Brain Developement and Plasticity Flashcards
What changes occur in the brain during childhood?
- Cell proliferation and migration
- Development of synapses
- Myelination
Not a linear process of growth
(Figure in slide 3)
Synapse development
1.— Initial synaptogenesis (increase in synpases)
2.— Subsequent synaptic pruning (decline in synapses)
(see table in slide 3)
Neurogenesis
Starts in ventricles
Progenitor cells divide and create daughter cells
— divided cells either become progenitor cells or migrate
Eventually becomes the fetal brain
————-
Neurulation
— Formation of the hollow tube that becomes the CNS
— With time, the tube folds, turns, and expands to become the fetal brain
— The hole inside the tube becomes the ventricles
Neurogenesis
— Generation of new nerve cells occurring in the area right around the ventricle
Migration of Nerve Cells
Relies on glial cells
— provide “roads” or “scaffolding” for migration
— After 6 months, most neurons have been produced
Synaptogenesis
After birth, dramatic increase in synapses
Dendrites increase greatly early in life, allowing greater surface area for connections
Synaptic Blooming and Pruning
Blooming: Proliferation
Pruning: follows, process of reducing neural connections
Time course varies across cortical regions
—- Earliest: sensory and motor regions
—- Next: Parietal and Temporal association cortex
—- Latest: frontal cortex (not complete until late adolescence
Blooming allows the brain to have maximal capacity to respond to the environment
Connections that do not recieve much stimulation are pruned
Myelination
– Longer process
– Varies by region of nervous system
– Myelination of basic sensory and motor system: within 1st year of birth
– Myelination of integrative systems occurs later
What is the result of synaptic pruning and myelination?
Relative amount of white matter increases, grey matter decreases (slide 11)
What changes occur in the brain during adolescence?
uses a Dual-Systems Model
Developmental mismatch between two systems in adolescence
1. Limbic structures maturing: more incentive to seek reward
2. Prefrontal cortex still immature: multiple consequences related to executive function
… Limbic structures maturing, prefrontal is not yet developed = risky adolescent behaviour
Dual-Systems model evidence
> When no reward is involved, adolescents show adult-like logical reasoning skills
Strong emotional incentives = riskier choices
Activity in the nucleus accumbens (AKA ventral striatum) increases when adolescents when anticipating or recieving a reward.
Experience-expectant systems
Influence of the environment of the developing brain
– Develops in response to experience common to most members of the species
– Neural systems develop normally when the expected input is received, but is seriously affected when that is absent
– like learning to speak
Experience-dependent systems
– Develops in response to experiences that are not universal, but vary based on unique experiences
– like riding a bike
Influence of environment on the devleoping brain
Environmental Enrichment vs. Deprivation
Enriched environments positively influence synaptic connectivity in early development and adulthood
Changes persist when the animals are later removed from the enriched setting (slide 16 experiment on rats)
Bucharest Early Intervention Project
Orphaned children in state care randomly chosen to receive:
1. Continued care in state-run orphanage (little social or intellectual stimulation)
2. Placement with a highly trained foster family
Those in the foster care before age 2 showed improvements in intelligence and normalized EEG activity
Sensitive Periods in Development
Organism is particularly sensitive to certain external stimuli during a specific developmental period
EG:
– Visual system: exposure needed in the first months of life
– Language: becomes more difficult in adulthood
Developmental Disabilities
- Intellectual disability
- Dyslexia
- Autism
- ADHD
Typically make their appearances during childhood
Represent a departure from the difficult developmental path
Intellectual disability-Mild
IQ Level: 55-70
%: 85
Typical presentation:
– develops normally during preschool but do not acquire academic abilities above the 6th grade level
– As adults, can be self-supporting, and live independently with community and support
Intellectual Disability-Moderate
IQ Level: 35-55
%: 10
Typical Presentation:
– Can acquire communication skills during early childhood
– As adults, need some supervision for living and work, but can take care of themselves in those contexts
Intellectual disability (severe)
Intellectual disability (profound)
Genetic Disorders
Can cause intellectual disabilities
Example: Down Syndrome
Down Syndrome
Most common genetically cause of intellectual disability
Associated with IQs in the lowest 2%
1 in 700-800 births
Caused by trisomy 21 (3 copies of the 21st chromosome)
Down Syndrome Symptoms
—- Characterized by a specific morphology of body and face
—- Slower rate of cognitive development than peers
—- Characterized by reduced gray-matter volume due to reductions in cortical surface area
—- In middle age, many people with Down syndrome begin to exhibit symptoms similar to those of Alzheimer’s disease.
Fetal Alcohol Spectrum Disorders
> > Intellectual disorders caused bt alcohol consumption during pregnacy
Most severe form: fetal alcohol syndrome
