Lecture 1 Flashcards
Introduction
1
Q
What is white matter in terms of brain areas?
A
The neuro-connections between the different brain areas.
2
Q
What is a neuron?
A
A special cell that can signal signals in an electrical or chemical way.
A neuron consists of a cell body and they have axons which can be very long.
3
Q
Where are the cell bodies located the most?
A
The cell bodies are mostly in the grey matter.
4
Q
How is grey matter defined?
A
By what we measure in an MRI.
5
Q
What is white matter?
A
The white matter is the long axon from the cell bodies connecting all the way to other neurons.
6
Q
Why is white matter white?
A
They are white because they have small layers of fat, myelin, around the axons. These layers of fat make sure that the electrical signal can be transferred much quicker.
7
Q
What types of images does an MRI have?
A
- Pictures of the brain; 3D reconstructions of e.g., the cortex.
- Measures (global axonal) connections between different brain regions.
- Movies using functional MRI with which we can get an impression of the activity in the brain.
8
Q
What does the abbreviation MRI stand for?
A
Magnetic Resonance Imaging
9
Q
What does the abbreviation fMRI stand for?
A
Functional MRI
10
Q
What can you see when looking at MRI pictures?
A
The brain structure.
We can make slices of the brain with MRI and we can stick them together to get a 3D construction of the structure of the brain.
11
Q
What can you see when looking at fMRI pictures?
A
The brain function.
You get the structure and an average map of where the activity in the brain was found.
12
Q
Why is it challenging to work with children when using an MRI machine?
A
You have to lay very still in the MRI machine.
Children have to be trained well, they will often do a mock scan, they get really good instructions and they sometimes even practice at home.
13
Q
How can you do an experimental task when using an MRI machine?
A
There is a little mirror in the MRI machine through which they can look outside to a screen, this way they can do tasks with buttons. This way you can measure what their brain does when they’re doing an experimental task.
14
Q
What kind of experiment is less practical to do when using an MRI machine?
A
Considering that a MRI machine is very loud, it is less practical to do an experiment with sound.
15
Q
What is fMRI compared to MRI?
A
fMRI is a special MRI technique to measure brain activity.
16
Q
What does fMRI measure?
A
fMRi measurements are an indirect measure of brain/neuronal activity.
We assume that if there is brain activity somewhere there is more oxygen needed which will cause more blood flow.
There is a change in hemoglobin in the red blood cells, these magnetic properties of hemoglobin is measurable.
The higher the neural activation, the higher the oxygen in the blood and the higher the fMRI signal.
17
Q
What does the abbreviation of the BOLD-effect stand for?
A
Blood Oxygenation Level Dependent
18
Q
What is something that you need to take into account when recording with an fMRI?
A
It takes some time because it takes some time for the blood/oxygen to go to the active areas.
So, you need to take into account that if you show a picture to a participant it will take some time before you can record activities.
19
Q
What does the abbrevation EEG stand for?
A
Electroencephalogram
20
Q
EEG (vs. fMRI)
A
- Non-invasive technique.
- Records brain signals.
- High temporal resolution (in ms) / Low spatial resolution.
- This is a more direct measure of electric signals, but it is more superficial. It also cannot go deep into the brain. It is also harder to locate where the signals are coming from, from which brain structures.
- You can do a very complicated analysis to get an idea of where the signal came from but in general the spatial resolution is very low and the temporal resolution is high.
- Activation during long periods of time (e.g., sleep).
- You don’t have to sit still for as long as with (f)MRI.
o So you can study children and even babies more easily. - Electrodes are placed on the outside of the scalp, you need glue to stick them on it. So afterwards you need to wash your hair very well to get the glue out.
21
Q
fMRI (vs. EEG)
A
- Non-invasive technique
- High spatial resolution (in mm)/ Low temporal resolution (>5 sec)
o You know where the signal comes from, with high accuracy on millimeter level but it has a low temporal resolution due to the indirect measurement. - You don’t have to wash your hair afterwards.
22
Q
How can you set up an experimental design if you want to measure something with fMRI?
