Memory Systems Quiz

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Questions and Answers

What differentiates implicit memory from explicit memory?

Explicit memory consists of skills and habits.

Explicit memory is often difficult to articulate.

Implicit memory includes conditioned responses. (correct)

Implicit memory involves conscious recall events.

What does forgetting a lot indicate about brain function?

The brain is retaining unnecessary information.

The brain is underperforming.

The brain is malfunctioning due to memory loss.

The brain is functioning well by filtering out unneeded information. (correct)

Which scenario best illustrates how declarative memory can become implicit?

Learning a phone number by heart.

Recalling the names of all US Presidents.

Memorizing a recipe for a cake.

Feeling fear after being bitten by a dog. (correct)

What is a characteristic of phylogenetic memories?

They are conserved across generations and species. Signup and view all the answers

What does the pulvinars' increased spiking activity in monkeys indicate?

Quicker responses to perceived threats. Signup and view all the answers

What was the main objective of Lashley’s experiments on memory?

To determine if specific memory functions are localized or distributed. Signup and view all the answers

What is a consequence of intense ECT treatments?

Memory issues due to resetting synaptic connections. Signup and view all the answers

How did the complexity of mazes affect the performance of rats in Lashley's study?

Simpler mazes showed no difference regardless of lesion size. Signup and view all the answers

What does the mass action principle suggest about brain function?

The brain functions as a whole rather than through isolated regions. Signup and view all the answers

What characterizes habituation in non-associative learning?

Decreasing response to a stimulus that is constantly present. Signup and view all the answers

In the context of sensitization, what role does serotonin play?

It strengthens the gill withdrawal reflex through prolonged depolarization. Signup and view all the answers

What primarily governs long-term sensitization changes at synapses?

Activation of protein kinase A (PKA) leading to gene transcription. Signup and view all the answers

What neurotransmitter primarily acts as an excitatory signal in the brain?

Glutamate Signup and view all the answers

How does the dentate gyrus contribute to memory processing?

Pattern separation to differentiate similar inputs. Signup and view all the answers

What happens when PKA is activated in the presynaptic sensory neuron during sensitization?

Blocks potassium channels, prolonging depolarization. Signup and view all the answers

Which main pathway transfers information from the CA3 region to CA1 in the hippocampus?

Schaffer collateral pathway Signup and view all the answers

How is the long-lasting change facilitated in the synapses during long-term sensitization?

Through persistent activation of PKA. Signup and view all the answers

What does the entry of information into the hippocampus mostly depend on?

The entorhinal cortex as the primary input. Signup and view all the answers

What effect does long-term potentiation (LTP) have on neurons?

Increases the strength of synaptic connections. Signup and view all the answers

Which mutations impair memory formation in Benzer's experiments?

Dunce and Rutabaga Signup and view all the answers

What is the primary role of GABA in the central nervous system?

To inhibit neuronal activity. Signup and view all the answers

Which aspect of the hippocampus is primarily responsible for processing spatial and contextual memory?

CA1 region Signup and view all the answers

What is the role of AMPA receptors in long-term potentiation (LTP)?

They enhance synaptic insertion and retention during LTP. Signup and view all the answers

Which factor is essential for the specificity of LTP?

Only active synapses during stimulation undergo potentiation. Signup and view all the answers

What initiates long-term changes in synaptic connections in LTP?

Activation of NMDA receptors that allows calcium to enter postsynaptic neurons. Signup and view all the answers

What distinguishes long-term depression (LTD) from long-term potentiation (LTP)?

LTD occurs with low-frequency stimulation, leading to synaptic weakening. Signup and view all the answers

What effect does the reduction of Mdga2 have on synaptic function?

Disrupts the balance between excitatory and inhibitory transmission. Signup and view all the answers

How does the activation of NMDA receptors influence synaptic strength?

Induces phosphorylation of AMPA receptors. Signup and view all the answers

What is a consequence of blocking protein synthesis during the LTP process?

