Neuroscience of Memory

Question 1

What does it mean to say that memory is an emergent property of the nervous system?

Answer 1

it is not a

property of the individual neurons, but it emerges when they work together.

Question 2

What is the function of dendrites?

Answer 2

Dendrites are used for receiving signals either from sensory cells or from other neurons. Generally speaking, dendrites collect information for the neuron

Question 3

What are terminal buttons

Answer 3

At the end of each axon are nodules called terminal buttons, which contain
the neurotransmitters.

Question 4

What produces myelin?

Answer 4

If a neuron

has a myelin sheath, the myelin is not created by the neuron but by glial cells associated with it.

Question 5

Describe what happens during an action potential to rehash

Answer 5

When a neuron fires, sodium ions in the surrounding extracellular fluid flood into the neuron because
the depolarization of the neuron causes sodium “gates” on the cell membrane to open. The sodium ions are positively charged and this is what produces the positively charged action potential. The electrical wave flowing down the axon is the wave of sodium gates opening and allowing these ions to enter the cell, much a like a row of dominos falling down. Each domino causes the next to falter. Immediately behind this wave of positive electrical charge, there is a second wave. This is a wave of potassium ions being forced out of the cell. This is part of the beginning process of the cell recovering its resting potential level of electrical charge.

Question 6

Name and describe the roles of 5 neurotransmitters important for memory

Answer 6

acetylcholine (ACh): When acetylcholine effects are enhanced, memory can improve, and it declines when acetylcholine effects are suppressed. Acetylcholine may work to enhance the strength of synaptic potentials during long-term potentiation

Glutamate (Glu) is a critical excitatory neurotransmitter involved in the alteration of synapses and creating new memories. In comparison,

gamma-amino butyric acid (GABA) is an inhibitory neurotransmitter, also critically involved in new memory formation. GABA is strongly related to glutamate in that GABA is formed by modifying the glutamate molecule.

Norepinephrine is involved in the consolidation of memories

dopamine is important to memory processing.

Question 7

What are the two general classes of neurotransmitters?

Answer 7

Excitatory neurotransmitters encourage the subsequent neuron to fire, causing the ion gates on the neuron’s cell membrane to open and let in the sodium ions. In contrast, inhibitory neurotransmitters encourage the subsequent neuron to not fire, encouraging the ion gates to stay closed.

Question 8

What is the purpose of inhibitory neurotransmitters?

Answer 8

one-way information is coded in the nervous system is as a pattern of activity across a wide set of neurons. To create this pattern, some neurons need to be firing and others not.

Question 9

Although communication between neurons occurs at the synapse, how do these connections get altered as new things about the world are encoded into memory?

Answer 9

One way that this is done is through a process known as long-term potentiation, or LTP. LTP strengthens the connections between neurons by altering the ease with which postsynaptic neurons will fire. The majority of the change that strengthens a connection between neurons is occurring at the dendrites.

Along the cell membrane of a dendrite, there is an increase in the number of receptor cites for the neurotransmitters, as well as the growth of dendritic spines, although there may be some changes in the presynaptic neuron’s axon as well. As a result, more neurotransmitters can bind to the post-synaptic cell membrane, making it easier to reach the level of depolarization needed to cause the neuron to create an action potential.

Question 10

Name a process analogous to LTP

Answer 10

long-term depression, or LTD, which weakens connections between neurons, which can also be important for learning

Question 11

What stage of memory formation is LTP important for and what characteristic of it demonstrates this?

Answer 11

Often, LTP can last for days or weeks, but it eventually dissipates. Thus, LTP is the type of neural change that occurs in memory formation early on, but another process will be needed for information to be stored more permanently in other parts of the brain.

Question 12

How is the occipital lobe involved in memory?

