Zygote
Fertilized egg
–> has 46 chromosomes ( 50% from each parent)
(0-14 days)
The development of the zygote into an embryo
- after 12h: cell begins dividing
- after 3 days: zygote is a small mass of homogeneous cells
- after 7 days: zygote shows 3 distinct cell layers that are the beginning of all tissues
a) Ectoderm
b) Mesoderm
c) Endoderm
–> as these thicken, they grow into a flat oval plate
- Neurolation
- -> the development of the neural PLATE into neural GROOVE, then neural TUBE - Development of an embryo
Neural groove
The groove between the neural folds
Neural tube
The ridges of the neural groove come together to from the neural tube
–> has subdivisions that correspond to the future:
a) forebrain
b) midbrain
c) hindbrain
Embryo
Developing human between the 3. to 8. week after fertilization
–> after this it is referred to as a fetus
The 7 stages of the development of the Nervous system
according to lecture
- Neurolation
- Neurogenesis/Proliferation
- Cell migration/Aggregation
- Differentiation
- Synaptogenesis
- Synaptic Pruning + Neuronal cell death
- Synapse rearrangement
(8. Myelination)
Neurogenesis/Proliferation
Mitotic division of the cells of the neural tube to provide progeny cells/ neurons
Cell migration
The produced cells migrate along the radial glial cells to their appropriate regions
–> ventricular –> intermediate –> marginal region
Differentiation
The transformation of these cells into dinsinctive types of neurons + glial cells
Synaptogenesis
The establishment of synaptic connections, as axons + dendrites grow
Neuronal cell death
Selective death of many nerve cells
Synapse rearrangement
Describes the loss of some synapses + the resulting development of others in order to refine synaptic connections
–> Result: ex.: each muscle fiber comes to be innervated by only one motor neuron, not many
–> this is evident in the thinning of grey matter
Cell - Cell interaction
The general process during development in which one cell affects the differentiation of the neighboring cells
Radial glial cells
Glial cells that extend from the inner to the outer surfaces of the emerging NS
–> serve as “guide” to the newly formed cells
Cell adhesion molecules
CAMs
Chemicals that promote the adhesion of the migrating cells with the radial glial cells
Expression
The process by which the cell makes an mRNA transcript of a particular gene
–> happens when the cell reaches its destination after migrating
–> shapes the cell into the distinctive forms & functions of the neurons found in that particular region
What influences differentiation ?
- Local environment (neighboring cells)
- Intrinsic self organization
ex. : purkinje cells –> have very specific dendritic branches
Notochord
Rodlike structure that releases a protein that diffuses tp the to spinal cord and directs some cells to become motor neurons
Induction
The process by which one set of cells influences the fate of neighboring cells by secreting a chemical
Regulation
If a cell is injured or lost, other cells will fill in for the missing cells
–> compensation
Stem cell
Cell that is undifferentiated and can therefore take on the fate of any cell
Growth cones
Growing tip of a dendrite or axon
Filopodia
Fine + tubular outgrowths from the growth cone (predendrites)
–> they adhere to CAMs, then contract to pull the growth cone in a particular direction
Chemoattractants
Chemical signal that attracts certain growth cones
Chemorepellents
Chemicals that repel growth cones
Why are chemoattractants + chemorepellents so important ?
Because some axons need to stay on one side of the body and some need to cross over
Apoptosis
Naturally occurring cell death
–> interfering with apoptosis may cause the brain to grow too large for the skull
Death genes
Genes that are expressed only when a cell undergoes apoptosis
How is Apoptosis regulated ?
It is regulated by
a) cell cell interactions
b) availability of synaptic targets
What do Neurons compete for ?
a) SYNAPTIC SITES
- -> those who make adequate synapses survive, those who don’t die
b) NEUROTROPHIC FACTORS
- -> chemical that feeds the neurons and thus helps them to survive
Nerve growth factor
NGF
Substance that affects the growth of neurons in the spinal ganglia + ganglia of the SNS
–> type of neurotrophic factor
Pruning
The killing/ Death of redundant synapses
Myelination
Development of sheaths around axons
- conducted by glial cells
- greatly changes the rate at which axons conduct message
- strong impact on behavior because it allows large networks of cells to communicate
The order of which parts are myelinated first
- Hindbrain
- Midbrain
- Forebrain –> most complex
The order of which parts of the human brain develop first
- Cerebral cortex (sensory + motor systems)
- -> basic functions - Temporal + parietal association cortex
- -> language, spatial attention - Prefrontal + Lateral temporal cortex
- -> higher order control
The development of grey and white matter
- grey matter loss during childhood/adolescence reflects the process of the immature brain to the mature ( U-shaped )
- white matter development increases in a linear pattern until young adulthood
Why does risk - taking increase in adolescence ?
a) Peers become important
–> one might engage in behaviors to demonstrate affiliation with others
b) Weakening of parental supervision
c) increased sensitivity to manipulation
d) heightened rate of hormonal change
Dual systems model of decision making
Decision making is the byproduct of an interaction between processes that support controlled/reasoned behavior and those that drive reactive/ emotional responding
–> the sum of emotions + controlled behavior = decision
Heightened sensitivity to reward
Is implicated in increases sensation + novelty seeking
–> more prevalent in adolescents, due to late development if the prefrontal cortex
(limbic system + amygdala are already developed)
Designs for examining development
- Cross sectional design
- Longitudinal Design
- Microgenetic design
- Sequential Design
- Experimental Design
- Naturalistic observation
- Structured observation
Cross sectional design
Comparing children of different ages on a given behavior
- -> everyone measured at roughly same time
- -> over a short period
What are the advantages vs disadvantages of a CROSS SECTIONAL DESIGN ?
Advantage:
–> useful for revealing similarities + differences between different age groups
–> quick + easy to administer
Disadvantage:
–> Uninformative about the stability of the individuals differences over time
Longitudinal design
Method in which the same children are studied twice or more over a substantial period of time
–> at least a year
What are the advantages vs disadvantages of a LONGITUDINAL DESIGN ?
Advantage:
–> yields findings about
a) the stability of individual differences over time
b) the individual childrens patterns of change
Disadvantage:
–> repeated testing can threaten the external validity
–> difficult to keep all participants in study ( non response bias)
Microgenetic design
Method in which the same children are studied repeatedly over a short period
What are the advantages vs disadvantages of a MICROGENETIC DESIGN ?
Advantage:
–> Provides insight into the process of change over brief periods
Disadvantage:
–> Does not provide insight about typical patterns of change over long periods
Sequential Design
Method in which 2 or more groups are observed of a long period of time
–> combination of longitudinal and cross-sectional designs, by following several differently aged cohorts over time.
Correlational design
Research that determines if a relationship exists between two or more variables, and if so, to what degree the relationship occurs
Experimental design
Method in which a controlled experimental factor is subjected to a special treatment for purposes of comparison with a factor kept constant
Imaging methods
- Structural MRI
- fMRI
- EEG / ERP recordings