Return of synaptic strength to baseline for long-term memory. Signup and view all the answers

What role does calcium play in LTP?

Calcium influx is necessary for activating kinases that mediate LTP. Signup and view all the answers

In the context of contextual fear conditioning, what change occurs in synaptic strength after exposure to a shock?

Synaptic transmission in the hippocampus is potentiated. Signup and view all the answers

What defines the characteristic of cooperativity in LTP?

Both pre and postsynaptic activities must occur simultaneously for LTP. Signup and view all the answers

Which subunit knockout leads to the blockage of LTP in the hippocampus?

NR1 subunit. Signup and view all the answers

What happens when there is a low influx of Ca²+ in the postsynaptic neuron?

Activation of phosphatases that lead to LTD. Signup and view all the answers

What is the outcome of repeatedly applying glutamate onto spine heads?

Growth of the spine head and increased expression of AMPA receptors. Signup and view all the answers

What is the primary role of the medial temporal lobes in memory?

Enabling recognition memory for previously seen objects Signup and view all the answers

Which type of amnesia is characterized by the inability to form new memories after a specific onset?

Anterograde amnesia Signup and view all the answers

What symptoms are typical of Korsakoff’s Syndrome?

Memory impairment, apathy, and loss of coordination Signup and view all the answers

What is the implication of A-beta protein accumulation in Alzheimer's disease?

High levels are associated with sleep deprivation effects Signup and view all the answers

How do monkeys with medial temporal lobe lesions perform with recognition tasks?

They perform normally with small delays but struggle with longer ones Signup and view all the answers

What distinguishes Alzheimer's patients from individuals with pure amnesia like patient H.M.?

Alzheimer’s patients have deficits in both executive and semantic functions Signup and view all the answers

Which executive function impairment is NOT typically associated with memory disorders?

Challenges in recalling specific events Signup and view all the answers

What is one potential consequence of sleep deprivation regarding A-beta protein levels?

Decreased A-beta clearance from the brain Signup and view all the answers

What type of memory does an individual with retrograde amnesia primarily struggle with?

Recalling pre-existing memories from before the condition Signup and view all the answers

What is a key characteristic of episodic memory impairment?

Difficulty with free recall and specific event retrieval Signup and view all the answers

What does a freezing response in rodents indicate?

They remember the association with shock. Signup and view all the answers

What role do NMDA receptors play in spatial memory?

They are crucial for the formation and retrieval of spatial memory. Signup and view all the answers

What change occurs in NMDA receptor subunits as a brain matures?

NR2A replaces NR2B, decreasing synaptic plasticity. Signup and view all the answers

What effect does the activation of Calmodulin Kinase II (CaMKII) have on memory?

It enhances AMPA receptor synaptic expression. Signup and view all the answers

How do hippocampal place cells function in spatial memory?

They encode specific locations within the environment. Signup and view all the answers

How is the posterior hippocampus affected in experienced taxi drivers?

It grows larger with more navigation experience. Signup and view all the answers

What do grid cells in the entorhinal cortex create?

A grid-like pattern of spatial activity. Signup and view all the answers

What characterizes immediate memory?

It can recall information for a few seconds. Signup and view all the answers

What is the primary function of the medial temporal lobe in memory?

It aids in memory encoding and storage. Signup and view all the answers

How can stimulating the medial temporal lobe during surgery affect patients?

It can cause vivid recall of past experiences. Signup and view all the answers

What do neurons in the medial temporal lobe respond to?

Categories of specific stimuli. Signup and view all the answers

What does synaptic consolidation refer to?

Long-term changes in synaptic strength post-learning. Signup and view all the answers

Which type of receptor is crucial for enhancing synaptic plasticity in youthful brains?

NR2B receptors. Signup and view all the answers

What happens to the hippocampus of heavy GPS users based on studies?

