Cognitive Development Part 4: A Medical Point of View

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This is the fourth in a 4-part series of articles on child cognitive development. Make sure to read other articles in the series: Cognitive Development Part 1: The First Three YearsCognitive Development Part 2: Years Four Through Six; and Cognitive Development Part 3: Education and What You Can Do.

ExpectingExpats.com thanks Amornrat Pooaramwatana M.D., Developmental and Behavorial Pediatrics at Samitivej Hospital, for answers to common medical questions concerning child cognitive development.

Cognitive Development


What prenatal factors influence brain development? What can expecting parents do before their child’s birth?

  • Genes: genes are responsible for forming all of the cells (neurons) and general connections between different brain regions
  • Maternal health (e.g. diabetes)
  • Substances exposures
  • Substance abuse (e.g. cocaine, alcohol, tobacco, narcotic drugs, caffeine, lead) can impair the formation and wiring of brain cells.
  • Some chemicals and forms of radiation are potentially harmful to fetal brain development. Women who should be concerned are usually exposed through their occupations – those who work on farms or in factories, laboratories, hospitals, dry-cleaning stores, or other sites that expose them to dangerous chemicals, radiation, or infections.
  • Infections pose perhaps the greatest risk to the developing fetus’ brain. Infections such as rubella, varicella, cytomegalovirus (CMV), toxoplasmosis, and several sexually transmitted diseases (syphilis, gonorrhea, and genital herpes) can seriously interrupt fetal development.
  • Maternal nutrition: pregnant women should gain about 20 percent of their ideal pre-pregnancy weight (e.g., 26 pounds for a 130-lb woman) to ensure adequate fetal growth. This requires consuming an extra 300 calories per day, including 10-12 extra grams of protein.
  • Some nutrients can affect brain development (e.g. folic acid deficiency during pregnancy has been associated with neural tube defect).
  • Maternal stress

What changes does a child’s brain undergo in the first three years of their life?

The first three years of life are a period of incredible growth in all areas of a baby’s development. Although all of the neurons in the cortex are produced before birth (a newborn’s brain is about 25 percent of its approximate adult weight) they are poorly connected. The cerebral cortex produces most of its synaptic connections after birth. By the age of 2 years old, the brain is about 80% of the adult size and a toddler’s cerebral cortex contains well over a hundred trillion synapses. This period of synaptic exuberance varies in different parts of the cerebral cortex. Nonetheless, the number of synapses remains at this peak, over-abundant level in all areas of the cerebral cortex throughout middle childhood (4-8 years of age). Beginning in the middle elementary school years and continuing until the end of adolescence, the number of synapses then gradually declines down to adult levels.

Neurons that are stimulated by input from the surrounding environment continue to establish new synapses, while those that are seldom stimulated soon die off in a process called synaptic pruning which facilitate changes in neural structure by reducing the overall number of neurons and synapses, leaving more efficient synaptic configurations. Besides synapse formation and pruning, the other most significant event in postnatal brain development is myelination. Newborns’ brains contain very little myelin, the dense impermeable substance that covers the length of mature brain cells and is necessary for clear, efficient electrical transmission. Myelination is a very extended process: although most areas of the brain begin adding this critical insulation within the first two years of life, some of the more complex areas in the frontal and temporal lobes continue the process throughout childhood and perhaps well into a person’s 20s.

cognitivegraphic1

cognitivegraphic2

Curved lines depict the formation of synaptic connections and synaptic pruning in the auditory and visual areas (green), language areas (purple) and frontal lobes (red) of the cerebral cortex. For each area you have an over production of synapses followed by synaptic pruning. Straight lines depict myelination, which occurs at rapid pace during first two years then at a slower pace thorugh childhood and adolescence. Timing of myelination differs among different brain areas.
There are sensitive periods in brain development. Expected experiences (physical stimulation, exposure to language, affection) must happen for normal brain maturation to occur (and they almost always do) – the brain is designed to expect them and use them for growth. Dependent experiences might happen for additional growth as a result of specific learning experiences and because of them one brain differs from another. So stimulation is vital for brain growing rapidly! Early, extreme sensory deprivation results in permanent brain damage and loss of functions.


What are the biggest factors that impact cognitive development in the first three years of a child’s life?

The caregiver: a good caregiver:

  • Is loving and Responsive
  • Respects the baby’s or children’s individuality
  • Provides a stimulating and child-friendly environment
  • Offers their children love, acceptance, appreciation, encouragement, and guidance

Quality of home environment: a good environment is safe and well organized to encouraging a child’s own exploration

Nutrition: brain development is most sensitive to a baby’s nutrition between mid-gestation and two years of age. Children who are malnourished throughout this period do not adequately grow, either physically or mentally.

Nutrients: iodine, iron, fat

Breast milk offers the best mix of nutrients for promoting brain growth, provided that breast-fed infants receive some form of iron supplementation beginning around six months of age. Iron deficiency has been clearly linked to cognitive deficits in young children.

Because of the rapid pace of myelination in early life, children need a high level of fat in their diets – some 50 percent of their total calories – until about two years of age. Babies should receive most of this fat from breast milk or formula in the first year of life, and breast milk remains an excellent source of liquid nutrition into the toddler years. However, whole cow’s milk can be introduced after the first birthday, and provides an excellent source of both fat and protein for toddlers in the second year. After two years of age, children should begin transitioning to a more heart-healthy level of dietary fat (no more than 30 percent of total calories), including lower-fat cow’s milk (1 or 2%).
Child health (e.g. perinatal asphyxia, congenital infection (TORCH infection))

Chemicals (e.g. lead, mercury)


What specific signs should parents look for to ensure that their child’s mental development is on the right track during the first three years?

Keep monitoring milestone developments in problem-solving and language domains because they relate to cognitive development.


What exercises (mental of physical) can help a child’s development in the first three years? What can parents do and what can parents expect educators/outside parties to do?

Normal, loving, responsive caregiving seems to provide babies with the ideal environment for encouraging their own exploration, which is always the best route to learning.

For language development, infants and children who are conversed with, read to, and otherwise engaged in lots of verbal interaction show somewhat more advanced linguistic skills than children who are not as verbally engaged by their caregivers. Because language is fundamental to most of the rest of cognitive development, this simple action—talking and listening to your child—is one of the best ways to make the most of his or her critical brain-building years.
If your child is interested and involved in an activity—and having fun—he is learning! It isn’t necessary to “teach” very young children. Formal classes and other activities that push toddlers to learn concepts before they are ready do not help their development or make them do better in school but they can even make children feel like failures when they are pushed to do something they can’t succeed at or don’t enjoy. So treasure these days of playing, exploring, and cuddling with child—it is exactly what she needs to grow and learn.


What are signs of potential cognitive development problems during a child’s first three years? What should parents do if they notice any of these signs?

Monitor child development and recognize these cognitive development red flags:

  • 2 months: Lack of fixation
  • 4 months: Lack of visual tracking
  • 6 months: Failure to turn to sound or voice
  • 9 months: Lack of babbling consonant sounds
  • 24 months: Failure to use single words
  • 36 months: Failure to speak in three-word sentences

Photo Credit: Pink Sherbet Photography via Compfight cc

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