Psychology of Infancy Defining development, prenatal development, brain development

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Psychology of InfancyDefining development,
prenatal development, brain development

• D. Messinger, Ph.D.

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Questions (single essay format)

• Define development. Argue for why you believe
  development does or does not have an endpoint.
• Describe genetic and experiential factors in
  brain development referring to experience
  expectant and experience dependent factors.
• Give examples of how prenatal sensory experience
  impacts sensory development.
• Is it is all over after age 3?
• Provide examples from Nelson.
• What are some basic patterns of synaptic and
  brain development in infancy?
• How they are influenced by experience?
• What can go wrong in this pattern?

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Development defined
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Development defined

• Individual change that is, normative,
  non-reversible, relatively stable, and
  sequential.
• Normative process
• Everyones doing it
• Non-reversible
• Reorganization of the entire person
• Relatively stable
• You cant go back,
• Sequential change
• Crawl before you walk
• Examples

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Is development

• Increasing functionality in all things?
• Loss of perceptual acuity in non-native languages
  between 6 12 months
• Old-age

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Is development

• Headed toward a goal?
• Development has normative outcomes,
• but time goes forward
• prior events cause subsequent events
• not the opposite
• What does Thompson (2001, p. 21) mean?
• A drive to development is inborn, propelling the
  human infant toward learning and mastery.

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Three models
In class assignment What would a cross-tab of
the transactional model look like?
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Stability and continuity

• Whats the difference?

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What does individual development look like?
Individuals
Group
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Prenatal brain development
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Overview

• Increasing differentiation of areas of cortex
• Infant is born during height of brain development
• Tertiary sulci develop from 1 month before to 12
  months after birth

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Human brain development
Wikipedia
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Four levels of brain development
From Nelson, 1999
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Creation of a tube
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Proliferation migration of neurons

• General pattern of brain development genetically
  specified
• By 20 weeks, most neurons present
• 3rd - 16th prenatal week most crucial
• At 8 weeks, head is half of fetus
• But specific connections depend on generic growth
  processes and sensory-motor stimulation
• Trillions of connections still forming
• Trimming of these connections is developmental
  task

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Synapses are connections between neurons
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Neural migration

• Many elements of initial neural migration
  specified genetically
• By 20 weeks gestation, 100 billion neurons!
• 50,000 500,000 neurons per minute
• Neurons follow path of glial cells outward from
  ventricles
• To form 6 layers of cortex

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Neural development Synaptogensis

• Once in place, synapses are overproduced somewhat
  haphazardly
• 1 year old has 150 more synapses than adult
• These are pruned (diminish) during development
• Repetition of sensory-motor patterns create more
  specific set of experience dependent synaptic
  linkages

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Time lapse sequences of radial migration (also
known as glial guidance) and somal translocation
neurite outgrowthhttp//www.youtube.com/watch?vn_
9YTeEHp1ENR1
Typical and Atypical http//www.youtube.com/watch?
vGBIa8G3gBH0featurerelated
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Increase in complexity of neural connections
Like a growing forest
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How do the correct synapses form?

• 15,000 synapses for every cortical neuron
• 1.8 million per second in first 2 years!
• Cerebral cortex triples in thickness in 1st year
• Sensory and motor neurons must extend to correct
  brain are and form correct synapses
• This quantity of information cannot be
  genetically micro-managed

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Two types of experience in brain development

• Experience-expectant

• Experience dependent

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Experience-expectant

• How common early experiences provide essential
  catalysts for normal brain development
• Early visual stimulation, hearing, exposure to
  language, coordinating vision and movement,
• The developing brain expects and requires
  these typical human experiences, and relies on
  them as a component of its growth.

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Experience-dependent

• How individual experience fosters new brain
  growth and refines existing brain structures
• Can be unique to an individual
• Reading
• Singing, music

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Neural Darwinism (Edelman)

• Use it or lose it
• What is not used, is pruned
• What is used, develops stronger connections
• Organism environment are system that shapes
  brain
• Brain development is guided by environment
• Brain enables behavior which shapes brain
• Synaptic development is not teleological

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The fetus as constructing its own development

• Fetal behavior impacts physical development
• In chicks prevented from moving, cartilage turns
  to bone
• Fetal sensory experience impacts sensory
  development
• Mice whose tongues were anesthetized had
  malformed cleft palates

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Prenatal sensory experience impacts sensory
development

• Hearing typically develops before sight
• Rats, ducklings, and quail chicks exposed to
  visual stimulation prenatally
• before they normally would
• lose hearing ability at birth

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Normal sensory development contingent on
extra-fetal environment

