Infancy: Physical

Cephalocaudal Development

Growth proceeds from the head downward

• the head and upper regions of the body develop before the lower regions of the body

  • the brain development leads to development of other things

Proximodistal Development

Growth proceeds from the centre of the body outward

• limbs catch up with head/torso

Synaptic Development

• all brain structures are composed of two basic cell types: neurons and glial cells

  • millions of these cells are present at birth

• synapses: connections between neurons, begin to form prenatally

• two development processes: synaptogenesis, synaptic pruning

Neurons

• nerve cells that store and transmit information from neuron to neuron

• important for communication

• responsible for what our bodies do

• the first neurons form early in prenatal development, in the embryo’s neural tube thru neurogenesis (i.e the production of new neurons)

  • folic acid helps close the neural tube

Brain Development in Infancy

• newborn babies are about 1/4 of the weight of an adult brain

• the neural networks of axons and dendrites are simple (immature) wtih few synapses

  • responsible for breathing, communicating for help

• major growth occurs during early infancy

• at birth, the midbrain and medulla are most fully developed, they are connected to the spinal cord

• the cortex develops in the final months prior to birth and continues to mature for many years after birth

• our life experiences influence the physical structure of our brains

Synaptogenesis

• the creation of synapses

• occurs rapidly in the cortex during the first few years after birth

  • quadrupling the overall weight of the brain by age 4

• occurs in spurts, instead of smooth and continuous

  • peaks in different brain regions at different ages

Synaptic Pruning

• each synaptic growth spurt generates more connection between neurons than the individual actually needs

• each burst of synaptogenesis is followed a period of pruning in which unnecessary pathways and connections are eliminated

Synaptogenesis/Pruning Cycle

• continues thru the lifespan

• with each cycle, the brain becomes more efficient

• 1-year olds have denser dendrites and synapses than an adult, but their network operates les efficiently than the adults

• because infants have more unused synapses, they can bounce back from a host of insults to the brain (eg. malnutrition, head injury) more easily than adults

  • plasticity

Plasticity

• the brain’s ability to change in response to experience

• the period of greatest plasticity is also the period in which the child is most vulnerable to major deficits

Implications of Synaptic Development

• changes in an infant’s behavior suggest they are engaging with the world in ways they did not before result from changes in the brain at the synapatic level

• a child growing up in a rich or intellectually challenging environment will retain a more complex network of synapses than one growing up with fewer forms of stimulation

• infant brains possess greater plasiticity

• a young infant needs sufficient stimulation and order in their environment to maximize the early period of rapid growth and plasiticity

• an inadequate diet or serious lack of stimulation in the early months may have subtle but long range effects on the child’s later cognitive progress

Myelination

• process of neurons being coated in a fatty substance (myelin) to speed up neural communication and transmission of info

• contributes to the numerous changes we see in children’s capacities

• the sequence of myelinization follows both cephalocaudal and proximodistal patterns

  • eg. nerves serving muscle cells in the neck and shoulders are myelinized earlier than those serving the abdomen.

• most rapid during the first 2 years after birth, but continues at a slower pace throughout childhood and adolescence

Experience-Expectant Brain Development

• dependent on basic environmental experiences, such as visual and auditory stimulation, in order to develop normally

• eg. lights on vs off, carpet vs hard ground

Experience-Dependent Brain Development

• brain development that occurs in response to specific learning experiences

• eg. exposure to many languages, raised in farm vs city

Reflexes

• involuntary and automatic response to stimuli to help them survive

• newborns respond to certain stimuli thru reflexes

• some reflexes last throughout life whereas others disappear

Reflexes: Adaptive and Primitive

• adaptive reflexes: lifelong, voluntary, and purposeful responses that allow us to adjust to our environment (eg. blinking, yawning)

  • some disappear in infancy or childhood, but others protect us over the whole lifespan

  • weak or absent adaptive reflexes in newborns suggest that the brain is not functioning properly

• primitive reflexes: involuntary, automatic movements present in newborns that aid survival

  • controlled by less sophisticated parts of the brain (the medulla and midbrain)

  • by 6-8 months, primitive reflexes begin to disappear, if such reflexes persist past this age, the baby may have some kind of neurological problem

Sleep and Wakefulness

• newborns sleep ~80% of each day, as much in the daytime as at night

• by eight weeks infants sleep less and may differentiate between day time and night time

• crying is communication: they develop different cries (hunger, dirty diaper, etc.)