A
- You have to ask yourself what brain regions are active.
- You have to have a good control condition.
- I’ts better to show images than voices.
Example: first you show a face (2500 ms), then you show a white cross (2000-5000 ms) and afterwards a picture of a house, etc.
It can take quite a long time (20-30 minutes).
23
Q
Why do you need to have a good control condition when measuring something with fMRI?
A
The brain is always active so you can’t know if the activation is from what you want to measure or something else.
24
Q
Why do you show a white cross in between images when measuring something with fMRI?
A
You show the white cross because it takes a little bit of time to see the brain activity you want to record that, by immediately showing the next image you can’t clearly take them apart.
25
What is a voxel?
One specific pixel we can map in the brain.
26
How can you measure the contrast between faces and houses with an fMRI?
- You contrast the brain activity between faces and houses.
- You average the signal of all of the face conditions and you average the signal of all of the house conditions and you subtract them from one another. Then you can see whether it is significantly more active when you see faces compared to when you don’t see faces.
27
What are the results of the measuring of faces compared to houses with fMRI?
It shows that a specific place in the brain is the Fusiform Face Area, which we know is specifically sensitive to seeing faces and face expressions.
28
How can you speed up the fMRI analysis?
Because it takes some time to record each slide, it will take less time to get one brain volume if you focus on a specific area in the brain.
29
How can you average the signal during fMRI analysis?
By alternating the slices.
30
In which ways can you measure a signal in slices when doing an fMRI analysis?
- Sagittal slice
- Voxel (volumetric pixel)
31
Sagittal slice (fMRI analysis)
- Number of slices
- Slice thickness
32
Voxel (fMRI analysis)
- 3D pixel from the images in the brain
- In-plane resolution
- Matrix size
- In each of these voxels you can measure the average signal. One area can be a hundred voxels wide, you can measure if all the 100 voxels are active during a certain task.
33
What is important to keep in mind with fMRI research?
- BOLD signal is not an absolute measure of brain activation but relative
- Control condition is thus crucial
- Many trials per condition (>20)
- Fixation between trials
- Engage participants
34
What is adolescence?
Growing up to be an ‘adult’; the time between childhood and adulthood.
35
What is the definition of adolescence (start and end)?
We define adolescence as that it starts with the onset of puberty, a biological process where you see hormone increases that will change physical characteristics.
When adolescence ends depends very much on the culture you grow up in. In some cultures you are an adult at 16, some 18, 21 or 25.
36
What kind of phase is adolescence?
Adolescence is a unique phase with a lot of changes in how people interact with their social environment. You often see a large shift from focus on family to focus on peers and finding their peers more important. It is often the first time people interact with romantic relationships, they learn a lot in school and there is a lot of cognitive development as well.
37
Does the brain between a child and adult differ much?
If you only look at what the brain looks like, the brain of a child and adult don’t differ that much in terms of size but if you look more detailed we see quite a bit of differences. Of course prenatally there is a huge difference.
38
How do grey and white matter develop from birth onwards?
Grey matter shows a massive increase from birth onwards until the age of about 7 or 8. White matter shows a delayed increase of the volume compared to the grey matter. This might reflect a difference in neuro connections in the grey matter that is exploding after birth and a little bit later the myelin will also increase and make the signal reductions faster.
After the age of 10 there is a decrease in grey matter which makes the brain more sufficient. There is still an increase in white matter so there is still an increase in the myelination process throughout the brain. Your brain becomes smaller as we become older and we have a lot of neurons in our brain that contribute to this.
39
What is the estimate of the number of neurons in our brain?
65 billion neurons, that is the same number as stars in our Milky Way.
40
What does the increase of grey matter in our early childhood reflect?
What we think the increase of grey matter in our early childhood reflects is an increase in the number of connections they make with other neurons.
At birth there are 500 trillion of these connections that explode after birth until the age of 3 into 6 times more. These connections will disappear if they are not used. This is very efficient because it takes a lot of energy for the brain to make these connections and make them stable.
You can still make new connections throughout your whole life; you can learn new things but the ratio with which the connections are formed and eliminated will change over the course of development.
