Chapter 5 - Physical Development in Infancy and Toddlerhood Flashcards
Brain Development: microscopic
- We start with an overabundance of synapse which serve identical functions to ensure the child can acquire motor, cognitive and social skills.
- The neurons that are seldom stimulated start to lose their synapses.
- Brains size increase in the first 2 years is do gins in neural fibers and to rapidly multiplying glia cells.
- “living sculpture” start with too much then slowly remove the excess.
Physical Development
- By the end of the first year infants height has increased by 50% and weight has tripled
- by the end of the second year infants height has increased by 75% and weight has quadrupled
- They grow in spurts and not steady
- “baby fat” peaks at 9 months and helps maintain body temputure
- In second year toddlers slim down a bit
- At birth head is 1/4 of body by age two it is 1/5
- Children of the same age can grow at a different rate but that does not mean they are more physically mature.
Fontanels
Fontanels is an anatomical feature on an infant’s skull comprising any of the soft membranous gaps between the incompletely formed cranial bones of a foetus or an infant. The softness helps the baby pass through the birth cannel. Fontanelles allow for rapid stretching and deformation of the cranium as the brain expands faster than the surrounding bone can grow.
The biggest t is filled during the second year the smaller ones close earlier. They are not completely done until adolescence.
The location that they grow together are called sutures.
Skeletal age
The “bone age” of a child is the average age at which children reach this stage of bone maturation. A child’s current height and bone age can be used to predict adult height.
It is the best estimate of a child’s physical age.
There is a gap in boys and girls at birth by 4 to 6 weeks and the gap widens through infancy and childhood. This may contribute to girl’s greater resistance to harmful environmental influence.
Epiphyses
Special growth centers at the ends of a long bones that fuses with the shaft of the bone at the point where it was previously separated by cartilage to allow bone growth.
They increase in number through childhood then get thinner and disappear.
Cephalocaudal Trend
“head to tail”
Refers to the pattern of changing spatial proportions over time during growth. During prenatal growth, from conception to 5 months, the head grows more than the body.
The cephalocaudal trend is also the trend of infants learning to use their upper limbs before their lower limbs.
proximodistal trend
“near to far”
Prenatal growth from 5 months to birth when the fetus grows from the inside of the body outwards.
When referring to motor development, the proximodistal trend refers to the development of motor skills from the center of the body outwards.
Development of Neurons
Step 1: neuron production
Step 2: migration
Step 3: differentiation
- also forming synaptic connections with other neurons
Synaptic pruning
Synaptic pruning - loss of connective fibres by seldom-stimulated neurons, thereby returning them to an uncommitted state so they can support future development
- Synapses need space, so the ones that aren’t being used are pruned, to make room for others
- Around 40%
Neurons also are pruned, for the same reason
- As neurons form connections stimulation in vital to a neurons survival
Neurophysiological Methods
- Various procedures for ‘imaging’ brain composition and activity have been developed in recent years
- These techniques allow scientists to literally look inside the living brain
- Some of these techniques reveal information about brain activity as well as about anatomy
- PET and FMRI are not suitable for infants and young children because they have to lie still for periods of time.
- NIRS is better for children but it is limited to mapping the activity changes in the cerebral cortex.
- Limitation: A researcher using these methods need to make sure they know the cause of the activation, which is hard to determine.
EEG - Electroencephalography PET fMRI ERPs NIRS
EEG - Electroencephalography
The recording of electrical activity along the scalp. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain.
PET
PET scans measure metabolic activity in the brain through the injection of a radioactive isotope into the bloodstream
fMRI
The fMRI procedure uses a powerful magnet to record changes in the oxygen level in areas of the brain
When a brain area is active, there is an increase in blood flow and oxygenation in that area, and the oxygenated blood is more magnetized than nonoxygenated blood.
ERPs
Another technique involves measuring event-related potentials (ERPs)
Electrodes are attached to the scalp, and they record the neuronal activity that follows presentation of a particular stimulus
Measurement of ERPs can be used at any age, even in infancy
NIROT
Near infrared optical topography (NIROT) is a new brain-imaging method that works well in infancy and early childhood
Infrared light is beamed at regions of the cerebral cortex to measure blood flow and oxygen metabolism while the child attends to a stimulus
Because the apparatus consists only of thin, flexible optical fibres attached to the scalp, a baby can sit on the parent’s lap and move during testing
Brain Development: the Cerebral Cortex
Cerebral cortex - the largest, most complex structure of the human brain, responsible for the highly developed intelligence of the human species
- accounts for 85% of the brain’s weight and contains the greatest number of neurons and synapses
- last part of the brain to stop growing, and is thus sensitive to environmental influences over a more extended period of time
The order in which cortical regions develop corresponds to the order in which different capacities emerge
Year 1, a burst of synaptic growth in the auditory and visual cortexes and in areas responsible for body movement – this is a period of dramatic gains in auditory and visual perception and master of motor skills.
Language areas are particularly active from late infancy through the preschool years – when language development flourishes
The frontal lobes are the slowest part of the cortex to develop. Starting at 2 months there are some increase in efficiency, rapid myelination, neurogenesis, and pruning in preschool, adult level of synaptic connections by mid- to late-adolescence.