It becomes smaller due to reduced spatial mapping activity. Signup and view all the answers

Study Notes

Memory Types

Implicit knowledge is unconscious, like knowing how to ride a bike, whereas explicit knowledge is conscious information, such as a phone number.
Learning is the process of encoding information, while memory refers to the storage of that information.
Forgetting is a sign of a healthy brain, as it's how the brain discards unnecessary information.

Memory Systems

Nondeclarative memory, like playing the piano, is procedural and implicit.
Declarative memories, such as facts, can become implicit.
A dog bite, which is a declarative memory, can cause a lifetime fear of dogs, which is an implicit memory.

Phylogenetic Memory

The fear of heights may have contributed to the survival of our ancestors.
Phylogenetic memories are encoded through evolution and preserved in generations.
Young birds instinctually crouch in response to a predatory bird, an example of phylogenetically conserved memory.
Genetic markers can help researchers understand how information is carried across generations.

Neural Correlates of Memory

Monkeys raised in captivity showed increased neural activity in the thalamus when presented with images of predators, even if they had never encountered them in real life.
Thalamus plays a role in rapid attention shifts and threat detection.
Pulvinar neurons in the thalamus show greater spiking activity (electrical impulses) in response to potential threats like snakes.
The speed of neuronal activity is linked to the efficiency of threat assessment.

Lashley's Research on Memory Localization

Lashley's experiments aimed to determine if memory is solely stored in a specific area of the brain (localization) or distributed across the brain (equipotentiality).
His research found that larger lesions in rats resulted in worse performance, especially on complex memory tasks.
Lashley concluded that memory is not localized; rather, it is affected by the overall size of cortical lesions, supporting the "mass action principle" - the brain functions as an interconnected whole.

Non-associative Learning

Non-associative learning is a type of implicit memory that does not involve linking one stimulus with another.
Two types of non-associative learning are habituation and sensitization.
Sea snail research is particularly useful because its simple neural circuits are conserved across species.
Habituation: Decrease in response to repeated stimuli. For example, the constant sound of a door closing may become less noticeable over time.
Sensitization: Increased response to stimuli triggered by dramatic events. For example, after a gunshot, a person might become more vigilant and sensitive to sounds.

Habituation and Sensitization in Sea Snails

Sea snails exhibit habituation. When repeatedly touched on the siphon, their gill contraction reduces over time.
When a shock is applied to the tail alongside the siphon touch, sensitization occurs, and the gill contracts more strongly.
This paired stimulation (siphon touch and shock) strengthens the response, even without the shock.

Molecular Mechanisms of Memory

Glutamate is the main excitatory neurotransmitter, depolarizing neurons, while GABA is the main inhibitory neurotransmitter, hyperpolarizing neurons.
Glutamate receptors include metabotropic receptors, which activate signaling cascades, and ionotropic receptors, such as AMPA and NMDA receptors.
AMPA and NMDA receptors allow ions to pass through.

Synaptic Plasticity: Short-Term Sensitization

When a sensory neuron is stimulated, it releases glutamate, which activates the motor neuron, causing the gill to contract.
Serotonin is released in response to a stimulus, activating adenylyl cyclase, which converts ATP to cAMP.
cAMP activates PKA, leading to the blocking of potassium channels, which prolongs depolarization and allows more calcium to enter the neuron.
More calcium triggers more glutamate release, strengthening the response.

Synaptic Plasticity: Long-Term Sensitization

In long-term sensitization, repeated stimulation results in increased serotonin release. PKA translocates to the nucleus of the sensory neuron, where it activates CREB.
CREB promotes the production of ubiquitin hydrolase (UH), which degrades proteins limiting PKA activity, ensures PKA remains active.
CREB also upregulates pro-synaptogenic signals, leading to an increase in the number and strength of synapses.

Molecular Mechanisms of Memory and Genetic Mutations

Benzer's experiments with fruit flies showed how mutations affecting cAMP signaling can impair memory formation.
Mutations in the genes "Dunce," "Rutabaga," and "Amnesiac" affect cAMP-PKA pathways, interfering with the formation of memories in flies.