• Differences in the timing of augmented prenatal
  stimulation led to different patterns of
  subsequent auditory and visual responsiveness
  following hatching.
• No effect on normal visual responsiveness to
  species-typical maternal cues was found when
  exposure to tactile and vestibular stimulation
  coincided with the emergence of visual function
  (Days 14-19)
• When exposure took place after the onset of
  visual functioning (Days 17-22), chicks displayed
  enhanced responsiveness to the same maternal
  visual cues.
• When augmented tactile and vestibular stimulation
  coincided with the onset of auditory function
  (Days 9-14), embryos subsequently failed to learn
  a species-typical maternal call prior to
  hatching.
• Honeycutt, H. R. Lickliter (2003).
  Developmental Psychobiology 43 71-81. The
  influence of prenatal tactile and vestibular
  stimulation and visual responsiveness in bobwhite
  quail A matter of timing

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Prenatal behavioral development

• 9 weeks - movement
• 16 weeks - frowning, grimacing
• 25 weeks - moves to drumbeat
• 26 weeks - remembers sounds
• 32 weeks - all brain areas functioning
• 34 weeks - can habituate

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1st Trimester

• Behavioural Repertoire
• 8 weeks Startle (arms and legs shoot outward)
• 9 weeks graceful general movements of the
  head, trunk, limbs
• 10 weeks Stretch (head moves back, trunk arches,
  arms lifted)
• 11 weeks Yawning
• Cause and Function of Prenatal Movement
• Unable to inhibit movement inhibition comes with
  the connection to higher brain centres
• Fetal movement is necessary for the physical
  systems to develop normally (stimulate
  development of muscles, tendons, ligaments)
• Breathing movement important for lung development
• Changes in position may promote better
  circulation help prevent skins from sticking
  together
• Motor behaviour moves amniotic fluid
• structural growth of fetus
• Some behaviours (e.g., sucking) may be
  preparatory
• http//web.uvic.ca/psyc/coursematerial/psyc435a.f0
  1/435A/Week20220Lecture20Notes.pdf

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Role of experience
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Overview of brain growth

• Subcortical areas responsible for reflexes
  develop first
• E.g. spinal cord
• Followed by cortical areas in a specific
  progression
• What is most human develops last
• Most but not all neurons present at birth
• Synapses develop
• Myelin develops

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At the same time - Myelinization

• Fatty sheaths develop and insulate neurons
• Dramatically speeding up neural conduction
• Allowing neural control of body
• General increase in first 3 years is likely
  related to speedier motor and cognitive
  functioning
• allowing activities like standing and walking
• Endangered by prenatal lead exposure

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Promoting early brain development?

• Re-discovery of importance of early experience
• How brain connections grow and change as a
  result of stimuli from the environment.
• How early stress can be harmful to the developing
  brain.
• Principle of "use it or lose it"
• Seven ways to support brain development
• http//www.pitc.org/

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• Considerable misunderstanding of early brain
  development occurs when neurons and synapses are
  considered independently of the development of
  thinking, feeling, and relating to others.
• Thompson, 2001, p. 29

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Is it all over after 3?

• Is the course of development set in infancy?
• Early experience is important
• But, with some exceptions, human beings remain
  open to the positive effects of additional
  experience
• The same is true for the impact of experience on
  brain development
• How important is it to stimulate your childs
  brain?

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What does Nelson say

• Acrobatic rats (p. 423)
• Adult neurogenesis

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Implications for practice

• It is important to provide a safe, warm,
  supportive, stimulating environment for infants
• But its never too late to improve developmental
  outcome for an individual
• At any point, current conditions are as important
  as past conditions
• No flashcards

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Brain Overgrowth in the First Year of Life in
Autism

• The clinical onset of autism appears to be
  preceded by 2 phases of brain growth abnormality
  a reduced head size at birth and a sudden and
  excessive increase in head size between 1 to 2
  months and 6 to 14 months. Abnormally accelerated
  rate of growth may serve as an early warning
  signal of risk for autism
• Courchesne, Carper, Akshoomoff, (2003)
• Why overgrowth?

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Nelson

• Later developing processes more susceptible to
  the effects of experience
• Motor development more plastic than language
  development
• Sensitive periods
• Genetics and experience Indissoluble

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Birth Process
Midwifery the first profession
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Human birth cephalo-pelvic proportionality

• Are human beings evolving?
• How might the rise in the rate of delivery by
  c-section be related to evolution?

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Human birth a social process

• "In nonhuman primates, the fetus usually emerges
  with its face toward that of its mother. She may
  then reach down and pull it up toward her along
  the normal flexion of its body.
• "In humans, however the close equivalence of
  cephalopelvic dimensions has resulted in
  infant being born facing away from its mother.
• In this position, the use of her own hands to
  assist delivery before the shoulders have emerged
  could result in pulling the infant against the
  normal flexion of its body, again with the risk
  of injury particularly to the nerves of the
  neck."
• Wenda R. Trevathan, Human Birth, (New York
  Aldine de Gruyter, 1987), p. 89-92

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Final project ideas

• Prenatal maternal stress
• Prenatal behavior
• Impact on outcomes (after birth)

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Human birth graphic content

• More medical, produced video
• http//video.google.com/videoplay?docid-717005241
  5220169972qbirthvideos
• Just video of birth
• evtv.com
• NPR segment on birth process