Lecture 16 - Cellular Learning and Memory

Question 1

What percentage of the population is affected by insomnia regularly?

Answer 1

Insomnia affects 9% of the population regularly.

Question 1

What are some potential consequences of untreated insomnia?

Answer 1

Untreated insomnia can lead to fatigue, concentration issues, mood disturbances, and increased health risks like heart disease.

Question 2

What is Fatal Familial Insomnia?

Answer 2

Fatal Familial Insomnia is a rare, progressive insomnia due to neurodegeneration, leading to hallucinations, delirium, coma, and eventual death.

Question 3

Which brain regions are primarily affected in Fatal Familial Insomnia?

Answer 3

The thalamus, hypothalamus, and brainstem are primarily affected.

Question 4

What are non-REM parasomnias?

Answer 4

Non-REM parasomnias are sleep disorders that occur during non-REM sleep or sleep-wake transitions, such as sleepwalking and sleep talking.

Question 5

What are sleep terrors, and who are they more common in?

Answer 5

Sleep terrors involve sudden waking with intense fear and panic behaviors, with no memory of the episode, and are more common in individuals with PTSD.

Question 6

What is REM Sleep Behavior Disorder (RBD)?

Answer 6

RBD is characterized by the absence of muscle paralysis during REM sleep, allowing individuals to act out their dreams, potentially causing self-harm or injury to others.

Question 7

How is REM Sleep Behavior Disorder associated with neurodegenerative diseases?

Answer 7

REM Sleep Behavior Disorder (RBD) is associated with neurodegenerative diseases because it involves damage or dysfunction in brain areas (like the pons and the medulla) that regulate REM sleep muscle atonia (the natural paralysis during REM sleep). In people with RBD, these areas are compromised, leading to physical movement during REM sleep. This dysfunction is often an early sign of neurodegenerative diseases like Parkinson’s or Lewy body dementia, where similar brain regions (especially those involving dopamine and movement control) are affected.

Question 8

What is the definition of learning?

Answer 8

Learning is the process of acquiring new information.

Question 9

How is memory defined?

Answer 9

Memory is the ability to store and retrieve information.

Question 10

What are the two types of memory?

Answer 10

The two types of memory are explicit memory, which is consciously recalled (e.g., facts and events), and implicit memory, which is automatic and unconscious (e.g., skills and habits).

Question 11

What is neuronal plasticity?

Answer 11

Neuronal plasticity is the brain’s ability to adapt and change in response to experiences.

Question 12

What does intrinsic excitability refer to?

Answer 12

Intrinsic excitability refers to how responsive a neuron is to incoming signals, measured by the number of action potentials it generates.

Question 13

What is synaptic strength?

Answer 13

Synaptic strength refers to the strength of connections between neurons, which can be altered through learning.

Question 14

What are presynaptic changes in synaptic plasticity?

Answer 14

Presynaptic changes involve alterations in neurotransmitter release, including:
- Number of vesicles: More vesicles result in a stronger or more sustained signal.
- Neurotransmitter quantity: Increased neurotransmitter release per vesicle strengthens the postsynaptic response.
- Release frequency: Higher frequency of release enhances the postsynaptic effect.
These changes play a key role in synaptic plasticity, affecting processes like long-term potentiation (LTP) and long-term depression (LTD).

Question 15

What is habituation in the context of non-associative learning?

Answer 15

Habituation is a type of non-associative learning where an organism’s response to a repeated, harmless stimulus decreases over time. In simpler terms, it’s when you stop reacting to something that doesn’t pose any threat or danger after experiencing it multiple times.

Question 16

Provide an example of habituation of reflexes.

Answer 16

Habituation is a type of non-associative learning where an organism’s response to a stimulus decreases after it is presented repeatedly and does not result in any harm or significant change. Essentially, the organism learns that the stimulus is not a threat and reduces its response to conserve energy for more important situations. For example, the sea slug (Aplysia) weakens its gill withdrawal reflex when touched repeatedly without harm. Similarly, a cat that initially startles at a vacuum cleaner’s noise will eventually ignore it after repeated exposure, learning that it poses no threat.

Question 17

What occurs during long-term habituation?

Answer 17

In long-term habituation, repeated exposure to a harmless stimulus leads to a lasting reduction in response. This occurs due to structural changes in synapses, including fewer or less responsive receptors on the postsynaptic side and changes in the presynaptic side, such as increased vesicle storage but less frequent neurotransmitter release. These changes make the neural response weaker, causing the organism to ignore the stimulus over time.

