NEURODEVELOPMENT

Question 1

What are the 5 processes of early brain development?

Answer 1

Cell-birth, cell-migration, cell differentiation/maturation, synaptogenesis, cell death/apoptosis, myelination

Question 2

What is cell-birth?

Answer 2

250,000 neurons born per minute, initially one cell thick, stem cells divide to form progenitor (precursor) cells.

Question 3

What is a progenitor cell?

Answer 3

each progenitor cell can be a neuroblast or a glioblast.

Question 4

what is the ventricular zone?

Answer 4

cells undergoing mitosis were always closer to the inner surface of the neural tube. neural tube forms the mature brain, lining of our ventricles contains stem cells

Question 5

What is cell migration?

Answer 5

refers to the movement of the newly formed cells towards the outer layers. cortex develops in an inside out-manner. cells born in a certain region migrate to a certain cortical location

Question 6

How do cells migrate?

Answer 6

Chemical signals (immunoglobins and cytokinesis), physical support (provided by the radial glia) - the cell climbs along the radial glia with the help of extensions. migrate to form areas such as basal ganglia and amygdala

Question 7

What is cell differentiation/maturation?

Answer 7

once they arrive at their destination, immature cells begin to differentiate and become a specific cell. forming axons and dendrites. (dendritic arborization, growth of dendritic spines)

Question 8

What is induction?

Answer 8

cells can influence the production of their neighbouring cells

Question 9

What is pluripotency

Answer 9

if immature cells removed from a region, they will be replaced by subsequent neurons that will arrive and acquire the same characteristics. once they differentiate they lose that property

Question 10

What is synaptogenesis

Answer 10

it is guided by cues and signals. the growing end of an axon is called a growth cone. growth cones develop into thin extensions known as filopodia. growth cones are attracted to chemicals released from target sites.

Question 11

What molecules guide growth cones?

Answer 11

cell adhesion molecules (CAMS)
tropic molecules

Question 12

Synaptogenesis process

Answer 12

once a successful contact has been made, axon and target induce each other to construct machinery to help them attach to one another (neurexins and neuroligins) which forms a synapse.

Question 13

What do synapses do after creation?

Answer 13

once synapses are formed they are slow and sluggish in their firing compared to adult ones, but get faster with time. takes place after birth and continues to rearrange themselves throughout life.

Question 14

Growth Cone process

Answer 14

Filopodia advance by adhering to other cells by sensing their way around. make physical contact with other cells (contact guidance). or they are chemically guided (chemotropism). they have protein receptors on their membrane - recognising various molecules which will adhere or not. can either be attractive or repulsive. which also may change over time.

Question 15

What is synaptic pruning?

Answer 15

Successful synapses are those that are active and maintained -> strengthened. those which are weak will be removed. ‘use it or lose it’ principle. related to learning and experience

Question 16

Synaptic pruning in adolescence

Answer 16

adolescence is a period of increased synaptic pruning. prefrontal cortex still immature - limbic system much better developed. study brain scans of 4-25 years show grey matter thickens in childhood but then begins to thin out gradually. increase in white matter (myelination).

Question 17

Cell death - chick embryos

Answer 17

chick embryos had about 20,000 motor neurons but in second week of incubation they dropped to 2,000.

Question 18

What is Apoptosis?

Answer 18

apoptosis is a normal, quiet, natural way of cell death. expresses genes to enable cells to die. (caspases). cells influence phagocytosis

Question 19

What is necrosis?

Answer 19

is an unnatural type of cell death from injury or disease. can cause inflammation around its surroundings causing more damage (leakage of cell contents).

Question 20

Redundancy to Refinement

Answer 20

experience shapes brain architecture -> apoptosis -> refinement of synaptic connections based on learning and exposure to stimuli.

Question 21

Which neurons will live and which will die?

Answer 21

rich levi-montalcini (survival signals), nerve growth factor, neurotrophins, active communication,

Question 22

What are survival signals?

Answer 22

proteins secreted by target cells promoting survival and growth of neurons.

Question 23

Nerve growth factor (NGF)

Answer 23

in order to avoid apoptosis and survive, a neuron will need: neurotrophins (growth factors) from its target cells. active communication (with other neurons leads to strengthening of synapses.

Question 24

What is myelination?