Answer 12

The occipital lobes detect features in the environment, but the sensitivity to these features is based on experiences with the world. For example, if kittens are reared in an environment in which they only see horizontal lines, when they are adults they will walk into a table leg because they cannot see vertical lines. They lack the feature detectors for vertical objects

Question 13

How are the parietal lobes involved in memory

Answer 13

Less thought of than temporal and frontal lobes but are used in a wide range of circumstances. For example, working memory processes for visual memory or the spatial manipulation of information involve the parietal lobes. Animals that have had their parietal lobes surgically removed have trouble remembering spatial relations.

Question 14

Which lobe is most closely associated with memory? Why is this not surprising?

Answer 14

temporal lobes, This is not surprising as they surround the hippocampus

Question 15

What part of the temporal lobe is most often studied in regards to memory?

Answer 15

The part of the temporal lobe that is often studied with regard to memory is directly adjacent to or surrounding the hippocampus. The area adjacent to the hippocampus is often referred to as the medial temporal lobe. The temporal lobes are where many of our long-term memories for different types of information may be stored.

Question 16

What does damage to the temporal lobes often result in?

Answer 16

Damage to this part of the brain often results in some memory loss. This part may be involved in remembering events from one’s own life, something called autobiographical memory. It may also be important for priming

Question 17

How are the frontal lobes involved in memory? (3)

Answer 17

they are involved in the coordination of information, so they are critical for working memory

Knowledge of the information content, as well as knowing where it came from, must be put together using a
process of source monitoring

The frontal lobes are also involved in remembering what we need to do in the future, something called prospective memory

Question 18

What is the DMN?

Answer 18

The default mode network is a collection of brain structures whose activity is highly correlated.

Question 19

When is the DMN activated?

Answer 19

The DMN is more active when a person does not have attention strongly engaged in some activity. That is, the activation of the DMN is negatively correlated with activity in of various attention networks in the brain. In some sense, this network in the brain that is more active by default when people are colloquially thinking about “nothing in particular,” such as when they are daydreaming etc. It is also activated when watching TV and so may be involved in basic comprehension.

Question 20

What previously mentioned process is the hippocampus very involved in?

Answer 20

Much of the research on long-term potentiation has been done by studying neurons from the hippocampus. While it is strongly associated with LTP, and thus may be able to retain information for up to several weeks, it does not appear to be the location where very long-term declarative memories are actually stored.

Question 21

What surround the hippocampus?

Answer 21

important cortical areas, which are collectively known as the hippocampal complex.

Question 22

Name 3 associated areas of concern outside of the hippocampus proper and their location relative to the hippocampus. Also name a function associated with them

Answer 22

First, for processing spatial information there is the parahippocampal cortex, which is posterior (behind) and inferior to (below) the hippocampus.

Next, for processing object information, there is the perirhinal cortex, which is inferior to the hippocampus and anterior to the parahippocampal cortex.

Finally, there is the entorhinal cortex, which is anterior to and inferior of the hippocampus. The entorhinal cortex takes information from the parahippocampal and perirhinal cortices and passes it along to the hippocampus itself.

Question 23

Name the areas of the hippocampus (not necessary)

Answer 23

it is composed of the dentate gyrus, regions CA1, CA2, CA3, and CA4 (with areas CA1 and CA3 being more implicated in memory processing), and the subiculum.

Question 24

Describe the connections of the hippocampus and the surrounding structures (not necessary)

Answer 24

The hippocampus itself, by and large, the dentate gyrus and area CA3 receive inputs from the medial entorhinal cortex. Moreover, the dentate gyrus also sends signals to areas CA3. In comparison, area CA1 receives different inputs from the lateral entorhinal cortex and passes this information on to the subiculum. Area CA1 also receives inputs from area CA3. The subiculum sends its processes on to the entorhinal cortex. Some fibers from the hippocampus also travel to the fornix, the mammillary bodies, and the thalamus.

Question 25

What symptoms can occur through damage to the hippocampus and what function may this demonstrate?