• most infants stop crying when picked up, held and talking/sung to

  • essentially when in motion, b/c they are constantly in motion due to amniotic fluid

Sleep Patterns

• infants’ sleep patterns change over the first few months as the neurological systems that synchronize their bodily function with the circadian rhythms outside the womb mature

  • the light/dark cycle of the world

• by 8 weeks of age, the total amount of sleep per day has dropped and signs of day/night sleep rhythms become evident

  • babies of this age begin to sleep thru two or three 2-hour cycles in sequences without coming to full wakefulness

  • thus are often said to “sleep thru the night”

• by 6 months, babies still sleep over 14 hours per day, but sleep is more regular and predictable (clear nighttime sleep patterns and predictable nap times)

• cultural beliefs play an important role in parent’s responses to infants’ sleep patterns (eg. choosing to intervene with crying during the night or not)

Crying Patterns

• infants have different cries for pain, anger and hunger

• Basic cry: often signals hunger, has a rhythmical pattern (cry, silence, breath, repeat) with a whistling sound accompanying the in-breath

• Anger cry: louder and more intense

• Pain cry: very abrupt onset (other 2 cries begin with whimpering/moaning)

• crying increases in frequency over the first 6 weeks and then tapers off

Colic

• 15-20% of infants develop colic

• pattern involving intense bouts of crying totaling 3 or more hours a day, for no apparent reason such as hunger or a wet diaper

• to be diagnosed w/ colic, an infant must have manifested symptoms for at least 3 weeks

• psychologists or physicians don’t know why colic begins or why it stops without any intervension

Wakefulness Patterns

• on average, neonates are awake and alert for 2-3 hours each day

  • this time is unevenly distributed over a 24 hour period

• over the first 6 months, advances in neurological development enable infants to remain awake and alert for longer periods of time, as their patterns of sleeping, crying and eating become more regular

Growth Norms

Expectations for typical gains and variations in height and weight based on chronological age, biological sex and potentially whether breastfed or formula fed

• is infant growing faster/slower in comparison to age norms?

• trouble is there’s a drop in percentile in comparison to the growth curve

  • growth curves are specific to the individual

Growth during Infancy and Toddlerhood

• “average” applies to full gestation only

• the most amount of growth in life for weight and height occurs in the first 2 years

  • by 2, toddlers are half as tall as they will be as adults

• it’s ok to sometimes lose weight b/c the babies need to learn how to eat and digest food

  • also possible if the mom was given IV fluids during birth

• despite gender differences in physical development rate, the sequence of motor skill development is the same for all children, even those with physical or mental disabilities

Head Circumference

• often indicates brain growth

• there are 4 plates that are not fused

  • allows for compression during birth

  • lead to soft spots and dents can indicate dehydration

Genes and Hormones

• genes influence the rate of growth by stipulating the amount of hormones to be released

• hormones are chemicals produced and secreted into the bloodstream to affect and influence physiological functions

Developmental Milestones

• almost universal, age-related events (physical, cognitive, socio-emotional) that mark major developmental changes

Growth Motor Development

• development of the ability to control large movements of the body

  • eg. sitting, standing, crawling

• once babies can walk, their entire visual field changes which influences cognitive and socio-emotional development, and how they interact with the world

Fine Motor Development

• tiny manipulations of fingers/hands

• voluntarily reaching is important for cognitive development

• infants’ attention moves away from the motor skill, to the object, as well as the events that occur before and after acquiring the object

Dynamic Systems

• Motor skills result from ongoing interactions among physical, cognitive and socioemotional influences and environmental supports…

  • in which previously mastered skills are combined to provide more complex and effective ways of exploring and controlling the environment

• environmental supports: what are they exposed to? caregiver response?

