Brain development Flashcards
Briefly explain this key stage in brain development:
1.Neural Induction
The neural tube forms between days 18-24 post conception
Forebrain, mindbrain, hindbrain and spinal cord exist
Neural patterning
What is neural patterning? When and where does it occur?
During first key stage of brain development, during neural induction
The cells in the neural tube are taking on different identities and dimensions i.e determining which part of the brain (fore, mid, hind, spinal cord) its going to belong to
Briefly explain this key stage in brain development:
2.Proliferation
Massive proliferation/increase in the number of cells in neural tube
By day 125, halfway through pregnancy, all the cells have been formed
What is the ventricular zone? Where is it?
Its a single layer of cells that forms in the inner surface of the neural tube
Briefly explain this key stage in brain development:
3.Migration
The neural cells formed migrate through the ventriculare zone out to the other layers of the neural tube - the intermediate and marginal zone
The cells are migrating to their final destinations
What are radial Glial cells? where are the found and what is their purpose during migration?
Radial glial cells provide scaffolding relief, helping other cells migrate to their final positions within the neural tube
Briefly explain this key stage in brain development:
4.Differentiation
Cells are differentiating into what brain structure they will belong to (whether hippocampal, cerebellum)
Briefly explain this key stage in brain development:
5.Synaptogenisis
The connections/synapses between cells increased, the neurons grow more axons and dendrites
Briefly explain this key stage in brain development:
6.Cell death/stabilisation
After synaptogenisis, lots of cells have reached out to eachother and have formed widespread connections, this levels off after the first year of conception and declines. Now connections are being pruned into positions we need them in - form efficient and final arrangement
Briefly explain this key stage in brain development:
7.Synaptic rearrangement
Axons reached out widely to eachother making widespread pattenrs of connections but over time, pattenr gets adjusted, the snypases that are used often becomne stronger and weaker ones become lost.
How is the brain looking 2 years after birth?
Total volume has doubled
Not forming new areas and connections but rather fine tuning and stabilising and reorganizing circuits that have already formed
Name the changes occuring during childhood into adolescnece
Grey matter rapid postnatal growth in first few years
White matter increases more steadily over the years continuing throughout childhood into adolescence
Name the changes occuring in the adolescent brain (<30 years)
Decrease in synaptic connections, pruning away ones that arent used to have efficient and streamlined brain
Process of fine tuning and streamlining continues until around 30 years of age, happening earlier in occipital and parietal lobes, then temporal and lastly in frontal lobe
What is a streamlined brain?
Imbalance model of brain development
There is an imbalance in adolescent brains that is likley why they take more risks, seek rewards and need social approval
This is because subcortical regions such as the ventral striatum associated with reward seeking behaviours develop and are fully active earlier than the PFC, which is the part responsible for cognitive control. The PFC does not develop until adulthood around the age of 25. This imbalance is what potentially gives rise to the adolescent risk taking behaviour
Environmental influences on brain development - prenatal:
Tobacco exposure
Tobacco toxins can cross placental barrier and dampen gene expression, slow the myelination process and migration, which in turn alters brain structure and function
This may cause long lasting effects affecting a person in adulthood too. It is a risk factor for developing psychiatric disorders and addictions
!!Environmental influences on brain development - prenatal:
Maternal stress
Cortisol of mother may get exposed to fetus affecting both the structure and function of the brain
Affect HPA axis
!!Environmental influences on brain development - prenatal:
Maternal depression
Similar effects to maternal stress, there are high levels of cortisol that will be exposed to fetus
Child more liekly to have emotional difficulties, with amygdala volume increasing
Functional connectivity also affects, amygdala sending signals to PFC
!!Environmental influences on brain development - postnatal:
Socio-economic status
-Repeated activation in stress related activity means that this circuitry will mature faster than other cirucits
-Faster aging of whole body because of allostatic load
What is allostatic load?
Environmental influences on brain development - postnatal:
Poverty
Children living below poverty line shown to have structurally smaller frontal and temporal cortex as well as hippocampus
Also reduction in gray matter
Environmental influences on brain development - postnatal:
Neglect
Where development has been affected by extreme neglect the frontal-occipital circumference shown to be smaller.
Good news is that the earlier the child is taken out of this neglect, because of the plasticity of a childs brain, there is huge opportunities for recovery to save and restore brain structure and associated life outcomes
Name the changes that occur in the brain with ageing:
Retrogensis - Last in, first out hypothesis –> PFC takes longest to develop but no sooner has it developed we see it starts to decline.
Brain structures that develop earliest eg visual, primary sensory, auditoy seem to be more robust to change
Structural changes result in cognitive decline - Decrease in size of hippocampus (which is associated with more pronounced difficulties with cognitive abilites such as episodic memory, working memory, processing speed..)
Compensatory brain changes - HAROLD Model
Hemispherich Asymmetry Reduction in OLder Adults
Increased bilateral recruitment of prefrontal areas, compared to younger adults that primarily acitvate their right hemisphere for working memory tasks, brain of older adults is potentially being activated differently to complete certain tasks to compensate for the structural changes that occur with aging
Compensatory brain changes - PASA Model
Posterior Anterior Shift in Aging
With structural changes occuring with aging, the functional areas to perform tasks has to change to adapt
Older adults recruit anterior regions such as the PFC. Suggested that older adults recruit anterior regions to compensate for the sensory processing deficits in occipitotemporal regions
