Lecture 4: Flashcards
Physical and cognitive development in infancy
Labour & Delivery: Stages of Birth
- 1
st stage: contractions leading to dilation of cervix
– 12-14 hrs for first born on average
– 4-6 for subsequent children
– Ends when cervix is dilated to about 10 cm - 2
nd stage: delivery
– 20-50 minutes
– Contractions + urge to push - 3
rd stage: detachment and expulsion of the
placenta, umbilical cord, and other membranes
– 5-10 minutes
Neonate appearance
- 20” long
- 7.5 lbs
– Boys longer, heavier than
girls - Large head
- Short, bowed legs
- Round face, large forehead
and eyes
The Apgar scale: Assessing vital signs
A – appearance
(colour)
P – pulse
(heart rate)
G – grimace (reflex
irritability: sneezing,
response to
stimulation, cry)
A – activity (muscle
tone)
R – respiratory
effort
Prematurity & Birthweight
Gestational age
* Preterm: born before 36 weeks gestation
* Full-term: born between 37 and 42 weeks gestation
* Postterm: born after 42 weeks gestation
Birth weight
* LBW: less than 2500g (5lbs, 8oz)
* VLBW: less than 1500g (3lbs, 5oz)
* ELBW: less than 1000g (2lbs, 3 oz)
Size for gestational age (small for date)
* AGA: BW between 10th and 90th percentiles
* SGA: BW below 10th percentile
* LGA: BW above 90th percentile
Viability
- 22 weeks gestation
- 1 lb
– 9-30% survive
– 50% of these have major
disabilities
Risk factors for preterm birth
- Immature uterus (mom <20yrs)
- Poor nutrition
- Poor prenatal care
- Low SES
- Alcohol, drugs
- High BP
- Fetal malformations
- Stress
Issues in Low-Birth Weight Infants
- LBW infants 25X more likely to die
in first month than NBW infants - Smaller and younger at birth:
increased number and severity of
problems - Increased risk of vision/hearing
loss, learning disability, epilepsy,
cognitive impairments, anxiety
But…
* Parental contact important for
both infants and parents
* Good nutrition: catch up & grow
at same rate, though average IQ
lower than full-term kids
* Delayed in first few years in
language, motor skills, visual
attention. Most grow out of it,
but outcomes are hard to predict.
Issues in Preterm Infants
- respiratory distress, death. Lungs not fully
developed, lack surfactant
– Treatment: pressurized O2
to prevent lung
collapse, surfactant replacement - temperature regulation
– Little fat, sweat glands and brain mechanisms
underdeveloped - brain bleeds, heart valve problems
Reflexes 2 types
Adaptive reflexes
– help newborns survive; some adaptive reflexes
persist throughout life
* sucking, withdrawal from pain
- Primitive reflexes
– controlled by primitive parts of the brain; these
reflexes mainly disappear by the end of the 1st
year - Moro, Babinski
6 reflexes
Babinski: foot strock
Grasping: palm of hand
Moro: arch back throw arms
Plantar: curls toes
Rooting: soft touch on cheek
Tonic neck: fencing position
Infant States
- Two significant infant states are sleeping and crying
- The amount of sleep children engage in and the
nature of their sleep both change gradually until
adolescence
Sudden Infant Death Syndrome
- SIDS: the sudden death of an apparently healthy
infant under one year of age which remains
unexplained after a thorough case investigation,
including performance of a complete autopsy,
examination of the death scene, and review of
the clinical history (Willinger et al., 1991) - Unknown cause, only risk factors
Incidence
- 1/2000 live-born babies in Canada
– rate varies by place and year - 1st month: rare
- 2-4 mos: peaks
- 6 mos: 90% of cases
- After 12 mos: rare
Risk factors
- LBW (< 3.5 lbs)
- Sibling died of SIDS
- Exposure to cocaine, heroin, or methadone during
pregnancy - Parental smoking
- Male
- Minor respiratory illness
- Teen mom with previous children
- Short interval between pregnancies
Reducing the risk
- A healthy pregnancy reduces risk of
prematurity/LBW, which reduces SIDS risk - Breast-feed babies whenever possible
– Breast milk decreases the occurrence of
respiratory and gastrointestinal infections
(antibodies in colostrum)
– SIDS lower in breast-fed babies than formula-fed
babies - No objects in the crib including bumpers, toys,
pillows, etc… - Avoid overheating
- No smoke in the home or near baby (including
on parents’ clothes) - Put babies to sleep on their BACK
– Hard to convince: Parents often say babies sleep
better on their tummies, wake less, are easier to
soothe, fall asleep more easily, cry less
“Back to Sleep”
- Babies more likely to have sleep
apnea on their stomachs possibly
due to overheating - They are also more likely to rebreathe the air they have just
exhaled, which can raise their levels
of carbon dioxide - Compared to back sleep, stomach
sleep has 13X higher risk for SIDS!
