Infant brain development

• Humans have the largest brain of all primates and the longest period of brain development
• From birth to teenage years, there is a fourfold increase in the volume of the human brain
• Humans are the only species to show differential development in timing across cortical brain areas
• At birth, the child’s brain consists of 100 billion neurons, organized into groups that perform particular functions like interpreting sounds, storing memories, and learning new skills
• Brain growth begins in utero at 18 days after fertilization
• During the prenatal period, brain development consists of three stages: Geminal (Fertilization – 2 weeks), Embryonic (2 – 8 weeks), and Fetal (8 weeks – birth)
• During the Geminal Stage, the fertilized egg attaches itself to the uterus wall and undergoes rapid and methodical cell division
• The Embryonic Stage involves the development of major organs and basic anatomy, with the fetus having three layers: Ectoderm, Mesoderm, and Endoderm
• During the Fetal Stage, rapid changes in development occur, including the development of physical characteristics, organs, and bodily systems
• The brainstem (hindbrain) and midbrain are the first areas to develop, governing autonomic functions necessary for life and reflexes
• Post-natal brain development involves fine-tuning the brain's circuitry through processes like synaptogenesis, synaptic pruning, programmed cell death, and myelinization
• The brain continues to refine and develop connections through dynamic and adaptive processes influenced by genetic expression, Epigenetics, social learning, and experience
• An enriched environment causes cortical neurons to thicken, sensory experiences trigger electrical activity that strengthens connections, and the cortex prunes itself into the most efficient structure around 3 months
• Beyond infancy, the limbic system regulates emotions, the frontal lobes support advanced cognitive functioning, and the pre-frontal cortex continues to grow until the early 20s
• Brain growth occurs in fits and spurts, coinciding with changes in cognitive behavior, and the timing of events in brain development is crucial
• The prenatal brain is sensitive to negative influences like alcohol and malnutrition, as well as positive influences like enrichment
• Teratogens are substances that exert adverse influences on development, such as drugs, smoking, disease, radiation, and maternal stress
• Fetal Alcohol Syndrome (FAS) can lead to physical defects, growth retardation, central nervous system impairments, and permanent effects
• Moderate drinking and binge drinking during pregnancy increase the risk of FAS (fetal alcohol syndrome), and even small amounts of alcohol can impact fetal development
• Neglect during early experiences can alter brain growth and organization, leading to long-term impacts on emotional processing, social relationships, and IQ
• The extent of environmental impact can determine the severity of atypical brain development
• Neuroimaging of 122 neglected children showed altered brain growth
• Some neglected children were raised in cages in dark rooms for the first years of their lives
• Frontal Occipital Circumference, brain growth, and organization were worse in neglected children compared to normal children
• Mainly affected the globally neglected children
• Global neglect likely caused by lack of sensory experiences (sound, smell, touch) and poor nutrition
• Brain structure is genetically determined, but brain plasticity means stimulation received also crucial for development
• FAS symptoms are most severe when the "dose" of alcohol is highest
• Moderate drinking (1-3 oz per day) can lead to serious (though less pronounced) symptoms of FAE
• FAE/FAS risks are greatest following periods of binge drinking
• Even drinking less than 1 oz of alcohol per day increases the likelihood of the fetus developing FAS
• Physical defects associated with Fetal Alcohol Syndrome (FAS) include:

  • Flattened midface
  • Thin upper lip
  • Indistinct/absent philtrum
  • Short eye slits
• Growth retardation in FAS can result in:

  • Lower birth weight
  • Height and/or weight low
• Central Nervous System effects of FAS include:

  • Impaired fine motor skills
  • Learning disabilities
  • Behavioural disorders
  • Mental handicap (found in approx 50% of those with FAS)
• Alcohol drunk by the mother reaches the placenta quickly, making it more dangerous than all drugs (including cocaine), leading to low birth weight, birth defects (FAS), miscarriage, etc.
• Effects of FAS are permanent and cannot be outgrown
• Children born with FWS can present with:

  • Nasal hypoplasia (stunted growth of the septum and nasal bridge)
  • Chondroplasia (bone calcifications)
• FWS typically presents in only 1/3 of mothers who take warfarin, and only when taken within the first trimester
• Cognitive impairments are associated with FWS, but by age 10/11 the majority of FWS children show no difference to matched controls with no exposure
• Teratogens are substances that exert an adverse influence on development

  • Examples include drugs (thalidomide, warfarin, tetracycline, heroin, cocaine), smoking, disease (rubella, herpes simplex, chicken pox), radiation
  • Maternal stress affects birthweight and behavioral development