Answer 25

A great deal of research on the hippocampus is focused on its role in the formation and storage of new memories. Damage to the hippocampus can lead to severe declarative memory deficits, such as antero-grade amnesia. . That said, it also may be involved in the retrieval and the replaying or re-experiencing of prior events

Question 26

Where are place cells and grid cells located? Name a third cell similar to these and its location and a possible fourth cell which there is some evidence for

Answer 26

place cells (which are active when an organism is in a particular location) are found in the hippocampus, grid cells are found in the
entorhinal cortex, and boundary cells are found in the subiculum and entorhinal cortex. There is also some evidence for hippocampal time cells that track when events occur

Question 27

What conclusions can therefore be drawn about the function of the hippocampus based on these cells?

Answer 27

the hippocampus is important for processing the spatial-temporal framework within which episodic memory events occur.

Question 28

Summarise the function of the hippocampus

Answer 28

Overall, the hippocampus is specialized for processing and binding conjunctions of stimuli that appear together in the environment. It is well designed for the rapid encoding and binding of episode-specific conjunctions— that is, whatever is co-occurring at the moment. This includes the spatial and temporal contexts, as well as the objects within the current event. The hippocampus does this by processes of pattern separation (segmenting experience) and completing missing elements from general world knowledge. That is, the hippocampus binds together information from a variety of sources to create integrated memories of individual scenes or events

Question 29

What role does the 
1. Amygdala
2. basal ganglia
3. Cerebellum 
4. Diencephalon (3)
Play in memory?

Answer 29

The amygdala is involved in processing emotional aspects of memories

Basal ganglia are important for motor memory—that is, the control of the voluntary muscle groups. The basal ganglia are implicated in memory for habits and motor skills, such as riding a bicycle.

cerebellum is similar to basal ganglia, used in memory for procedural skills that involve the complex coordination and control of the muscles, such as walking. This is a more primitive form of memory.

The diencephalon, including the thalamus and hypothalamus is involved in memory for conscious, factual knowledge. It has been suggested that the diencephalon is important in processing information about the temporal sequence of events. More indirectly, the diencephalon is involved in controlling the neurotransmitters that are present in the nervous system at any given time, and so it has a roundabout influence on memory.

Question 30

Describe two ways to measure the structure of the brain apart from after death and during brain surgery

Answer 30

take a series of X-rays of the skull, each of them taking a different “slice” of the head, and then examine the brain structures revealed. This is known as a computer-assisted tomography scan, or CT scan (also known as a CAT scan).

magnetic resonance imaging, or MRI works with the resonant frequencies of different molecules in the brain. First, a person is placed in a strong, controlled magnetic field. This is the magnetic part of MRI. This magnetic field affects the spin of all of the atoms of a certain type in the body, such as all of the hydrogen atoms, causing the protons in those atoms to line up along a specific axis, with about half oriented in each direction along that axis. After this, a radio frequency pulse is passed through the body. This pulse causes unmatched protons to spin in a different direction at a specific frequency. Con-currently, a set of gradient magnets are cycled on and off, which alter the primary magnetic field, allowing images or slices of the brain to be acquired. When this pulsing stops, the hydrogen atoms go back to their normal state and release the energy absorbed from the pulses. This is the resonance in MRI. This energy is detected by the coils in the machine and sent to a computer for analysis. The computer then interprets the data and creates the MRI image.

Question 31

What other functions can a cat scan carry out?

Answer 31

CT scans show the structure of a living brain and can reveal things such as the location of a tumor, damage from a stroke, or just the general condition of a brain.

Question 32

Given how an MRI works, what molecules typically determine the structure?

Answer 32

Typically, the density of water molecules, which contain hydrogen, is used to determine structure. The density of hydrogen atoms varies as a function of whether a particular region contains unmyelinated neurons, myelinated axons, cerebral spinal fluid, and so on

Question 33

What advantages are there to MRI compared to other methods?

Answer 33

An advantage of MRI is that it is not necessary to inject a chemical into the body, as with PET scans (see later), or use harmful radiation, as with CT scans. Perhaps the biggest advantage of MRI scans is their clarity. These images are of a higher quality than those from a CT scan.