Prefrontal cortex
Responsible fore consciousness, inhibition of impulse, integration of information, and use of memory, reasoning, and planning
Lateralization
The two hemispheres of the brain are lateralized—the right and left hemispheres are somewhat specialized
- Each controls opposite side of body
- Experience influence how it will develop
- Early acquisition of language skills or a second language greater left hemispheric specialization. Sign language shows that they use the right hemisphere more for language processing.
Hemispheric specialization shows individual differences
Some people have right-brain dominance for language, and some people have mixed dominance
Right – special abilities, shapes, negative emotions
Left – verbal abilities, spoken, written, positive emotion
Left-handed people more often have right-brain or mixed dominance than do right-handed people
People who have problems with reading performance sometimes are associated with mixed or right-brained dominance for language
- Children with dyslexia are more likely to lack strong left-brain dominance than are normal readers
Signs that Hemispheric specialization appears quite early
- Newborn infants produce more activity in the left than right side of the brain in response to speech sounds
- Some physical differences in size and shape between the hemispheres are already present at birth
- Newborns and infants don’t show all the forms of lateralization that will eventually develop, though
Brain plasticity
Brain plasticity - the capacity of various parts of the cerebral cortex to take over functions of damaged regions
- In a highly plastic cerebral cortex, many areas aren’t yet committed to specific functions
- This is due to an overabundance of synaptic connections
Although lateralization has already begun by birth, the brain remains relatively plastic for the first few years
Sensitive Periods in Brain Development
Both humans and other animals have been shown to have sensitive periods in development
- Experiments in which animals are deprived of experiences
- Babies both with cataracts in both eyes – early corrective surgery = face perception limitations. Late surgery = permitly impair red vision.
- Children overwhelmed with too much stimulation – no help but may cause them to withdraw causing conditions like simulations deprivation. Can also harm neural circuits and reduce sensitivity to the everyday experiences that it need to be learning from.
Romanian orphanage adoptees
Children reared in overcrowded orphanages showed deficits in all domain of development. Adopted before 6 months they quickly caught up. More than 6 months = serious intellectual deficits that improved some during middle childhood but remained below average and most showed at least 3 serious mental health problems like: inattention, over activity, unruly behavior, and autistic like symptoms. Prefrontal cortex might be the area of the most concern. Their head size was even smaller. Early stress = problems with reactivity and stress management, limit physical growth, learning and behavior problems, attention, anger and impulses. Limit typical oxytocin levels which lowered response to to pleasurable activities.
Oxytocin in brain development
Hormone released by the brain that evokes calmness and contentment in the presence of familiar, trusted people.
2 types of brain development
Experience-expectant brain growth
Experience-dependent brain growth
Experience-expectant brain growth
the young brain’s rapidly developing organization, which depends on ordinary experiences – opportunities to see and touch objects, to hear language and other sounds, and to move about and explore the environment
- Occurs naturally in a good environment
- Age appropriate toys and stimulation, and enjoyable daily routines are key.
Experience-dependent brain growth
Occurs through the life span.
Consists of additional growth and the refinement of established brain structures as a result of specific learning experiences that vary widely across individuals and cultures
Changing States of Arousal
Sleep
During the first 2 years of life
- Sleep declines slightly (from 16-18 hours to about 12-13 hours)
- Fussiness and crying decline
- Daytime naps decline, while nighttime sleeping increases
- Babies (1 to 8 months) who sleep with parents have a consistent sleep time of about 3 hours at a time.
- At the end of the first year REM sleep decreces
- When they can crawl and walk they often show periods of disrupted sleep.
- Night waking’s increase between 1 ½ and 2 years then decrease again
Sleep patterns and Melatonin levels
Melatonin levels aren’t substantially higher at night than during the day until about 6 months of age
- The tendency of Western children to increase nighttime sleeping and decrease daytime sleeping before this time seems to be a response to parents’ attempts to promote this. (rare elsewhere in the world) This may be at odds with a young infant’s neurological development.
- Babies over six months sleep better if they are exposed to sun light during the afternoon.
Heredity Influences on Growth
What to do?
What to do?
- Breastfeeding for the first 6 months is associated with slower weight gain
- Avoiding foods that are high in sugar, salt, and saturated fats is useful
- Encouraging energetic play once toddlers learn to walk, climb, and run
- Less TV; research shows a correlation between excessive television viewing and overweight in older children
Chubby babies
Pound for pound babies need twice as much food as adults.
Most chubby infants thin out during toddlerhood and the preschool years
Infants and toddlers can pretty much be allowed to eat freely, as long as the food being provided is nutritious
When parents provide too many unhealthy foods and options, obesity is a frequent result. Rapid weight gain
Brest feeding versus bottle feeding
Because breast milk is essentially designed for optimal health, breastfed babies in poverty-stricken regions of the world are much less likely to be malnourished and are 6 to 14 times more likely to survive the first year of life. Also breast feeding can increases spacing of siblings. Young mother in developing countries might not know.
(W.H.O.) Breast feeding is recommended until age 2, with solid foods added at 6 months
Even a few weeks of breastfeeding offers some protection against respiratory and intestinal infections.
Breast-fed babies are hungry more often, so it can be harder for Mom to keep up with feeding times. (1 ½ - 2 hours versus 3 to 4 for bottle fed)
Breast and bottle can be mixed after about 6 months
Does not impact mother baby relationship and attachment in industrialized countries