Hippocampus and Memory Consolidation

The hippocampus plays a vital role in memory formation and consolidation. Information is temporarily stored there while being processed.
The hippocampus' role in memory consolidation is demonstrated by the presence of three main synaptic connections:
- Entorhinal cortex: The main input to the hippocampus.
- Dentate gyrus: Helps to differentiate similar experiences.
- CA3: Completes incomplete information.
- CA1: Processes spatial and contextual memory and sends information to the cortex.

Long-Term Potentiation (LTP)

LTP is a long-lasting increase in synaptic strength discovered through experiments stimulating the hippocampus of rabbits.
Features of LTP:
- Associativity: Multiple active synapses at the same time are needed for LTP.
- Cooperativity: LTP requires both pre and postsynaptic activity.
- Specificity: Only active synapses undergo potentiation.
- Enduring: LTP can last for long periods, even years in vivo.

Cellular Mechanisms of LTP

AMPA receptors are activated during normal synaptic transmission. Increased AMPA receptor insertion and phosphorylation contribute to early LTP, a temporary increase in synaptic strength.
NMDA receptors are activated after repeated stimulation, leading to synaptic enlargement and long-term changes. These changes contribute to long-term memory.

Role of NMDA Receptors in LTP

NMDA receptors mediate the induction of LTP. They need both membrane depolarization and glutamate binding to activate.
When activated, NMDA receptors allow calcium to enter the postsynaptic neuron, a crucial event for LTP.
AMPA receptor phosphorylation and increased expression contribute to maintaining LTP.
Increased glutamate release leads to spine head growth and AMPA receptor expression, strengthening synaptic connections.

Molecular Pathways Involved in LTP

Activation of NMDA receptors increases postsynaptic calcium levels.
Calcium activates CaMKII and PKC, triggering downstream signaling.
Kinases phosphorylate AMPA receptors, promoting their trafficking to the synaptic membrane and stabilizing them.
Long-term LTP involves protein synthesis and transcriptional programs for lasting synaptic modifications.
Epigenetic modifications also play a role in LTP.
Once CaMKII is fully activated, it becomes constitutively active, meaning it remains active even without continued calcium.

LTP and Protein Synthesis

Long-term LTP requires translation and post-translational regulation.
Blocking protein translation leads to a loss of long-term memory. However, both learning and short-term memory remain intact.

Long-Term Depression (LTD)

LTD is a long-lasting decrease in synaptic strength.
It is induced by low-frequency stimulation (1 Hz) of Schaffer collateral axons, resulting in a small increase in calcium levels in postsynaptic CA1 neurons.
This low calcium activates protein phosphatases, leading to internalization of AMPA receptors from the synaptic membrane, weakening the synapse.

Regulation of LTP and LTD

LTP involves high, transient calcium influx, which activates kinases, leading to AMPA receptor insertion and synaptic strengthening.
LTD involves low, sustained calcium influx, which activates phosphatases, promoting AMPA receptor internalization and synaptic weakening .
This balance between kinases and phosphatases is crucial for the regulation of synaptic plasticity.

Behavioral Evidence for LTP as a Memory Mechanism

Rats that were shocked in a dark box subsequently showed increased synaptic strength in the hippocampus.
This demonstrates the link between LTP and the formation of memories associated with aversive experiences.

Evidence for LTP in Humans

Electrical stimulation of the temporal lobe in humans during brain surgery can evoke vivid memories.
Individuals with temporal lobe epilepsy sometimes experience unintended recall of memories.
These findings suggest that the temporal lobe is involved in both memory formation and retrieval.

Selective Neural Representations in the Medial Temporal Lobe (MTL)

Neurons in the MTL show highly specific responses to particular categories, such as faces, objects, or scenes.
This demonstrates the MTL's role as a storehouse of specific information.
Specific MTL neurons can be associated with specific famous people.