Question 34

What does EEG measure?

Answer 34

event-related potentials, or ERPs. An ERP is a regular change in the pattern of electrical energy measured as a function of the particular task or event that the person is thinking about (Coles, Gratton, & Fabiani, 1990). The memory researcher has a person engage in various tasks at predetermined points in time. These are the “events” of event-related potentials. Then the researcher looks at the EEG waves that were recorded at that time relative to when the events occurred. These electrical “potentials” in the EEG waves are what are “related” to the earlier “events”—hence the name event-related potentials.

Question 35

If you’ve ever seen an EEG wave, it looks like a random bunch of squiggles. How does the researcher get an idea of what’s going on?

Answer 35

for each trial of an ERP study, this is largely what it is, the researcher needs to average the electrical potentials across a large number of trials. This averaging process washes out much of the noise, leaving a clearer signal. As more trials are averaged together, the ERP wave becomes more pronounced. This ERP signature is often a relatively large wave of positive or negative electrical charge in a region of the brain occurring at a particular point in time after the target even

Question 36

What is an advantage of EEG compared to other methods?

Answer 36

Temporal resolution

Question 37

How do people refer to or label a wave?

Answer 37

in terms of interesting components in the waveform and the nature of these components. For example, people might talk about a P300 wave, which refers to an electrically positive wave occurring about 300 ms after the beginning of an event. An N400 wave refers to a negative wave occurring about 400 ms after the beginning of an event

Question 38

Describe disadvantages to ERPs

Answer 38

the spatial resolution —where things happen in the brain—is poor. One can get a general idea about what part of the brain is involved but determining a precise location is difficult.

there is a lot of “stuff” between the electrodes and the brain activity they are recording—skin, blood vessels, meninges, and bone. In some ways, using EEG recordings to figure out what is going on in the brain is like trying to figure out what is going on in a factory by listening through the wall.

Question 39

While ERPs provide information about the level of positive or negative electrical charge at a point in time, there is other information that can be extracted from EEG signals

Describe this

Answer 39

The nervous system has a tendency to have various oscillators throughout it. That is, groups of cells tend to fire together. This is called synchronization, and when this increases after an event it is called event- related synchronization, or ERS. When a person is at rest, synchronization is stable. However, when a person is engaged in a mental activity there may be a desynchronization. This is called event-related desynchronization, or ERD.

Question 40

How else may these frequencies differ?

Answer 40

These oscillations occur at different frequency bands, depending on how fast the oscillations are. One way of dividing up the frequency bands is to have different regions separated by about 2 Hz each, using a person’s based frequency as a reference point, defining the delta band as –8 to –6 Hz, the theta band as –6 to –4 Hz, the lower 1 alpha as –4 to –2 Hz, the lower 2 alpha as –2 to 0 Hz, and the upper alpha as 0 to +2 Hz. Changes in any of these bands can vary as a function of the memory task.

Question 41

How are ERD patterns related to memory?

Answer 41

ERD patterns are related to memory performance. For example, during effective memory processing there is decreased alpha synchronisation and increased theta synchronisation.
Essentially, the resting alpha synchronization is disrupted by activity of a particular type. The theta synchronization is associated with increased activity in the hippocampus and surrounding structures.

Moreover, alpha and theta band power have been related to activation and inhibitory processes in memory.

Finally, the distinction between episodic and semantic memory is supported by ERD work showing greater upper alpha desynchronization for semantic memory, and increased theta band synchronization for episodic encoding

Question 42

Name two other measuring methods which exploit the electrical aspect of the brain

Answer 42

transcranial magnetic stimulation (TMS)

magnetoencephalography, or MEG

Question 43

How does MEG work?

Answer 43

Uses magnetic fields to measure cortical electrical activity.Many parts of the brain are always active, doing lots of different things at any one time. To get an idea of what part of the brain is involved in a process measured in a MEG scan, the subtractive method is used.