Dynamic Systems Theory

• the inborn timetable for motor skills development interacts with other aspects for physical development

  • the notion that several factors interact to influence development

• all movement requires coordination of our senses and cognitive abilities to plan and predict actions (learn cause and effect)

• motor development reflects goal-oriented behavior

• differences in caregiver interactions and caregiver environments affect children’s motor skills

• infants attain the same motor tasks at about the same age, yet differ in how they approach the tasks (eg. types of crawling styles)

  • individual differences can be accounted for by the dynamic systems perspective

Motor Development: Experience

• experience influences motor development

• opportunities to practice motor skills is important for young children who have disorders that impair motor functioning

• eg. babies placed on their backs in cribs learned to walk later than babies in less restrictive settings

Motor Development: Culture

• traditional cultural practices intentionally and coincidentally promote motor development 

• eg. African mothers who vigorously massage their babies muscles to mimic motor actions like walking)

Bone Development

• wrist development is critical to the development of fine motor skills

  • at birth, the wrist contains a single mass of cartilage which develops into 9 separate bones over several years

• ossification: process of bone hardening

  • begin in the last weeks of prenatal development and continue thru puberty

  • bones in different parts of the body harden in a sequence that follows the typical proximodistal and cepalocaudal patterns

  • motor development depends to a large extent on ossification

Muscle Development

• a newborns’s muscle contain a high proportion of fat 

• by age 1, the water content of an infant’s muscles is equal to that of an adult’s, and the ratio of fat to muscle tissue has begun to decline

• changes in muscle composition lead to increases in strength that enable 1-year olds to walk, run, jump, climb

Lungs and Heart

• lungs grow rapidly and become more efficient during the first 2 weeks

• improvements in lung efficiency, together with the increasing strength of heart muscles, give a 2-year old greater stamina than a new born

  • consequently, by the end of infancy, children are capable of engaging in long periods of sustained motor activity without rest (exhausting their parents)

Infant Health: Breastmilk

• breastmilk provides newborns and infants with everything they need for the first 6 months of life

• breastmilk is tailored to infants and has the right amount of fat, sugar, water and protein needed for the baby’s growth and development (no ned to alter the size of serving)

  • contains bioactive components (e.g. immunizing agents that protect from infections)

• breastmilk is substantially superior nutritionally to formula feeding

Benefits of Breastfeeding

Growth: breast milk contributes to more rapid weight and size gain

Health: breastfed infants are less likely to suffer from problems, such as diarrhea, ear infection

Preterm babies: their intestinal tracts are not as mature as those of full-term infants, and they require special formulas that contain amino acids and fats that full-term babies can manufacture on their own

• physicians recommend feeding preterm babies expressed breast milk that has been fortified with fats, proteins, vitamins and minerals their bodies need

Alternatives to Breastfeeding

• sometimes is impossible, like if drugs are present in the breast milk whether from substance abuse or medications. These drugs would negatively impact infant development

  • doctors recommend avoiding breastfeeding here

• these babies are fed high-quality infant formula, prepared according to the manufacturer’s instructions and properly sterilized

Infant Health: Nutrition

• up until 4-6 months, babies only breast milk or formula accompanied by appropriate supplements

  • doctors may recommend supplemental formula

• pediatricians usually recommend withholding solid foods until a baby is at least 6 months old

• parents should introduce a baby to no more than one new food each week, allowing them to identify food allergies

• infants do not necessarily like new flavors and textures and therefore foods need to be introduced numerous times

Infant Health: Appetite

• appetite is lower compared to infancy

• meals may take longer, and self-feeding can mean eating less

• appetites continue to decrease ages 2-6

• some go thru picky eating ~ age 3

Malnutrition

• can seriously impair a baby’s brain because the nervous system is the most rapidly developing body system during the first 2 years of life

• although malnutrition is common is developing countries, it is also found in some of the wealthiest countires

• in Canada, 1 in 8 households was food insecure

• each type of malnutrition has unique effects on development

Macronutrient Malnutrition

• results from a diet that contains too few calories

• world’s leading cause of death among children under age 5

Marasmus

• when the calorie deficit is severe, marasmus (a disease) results 

• infants weigh less than 60% of what they should at their age, and many suffer permanent neurological damage from the disease

