Chapter 8 - Neurodevelopment and adaptation

Question 1

What’s the purpose of the Tower of Hanoi test?

Answer 1

• Used to test planning skills
• Also an indicator of frontal lobe development

Question 2

How does lower SES correlate to brain development?

Answer 2

• It’s associated with decreased cortical surface area in widespread regions on frontal, temporal, and parietal lobes

Question 3

How is Darwin’s view supported concerning embryos and evolution?

Answer 3

• Since all embryos of different species closely resemble one another, it supports the idea that all vertebrates arose from a common ancestor

Question 4

What are the three chambers of the vertebrate brain?

Answer 4

• Forebrain (cerebrum), midbrain and hindbrain (both are found in the brainstem.

Question 5

Neural plate vs. Neural tube?

Answer 5

• Neural plate - primitive neural tissue that gives rise to the neural tube
• Neural tube - Structure in early development from which the brain and spinal cord arise

Question 6

When do gyri and sulci start to appear?

Answer 6

• Around seven months
• By nine months, it resembles an adult brain

Question 7

What are stem cells?

Answer 7

• Unspecialized cells that can reproduce itself indefinitely and differentiate into more than one type of specialized cells

Question 8

What are the different types of stem cells?

Answer 8

• Totipotent/omnipotent - the most undifferentiated, make up the zygote and cells of the first two divisions, give rise to embryonic cells and placenta
• Pluripotent - Can differentiate into all embryonic cell types, but not placenta, also called embryonic stem cells
• Multipotent - Can differentiate into multiple specialized cell types found in specific tissues/organs (ex. bone marrow, neural stem cells)
• Unipotent - form a single lineage of cell types and are constantly renewing themselves (ex. Spermatogonial stem cells)

Question 9

What’s a progenitor cell?

Answer 9

• Precursor cell derived from a stem cell that migrates and produces a neuron or glial cell

Question 10

What’s a neuroblast and a glioblast?

Answer 10

• Neuroblast - Product of a progenitor cell that gives rise to different neuron types
• Glioblast - Product of a progenitor cell that gives rise to different glial cells

Question 11

What are the 7 stages of brain development?

Answer 11

1) Cell birth (neurogenesis)
2) Neural migration
3) Cell differentiation
4) Neural maturation (dendrite and axonal growth)
5) Synaptogenesis
6) Cell death and synaptic pruning
7) Myelogenesis (mainly in adulthood)
*Stages 4-7 continue well after birth

Question 12

When do neurogenesis, neuronal migration, and neuronal maturation occur?

Answer 12

• Neurogenesis: 6-25 weeks
• Neuronal migration: 8-29 weeks
• Neuronal maturation: 20 weeks till birth

Question 13

What role do the subventricular zone and the radial glial cell body play in neuronal migration?

Answer 13

• Subventricular zone - Where neuronal stem cells self-populate
• Radial glial cell body - act as scaffold for migrating neuronal cells. Migrating neurons end up climbing up these cells

Question 14

What two types of signals monitor and specify cell fate during the differentiation stage?

Answer 14

1) Intrinsic: Inherited from mother cell (physically separated and given to daughter cell)
2) Extrinsic: Chemical cues received from cell’s surroundings
- Together these help restrict the choice of traits a cell can express

Question 15

When does cell maturation occur?

Answer 15

• Takes place after neurons have migrated to their proper destination and have differentiated.
• Begins prenatally, but continues well after birth

Question 16

What two major actions occur during the maturation stage?

Answer 16

1) Dendritic growth - Helps provide SA for synapses with other cells. This is called arborization (very slow process)
2) Axonal extension - Helps appropriate targets to initiate synapse formation (very fast process)

Question 17

What is autism spectrum disorder characterized by?

Answer 17

• Occurs via accelerated rates of neuronal maturation, leading to excessive brain volumes in areas such as the amygdala, temporal and frontal lobes
• More common in boys
• Don’t really know what causes it

Question 18

How does axonal guidance/axonal pathfinding occur?

Answer 18

• Happens during the maturation phase
• the growing tips of axons are called growth cones
• Growth cones are responsive to two types of molecules.

Question 19

What are the two types of molecules that guide growth cones?

Answer 19

1) Cell adhesion molecules (CAMs) - manufactured by other cells and attached directly to the substrate along which the growth cones move
2) Tropic molecules - they are secreted and diffusible and will form a concentration gradient that either attracts or repels pathfinding neurons (chemoattraction or chemorepulsion)

Question 20

Which area of the brain has extensive synaptogenesis shortly after birth?

Answer 20

• The primary visual cortex (V1)
• The synaptic density doubles between 2-4 months and increases until 1 year of age

Question 21

How does the brain ‘chisel’ itself?

Answer 21

• Genetic signals, experience, reproductive hormones, stress, SES
• The cortex becomes thinner in a caudal-rostral gradient (back to front)

Question 22

What’s neural Darwinism?

Answer 22

• Processes of cell death and synaptic pruning are the outcome of competition among neurons for connections and metabolic resources in an aneural environment
• Neurons are dependent upon postsynaptic targets for survival
• These target cells produce neurotrophic factors regulating survival of the presynaptic cell
• Lack of neurotrophic factors leads to apoptosis (programmed cell death)

Question 23

T/F: Radial glia differentiate into astrocytes once neural migration is complete while oligodendrocytes myelinate axons.

Answer 23

• TRUE

Question 24

What’s a useful index of cerebral maturation?

Answer 24

• The myelination of axons via oligodendrocytes

Question 25

When does most myelination occur?

Answer 25

• Just after birth and continues until at least 20 years of age
• The latest myelinated areas usually control the highest mental functions

Question 26

What are some of the sex differences in brain development?

Answer 26

• Females reach maximum overall volume and grey matter volume sooner than males
• Decreasing grey volume corresponds to myelin development
• Increasing white matter volume corresponds to myelin development

Question 27

What is spine density used to determine?

Answer 27

• Can be an approximation of excitatory synapse count

Question 28

What are two important features of frontal lobe development?

Answer 28

1) The reduction in cortical thickness
2) The increase in connectivity between the medial regions of the frontal lobe, the posterior regions of the cingulate cortex, and the lateral regions of the parietal lobe
- Both of these appear adult-like by age 13 and are correlated to intelligence

Question 29

What’s the default network?

Answer 29

• Interacting regions of the frontal and parietal lobes that have highly correlated activity

Question 30

What’s the risk of ACEs and brain development?

Answer 30

• They may compromise frontal lobe development

Question 31

Summarize the case of the Romanian orphans.

Answer 31

• In the 1970s, Romania outlawed birth control
• Many kids ended up in orphanages and were severely neglected
• Made great recovery if adopted before age 2, but by age 12 if not the average brain size was up tp 20% smaller than normal
• Increased size of the amygdala, and decreased size of the hippocampus

Question 32

What did Donald Hebb discover?

Answer 32

• Reared a group of rats in his kitchen and they ended up performing better in the Hebbs-Williams maze than lab rats
• Kitchen rats were more complex and richer in synapses
• Demonstrated the importance of tactile stimulation

Question 33

T/F: Stress delays brain development.

Answer 33

• FALSE
• Stress accelerates brain development