What are the three core concepts of development?
- Brain architecture is established early in life and supports lifelong learning, behaviour and health
- Stable, caring relationships and serve and return interaction shape brain architecture
- Toxic stress in the early years of life can derail healthy development.
At what age does the central nervous system develop?
Between 3 weeks and 20 years of life
This is known as the window of susceptibility
List the highlights of neural development from prenatal to adolescence
- Prenatal (rapid physical growth)
- Infancy (motor)
- Childhood (abstract reasoning)
- Adolescence (identity and judgement, maturation of PFC)
What are the 5 phases of brain development?
- Neural plate induction
- Neural proliferation
- Migration and aggregation
- Axon growth and synapse formation
- Cell death and synapse rearrangement
List the steps for the induction of the neural plate
- Thickening of ectoderm leads to neural plate
- Neural groove forms (20 days)
- Neural groove closes to form neural tube
- 4 major divisions of brain observable (telencephalon, diencephalon, mesencephalon and rhombencephalon)
After mitosis of proliferating neurons in the neural tube, daughter cells become fixed. Where does this occur? Where does differentiation begin?
The ventricular zone.
Differentiation begins as neurons migrate. They develop neurotransmitter making ability and action potential ability.
When does brain development begin?
When the neural plate closes (3-4 weeks)
True or false? Each secondary brain vesicle (eg. telecephalon, diencephalon, mesencephalon, rhombencephalon) have their own adult neural canal.
True
Eg. lateral ventricles (telencephalon), third ventricle (diencephalon), cerebral aqueduct (mesencephalon), fourth ventricle (rhombencephalon)
Central canal (spinal cord)
What is aggregation in brain development?
The completion of migration and forming of structures (eg. dendrites have begun to sprout). Synaptogenesis occurs after this.
Describe the growth cone of axons.
They use chemo-attractants for directionality.
They have an actin-myosin meshwork that form a lamellipodium. Smaller filopodia project from the lamellipodium.
Why are there virtually no synaptic connections during gestation? When does the most synaptogenesis occur?
It is experience and interaction with the environment that forms the synaptic connections.
The most synaptogenesis occurs through the second year of life. Much is random. This is followed by massive pruning in adolescence.
What are the primary processes that takes place in brain development after birth?
- Refinement of neural connections (synaptogenesis and neuronal death)
- Maturity of neurons
- Increasing complexity of dendrite interconnections
- Myelination
What do neurotrophins (eg. NGF) do in the developing brain?
- Promote growth and survival
- Guide axons
- Stimulate synaptogenesis
- Axons that are not exposed to neurotrophins after making connections undergo apoptosis, a preprogrammed mechanism of cell death
- Therefore the healthy adult nervous system contains no neurons that failed to make appropriate connections
What are the two types of synapse development?
- Experience-expectant development (prune with experience, experience leads to less, critical periods, organizes universal brain processes for all humans)
- Experience-dependent development (new synapses formed, experience leads to more, continues through life, person specific)
How do infant and adult rats differ in regards to neural pruning and an enriched environment?
Enriched infant rats: prune>gain
Enriched Adult rats: gain>prune
Describe myelination throughout life.
- Begins at birth
- Rapidly increases to 2 years old
- Continues to slowly increase through 30 years old
Why do doctors recommend milk for babies, in regards to neural development?
Myelin is composed of 15 percent cholesterol and 20 percent protein.
Why are young brains more able to recover function after injury, as compared to older brains?
Greater plasticity in young brains, may be due to overproduction of synapses.
Why do adolescents demonstrate more risky behaviour?
The brain matures from the back to the front. Leading to a preference for physical activity and more risky, impulsive behaviour (PFC not fully developed yet).
The prefrontal cortex develops feelings of vulnerability
Which lobe of the brain is particularly sensitive to early experiences?
The frontal lobe.
Its development is a long process beginning prenatally and continuing until adulthood.
Where is neurogenesis observed in the brain of adult mammals?
The olfactory bulb and hippocampus