41
Structural brain development
Increase in connections between brain cells (neurons).
Increase in myelination of the cortex.
Non-linear decrease until young adulthood.
1. Synaptogenesis
2. Pruning
42
Synaptogenesis
Increase in synapses.
43
Pruning
Elimination of excess synapses.
44
Non-linear decrease until young adulthood.
Differential trajectories across brain regions. It will follow a plateau and there will be faster changes in some brain regions than other in some parts of the development.
45
What happens to the pace of changes as you get older?
At 3 years there is a lot of increase in the brain, at the age of 6 there is still an increase but less.
From the age of 12 there are decreases in the brain, this is a lot more at the age of 15, and somewhat less at the ages of 18 and 21 but more than the age of 12.
46
What brain regions develop early?
In general the visual regions develop early.
This is what you can test in behaviour with young children: young children already perceive the same way and have the same visual accomplishments as adults.
47
What brain regions develop late?
The frontal and temporal regions develop late. The frontal regions can have an increase up till 25.
48
Ventral
On the side of the belly (versus the sky).
49
Dorsal
The side to the sky/back (versus the belly).
50
Anterior
The side in front of you; that you are facing.
51
Posterior
The side that's facing what's behind you.
52
The theory/model of Nelson et al. (2005)
It discusses one of the theories on adolescent brain development. It is not the only or the only true theory, but it’s a model that is very useful for us to work with and to understand that the main processes that are going on. We will mostly use this theory to understand the highlights of what we now know of adolescent brain development.
53
What does Nelson et al. (2005) discuss?
The changes that we see in the brain, in specific brain regions and in social changes are not specifically limited to humans, we see them in animals as well.
Understanding how the dramatic changes in social behaviour in adolescence relates to social re-orientation and how that relates to neurobiological mechanisms.
- This is an interaction between a change in a social environment and expectations and how your brain changes.
A neurobiological model.
54
The neurobiological model of Nelson et al. (2005)
- It may serve as a naturally occurring model for the study of developmental changes in brain-behaviour relations.
- We also try to understand whether the specific brain changes during adolescence makes them more vulnerable to develop psychopathology.
55
What three nodes does the brain consist of?
- An early detection node of social stimuli.
- Affective node, the stimuli are labeled with roughly good/bad or approach/avoid.
- Cognitive-regulation-node, this system can inhibit and regulate your responses.
56
How does the information move through the different nodes?
The information doesn’t just move forward to the next node, it also has feedback interactions/a feedback loop.
E.g., if you have a predefined way of thinking about a situation in the cognitive node, this will change the way you perceive a situation. An example is that if you think someone is scary you will perceive a smile as insincere.
57
Superior temporal sulcus
- Superior = above others (there are three sulci in the temporal lobe)
- Temporal lobe = temporal
- It’s a sulcus so the sulci are the grooves in the cortex and the gyri are the outer sides of the cortex
- Part of the detection node
58
Anterior temporal cortex
- Anterior = in the front
- Temporal lobe
- Part of the detection node
59
Fusiform face area
- It's not an anatomical name but it describes what it does.
- Temporal lobe
- At the back
- Part of the detection node
60
Amygdala
- Structure known in emotional and fear processing.
- Deeper in the temporal lobe with the shape of a bean.
- Right in front of the hippocampus.
- Part of the affective node.
61
Hypothalamus
- Hypo = under
- Underneath the thalamus
- Part of the affective node
62
Nucleus accumbens
- A deep structure of the subcortical brain circuitry.
- It's a small nucleus on the bottom of the striatum.
- Part of the affective node.
63
The striatum
The striatum is a complicated 3D structure that will look different depending on how you slice the brain and whether you show it in 3D or not.
64
Dorsal medial prefrontal cortex
- Medial = in the center, you can only look at it when you slice the brain open/open it up.
- It's dorsal of the prefrontal cortex.
- Prefrontal cortex is in the front of the brain.
- Part of the cognitive-regulation node.
65
Ventral prefrontal cortex
- Ventral = on the bottom
- It's ventral of the prefrontal cortex.
