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Question 1

What is plasticity?

Answer 1

The capacity of the nervous system to modify itself, functionally and structurally, in response to experience and injury.

Question 2

What are the 8 stages of cell development in brain?

Answer 2

1. Birth
2. Migration
3. Differentiation
4. Maturation
5. Synaptogenesis
6. Death
7. Rearrangement
8. Myelination

Question 3

What is cell birth?

Answer 3

After 4 weeks of conception, within the neural tube you get neural stem cells.
Every neurone starts as a neural stem cell.
Then they specify later on in their development.
Production of neurones is called neurogenesis.

Question 4

How does migration happen?

Answer 4

Pioneer axons from the neural tube move out and lay down paths for follower axons to use.
These axons use this path to form multiple connections.

Question 5

What happens when there is disruption to migration?

Answer 5

If pioneer axons do not migrate to the correct location, this can disrupt brain development.

Question 6

What is an example of disruption to brain development?

Answer 6

Agenesis.
Agenesis means lack of development.
Agenesis of the corpus collousm is when the corpus develops partly or not at all.

Question 7

What is differentiation?

Answer 7

The location and the chemical signals in the location where axons migrate to will determine the type of cell they become.
Cells all start as stem cells and then they differ to have specific roles.

Question 8

What do embryotic stem cells differentiate into?

Answer 8

Embryotic stem cells differentiate into any type of cell in the body

Question 9

What do neural stem cells differentiate into?

Answer 9

Neural stem cells differentiate into the cell types found in the brain and central nervous system

Question 10

What is migration?

Answer 10

Brain starts with not that many connections and then neurones start growing and connecting and finding their function within the brain

Question 11

How many neurones are there in the brain by 7 months of pregnancy?

Answer 11

By 7 months of pregnancy nearly all of the 100 billion adult neurones have been produced.
Yet at birth the brain is a quarter of the weight of the adult brain.

Question 12

Where does the extra weight of the adult brain come from?

Answer 12

Synaptogenesis (dendrites making connections)
Glial cells
Myelination (axons get fatty layer around to make signals faster and more efficient)

Question 13

What is synaptogenesis?

Answer 13

Creation of synapses
With age synapses start to decrease due to cell death.

Question 14

What is cell death?

Answer 14

When neurones that do not make stable connections die.
Those that have made connections stay in place.
Synaptic pruning - number of synapses decrease

Question 15

What is synaptic rearrangement?

Answer 15

Synapses are not always efficiently connected to the right places so there is a rearrangement to make more efficient and stable connections.

Question 16

What is myelination?

Answer 16

Starts before birth
Continues up to 30 years of age
Layer around axon to speed up connections

Question 17

Is plasticity limiteless?

Answer 17

No
Cells are not free to migrate to new areas.
They can make little adjustments in the area they are in .
They do not make large changes in long-distance connectivity.

Question 18

What are sensitive periods?

Answer 18

There are periods in which certain changes are much more likely to take place.
Sensitive periods generally observed through behaviour are due to neural circuits.

Question 19

What is axon elaboration?

Answer 19

Axons elaborate during a sensitive period - when you are more likely to learn a certain thing

Question 20

What is synapse elimination?

Answer 20

After a sensitive period, pruning goes on for those connections that aren’t viable. Then you are left with highly selective connections.

Question 21

What is synapse consolidation?

Answer 21

Prior to sensitive period, the synaptic connections are vulnerable to death.
After sensitive period, they become more stable and less vulnerable.

Question 22

What are the limits to sensitive periods?

Answer 22

Not all circuits are shaped by sensitive periods. Some are innate and robust from the start e.g. spinal cord
Some regions demonstrate plasticity throughout life

Question 23

What happens after sensitive periods?

Answer 23

Circuits become more resistant to change.
Change can still occur but it requires more energy to maintain less stable connections.
Complex behaviours rely on hierarchies of circuits which operate in parallel.
If one goes wrong, complex behaviour will be preserved as other circuits compensate for abnormal processing.

Question 24

What is an example of sensitive period - visual deprivation?

Answer 24

One of a kitten’s eyes was sewed shut for the first 4-6 weeks of life.
After removing stitches, the visual cells in the deprived eye could no longer process visual stimuli.
Sewing the eye shut after the sensitive period had no effect on vision.
Visual development needs environmental input during sensitive period of neural development.

Question 25

What is the sensitive period for language aquisition?

Answer 25

Exposure to language in the first year of life is vital
There is a systematic decline in the ability to learn new languages after 7.

Question 25

What about visual deprivation in humans?

Answer 25

Lazy eye
Requires surgical correction before 7-8 years.
If later, vision is almost completely suppressed in the lazy eye.

Question 26

What is the phonetic differentiation?

Answer 26

Key phonetic units – sounds that are difficult to distinguish if they are not in your native language

At 6 months, babies can differentiate the key phonetic units in all languages

By 10 months, babies are showing a preference for their own langauge

Between 6 to 10 months there is a sensitive period for phonetic differentiation

Question 27

Can we manipulate exposure to maintain children’s capacity to learn other languages?

Answer 27

American 9 months old had 12 sessions with a mandarin Chinese speaker

Significant learning of Chinese phonemes – they were able to learn

But it had to be with a live Chinese speaker
There was no effect if they watched on tv or just audio

Question 28

What does this evidence tell us?

Answer 28

Some brain and behavioural changes are:
Predisposed to occur
Time sensitive
Affected by the environment

Question 29

How does environment affect the animal brain?

Answer 29

60 day old rats were placed in enriched or impoverished environments
Rats in enriched environments had more and thicker dendritic connections.
Those in enriched environments had greater cortical depth and more glia.

Question 30

How does the environment affect animal behaviour?

Answer 30

The water maze task: measure of learning and memory
Rats had to swim in the tank to find the platform
Better performance on spatial learning task for animals in enriched environments

Question 31

What is the effect of environment in humans?

Answer 31

Measured IQ at 4.5 years old
Children adopted early had IQ =98
Children adopted later had IQ = 90
Lower IQ associated with both duration and severity of deprivation

Children tested at 6 years then at 11.
Most showed improvements - plasticity going on
Many remained impaired
Environment affects behavioural and cognitive outcomes