For example, a cat may stop reacting to a creaking door after hearing it many times because the brain becomes less responsive to the sound due to these neural changes.

Question 18

What is Long-Term Potentiation (LTP)?

Answer 18

Long-Term Potentiation (LTP) is a process where the strength of synaptic connections between neurons increases after repeated, high-frequency stimulation (often around 100 Hz). This strengthening makes it easier for the neurons to transmit signals to each other, and it is thought to play a key role in learning and memory formation. Essentially, LTP enhances the effectiveness of synaptic communication, helping neurons “remember” past activity patterns.

Question 19

What is Long-Term Depression (LTD)?

Answer 19

Long-Term Depression (LTD) is a process where the strength of the synapse between two neurons decreases over time. This is usually triggered by low-frequency stimulation (around 1 Hz) of the synapse, meaning the neurons fire at a slow rate. LTD can lead to a weakening of the synaptic connection, which is the opposite of Long-Term Potentiation (LTP), where synaptic strength is increased. LTD is thought to be involved in processes like learning and memory, as it helps the brain to refine and adjust neural connections, removing or weakening unnecessary or less-used pathways.

Question 20

How does high-frequency stimulation induce LTP?

Answer 20

High-frequency stimulation, when applied to a synapse, increases the communication between two neurons. The postsynaptic neuron (the neuron receiving the signal) responds by adding more AMPA receptors to its surface. AMPA receptors are proteins that allow the neuron to respond to signals from the presynaptic neuron (the one sending the signal).

When more AMPA receptors are present on the postsynaptic membrane, it becomes easier for the postsynaptic neuron to be activated by the presynaptic neuron, strengthening the synapse and making future communication more efficient. This process is part of long-term potentiation (LTP), which is a key mechanism for learning and memory.

Question 21

How does low-frequency stimulation induce LTD?

Answer 21

Low-frequency stimulation weakens synaptic strength because it doesn’t generate enough excitation in the postsynaptic neuron. As a result, the postsynaptic neuron removes some AMPA receptors from its surface. Since AMPA receptors are responsible for receiving signals from the presynaptic neuron, removing them makes the synapse weaker and reduces the efficiency of communication between the neurons. This process is part of long-term depression (LTD), which is the opposite of long-term potentiation (LTP).

Question 22

What role do NMDA receptors play in LTP and LTD?

Answer 22

NMDA receptors are a type of glutamate receptor found on the postsynaptic membrane. They allow calcium ions (Ca²⁺) to enter the cell when activated by glutamate and depolarization.
- In LTP (Long-Term Potentiation): A strong and brief calcium influx through NMDA receptors activates signaling pathways that increase synaptic strength, typically by inserting more AMPA receptors into the postsynaptic membrane.
- In LTD (Long-Term Depression): A smaller, sustained calcium influx activates protein phosphatases that remove AMPA receptors from the postsynaptic membrane, weakening synaptic strength.
These processes are critical for synaptic plasticity, which underlies learning and memory.

Question 23

What are AMPA receptors and how do they contribute to synaptic plasticity?

Answer 23

AMPA receptors are proteins on the postsynaptic membrane that allow sodium (Na+) ions to flow into the postsynaptic neuron, which causes depolarization and contributes to the transmission of signals between neurons. These receptors are responsible for fast synaptic transmission.

• In Long-Term Potentiation (LTP): The synapse becomes stronger after repeated stimulation. This happens because more AMPA receptors are inserted into the postsynaptic membrane. With more AMPA receptors, more sodium can enter the postsynaptic neuron, which makes the synapse more responsive and strengthens the connection between neurons.
• In Long-Term Depression (LTD): The synapse becomes weaker after less frequent stimulation. This happens because AMPA receptors are removed from the postsynaptic membrane, reducing the amount of sodium that can enter the postsynaptic neuron. With fewer AMPA receptors, the synapse becomes less responsive and weaker.

In short, more AMPA receptors make the synapse stronger, while fewer AMPA receptors make it weaker.

Question 24

In the experiment setup, what is the difference between high-frequency and low-frequency stimulation?

Answer 24

High-frequency stimulation (100 Hz) strengthens synaptic connections by promoting LTP, while low-frequency stimulation (1 Hz) weakens synaptic connections by inducing LTD.

Question 25

How can the hypothesis about synaptic strengthening being dependent on membrane potential or action potentials be tested?

Answer 25

To test if synaptic strengthening depends on membrane potential or action potentials, researchers can stimulate neurons at high or low frequencies. High-frequency stimulation induces action potentials in the postsynaptic neuron, potentially causing long-term potentiation (LTP). Low-frequency stimulation, which typically doesn’t induce action potentials, can lead to long-term depression (LTD) due to changes in membrane potential. Comparing these responses helps determine if synaptic strength is more influenced by action potentials or membrane potential changes.