- Prefrontal cortex is in the front of the brain.
- Part of the cognitive-regulation node.
66
Detection node
It perceives social stimuli and processes perceptually.
All the brain regions work together, they are part of a network, they don’t work in isolation.
67
What brain regions are part of the detection node?
- Anterior temporal cortex
- Superior temporal sulcus
- Fusiform face area
68
What does the detection node process perceptually?
- Face perception
- Facial expressions/ basic emotions
- Biological motion
- Other sensory modes
69
What kind of questions does the detection node ask itself?
- Is this a social stimulus?
- Is this object moving?
- Is it a living being?
- What kind of being?
- Who is this? Do I know this person or not?
70
Affective node
It adds a salience to the social stimuli that were just processed by the early detection node.
It's responsible for the emotional response.
Questions:
- Should I approach or avoid the stimulus?
71
The emotional response of the affective node
- Positive (& negative) emotional arousal: amygdala
- Negative emotions (it can distinguish disgust, fear and unfairness): insula
o Insula is an island in between the temporal lobe, the frontal lobe and the parietal lobe
- Reward: nucleus accumbens/ (ventral) striatum
o Specific developmental trajectory
o Will tackle whether the stimulus is rewarding or not
o A lot of neurotransmitters are involved, such as dopamine
72
What brain regions are part of the affective node?
- Nucleus accumbens
- Bed nucleus of stria terminalis
- Hypothalamus
- Amygdala
73
Cognition/regulation node
Regulation and monitoring of perception and affection
- Self-referential processing, self-reflection, mentalizing processes: medial prefrontal cortex (mPFC)
o The inside of the frontal cortex
- Behavioral control, working memory: dorsal lateral PFC (dlPFC)
o The inside on the top
- Detecting and monitoring of affective state and whether you are going to take action or stop action: anterior cingulate cortex (ACC)
o On the anterior of the cingulate
Questions:
- What are the intentions of the social stimulus (TOM)?
- How should I respond?
74
What brain regions are part of the cognition/regulation node?
- The dorsomedial PFC
- The ventral PFC
75
What is the developmental pattern of the three nodes? And how is this related to adolescence?
The three nodes all have different developmental patterns and different ways of processing.
These different ways of developing may also explain some adolescent specific behaviour.
Detection nodes: early maturation
- Young children are already able to process social information very well, on the level of adults.
Affective nodes: maturation in early adolescence
- Hypersensitive during adolescence
Cognitive node: maturation in late adolescence
- E.g., The frontal cortex shows late development all the way into early adulthood
- Because of this late developmental trajectory we assume it is not influenced by puberty in the same way as other nodes but that it’s influenced by other developmental processes.
76
What drives the development of some of the nodes?
Some of these nodes are driven by hormone levels that change during puberty and we also see this by the receptor density in these brain regions. The affective node shows high density of androgen receptors which bind i.e., testosterone.
77
How is the affective node dependent on pubertal processes?
Affective node: functional and anatomical reorganization during puberty
- Gonadal hormones (e.g., estradiol, testosterone) are related to how affective node structures respond to social stimuli.
- Heightened emotional responsiveness to affective stimuli, especially in particular contexts (e.g. the peer context).
78
How is the cognitive node dependent on pubertal processes?
Cognitive node: maturation in late adolescence
- PFC (including OFC, VLPFC, DLPFC, mPFC) do not reach maturity until early adulthood.
- Performance on inhibitory tasks improves until late adolescence.
o Important in inhibitory cognitive control responses
- This development is independent of hormonal status
o This is related to myelination and pruning of specific synaptic connections.
79
What does the slow maturation of the regulation-node and the overactive affective-node in early adolescence show?
That social stimuli of peers are more rewarding in adolescence than in childhood or in adulthood. Cues of peers are processed stronger, this can be seen in neural activity and emotional processes. An emotional facial expression elicits more brain activity in an adolescent than in a child or adult.
80
The neurological model of adolescent brain development
The “Dual-systems model” or the “Imbalance model”
Different researchers use different terminology but they refer to the same idea.