Answer 24

refers to the process by which glia form fatty shealth that covers the axons of the neurons. myelin speeds up transmission of neural impulses. first occurs in spinal cord -> hindbrain -> midbrain -> forebrain. slow process occurs gradually for decades, depending on the region i.e., in the cortex it continues until adulthood. correlation between myelination and the ability to grasp objects as an infant

Question 25

How long does cell migration occur?

Answer 25

A large wave of neurons is still migrating in the frontal cortex after birth. 3 months -> some persist to 7 months. most of these will become inhibitory GABAergic interneurons

Question 26

Does the brain produce new neurons in adulthood?

Question 27

Does the brain produce new neurons in adulthood?

Answer 27

Few neurogenic regions in adult human brain: olfactory epithelium -> contains cells that continuously divide to provide new olfactory sensory neurons and replace damaged ones (in the nose from toxic air).

Question 28

What is the subventricular zone (SVZ)

Answer 28

cells produced in SVZ of lateral ventricles migrate to replace interneurons in the adult olfactory bulb. this long path olfactory bulb is called the rostral migratory stream (RMS).

Question 29

Rostral Migratory Stream (RMS)

Answer 29

New-born cells from the subventricular zone (SVZ) migrate to the olfactory bulb and become interneurons. Astrocytes wrap around the migrating neuron to create a pipeline to keep them on the right path. this occurs throughout life.

Question 30

Hippocampus - neurogenic area

Answer 30

Granule layer of the dentate gyrus of the hippocampus first neurogenic area to be discovered. new neurons are created and added to dentate gyrus throughout life. associated with learning and memory ->elderly adults can still learn new things.

Question 31

Neurogenic area of Cerebral cortex

Answer 31

few adult-born neurons in cortex, created in the SVZ. neurogenesis can be induced by injury - depends on the extent of the injury.

Question 32

Recovery following injury

Answer 32

better in younger brains. better in periphery. new branching of axons and dendrites -> collateral sprouting. non damaged axons attach to vacant spots. secrete neurotropins that allow collateral sprouting to occur. rate of synapses forming very fast.

Question 33

Brain Adaption

Answer 33

occurs throughout life. In blind ppl since infancy-enhanced tactile (finger sensitivity) and auditory ability. people who are deaf have better sense of touch and vision. cases of amblyopia (lazy eye) can wear an eye patch to reinstate good vision.

Question 34

Monkey study on brain adaption

Answer 34

monkey’s finger amputated. results show neurons connected with neighbouring fingers enlarge fill the space due to no incoming info from the adjacent finger linked to cortex

Question 35

Study in rats - enrichment

Answer 35

rats raised in an enriched environment develop a thicker cortex and have increased dendritic branching. due to physical activity. improved ability to learn.

Question 36

What are critical periods?

Answer 36

period in the brain which is most sensitive to a specific experience (e.g., imprinting). absence of visual stimuli can lead to blindness, lack of language exposure, motor development etc
brief opening of a window vulnerability of need and also opportunity

Question 37

Critical period Cat study

Answer 37

Blakemore and Cooper 1970 - kittens exposed to vertical/horizontal lines only. kittens later cannot see any other orientation.

Question 38

Case of Genie

Answer 38

deprived of social interaction and language development. improved but never able to express language through emotions. socially deprived skills.

Question 39

Richards Tees - ‘train ride’

Answer 39

human sensitivity to learning seems to divide into three waves. first wave is open to vision in infancy. second wave is open for language and third wave is higher cognition

Question 40

Blindness Study in brain adaption

Answer 40

Asked sighted and blind people to feel braille letters or other items + say whether they were same letter or different. They found blind people performed better -> PET and fMRI scans indicated substantial activity in occipital cortex of blind people. auditory stimuli had increased responsiveness in visual areas of cortex

Question 41

Music Training - Brain adaption

Answer 41

musicians have larger brain areas responsible for hearing MRI scans reveal -> temporal cortex in right hemisphere is 30% larger. thicker grey matter for hand control and vision. larger post-central gyrus in right hemisphere for movements of left hand (string control).

Question 42

Complications in early development

Answer 42

epidemiological studies show evidence for environmental factors -> leading to autism, schizophrenia etc. activation of mother’s immune system. prenatal malnutrition (folic acid, thiamine deficiency). substance abuse, complications in pregnancy and delivery. maternal mental health, low economic status.