With the subtractive method, scans are taken both when the person is doing the mental activity of interest as well as a control condition in which the person not thinking about anything in particular. The brain activity of the control condition is subtracted from the activity recorded during the process of interest.

Question 44

How does MEG compare to EEG?

Answer 44

Overall, researchers can use MEG technology to pinpoint which parts of the brain may be active for various memory tasks. MEG scans have better spatial resolution than EEG and have a good temporal resolution, of about 10 ms. This is not as good as ERPs but still respectable.

Question 45

What do other neuropsychological methods use instead of electrical impulses? Name two of these methods

Answer 45

Some involve measures of cerebral blood flow. Collections of neurons that are working harder need more nutrients to be replenished and keep going. As a result, blood flow to those areas increases to compensate for this.

positron emission tomography, or PET

functional MRI, or fMRI

Question 46

Describe PET

Answer 46

For positron emission tomography, or PET, people are injected with a radioactive isotope of oxygen called oxygen-15 or 15O. This isotope decays to 16O, which is reasonably stable. The level of radioactivity is very low and short- lived (it has a half-life of just over two minutes), so there is little harm to the body. Once the isotope is in the bloodstream, the person is placed in a scanner that measures the levels of the isotope in the brain. Recording levels in control conditions are compared with experimental conditions where the person is engaging in the type of thought that is of interest for the study.

Question 47

How does PET compare to ERPs?

Answer 47

Compared to ERPs, the spatial resolution in PET scans is much better. However, with PET it takes a long time for a good image to be generated, typically no faster than 20 seconds.

Question 48

How does fMRI work?

Answer 48

The MRI technology discussed earlier also has an advantage over CT scans in that it can be adapted to look at function as well as structure. This is called functional MRI, or fMRI. fMRI uses the detection of oxygen atoms as a measure of mental activity. The density of oxygen molecules is associated with the operation of neural assemblies and the flow of blood to fortify those cells. After all, the delivery of oxygen is one of the primary purposes of the bloodstream.

Question 49

How does fMRI compare to PET?

Answer 49

An fMRI scan has an advantage over PET because no injection is required and the images can be taken in a shorter period of time, in the order of a few seconds. Still, fMRI scans cannot match the temporal accuracy of ERP measurements.

Question 50

Apart from these types of measurements, how can the function of brain areas be measured in people?

Answer 50

from case studies of people who have suffered some damage or lesion to the brain (altered brains)

Question 51

Although brain lesions provide valuable insights, why are they imperfect? (3)

Answer 51

First, seldom is there a pure lesion, with one structure being affected and the other structures remaining unharmed. This is true for both accidents and diseases affecting humans, as well as animal studies in which lesions are intentionally made surgically.

Another problem with lesion studies is that there are never two cases of people with identical lesions. Thus, it cannot be determined whether the consequences of the damage are unique to that person or are a generalizable consequence.

Finally, lesions are haphazard both in terms of where and when they occur. They do not afford the sort of control one would have in a systematic study.

Question 52

Apart from case studies how else can altered brains give insight?

Answer 52

Studies of special populations of people who have a neurological condition also provide useful data. (amnesia caused by alcohol overuse etc). Also, there are systematic neurological changes that occur as a result of the natural aging process. Thus, age-related changes in memory can be viewed as neurological assessment of memory. Finally, some diseases, such as Alzheimer’s, have systematic effects on the central nervous system. In these special populations, there is some regularity in the change that occurs, so we can observe a systematic change in neurological function that results in altered thoughts and behaviors.

Question 53

What is meant by consolidation

Answer 53

The information that is currently being thought is short-term/working memory in the language of the modal model of memory. However, for information to be useful beyond the current moment it needs to be stored in a state that does not require active neural firing. The process of making memories stable beyond the current moment is called consolidation.

Question 54

What is meant by Ribot’s gradient? How is it explained through consolidation?

