Neurodevelopment

Question 1

What are the 6 stages of brain development?

Answer 1

1. Proliferation (cell birth)
2. Cell Migration
3. Differentiation and Maturation
4. Synaptogenesis and Synaptic Pruning
5. Cell Death
6. Myelination

Question 2

How do neurons proliferate?

Answer 2

Stem cell (progenitor cell) division

Question 3

Where does neurogenesis occur?

Answer 3

Ventricle walls (ventricular and subventricular zones)

Question 4

What happens in symmetrical division of progenitor cells and how long does it last?

Answer 4

Forms 2 progenitor cells; during the first 7 weeks after conception

Question 5

What happens in asymmetrical division of progenitor cells and how long does it last?

Answer 5

Forms 1 progenitor cell and 1 brain cell; lasts around 3 months.

Question 6

What are the first brain cells to be produced through asymmetrical division of progenitor cells?

Answer 6

Radial glia

Question 7

What 2 processes do cells use to migrate?

Answer 7

Chemical signals and physical support (radial glia)

Question 8

How do radial glia support the migration of immature cells?

Answer 8

Immature cells ‘climb up’ the fibre of a radial glia or move from one to another tangentially (“like Tarzan”)

Question 9

How long after birth does mass migration of cells occur?

Answer 9

1-3 months; some migration up to 7 months

Question 10

Name the 2 migration streams

Answer 10

Rostral vs medial migration stream

Question 11

What 3 things happen during differentiation and maturation?

Answer 11

• Expression of particular genes
• Formation of axons (mm/day)
• Formation of dendrites (um/day)

Question 12

What are 2 processes of dendrite formation?

Answer 12

Dendritic arborisation and growth of dendritic spines

Question 13

What is the function of dendritic spines?

Answer 13

Provide a larger surface area for other neurons to synapse onto

Question 14

What is induction (cell-cell interactions)?

Answer 14

When the differentiation of immature cells is influenced by the area they migrate to

Question 15

What does ‘growth cone’ refer to?

Answer 15

The growing end of an axon

Question 16

How do filopodia (extensions of the growth cone) form connections?

Answer 16

Through physical contact or chemotropism (receptors detect chemicals released from target sites; can be repelled or attracted)

Question 17

What is synaptic pruning?

Answer 17

The maintenance (and strengthening) and active synapses and the elimination of inactive synapses

Question 18

How long does synaptic pruning occur for?

Answer 18

Throughout life; related to learning and experience

Question 19

Gogtay et al (2004) used longitudinal brain scans to investigate synaptic pruning in adolescence; what did they find?

Answer 19

• Grey matter thickens in childhood but thins in adolescence
• White matter (myelin) increases in adolescence; peaks in adulthood
• Synaptic pruning by early adulthood (from back to front)

Question 20

What are the 2 types of cell death?

Answer 20

Apoptosis and necrosis

Question 21

What is the difference between apoptosis and necrosis?

Answer 21

Apoptosis is initiated by the cell itself and results in no inflammation or debris, whereas necrosis is typically a result of disease and is highly disruptive (causes inflammation)

Question 22

How do cells avoid apoptosis?

Answer 22

• Target cells secrete neurotrophins
• Active communication with other neurons (strengthening of synapses)

Question 23

What are neurotrophic factors?

Answer 23

Growth factors for neurons

Question 24

What cells carry out myelination in the peripheral nervous system and how?

Answer 24

Schwann cells, completely wrap around an axon; dedicated, “monogamous”

Question 25

What cells carry out myelination in the central nervous system and how?

Answer 25

Oligodendroglia, many extensions around many different axons; “promiscuous”

Question 26

What motor behaviour correlates with myelination?

Answer 26

Ability to grasp (reflects a refinement)

Question 27

Specter (2001) investigated neurogenesis in adult songbirds; what did they find?

Answer 27

Evidence of new neurons in adult songbirds which were generated in the lining of ventricles

Question 28

Name 2 examples of neurogenic regions in the adult human brain

Answer 28

• Olfactory epithelium
• Hippocampus

Question 29

What happens in the rostral migratory stream?

Answer 29

Astrocytes (glia) wrap around migrating neurons to form a pipeline and keep them on the right path

Question 30

What is the only thing that may induce neurogenesis in the cerebral cortex?

Answer 30

Injury; but still not substantial

Question 31

What does collateral sprouting refer to?

Answer 31

The rearrangement of neuronal branching after injury to fill vacant synapses

Question 32

What effect did enriched environments have on rats and what was the main contributor?

Answer 32

Thicker cortex and increased branching - mostly due to physical activity

Question 33

What are critical periods?

Answer 33

Periods where the brain is sensitive to specific experiences

Question 34

What is an example of a critical period?

Answer 34

The absence of visual stimuli leading to blindness

Question 35

Blakemore and Cooper (1970) conducted the kittens in tubes study to investigate critical periods; what did they do/find?

Answer 35

The kittens’ only visual stimulation was being kept in a tube surrounded by vertical black and white lines; found that their neurons only fired for vertical lines, not horizontal.

Question 36

What did the case of Genie, the 13-year-old girl discovered to have been socially and experientially deprived, show?

Answer 36

Despite intensive training, she never developed a language ability to the same level as typical (e.g. could name objects but couldn’t talk about future, self etc.); suggests there is a critical period for language