Week 3-Prenatal and infant brain development Flashcards
Define morphogenesis
the process from a single cell to a complex brain
Define genetic guidance
genetically determined sequence of events that can be modulated by environment
What would be the impact of having no cortex on brain function?
no vision/audition/reasoning/memory/planning
State the three main stages of prenatal development (with time period)
1.Germinal (clump of cells) 0-2 weeks
2.Embryonic (focusing on this stage onwards) 3-8 weeks
3.Fetal 9 weeks-birth
What are the 3 main characteristics needed in an adult brain network?
1.laminar organisation of the cortex (neurones organised across different layers)
2.different layers=different roles in network e.g. perceiving sound,colour etc.,
3.different connections/wires of the brain=all areas communicate
True or false: some structures are already in place before birth which isn’t the big event
True, maturation comes post-birth but a baby’s brain needs different cells/layers/connections
Explain the gross neuroanatomy in prenatal brain development (image to learn on notes)
-early brain is a tube (neural tube)
-neural tube rapidly evolves and differentiates via a series of thickening/constrictions (4 weeks-6 months)
Explain the micro development of a prenatal brain
-embryonic brain undergoes a series of massive cellular changes
-a series of genetically programmed events create a brain pre-birth
True or false: A baby’s brain is mature at birth
false it tends to take 40 weeks of gestation for a baby to be mature
Define gestation
a process of something developing over a time period (can be in the womb)
State the 5 genetically programmed events which develop the neural structure
1.Cell proliferation
2.Cell migration
3.Cell differentiation
4.Programmed cell death
5.Synaptic rearrangement
Explain the process of neural (cell) proliferation
-cell creation
-massive production of cells occurs 2-4 months after gestation but continues until/after birth
True or false: no more neurones are produced after birth
True, but in some instances adults can produce new ones but its the glial cells (‘babysitter of neurons’) that continues being produced after birth
Explain the process of cell migration
1.All neurones come from neural precursor cells (which can become any type of cell)
2.These undifferentiated cells become either neurones or glia cells
3.Then the immature neurons migrate to colonise all parts of the embryonic brain
Explain the process of cell migration: layer differentiation
1.neurons migrating to target layers=cortex layers created
2.neurones use glial cells as a ladder and first cells arrive at own layer and are in the deepest layer (layer 6)
3.cortex assembled from inside out
What is the purpose of glial cells in cell migration?
they act as the ‘nurse of the neurons’ (neurones travel through the layers of this cell to form new layers)
Explain the process of cell differentiation
Cells start to differentiate when they migrate and become the neural cell they’ll be throughout our lives
-neurons come from precursor cells and there are different types of neurons
Explain the genesis of connections
-neurons formed from cell body,dendrites (receiver) and axons (output)
-neurons interconnect with axons forming a network (GoC)
-as neurons differentiate, growing tip of an axon extends to travel and find appropriate target (guided by special proteins and repulsed by others until proper target found to connect with)
True or false: connected neurons process the same information in the chain
True
Explain programmed cell death: apoptosis
-aims to discard input neurones that didn’t connect to other target neurones as it doesn’t help to process info in the network
-survival of the connected (no role=discarded from neural network)
-brain doesn’t keep things that aren’t useful for processing
True or false: neurons are cells
True
6.Elimination of synapses: explain what synaptic re-arrangement is
-it’s the change of connection between the synapses/neurons (like wires and all genetically programmed/modulated by environment)
-no signal received however=eliminated (the arrangement is activity-dependent e.g. visual system)
True or false: a prenatal brain has 70% more synapses than the adult brain
false it’s 50% (still a crazy amount of wiring in the prenatal brain)
True or false: info from the left/right visual field are processed in different sides/parts of the brain
True (links to contralateral theory)
How does synapse elimination occur in the visual area?
-before birth we experience little to no visual stimuli so our primary visual cortex isn’t specialised
-once born we gain visual experience causing synaptic rearrangement/specialisation to occur and the synapses connect to a specific eye becoming more specialised (PVC matures)
Is vision innate?
no, argued our visual systems learns by adapting to visual input (can’t separate genetics/environment which is a key theory in this lecture)
Influence of stimulation on perception: what was learnt adding prism goggles on chicks?
-ability to localise food solely visual/auditory not as good as combined but 42 days after displacement they realign
-shows good localisation achieved with both 2 senses
Define plasticity
the brains ability to modify/reorganise i.e., learns and adapts through experience
What factors can affect plasticity?
forgetting, aging, injury, illness, drugs
Give 2 studies supporting plasticity
1.Juggler group compared to the control group (no juggling) MRI scans showed modified brain structure after 6 months of practise
2. Maguire’s taxi study: experienced taxi drivers had a larger hippocampus
Explain a brain plasticity limitation: ODC modification
-the visual neural system acquires eye specialisation (if one eye occluded a different pattern is seen)
-occluding for a whole period causes the occluded eye to take up less cortical space (not seen as useful i.e. survival of the most efficient) and for too long a period causes the ODC to never change (showing plasticity can be damaging)
Define the critical period
a time window for plasticity where development of brain mechanism/organ can be influenced
Give an example of the critical period in relation to the visual system
-no occluded eye=no ocular dominance initially, synaptic re-arrangement=normal ODC distribution both eyes have equal brain resources
-occluded eye=no ocular dominance initially, synaptic re-arrangement=abnormal ODC distribution one eye took all of the brain resources
What is one of the key ideas in this lecture?
no stimulation=no function=elimination
True or false: adult brain plasticity is higher than in infancy
false things such as sensory, motor, language are easier learned at a younger age
Staudt 2010: what was found when children younger than 5 had a lesion in the left hemisphere?
reorganisation of language processing in the right hemisphere
Why are infants’ brains so plastic?
-the brain is not yet finished as grey maturation still needs to happen over time (seen in brain scans)
-the brain network put in place during infancy will be ‘crystallised for life’
Explain the link between sociopathy, infancy, plasticity and the critical period
-MAOA gene aka the ‘aggression’ gene (more likely to occur with low MAOA genotype)
-found MAOA genotype structurally affects the brain (scans show difference in size between left/right amygdala)
-however only activated with environmental factors e.g. severe maltreatment so the risk of becoming violent as a result is nature THROUGH nuture (not vs)
What aspects of brain structure crystallise during infancy?
vision and ODC
True or false: the network is hard wired
False it’s pre-wired (nature) and then influenced by the environment (nurture)
What’s vision like for infants?
-immature vision with blurry perception at 6 months of age
-have 2D perception at birth not 3D but develops over time
What is face perception like in infants?
-infants display same electrical pattern as adults (processing stimuli records electrical component P1) BUT response time slower
-face perception and discrimination gradually improves with age
What is sound perception like in infants?
-external sounds processed via auditory system 30 weeks GA
-newborns discriminate mother’s voice at birth or recognise songs
-auditory perception follows some maturation and sounds are filtered
Explain language in infants
-same language network activated in infants even though they can’t process speech
-newborns extract words from continuous