Physical skills present at birth: Looking
- Can direct head and eyes to look at particular stimuli
Physical skills present at birth: Sucking
Quite complex; some babies need practice
Means of exploration
Buffers against pain
-Babies cry less in response to pain when given pacifier to suck
More than just a simple reflex
- Stops with distraction (visual or auditory stimulus)
- Varies with conditions (changes if amount or type of fluid available
changes)
- Can be used to control access to stimuli (non-nutritive sucking paradigm)
Physical skills present at birth: Crying
- Complex
- Different types (hunger, fear, pain)
- Have different pitches and patterns of
crying/breathing - Parents think they’re good at discriminating types of
crying, but no better than chance - But parents are more likely to respond to highintensity crying than low-intensity
- Infant-controlled variation is a communicative tool
- Survival mechanism
- Gets infants attention, care
Early motor development
- Postural and locomotor
development
– Control of trunk of body
– Moving around - Prehension
– Using hands to do tasks - Proximodistal
– Centre of body is controlled before extremities - Cephalocaudal
– Development moves from head to toe - Note that we see these trends in growth as
well
3 early phases of brain
development
Cell production: Neurons are produced
between 10 and 26 weeks post-conception
- almost all neurons we’ll ever have are produced
during this time!
Cell migration: Nerve cells travel from inner
neural tube outward to final location
- complete by 7 months gestation
Cell elaboration: Synapses are formed, nerve
cells are “pruned”
- continues for years after birth
Research Methods in Infancy
Preference method
– Two stimuli presented simultaneously
– Infant’s attention (looking) to each measured
* Gross measures of looking
* Eye tracking
Habituation method:
– Stimulus presented repeatedly until infant’s response
decreases
– Habituation: Infants (and adults) look less and less as a result
of consistent exposure to a particular stimulus
* What cognitive process does this reveal ?
– Dishabituation: Re-orienting to a presented alternate stimulus
(after habituation to the original stimulus)
* What cognitive process does this reveal?
Brain activity
– fMRI, EEG
– Observe changes in activity for different stimuli
– Changes may indicate ability to discriminate
Violation of expectation
– Tests infant perception, understanding, beliefs
– Shown possible and impossible event
* Impossible event surprising/novel: more time looking
Non-nutritive Sucking
– Pacifier sucking controls stimulus
presentation
* Sucking pressure is measured
* Changes in sucking pressure indicate
changes in attention/interest
Facial expressions
– Detailed coding systems
* Video of responses, coding done at
slow speed
Smell
- Important to survival: helps in determining what is edible
- Within hours of birth, infants have relaxed, happy-looking
faces when exposed to sweet smells - When exposed to unpleasant smells, they frown and/or turn
away from the smell - In many animals, odor aids in parent-child recognition
- Is this true of humans?
Taste
- Develops prenatally:
– How could we test preference during this time? - Born with fully functioning taste receptors
- Similarly to odors, infants have specific facial
expressions and behaviours associated with each
taste
Touch
- Skin is receptive to touch, pressure, pain, and
temperature - This sense develops prenatally (1st to develop)
- Infants can demonstrate a sensitivity to touch as
soon as they are born: they react to touch, can be
soothed by touch
– Infant massage: increase in growth, attentiveness - Also react to pain
e.g., crying when receiving a shot, cortisol increases
Temperature
- Infants are very susceptible to changes in temperature
- Have difficulty regulating temperature through sweat
- They can’t regulate the temperature around them
because of a lack of motor and verbal skills
Results of study where they assigned some babies to crib and others to skin to skin then did heel prick
Results
Facial expression:
skin-to-skin lower score overall, faster return to baseline
Heart rate:
skin-to-skin lower (non-significant trend)
Cry:
skin-to-skin less likely to cry and cried for shorter period
Sleep/wake state:
skin-to-skin more likely to return to sleep sooner after procedure
Important because early experiences with pain can
sensitize the child to pain
Hearing
- Develops prenatally (eyeblink reflex)
– Reliably shown after 28 weeks gestation - Fetus can hear specific language patterns
– Moms read story in utero; babies prefer familiar story
3 days after birth
– French babies can discriminate when a voice is
speaking French and Russian
– Cry patterns match accent - Fetus can learn mom’s voice
– Physiological responses to mom’s voice but not
stranger’s - Infants do not hear as well as adults
– Worse at hearing very quiet sounds
– Up to 3 mos: lower pitch > higher pitch
– By 6 mos: more sensitive to high-pitched sounds
– Hearing continues to improve until 10 years of age - Prefer sounds within range of human voice
- Prefer vocal music over instrumental
- Prefer female over male voice
- Prefer mother’s language
- By 4.5 mos, prefer own name
- Have good speech sound discrimination
e.g., /ba/ vs. /pa/
– even better than adults
Werker & Tees (1984)
- Infants 6-12 mos; longitudinal
- Conditioned head turn procedure
- Hindi or Salish phoneme contrasts
- How many infants (at each age) can make
distinction?
The Sensorimotor Period
- Children move from reflexive
behaviour to the beginnings of
symbolic thought and goal-directed
behaviours - Circular reactions
Body-centred → object-centred →
environment expts
1: Reflex activity (0-1 month)
…
6: Mental representation (18-24 mos)