• suffer from parasitic infections that lead to chronic diarrhea

  • makes it difficult to treat marasmus by simply increasing an infant’s intake of calories

• a program of dietary supplementation with formula combined with intravenous feedings and treatment for parasites can reverse marasmus

Kwashiokor

• some infants’ diets contain almost enough calories, but not enough proteins

• also seen in children who are chronically ill because of their bodies’ inability to use the protein from the foods they eat

• can lead to variety of health problems as well as permanent brain damage

Micronutrient Malnutrition

• a deficiency of certain vitamins and/or minerals 

• eg. infants who are still getting most of their calories from milk after the age of 12 months frequently develop iron-deficiency anemia

• common among low-income families, but also children of all economic levels

Infant Health Care

• routine appointments:

  • check ins

  • screening: pre-assessment before a real assessment is needed

  • referrals: meet with specializations

  • immunization: protects against a variety of disease

    • is most effective when it beings the first month of life and continues through childhood and adolescence

    • even adults need occasional “booster shots” to maintain immunity

• the more people a baby is exposed to, the more often they’re likely to be sick

Adjusted Age

• allows premature babies to catch up on development

• assess development by backtracking

• eg. a baby that is 5 weeks early is assessed by backtracking 5 weeks

Respiratory/Ear Infections

• the average baby has 7 respiratory illnesses in the first year of life

  • babies in daycare centers have 2x as many infections

• the timing of respiratory illnesses can lead to ear infections

• those who have chronic ear infections are more likely to have learning disabilities, attention disorders and language deficits during school years

• because ear infections temporarily impair hearing, they may compromise brain development areas essential for language learning during the first 2 years of life

Hearing Development

• capacity to hear develops prenatally

• hearing is the most well-developed sense at birth as newborns are able to hear about as well as adults

• through listening, the process of learning language begins at birth

• able to determine location of sounds, by turning their head roughly in the right direction

• limited in hearing high-pitched sounds, as it needs to be louder in order to be heard

Sensation and Perceptual Development

Sensation: occurs when our senses detect a stimulus

Perception: the sense our brain makes of the stimulus and our awareness of it

• actively paying attention to stimuli

Vision Development

• the least developed of all senses at birth, but improves rapidly

  • since we don’t need to see anything in utero

• the way infants explore visual stimuli changes with age

• outer perimeter vs centre of objects

• can pick up on contrasts of color and distance

• preference to see human faces

• adults are naturally driven to capture infants’ attention (eg. going closer to their face, dancing)

• newborns are pretty nearsighted and can focus well at about 8-10 inches, the distance between a parent’s face and baby’s eyes when feeding

Vision Development: Visual Tracking

• the ability to follow an object’s movement with the eyes

  • limited at first, but improves quickly

• because newborns can’t move independently yet, a lot of their experiences with objects are with things that move toward or away from them

• if the baby wants to successfully recognize objects, they have to be able to keep their eyes on the objects as the move

Vision Development: Depth Perception

• the ability to perceive the distance of objects from each other and from ourselves

• we must learn about depth thru experience, which is why toddlers are accident prone (eg. crawling off the bed)

Visual Acuity

• aka 20/20 vision: you can see and identify something 20 feet away that the average person can also see at 20 feet

  • the higher the second number, the poorer the person’ s visual acuity

• at birth, the infant’s acuity is in the range of 20/200 - 20/400, but improves rapidly during the first year as a result of synaptogenesis, pruning and myelination

• most babies reach 20/20 vision by 6 months

• it’s difficult to test an infant’s true visual acuity because children can’t be tested with conventional eye exams until they are old enough to respond verbally to the examiner 

Depth Perception: Binocular and Monocular Cues

• Binocular: involve both eyes, each of which receives a slightly different visual image of an object; the closer the object is, the more different the two views are

• Monocular: requires input from only one eye

Kinetic Cues

• come from either your own motion or the motion of some object

• infants use kinetic cues first, then binocular, then monocular

Color Vision

• the eye cells necessary for perceiving red, green and blue are present by 1 month, and perhaps present at birth

