- In LTP, strong depolarisation will lead to high levels of Ca2+
- In LTD, weak depolarisation will lead to little Ca2+ influx = Mg2+ only partially shifts in the channel
43
Physiological functions of LTD
- Hippocampus dependent learning & memory (working and episodic memory, novelty detection)
- Fear conditioning in Amygdala (classical conditioning of fears)
- Recognition memory in perirhinal cortex
- Cerebellar learning
44
What pathological states is LTD involved in?
- Psychiatric disorders (e.g. depression, schizophrenia)
- Drug addiction
- Mental retardation (fragile X syndrome)
- Neurodegenerative diseases (e.g. Alzheimer’s disease)
45
What is the significance of patient HM in amnesia studies?
- Most studied individual in the history of neuroscience
- Had a bilateral medial temporal lobe resection that led to anterograde amnesia
- Couldn’t remember anything after the operation but his memory of events/people before the surgery were intact
- Led to scientists being able to discriminate between short and long term memory and declarative and non-declarative memory
46
What are the different types of dementia?
- Alzheimer’s disease
- Vascular dementia
- Dementia with Lewy bodies
- Frontotemporal dementia
47
What are the symptoms of Alzheimer’s disease (AD)?
Memory loss is the key symptom together with a continuous decline in thinking, behavioural and social skills
Currently no cure
48
How many people are affected by AD?
>80% of total dementia cases in the elderly
In England and Wales, one new case is diagnosed every 3.2 minutes
49
What is vascular dementia (VD) and how is it developed?
Second most common cause of dementia
Developed after a stroke or can result from other conditions that damage blood vessels and reduce circulation (e.g. atherosclerosis, high blood pressure or diabetes)
50
What are the symptoms of vascular dementia (VD)?
Symptoms vary depending on the part of brain affected
Can include problems with memory, reasoning, planning or judgement
51
How can VD be treated?
Treatment focuses on managing the health conditions & risk factors that contribute to vascular dementia (e.g. drugs reducing blood pressure)
52
What is the primary nervous system structure of Aplysia?
Ganglia
Ganglia communicate through connectives and are arranged in bilaterally symmetrical pairs.
53
What does the abdominal ganglion control in Aplysia?
Abdominal ganglion is unpaired
Controls heart rate, blood circulation, and respiration
It contains primary sensory neurons, interneurons, and motor neurons involved in the gill and siphon withdrawal reflex.
54
What type of long-term memory does Aplysia show?
Classical conditioning and sensitisation
## Footnote
Aplysia demonstrates long-term memory for both classical conditioning and sensitisation.
55
What are the three types of mechanistic analysis of learning?
* Synaptic analysis
* Biophysical analysis
* Molecular analysis
56
What is presynaptic facilitation in the context of synaptic analysis?
Increased EPSP due to sensitisation input
Increases influx of Ca2+ & neurotransmitter release
Increased duration of depolarisation (spike broadening) and increased reflex amplitude.
57
What role does serotonin play in synaptic facilitation?
Induces facilitation
Increases sensory neuron excitability
Increases motor neuron EPSP
Increases reflex amplitude.
58
What is required for long-term synaptic facilitation?
Postsynaptic protein synthesis
## Footnote
Short-term facilitation does not require this, but long-term facilitation does.
59
What is the effect of repeated serotonin or cAMP applications?
Persistent phosphorylation of preexisting proteins and synthesis of new proteins
## Footnote
This leads to dramatic growth of sensory neuron processes and long-term increases in synaptic facilitation.
60
What does cAMP activate in the sensory neuron?
Protein Kinase A (PKA)
## Footnote
Active PKA phosphorylates substrate proteins.
61
What is the effect of serotonin on potassium channels in sensory neurons?
Temporarily closes potassium channels
## Footnote
This slows outward potassium current and increases calcium influx.
62
What is the difference between short-term and long-term memory in Aplysia?
Short-term memory lasts hours
Long-term memory lasts days to weeks.
63
What type of training leads to optimal learning in Aplysia?
Distributed training
## Footnote
This consists of 10 trials every day for 4 days, compared to massed training.
64
What is habituation?
Loss of response due to repeated stimulus.
65
What is sensitisation?
Response stronger than normal.
66
What is dishabituation?
Recovery of innate response.
67
What are the key components of classical conditioning?
* Unconditioned stimulus (UCS)
* Unconditioned response (UCR)
* Conditioned stimulus (CS)
* Conditioned response (CR)
68
Who is a notable researcher in the field of learning and memory in Aplysia?
Eric Kandel
## Footnote
He received the Nobel Prize in 2000.
69
What is the significance of the Aplysia animal model?
Instrumental in understanding cellular and molecular mechanisms of learning and memory.
70
Describe the respiratory apparatus of the Aplysia
- 15-30 cm in length
- Gills located on its back
- Mantle shelf covers the gills
- Parapodium attached to the sides of the body and protects the gills
71
What is the tactile stimulus in Aplysia
The gill and siphon withdrawal reflex
72
What are the types of learning in Aplysia?
**Non-associative learning**
1. Habituation
2. Dishabituation
3. Sensitisation
**Associative learning**
Classical conditioning
73
What is important about associative learning in Aplysia?
- No learning with backwards pairing
- Optimal learning occurred only if CS preceded US by 0.5 seconds (CS first then the US)
74
What is the difference between distributed vs mass training in Aplysia?
Distributed training (10 trials every day for 4 days) produced better learning and retention
Mass training (40 trials in 1 day)
75
Describe biochemical analysis of the sensory neuron
1. Serotonin temporarily closes K+ channel (S current) in sensory neuron
2. Outward K+ current is slowed
3. Repolarisation of membrane potential is slowed = spike broadening
4. Increases Ca2+ influx
5. Increase in neurotransmitter release
6. Enhanced excitability
76
Describe molecular analysis of the sensory neuron EPSP
Serotonin increases levels of cAMP
cAMP acts a second messenger
cAMP activates PKA
Active PKA phosphorylates substrate proteins
77
Describe mechanistic analysis of long-term memory
- Repeated serotonin or cAMP application
- Results in synthesis of new proteins or persistent phosphorylation of pre-existing proteins
- Long term increase in synaptic facilitation
- Long term increase in synaptic transmission
- Dramatic growth of sensory neuron processes
- Results in long term memory for sensitisation
78
What is the effect of long term sensitisation on neuron synapses?
Lots of branching
