brain development and plasticity Flashcards
what brain processes happen during development
cell proliferation and migration
development of synapses
myelination
each process has their own time course (some happen at birth, others through adolescence)
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
around the 7th week of gestation, nerve cells and glia near inside tube divide, proliferate and begin to migrate outward
neurogenesis
generation of new nerve cells occurring in the area right around the ventricle
migration of nerve cells
happens during early development
glial cells provide the scaffolding or “roads” along which nerve cells can migrate to their ultimate destinations
- cells that migrate often travel along radial glia
by six months of gestation, most neurons have been produced
synaptogenesis
dramatic increase in the number of neuronal connections (synapses)
one of the largest changes after birth
dendrites in the cortical regions increase greatly, providing greater SA for synaptic connections
occurs rapidly (increase more than 10 fold during the first year of life)
regional differences across brain regions
- occurs most rapid in primary sensory and motor area (functionally needed before learning more complex things) then the prefrontal cortex
synaptic pruning
reducing the number of neural connections
happens because cells do not receive the “survival factor” signals from other neighbouring cells. The ones not getting enough stimulation wither
this allows the brain to fine tune and specialize in specific environments. allows it to be sculpted according to experience
earliest in sensory and cortical regions
latest in frontal cortex (not complete until late adolescence)
synaptic overproduction
allows the brain initially to have maximal capacity to respond to the environment
myelination
glial cells provide myelin sheath
which matter increases and grey matter
a longer process that varies by region of the nervous system
myelination of basic sensory and motor systems: within 1st year after birth
myelination of integrative systems occurs later
medulla and spinal cord and myelinated early on in life - support basic functions
myelination in childhood and teenage years
relative amount of white matter increases and gray matter decreases
brain volume generally larger in boys for both grey and white matter
dual systems model
when no reward is involved, adolescents show adult-like logical reasoning skills
when strong emotional incentives are present, adolescents make riskier choices
activity in the nucleus accumbens (ventral striatum) increases in adolescents when anticipating of receiving a reward. Combination of this and the still developing prefrontal cortex leads to riskier behaviours. decreases in adulthood b/c prefrontal cortex matures and has better control over the limbic system.
experience-expectant systems
develop in response to experiences are common to nearly all members of that species
ie/ patterened light, presence of caregiver, exposure to language
neural systems develop normally when the expected input is received, but are seriously affected when the expected experience is absent
experience-dependent systems
develop in response to experiences that are not universal, but vary across people based on their unique experiences
ie/ musical training early life, learning to juggle, learning to ride a bike
we are likely to develop different motor and musical skills
environmental enrichment and deprivation
many studies have been conducted in other species
control condition: rat alone in a small plastic cage
enriched condition: large area with varied spatial arrangement, toys and social interaction with other rats
enriched environments positively influence synaptic connectivity in early development and adulthood
changes persist even when the animals are later removed from the enriched setting
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 family
those placed in foster car before two years of age showed improvements in intelligence and normalized EEG activity
effects of environmental deprivation during critical developmental windows in orphaned Romanian children
sensitive periods
organism is particularly sensitive to certain external stimuli during a specific developmental period
(though certain effects can influence over a lifetime)
- allows for locking in influence
visual system: exposure to visual input in both eyes needed in first months of life to develop normal binocular vision
language: learning a new language becomes more difficult in adulthood
deprivation of social contract during this time can effect development
developmental disabilities
conditions that typically make their first appearances during childhood
represents a departure from normal developmental path
lots of unknown causes
intellectual disability
mental retardation
can be caused by genetic disorders, infections, toxins and oxygen deprivation
classified based on severity
genetic disorders
some genetic disorders can cause intellectual disability
ie/ down syndrome
down syndrome
most common genetic cause of intellectual disability
severve disability
associated with IQs in the lowest 2 percent
occurs in 1 in 700-800 births
caused by trisomy 21 (three copies of 21st chromosome results in down syndrome)
characterized by morphology of face and body (aids early diagnosis)
deficits in language and verbal memory - sometimes better functioning in visuospatial and social tasks
trisomy 21
a condition where the 21st pair of chromosomes contain 3 chromosomes instead of 2
