Neurodevelopment 2 Flashcards
What can cause degeneration of Neuroplasticity?
Traumatic head injury, Tumour, Infection, Toxic substances (drugs), Radiation, Degenerative conditions, Aging.
Post Birth Neurogenisis
In humans majority of neurones have been created at birth
Exceptions:
Cerebellar cells – neurogenesis continues for a few months after birth
Olfactory receptors neurones – replaced throughout life
Hippocampus and some cortical areas – allows lifetime plasticity
Neuroplasticity: Degenration Types
Axonal damage – anterograde and retrograde degeneration
Anterograde degeneration: (towards terminals)
decrease connectivity
Retrograde degeneration: (towards soma)
can lead to cell death
Neuroplasticity: Regeneration (Neurotrophine)
Family of neurotrophins called nerve growth factor (NGF)
During development - match the correct number of neurons with their targets.
Regulate axonal and dendritic growth, the formation of synaptic structure and connections, and neurotransmitter release.
Promote neuronal cell survival, or cell death, depending on the environment.
What is collateral axonal sprouting?
If neurones are stimulated they can form new connections. May be activity dependant because electrical stimulation leads to sprouting.
Transplant Neuronal Tissue with Parkinsons
Foetal transplants have been used to restore some motor function. Because the tissue has not been differentialised yet so you can transplant it into the substansia nigra cell so it thinks that it is one of those.
What is brain plasticity?
Brain plasticity: capacity of the brain to change in response to chemicals, activity or experience. Donald Hebb said that environmental richness maximises intelligence.
Experience and Brain Development
Experience changes the structure of the neurones in the hippocampus and cortex. Animals who live in enriched conditions have larger dendritic fields, more neurones and greater connectivity.
The critical period - Konrad Lorenz
A period which the brain is most sensitive to a specific experience. e.g. imprinting. First 6 months after birth are important for a baby’s occipital lobe to develop.
What can neglect and trauma do?
A child raised in an environment characterized by persisting trauma (e.g., domestic violence, physical abuse) will develop an excessively active and reactive stress-response apparatus. The majority of the stress response systems reside in the brainstem and midbrain (e.g., locus coeruleus). Overdevelopment of these areas, even in the presence of optimal emotional or cognitive experience will result in an altered Cortical Modulation ratio and, a predisposition to act in an aggressive, impulsive, behaviorally reactive fashion.
Injury and Brain Development: Vulnerable times in utero
Most vulnerable time is the second/third trimester. Neurotoxic damage in utero: foetal alcohol syndrome. Anoxia in utereo or during birth: cerebral palsy
Early life
Stroke Intracerebral bleeding Collision injuries can show some recovery of function
FAS - Foetal Alcohol Syndrome
Babies born with this have a particular look, sunken nasal bridge and they have a lack of a philtrum (the gap under your nose)
ADHD
Genetic component (multifactorial – many genes involved) – lot of genetic variability
- Distractibility, hyperactivity, impulsivity
- 5% children (greater in boys than girls)
- Smaller brain volumes (especially PFC and cerebellum)
- Delayed cortical thinning
- Reduced signalling in reward pathways
Autism
Characterised by rapid brain development within the first 6th months. Increase in both grey and white matter across the brain lobes.
What is happening during adolescence?
New synaptic connections are forming, pruning and myelination occurring. The prefrontal cortex is immature: decision making task. Well-developed nucleus accumbens: pleasure and reward
compared to children and adults:
no response to small reward
larger response to medium and large rewards
