The Science of Early Brain Development Stuart G. Shanker by pzs15406

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									    The Science of Early
     Brain Development
               Stuart G. Shanker
  Director, Milton and Ethel Harris Research Initiative
   Director, Canada-Mexico-Cuba Research Initiative
      Co-Director, Council of Human Development
Past President, The Council for Early Child Development
                                             Zero to Twelve, Calgary, February 22, 2008
Time Magazine from the MEHRI Neuroscience lab




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The Descent from the
       Trees




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                Bonobos


•Discovered in the early 1970s
•Closest human ancestor: approx 99% of our DNA
•Partially bi-pedal
•Live in small groups, social harmony, strong
matriarchal presence
•Thought to provide us with the best model we
have of our early human ancestors, the
Australopithecines
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     The Evolutionary History of
            H. sapiens

•5 mya Australopithecines descended from
the trees and began to walk upright
•As a result the brains of early human
species grew larger and larger
•In order to accommodate bipedalism and
our large brains human babies are born
„prematurely‟ with their brains less than ¼
quarter the size of an adult brain
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              Secondary Altriciality



• Post-natal plasticity enables child‟s brain to become
  attuned to environment in which she is born
• Synaptic growth in the first 2 years is massive
• There is huge over-production of synapses that, at
  8 months, will start to be „pruned‟ back
• Synaptic pruning is regulated by baby‟s dyadic
  interactions with her caregivers
• Primary modalities are shared gaze and touch
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         What are the Primary Systems
                    at Birth?


• Sensory systems
• Primitive reflexes
• Primitive emotion circuits

• What is missing are self-regulating mechanisms
• Child acquires these by experience: by being
  regulated

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04-212




         Sound    Touch
         Vision   Proprioception
         Smell    Taste
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                                   Neal Halfon
          The Role of the Primary
       Caregiver in Early Brain Growth


•The primary caregiver serves as an „external
brain‟, regulating and stimulating baby‟s brain
•Caregiver provides regulatory mechanisms
not yet present in child‟s brain
•Through countless interactions, the child
develops these self-regulatory mechanisms
and the capacity to pay attention
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     The Critical Importance of Affect


•Affect is overarching mechanism that binds
the dyad together
•The earliest affects an infant experiences
are pleasurable and aversive sensations
•She seeks out those experiences that are
positive and avoids those that are aversive
•i.e., an infant will only seek out dyadic
interactions if she finds them pleasurable 12
             Biological Variability


•Every infant is unique in the stimulation she
likes, how much, when, and how she shows
this
•Infants with hyper/hypo-sensitivities, or motor,
or processing compromises, can find
interaction aversive and shut down
•A similar phenomenon is seen in severely
depressed caregivers or those who, for
whatever reason, fail to read their infant‟s cues
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            Social Transmission of
             Caregiving Practices


•Caregivers unconsciously adjust their behavior
to suit the individual child, thereby promoting
interaction which develops the infant‟s capacity
to self-regulate and pay attention
•These behaviors are not HARDWIRED; they
were slowly developed and passed down from
one generation to next over millions of years
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          The Human Developmental
                 Manifold


•Womb provided a stable developmental milieu
•Secondary altriciality ensured that infants were
closely tied to their caregivers for first years of life
•For millions of years, early humans lived in small
hunting-gathering groups
•E.O. Wilson‟s biophilia hypothesis postulates that
our nervous systems are closely bound to nature

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        Striking Changes to the Human
             Development Manifold


•Approximately 83% of Canadians live in cities
•Heightened stress during pregnancy
•Cohesive, homogenous communities are becoming rarer
•Children are exposed to vast amounts of stimuli far in
excess of our evolutionary environment
•Exposure to nature is becoming increasingly rare
What is the impact of changes to a developmental
system that evolved over millions on early brain
development?
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           The Creation of Nurseries in the
                       1950s

•let mothers rest; protection from infections; keep baby warmer
•Soon there was a huge increase in breast-feeding problems
•Mechanisms triggered by skin-to-skin contact were compromised
    –a newborn will crawl up its mother‟s ventrum searching for
    the breast and begin rooting and suckling
    –This action dramatically reduces infant crying
    –triggers a surge of oxytocin and GI hormone that enhances
    capacity to cope with the caloric demands of breast-feeding
    –affects the expression of serotonin receptor genes
    –has an organizing effect on the development of the brain
•Ironically, it turns out that babies placed immediately with their
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mother are warmer than „cot babies‟
       Cognitive Social Neuroscience


• One of the most exciting recent developments in
  neuroscience has been the growth in our
  knowledge of the social nature of the brain
• The essence of the brain appears to be that it is
  primed to resonate with other brains
• Much of this is automatic: a “low road” in social
  interactions that operates beneath the threshold
  of consciousness
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        The Role of the Amygdala


• The amygdala modulates neural systems
  serving cognitive and social behaviors
• The responsiveness of the amygdala to
  stress is a result of secondary altriciality and
  not a hard-wired phenomenon
• A child‟s reaction to stress is set in the early years
  and has life-long effects on her mental and physical
  health
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                 Theory of Mind


• A child‟s unconscious processing of her
  community‟s nonverbal communicative signals,
  and thus her capacity to understand what others
  are thinking and feeling (Theory of Mind) is set in
  the early years
• The better the child‟s Theory of Mind the better
  the child‟s language and cognitive development


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      Building Healthy Families:
      Building Healthy Minds


•Both members of the dyad need to be exposed to
other members of community
•This has a profound effect on the caregiver‟s
mental health, and as a result, the baby‟s brain and
social development
•There is more involved here than simply a matter
of transmitting information about parenting: healthy
brain development appears to depend critically on
community involvement
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            It takes a Child to Raise a
                      Village


•On the one hand, a child‟s interactions with other
members of her community – or the lack of such
interactions – has a profound effect on her early
brain development
•On the other hand, the more a community invests
in its children by reaching out to its families – to all
of its families – the healthier the community


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        Involving the Community


•The lesson from successful national early child
development programs is clear: the greater a
community‟s social capital the better its children do
on virtually all physical and mental indices
•The single most important factor is political will, not
capital investment
•The Cuba phenomenon

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                 Further Reading


•Fogel, Alan, Barbara King & Stuart Shanker (2007) Human
Development in the 21st Century (Cambridge UP)
•Goleman, Daniel (2006) Social Intelligence (Bantam)
•Greenspan, Stanley & Stuart Shanker (2004) The First
Idea (Perseus Books)
•McCain, Margaret, Fraser Mustard & Stuart Shanker
(2007) Early Years Study II: Putting Science into Action



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