Answer 54

A great deal of the evidence for consolidation comes from work on brain damaged individuals, particularly those with retrograde amnesia. Essentially, people are more likely to lose recent memories, while older memories remain intact. The idea is that newer memories have not yet been sufficiently consolidated, and so they are easier to disrupt in the face of head trauma. In comparison, older memories are more consolidated and so are harder to disrupt.

Question 55

What is very important for memory consolidation?

Answer 55

While memory consolidation is going on all of the time, these processes become more intense when a person is sleeping. Even better, if you dream about what you learned prior to sleep you are more likely to remember it later. Part of the reason we sleep is to provide our brain with an opportunity to engage in activities that are not possible or are less effective when we are awake.

Question 56

What else is helpful for memory consolidation

Answer 56

Finally, in addition to sleep, some memory consolidation can also be boosted through physical exercise

Question 57

Name different types of consolidation

Answer 57

synaptic and systems consolidation

Question 58

How is there a bias in the information here about consolidation?

Answer 58

Our discussion is focused on declarative memory consolidation. There are consolidation processes for nondeclarative memories, but these involve different neural systems, such as the basal ganglia and cerebellum

Question 59

Describe synaptic consolidation

Answer 59

Synaptic consolidation is the creation of relatively enduring memories that have just been actively thought about. It occurs in the hippocampus through LTP. This is a relatively rapid process that involves information that is currently active in the firing neural assemblies of short-term/working memory. If people are given an opportunity to briefly rest (say 2.5 seconds) after viewing information, this gives synaptic consolidation an opportunity to occur without further incoming and interfering items. Moreover, from what we know about LTP, we can estimate that synaptically consolidated memories may be
retained for a few days or weeks. How ever, this type of consolidation is transient and is not the final permanent storage of memories.

Question 60

Describe systems consolidation

Answer 60

After synaptic consolidation, there is a wider consolidation that occurs in larger brain systems. Much less is known about systems consolidation, other than it involves long-term memories becoming more independent of the hippocampus. As memories became consolidated in the cortex, the hippocampus became less involved and the cortex became more involved.

Question 61

Look at the graph for retention in the four different stages. What does the red line represent?

Answer 61

This is the availability of a given memory trace. It is the sum of the three other com ponents. This is a negatively accelerating function, as is observed with Ebbinghaus’s for getting/retention curve. This is the case despite the fact that the three functions that give rise to it each have different shapes. Thus, the forgetting
curve that is derived from memory data may reflect the operation of multiple, different underlying processes that each have their own characteristics.

Question 62

What is meant by reconsolidating

Answer 62

A process of reconsolidation can occur when a memory that has been consolidated is later remembered. This causes it to be reactivated and this reactivated memory is then reconsolidated. What is interesting is that during reactivation a memory enters a fluid, malleable state where it can be changed! That said, the older and more strongly consolidated a memory is, the less malleable it is following retrieval and the harder it is to change.

Question 63

In what way can two memories be altered during reconsolidation?

Answer 63

The first is for information to be lost from the original memory. If a consolidated memory is retrieved and then disrupted, the consolidated memory is lost. (rats memory of fear inducing stimulus interrupted by protein synthesis inhibitor)

The other way for reconsolidation to have an influence is for new information to be added to a memory trace. Here, a previously consolidated memory is retrieved and then new information is presented at the same time. This new material is then incorporated into the memory. (consolidated list mixed with new list)

Question 64

What other process may aid in the formation of permanent memories?

Answer 64

Neurogenesis; While you already have most of the neurons you’ll have to work with, you brain is still creating new ones all the time. Thousands of new neurons are created in the hippocampus each day. However, the fate of many of these new neurons is to die off.

That said, there is some evidence that, if an organism engages in new learning during the day, more of these newly created neurons will stick around, perhaps because they become part of networks of knowledge created during learning. Thus, it seems likely that the more you learn during the day, the more of these new neurons you will retain. This gain in neural mass can then aid your ability to learn even more information later.