• infants’ ability to sense color, even in the earliest weeks of life is almost identical to that of adults

Smell and Taste Devlopment

• smell and taste are well developed at birth

• within a day of birth, newborns can detect and recognize their mother’s odour (postpartum smell that helps the infant determine who mom is)

• infants show an innate preference for certain tastes

  • eg. sugary, and breastmilk is naturally sweet

Touch

• the mouth is the first part of the body to show sensitivity to touch prenatally and remains one of the most sensitive areas to touch after birth

• eg. rooting reflex when cheek/mouth is touched

• babies are sensitive to touches on mouth, face, hands, soles of feet, and abdomen

Intermodal Perception

• our interactions with the environment combine information from various sensory systems

Intermodal perception: the process of combining information from more than one sensory system

Infant Mortality

• death within the first year after birth; almost 2/3 of these infant deaths occur in the first month of life and are directly linked to either congenital anomalies or low birth weight

Sudden Infant Death Syndrome (SIDS)

• an apparently healthy infant dies suddenly and unexpectedly

• risk factors: season, apnea, prenatal smoking, delayed myelination

• deaths attributable to SIDS vary widely across ethnic groups

  • some groups are more likely to suffer from congenital abnormalities and low birth weight

SIDS: Season

• much more in the winter, when babies may be suffering from viral infections that cause breathing difficulties

SIDS: Apnea

• apnea: brief periods when breathing suddenly stops

• babies with a history of apnea are at an increased risk of dying from SIDS

• episodes of apnea may be noticed by medical personnel in the newborn nursery, or a nonbreathing baby may be discovered by parents in time to be resuscitated

• physicians recommend usually recommend using electronic breathing monitors that will sound an alarm if the baby stops breathing again while asseep

SIDS: Prenatal Smoking

• smoking by the mother during pregnancy or by anyone in the home after the child’s birth

• babies exposed to smoke are 4x likely to die of SIDS 

SIDS: Delayed Myelination

• babies are at a higher risk of SIDS when their myelination progresses at a slower rate than others

• babies’ sleep patterns reflect these neurological differences and also predict SIDS risk

  • infants who show increasingly lengthy sleep periods during the early months are at lower risk of SIDS than those whose sleep periods do not get much longer as they get older

• autopsies of babies who have died from SIDS have revealed that their brains often show signs of delayed myelination and deficiencies in the neurotransmitter serotonin 

SIDS: Prevention

• most frequent among babies who sleep on their stomachs or sides, especially on a soft or fluffy mattress, pillow or comofrter

  • healthy infants are to be positioned on their backs to sleep

Preference Technique

• babies are shown 2 pictures and researcher keeps track of how long the baby looks at each one

• if many infants shown the same pair of pictures consistently look longer at one picture than the other, this tells us that babies seem some difference b/w the 2, and about what kinds of objects/pictures that capture their attention

Habituation

• habituation: getting used to a stimulus

• dishabituation: responding to a somewhat familiar stimulus as if it were new

• Researchers first present the baby with a stimuli over and over until they habituate

• Then the researchers present another stimuli that is slightly different from the original and watch to see whether the baby shows renewed interest 

• if the baby shows renewed interest, you know they perceive the new stimuli as different from the original

Discriminating b/w Similar Speech Sounds

• as early as 1 month, babies can discriminate between similar speech sounds like pa and ba

• they can also rapidly learn to discriminate between words and nonwords in artificial languages

Perception of language-specific speech sounds

• each language uses only a subset of all possible speech sounds 

• up to about 6 months of age, babies can accurately discriminate all sound contrasts that appear in any language, including sounds they do not head in the language spoken to them

• by age 1, the ability to discriminate nonheard consonant constrasts begin to fate

Recognition of Voices

• newborn can tell the mother’s voice from another female, but not the father’s voice from another male voice

• they prefer the mother’s voice

• premature infants are less likely to recognize their mother’s voice than are full-term babies

  • in utero, learning appears to be responsible for newborns’ preference for the maternal voice