Week 1
Rapid brain growth fetus
- Critical stages of brain development regarding brain growth and connectional specificity occur
during pregnancy
- Primitive forms of neuronal networks can already be found in the fetal brain
- At birth all anatomical structures are present
Brain development happens (early brain development):
1. Hierarchical: in general, brain structures develop in hierarchical order (not everything develops at
the same time)
- Cerebellar (1st) ⇒ posterior ⇒ anterior ⇒ frontal (last, even developing late
adolescence)
2. Additive (adds to what is already there) and regressive (becomes less): many developmental
brain processes increase over time (myelination = additive), other processes show an inverse
development with an initial overproduction and then selective reduction (synaptogenesis followed
by synaptic pruning = regressive)
3. In growth spurts: most processes are not linear, but happen with growth spurts that often lead to
overproduction (and later pruning)
- Sensitive/ critical periods (windows of opportunity/ windows of risk)
Prenatal period (before birth)
- Damage during prenatal period mostly impact the structure of the brain (morphology) ⇒ you don’t
necessarily know anything about the function yet
- 1st to 2nd trimester ⇒ neurons migrate to their final location
- 2nd trimester ⇒ brain begins to fold
Postnatal period (after birth)
- Growth spurt in dendrites
- Synaptogenesis (more synapses)
- Myelination = increasing white matter (increased processing speed)
, - Damage mostly impacts the function of the brain (interconnections and functional networks),
functional disruptions
Early disruptions
- Early disruptions to early brain development can be numerous
- Injury: direct injury, too few nutrients/ oxygen
- Maternal (mental) health: severe depression/ anxiety, infections, sickness
- Environmental: exposure to toxins (e.g., lead, radiation), smoking or drug use of mother
- Genetic: genetic disorders (down syndrome)
Rapid growth: strength or vulnerability (if you add pos = strength, if neg = vulnerability)
- Strength: immature brains are extremely plastic and are able to recover better
- Clinical observations: children often show greater improvement after brain injury than
adults (not always the case, but earlier more plasticity)
- The young brain is less differentiated and more capable of transferring functions from
damaged tissue to health tissue (=plasticity)
- Equipotential = the view that all brain regions are equally able to take responsibility for
any function; any part of a healthy brain should be able to take on the function, e.g., left
hemisphere damaged, language abilities on right hemisphere (contrast: innate
specialization = every function has it own place in the brain)
- Vulnerability: as a result of dramatic developmental processes the brain may be extremely
sensitive to environmental influences early in life
- Critical periods: brain damage within a specific critical window may be more detrimental
than later brain damage outside of the critical window (if you don’t learn a specific skill
during this time, you may never learn it again, e.g., language learning)
- Functional plasticity may only be restricted to certain sensitive periods
- Model shows that it’s not one or the other, you can have strengths during certain periods and
vulnerabilities during the other period (both can be present)
- Depends on age, how bad injury is
,Cognitive reserve model
- Cognitive reserve (CR): the adaptability; i.e., efficiency, capacity, flexibility … of cognitive
processes that helps to explain differential susceptibility of cognitive abilities or day-to-day
function to brain aging, pathology, or insult; is modifiable
- Brain reserve (BR): commonly conceived as neurobiological capital (numbers of neurons,
synapses); non modifiable
- BR implies that individual variation in the structural characteristics of the brain allows
some people to better cope with brain aging and pathology than others before clinical or
cognitive changes emerge
Early brain damage - how is it different
- When working with children, you need to take into account the following factors:
1. Developmental stage of certain skills at time of insult:
- Emerging skills: early stages of acquisitions
- Developing skills: partially acquired abilities, but not fully functional
- Established skills: matured abilities (e.g. language ⇒ established, it is already localized,
may influence plasticity and the transfer; adults = all skills are established)
2. Normal development: even healthy children vary in their ability to perform certain cognitive tasks
3. Children may “grow into” deficits in later developmental stages
- Initially few deficits, but child runs into trouble when developing skills at a more advanced
level (especially when skills were emerging) (deficits were not visible yet)
4. Type of insult: more often widespread brain damage (instead of focal), so less specific
impairments in children. More general disturbances in different domains
5. Recovery trajectory: more difficult prognoses in early injury. No consensus about better or worse
trajectory (adults more clear to predict, children is difficult)
6. Testing: you cannot assume that adult neuropsychological tests measure the same skills in
children (RFT)
, Factors impacting recovery
1. Injury factors
- U-shape: large, unilateral lesions better than mediate, diffuse lesions (smaller but more
spread out lesions)
- Diffuse (spread out) worse than focal (one spot)
2. Age/ developmental stage
- Complex, non-linear relation (brain development also not linear)
3. Sex
- Potential vulnerability in males (they have later brain development) ⇒ worse recovery
compared females
- Girls have more connections and possibility of skill transfer
4. Psychosocial context
- Modifiable risk factors = clinically relevant
- Better recovery in a healthy family structure, SES, food intake (food scarcity)
⇒ Importance of long-term follow-up after early brain insult
Types of prenatal insult:
- Preterm birth (PB)
- Hypoxic-ischeamic encephalopathy (HIE)
- Prenatal stroke (PS)
NOTE: all can lead to cerebral palsy
Prematurity (born too early)
- Preterm: <37 weeks
- Extreme prematurity: <32 weeks
- Viable: >24-25 weeks
- Many complications, even if child survives:
- Exposure to hard noises, painful experiences, medical treatments (different than when it
is still in mother’s womb, not exposed to those things)
- Sensory overload (“overprikkeling”)
- Illnesses, complications
- Less physical contact
- Missing out on intra-uterine stimulation (e.g. maternal nutrients and hormones)
