Early Brain Development Flashcards
1
Q
3 core concepts of development
A
- Brain architecture is establish early in life and supports life long learning, behaviour, and health
- Stable caring relationships and “serve and results” interaction shape brain architecture
- Toxic stress in early years can derail healthy development
2
Q
Development of brain
A
- growth and differentiation of vertebrate brain
- CNS begins at 3 weeks
- development of neural tube
- at birth brain weighs 350g
- at one year brain weighs 1000g
- growth and development of neurons
- proliferation-production of new cells
- migration-move toward final destination
- differentiation- form axons and dendrites
- myelination- addition of insulating sheath
3
Q
Stages of development
A
- Prenatal - rapid physical growth
- Infancy (0-2) - motor development
- Childhood (2-12) - abstract reasoning
- Adolescence (13-25) - identity creation
4
Q
Piaget’s object permanence task
A
- infant sees toy and investigator places barrier in front of toy
- infants younger than 9 months fail to reach for hidden toy
- task depends on PFC (slow to mature)
5
Q
Phases of prenatal development
A
- ovum + sperm = zygote
- once zygote implants in uterus
- embryo (composed of germinal layers of cells)
- week 8-birth
- fetus
6
Q
5 phases of brain development
A
- Neural plate induction
- Neural proliferation
- Migration and aggregation
- Axon growth and synapse formation
- Cell death/synapse rearrangement
7
Q
Brain: embryonic development
A
- embryonic stage of development includes the process of organogenesis
- transformation from the embryo to a body structure including defined organs
- during 3rd week development of primitive streak provides an axis upon which other structure can organize
- neurulation generates a dorsal rod structure call notochord (generated from primitive streak)
- NS develops from ectoderm located above notochord
- NS proceeds from generation of neural plate, to neural folds, to neural tube
8
Q
Induction of neural plate
A
- 18 days after conception embryo implants
- patch of tissue on dorsal surface become nervous system
- consists of 3 germinal layers (endoderm, mesoderm, ectoderm)
- thickening of ectoderm leads to development of neural plate
- neural groove begins to develop at 20 days
- at 22 days neural groove closes to make neural tube
- a few days later brain subdivides into forebrain (telencephalon, diencephelon), midbrain (mesencephelon) and hindbrain (rhombencephelon)
9
Q
Mitosis/proliferation
A
- neuroepithelial cells are the stem cells of NS
- 3 sweepings at anterior end in human will become the forebrain, midbrain, hindbrain
- occurs in ventricular zone
- rate can be 250,000/min
10
Q
Migration
A
- slow movement to correct place
- migrating neurons are immature, lacking dendrites, with only a soma and immature axon
- undifferentiated at start of migration
- differentiation begins as neurons migrate
- develop NT making ability, action potential
- neuroepithelial cells of ventricular zone give rise to radial glial cells that further differentiate into neurons or glial cells
- radial glial cells act as guide wires from migrating neurons
- cells that are done migrating align themselves with other cells and form structures
11
Q
Axon growth/synaptogensis
A
- once migration is complete and structures have forms, axons and dendrite grow and mature
- axons (with growth cones on end) and dendrites form a synapse with other neurons or tissue
- growth cones and chemicals-attractants are critical for this (NGF)
- glial cells 10:1 neurons
- formation of new synapses = synaptogensis
- experience and interaction with environment that forms synaptic connections
- most synaptogensis occurs during 2nd year of life
- 83% of dendritic growth occurs after birth
12
Q
Neuronal death
A
- 40-75% of neurons made will die after migration
- due to failure to compete for chemicals provided by targets
- neurotrophins: family of proteins
- promote growth and survival
- guide axons
- stimulate synaptogensis
-axons not exposed to neurotrophins after making connections undergo apoptosis
13
Q
Synaptogensis and pruning
A
- in cortex synapses begin to form after neuronal migration (23 weeks)
- most synapses form after birth
- many form randomly as axons and dendrites meet
- flourish then selectively prune
- up to 100,000 synapses pruned per second
14
Q
Experience-expectant development
A
- overproduced synapses, pruned with experience
- experience leads to less
- tied to critical/sensitive periods
- organizes brain to process information, behaviours expected for all humans
- sensory processes
- parental attachment
- eye-hand coordination
- language capacity
15
Q
Experience-dependent development
A
- new synapses formed, maybe some pruning
- experiences lead to more
- continues throughout life
- codes experience/learning thata is person specific
- a particular language
- specific knowledge, memories, skills
16
Q
Rat experiments
A
- infant rates
- enrichment reduced synapse density
- facilitated pruning of excess synapses
- prune>gain
- adult rats
- enrichment increased synapse density
- facilitated growth of new synapses
- gain>prune
17
Q
Rearrangement of synapses during developement
A
- active synapses: receive enough neurotrophic factor to remain stable
- inactive: receive too little neurotrophic factor to remain stable
- myelination: glial cells war around axons
- increased speed of AP
- myelin composed of 15% cholesterol with 20% protein (which is why doctors recommend breast milk for babies)
18
Q
Postnatal cerebral development in human infants
A
- post natal growth is a consequence of
- synaptogensis
- increase dendritic branches
- myelination
-overproduction of synapses may underlie the greater plasticity of the young brain
19
Q
Implications of arrested development
A
- maturation occurs from back to front of brain
- earlier development of back of Brian and later development of front of brain
- preference for physical activity
- less than optimal planning and judgement
- more risky impulsive behaviour
- minimal consideration of negative consequences
20
Q
Frontal lobe sensitivity
A
- sensitive to early experience
- long process beginning prenatally and continue in until early adulthood
- altered by wide range of positive and negative experiences
21
Q
Neuroplasticity in adults
A
-mature brain changes and adopts
-neurogenesis
-seen only in olfactory bulb and hippocampus
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