81
What is the idea of the “Dual-systems model” or the “Imbalance model”?
The affective nodes, so the limbic regions, show a heightened activity and heightened brain growth during adolescence and the prefrontal regions lack behind in development. So there is a larger difference between the development between these two nodes/brain networks during adolescence. We think that this is predictive of risk seeking behaviour.
82
How can risk seeking behaviour be explained using the "dual-systems model"?
If you perceive rewarding stimuli as more rewarding but you are less able to inhibit the response to approach that, even if it’s dangerous, you will see risk seeking behaviour.
83
True or false: The dual-systems model or imbalance model are very complex ways of looking at adolescent brain development.
False.
The dual-systems model or imbalance model are very oversimplified ways of looking at adolescent brain development. We know that different kinds of context will influence this model and the way that the brain reacts.
Recent neuroimaging evidence does not support a simple model of frontal cortical immaturity.
84
There is growing evidence for importance of what?
Social-affective processing (i.e., role of motivational salience of the context).
- For example how motivation can influence performance.
- Overactivation or under activation is dependent on the context.
85
How can different tasks influence the brain activity?
In some tasks looking at developmental changes there is an increase in response to the task in specific brain regions. But using a slightly different task where the subject is motivated in a different way, you would see a heightened decreasing activity to the task across adolescence. So the activity to the task really depends on the specific context in which you measure something. Every dot is a different experiment.
86
What is the process of the role of motivational salience of the context and how this changes the brain activity and the response of the adolescent?
On the one hand motivation can enhance activity, for example the cognitive control system, but on the other hand you can interfere with the whole system by eliciting very emotional stimuli that will affect the affective network to a large extend which will interact with the performance of a specific cognitive task.
- Motivation (social/contextual) can modulate cognitive control (e.g., rewards can improve performance).
- Control can suffer when required to suppress action towards rewards.
87
Anti-saccade task
A fMRI experiment that was done to show how motivation can modulate cognitive control (e.g., rewards can improve performance).
Participants had to make an anti-saccade, so they were shown a dot on the right or left side and they were asked to look at the opposite direction of where the dot is. In some trials the participants were extra motivated to perform well by promising them money and in the other trials they couldn’t earn anything.
88
What type of task is the anti-saccade task? And why?
This is a cognitive control task because your attention is drawn to the dot and you have to make an eye movement to the other direction.
89
What are the results from the anti-saccade task?
Adolescents performed better when they could get a monetary reward and for the adults it didn’t matter as much as for the adolescents.
You could also see that there was heightened brain activity in structures that are specifically sensitive to reward processing (i.e., the ventral striatum). Also the engagement of the cognitive processing regions (i.e. prefrontal cortex) showed heightened activity.
90
What is the no go task?
This task was a no go task, which measures cognitive control, and people were asked to press a button on the neutral face and don’t press a button on a smiley face. This is very counter intuitive because you are more likely to approach someone with a smiley face so you really have to inhibit your response.
- “Go” or “Don’t go”
91
What is a false alarm with the no go task?
An incorrect response on a no-go trial => pressing to a smiling face
92
What are the results from the no go task?
Adolescents have more false alarms on this task than children or adults. So they perform worse.
You can also see that the ventral striatum is more active with the social facial expressions. The idea is that maybe this heightened response will make the frontal lobe work harder to inhibit the first response to approach. And this is specifically seen in the adolescent brain.
Control can suffer from specific salient stimuli, when required to suppress action towards rewards, more in adolescence than in childhood or adulthood.
93
The model of adolescent brain development
Role of social-affective engagement and goal flexibility.
On the x-axis is the time from puberty onset onwards to the transition to adulthood. The pubertal changes in the limbic system, so in the affective nodes, increase over the course of adolescence and show a heightened response in adolescence, specifically in the peer context.
There is the gradual development of the cognitive control system, which is late compared to the other brain systems.
It all really depends on motivation and contexts whether systems are active, inactive or interfering. This can relate to positive growth trajectories, or it can grow into negative growth trajectories where you see problem behaviour.