Hippocampal Place Cells and Spatial Memory

Hippocampal place cells are specialized neurons that encode spatial information. They fire when an animal is in a particular location, providing a spatial map of the environment.
Place cell activity is associated with the location the animal is in, and the strength of the activity (indicated by color intensity) reflects the significance of the location.
As an environment becomes more familiar, the place fields can change, indicating the adaptability of the hippocampus.

PET studies have shown that the right hippocampus is more active during navigation in a virtual environment.
However, hippocampal activity decreases if arrows are used for guidance, requiring less effort in navigating.
Frequent GPS users have smaller hippocampi.

Taxi Driver Studies

London taxi drivers, who memorize complex road systems, have larger posterior hippocampi, suggesting that spatial navigation can lead to structural changes in the brain.

Grid cells are located in the entorhinal cortex and generate a "grid" representation of the environment.
Grid cell firing pattern creates a grid-like pattern across different locations.
These cells contribute to our internal representation of space.

Different Memory Stages

Immediate memory: Recall of information for a few seconds, such as remembering the last few words in a sentence.
Working memory: Used for performing tasks, such as following directions or mental math.

Medial Temporal Lobe (MTL) Memory System

The MTL memory system is crucial for forming and storing memories.
The hippocampus helps to consolidate memories.
Long-term memories are eventually stored in the neocortex.
This system converts short-term memories into long-term memories.

MTL and Memory Recall

Electrical stimulation of the MTL during brain surgery can evoke vivid flashbacks in patients, suggesting the MTL's role in memory recall.
MTL epilepsy patients often experience involuntary memories, further demonstrating the MTL's involvement in memory processing and retrieval.

Synaptic Consolidation and Systems Consolidation

Synaptic consolidation involves long-term changes in synaptic strength, representing memories formed shortly after learning.
Systems consolidation involves the gradual transfer of memories from the hippocampus to distributed locations in the neocortex for more permanent storage. This process can take days, weeks, or even longer.

Memory Retrieval and Brain Regions

When recalling memories, the brain reactivates regions involved in the original experience.
For visual memory retrieval, the visual cortex is activated.

Anterograde and Retrograde Amnesia

Anterograde amnesia: Inability to form new memories after the onset of the condition. People retain past memories but struggle to retain new information.
Retrograde amnesia: Loss of pre-existing memories prior to the onset of the condition. Individuals can form new memories but cannot recall past events or experiences. This is less common and often caused by cortical tissue damage.

Medial Temporal Lobe (MTL) and Recognition Memory

Macaque monkeys trained on a task involving object recognition show significant memory impairment after bilateral MTL lesions, suggesting its role in recognition memory.
MTL lesions disrupt the ability to recognize previously seen objects, even with short delays.

Korsakoff’s Syndrome

Results from chronic alcoholism.
Symptoms include confusion, memory impairment, apathy, lack of coordination, tremors.
Lesions are typically found in the dorsal thalamus and mammillary bodies.
Anterograde deficits result from MTL lesions.
Retrograde deficits result from cell death in the neocortex.

Alzheimer’s Disease

Episodic Memory Impairment: Difficulty with free recall and recalling specific events or experiences.
Executive Function Impairment: Challenges in planning, organizing, and executing tasks.
Semantic Memory Impairment: Difficulties with knowledge about facts and concepts.
Anterograde impaired memories, also progressive.
Unlike pure amnesia patients, those with Alzheimer's show deficits in both executive and semantic functions, impacting their ability to learn new procedures.
Higher levels of A-beta protein in the brain, which can aggregate and form plaques, are associated with Alzheimer's.
Sleep deprivation can increase A-beta load, suggesting a role for sleep in its clearance.
Reduced neuronal activity, weakened connections, and decreased firing of action potentials.

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Description

Test your understanding of memory systems with this quiz that explores the differences between implicit and explicit memory, the role of forgetting, and the findings from Lashley’s experiments. Delve into concepts like declarative and phylogenetic memories, as well as the neurological implications observed in monkeys. Challenge yourself to deepen your knowledge of human memory functions.