Question 26

If a scientist observes an increase in neurotransmitter release from the presynaptic neuron and more receptors on the postsynaptic membrane, which process are they likely observing: LTP or LTD?

Answer 26

They are likely observing LTP, as it involves both the increase in neurotransmitter release and the insertion of more receptors on the postsynaptic membrane.

Question 27

In a real-life scenario, if someone undergoes repeated exposure to a rewarding stimulus, what type of synaptic plasticity might occur?

Answer 27

Long-Term Potentiation (LTP) might occur, as repeated exposure to a rewarding stimulus could lead to increased synaptic strength and enhanced neural responses to the stimulus.

Question 28

Imagine a scenario where someone experiences a repeated failure to respond to a stimulus despite repeated exposure. What type of synaptic plasticity might this result in?

Answer 28

Long-Term Depression (LTD) might occur in this scenario. With repeated, ineffective stimulation that fails to excite the postsynaptic neuron, the synapse can gradually weaken. This weakening typically involves a reduction in AMPA receptors in the postsynaptic membrane, leading to a decrease in synaptic strength, which reduces the likelihood of future responses to that stimulus.

Question 29

What is the role of calcium influx through NMDA receptors in the induction of LTP?

Answer 29

Calcium influx through NMDA receptors activates intracellular signaling pathways like CaMKII and PKC, which lead to the insertion of more AMPA receptors into the postsynaptic membrane, strengthening the synapse.

Question 30

How would the removal of AMPA receptors from the postsynaptic membrane affect synaptic strength?

Answer 30

The removal of AMPA receptors weakens synaptic strength by reducing the postsynaptic response to neurotransmitter release, contributing to LTD.

Question 31

What does high-frequency stimulation (100 Hz) induce in the postsynaptic neuron?

Answer 31

High-frequency stimulation induces depolarization of the postsynaptic neuron, which relieves the NMDA receptor block and allows calcium entry, triggering long-term potentiation (LTP).

Question 32

What is the effect of high-frequency stimulation on synaptic strength?

Answer 32

High-frequency stimulation strengthens the synapse by inserting additional AMPA receptors into the postsynaptic membrane, making the synapse more responsive to glutamate.

Question 33

How does low-frequency stimulation (1 Hz) affect synaptic strength?

Answer 33

Low-frequency stimulation leads to a smaller calcium influx through NMDA receptors, which activates protein phosphatases and results in the removal of AMPA receptors from the postsynaptic membrane, leading to long-term depression (LTD).

Question 34

What is long-term potentiation (LTP)?

Answer 34

Long-term potentiation (LTP) is the process by which repeated high-frequency stimulation strengthens synapses, making them more responsive to future stimuli.

Question 35

What is long-term depression (LTD)?

Answer 35

Long-term depression (LTD) is the process by which low-frequency stimulation weakens synapses by removing AMPA receptors from the postsynaptic membrane.

Question 36

How do NMDA receptors contribute to synaptic plasticity?

Answer 36

NMDA receptors act as coincidence detectors, requiring both glutamate binding and membrane depolarization to allow calcium ions to flow into the neuron, which strengthens synaptic connections.

Question 37

What is classical conditioning?

Answer 37

Classical conditioning is a learning process in which an animal learns to associate a neutral stimulus with a significant event, leading to a conditioned response (e.g., blinking when a tone is heard before a puff of air).

Question 38

How does classical conditioning differ from reflexive responses?

Answer 38

Reflexive responses are automatic reactions to stimuli that do not require learning, while classical conditioning involves learning associations between stimuli over time, leading to a conditioned response.

Question 39

In classical conditioning, how does a tone eventually trigger a blink in an animal?

Answer 39

Through repeated pairings of the tone with a puff of air, the synaptic connections between the tone-detecting neurons and the blink-controlling neurons strengthen, eventually causing the tone to trigger the blink response.

Question 40

What role do NMDA receptors play in classical conditioning?

Answer 40

NMDA receptors allow the synaptic connections between tone-detecting neurons and blink motor neurons to strengthen during repeated pairings, contributing to the learning process.

Question 41

What does it mean for NMDA receptors to be “coincidence detectors”?

Answer 41

NMDA receptors are called coincidence detectors because they require both glutamate binding to the receptor and the depolarization of the neuron’s membrane (removal of the magnesium block) to allow calcium influx.

