Brain development Flashcards
What are the 7 stages of brain development from conception through to 9 months (full term)
neural induction, proliferation, migration, differentiation, synaptogenesis, cell death/stabilisation, synaptic rearrangement.
Neural induction
- forming of the neural tube takes place 18 - 24 days post conception, genetically determined, neural tube forming and ends of it close
Proliferation
-first half of pregnancy (day 24 - 125) genetically determined, HUGE proliferation of the number of cells, so by day 124 foetus has all its cells.
The ventricular zone also forms during proliferation, what is this?
single layer of cells form along inner surface of the neural tube.
Migration
cells migrate from ventricular zone out towards their final destinations
Within migration, what do radial glial cells do?
Act as scaffolding to help other cells migrate (radiate out from the centre of the neural tube towards the end)
What are the 3 layers the cells are moving through in migration?
The ventricular zone, the intermediate zone and the marginal zone
Differentiation
day 125 - postnatal - cells differentiatie into what they will become (e.g hippocampus cell or cerebellum cell) then will start to express particular genes to make exact proteins it needs thus will acquire distinctive features
Synaptogenesis
growing new synapses (connections between cells) - neurons grow more axons and dendrites to create these new synapses
Cell death / stabilisation
initial surge in synaptic growth levels off and declines after first year - process of cell death can prune some cells allowing a more efficient final arrangement
Synaptic rearrangement
Once synapses are formed, synaptic rearragment occurs meaning unnecessary or weak synapses can be lost allowing active synapses that are strenghtended to stay. Allows a more focused pattern of synaptic contact left
From birth to the first two years, what are some changes that occur in the brain?
total brain volume doubles in the first year and reaches 80% adult size by age 2 (meaning basic structual and functional framework in place by age 2).
If the brain is only 80% developed at age 2, what else is required?
After age 2 brain development is mainly characterised by reorgansising and fine tuning major circuits already established.
Childhood brain development
Rapid postnatal growth of cortical grey matter over first 2 years - but slower growpth of cortical white matter throughout CHILDHOOD and adolescence
adolescence brain development
All about developing a more streamlined brain - increasing axon myelination to speed the flow of information, decrease of synaptic connections and dendrites
what is the imbalance of brain model produced by somerville and casey
What are some environmental influences on brain development
Could be prenatal - prenatal tobacco exposure, prenatal maternal stress, prenatal maternal depression or could be after birth - socio-economic status (SES), poverty, neglect etc
What are some changes to the brain that occur with ageing?
Changes to PFC also changes to hippocampus
Changes to prefrontal cortex (PFC)
Retrogenesis - “last in first out” - brain structures that mature earlier in development are more robust to effects of ageing compared to structures that mature later
Changes to hippocampus
age-related decreases in hippocampal volume associated with decline in multiple areas of cognition - affects working memory, episodic memory, processing speed, executive function etc
What models are in place to argue how the ageing brain compensated for structual declines to maintain normal functioning
HAROLD model and PASA model - these models describe how in a healthy ageing person, how the brain responds to ageing to try and maintain healthy functioning
What is the HAROLD model?
Hemispheric reduction in older adult model - suggets idea of increased bilateral recruitment of pre-frontal areas e.g in working memory tasks
What is the PASA model?
Posterior anterior shift in ageing model - suggests recruitment of PFC in repsonse to reduced visual cortex activation