Question 42

How does calcium influx through NMDA receptors strengthen synaptic connections?

Answer 42

Calcium influx triggers intracellular processes that strengthen the synapse, making the connection more likely to fire in the future when the same stimulus is present.

Question 43

Why is synaptic plasticity important for learning and memory?

Answer 43

Synaptic plasticity allows synapses to change in response to activity, strengthening or weakening over time, which is crucial for forming and retaining memories.

Question 44

How can researchers study memory by manipulating NMDA receptors?

Answer 44

By removing NMDA receptors, researchers can observe whether a memory disappears, helping to identify the role of specific synapses and receptors in memory formation.

Question 45

How are memories stored in the brain?

Answer 45

Memories are stored in the strength of synapses; stronger synapses help retain learned responses.

Question 46

Why is it difficult to pinpoint a specific location for memory storage in the brain?

Answer 46

Memories are likely distributed across multiple synapses and neurons, making them part of complex networks, which complicates isolating a single memory location.

Question 47

What might happen if NMDA receptors are removed from an animal’s brain?

Answer 47

If NMDA receptors are removed, the animal may lose the ability to form certain types of memories, demonstrating the critical role these receptors play in memory formation.

Question 48

Imagine a person is exposed to a repeated tone before a puff of air. Over time, they begin blinking when they hear the tone alone. What process is responsible for this change?

Answer 48

The process responsible for this change is classical conditioning, where the animal learns to associate the tone (neutral stimulus) with the puff of air (significant event), leading to the conditioned blink response.

Question 49

What is Associative Long-Term Potentiation (Associative LTP)?

Answer 49

Associative Long-Term Potentiation (Associative LTP) is a process where weak synapses, activated simultaneously with stronger synapses, become stronger. This process helps the brain “learn” associations between stimuli.

Question 50

How does Associative LTP strengthen weak synapses?

Answer 50

When a weak synapse and a strong synapse are activated together, the weak synapse strengthens and eventually becomes capable of independently triggering a neuron’s action potential.

Question 51

What is Hebb’s Rule?

Answer 51

Hebb’s Rule, or “Fire together, wire together,” explains that when two neurons fire together, their synaptic connection becomes stronger, making future communication easier. This mechanism is central to learning and memory.

Question 52

How does Hebb’s Rule relate to learning?

Answer 52

Hebb’s Rule suggests that learning strengthens synaptic connections between neurons that fire simultaneously, improving their future communication and facilitating memory formation.

Question 53

What is the significance of the hippocampus in memory?

Answer 53

The hippocampus is essential for forming long-term memories, especially episodic memories, which involve recalling specific events. Damage to the hippocampus impairs the ability to form lasting, conscious memories.

Question 54

What role does the hippocampus play in learning?

Answer 54

The hippocampus plays a critical role in memory formation and the consolidation of long-term memories, particularly those formed from individual events.

Question 55

How are brain slice preparations used in studying LTP?

Answer 55

Brain slice preparations allow researchers to stimulate neurons in isolated brain tissue, enabling them to observe how synapses strengthen over time and study mechanisms of learning and memory, particularly in the hippocampus.

Question 56

What happens to synaptic strength with different patterns of stimulation?

Answer 56

Synaptic strength can increase or decrease depending on the patterns of stimulation. Strong and weak stimulation patterns are used in research to understand how synapses adapt and change in response to learning.

Question 57

How does paired stimulation contribute to Associative LTP?

Answer 57

Paired stimulation, where weak and strong stimuli are presented together repeatedly, strengthens the weak synapse, enabling it to trigger an action potential independently, demonstrating synaptic connection reinforcement.

Question 58

What role do NMDA receptors play in Associative LTP?

Answer 58

NMDA receptors facilitate Associative LTP by allowing calcium ions to enter the neuron when it is depolarized, triggering changes that strengthen the synapse and improve future signaling.

Question 59

How do dendritic spikes influence synaptic strength?

Answer 59

Dendritic spikes occur when a neuron is strongly stimulated, causing depolarization to travel through the dendrites. This depolarization can influence nearby synapses, strengthening them through calcium influx via NMDA receptors.

Question 60

What is synapse-specific strengthening?

Answer 60

Synapse-specific strengthening ensures that only the synapses involved in paired stimulation are strengthened, making the connection between neurons more efficient for future signaling, without affecting unrelated synapses.

Question 61

What would happen if paired stimulation didn’t occur during LTP?

Answer 61

Without paired stimulation, the weak synapse would not strengthen, and the learning process would be less efficient, as synaptic connections would not be optimized for future communication.