Transcript Slides on brain development

Brain Development
Psyc of Violence
Jen Wright
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There are a lot of physical changes that
happen during the first years of life,
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The most important (and dramatic) of
which is brain development.
One of the last organs to fully develop…
brain development
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Largest brain/body mass of any animal.
Encephalization Quotient (EQ) = 7.4
• Dolphin = 5.3
• Chimp = 2.5
• Elephant = 1.9
• Whale = 1.8
Most development happens outside (instead of
inside) the womb
• Monkey newborn 70% adult size
• Human newborn 25% adult size
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Most growth occurs in first 3 yrs
• 3 yr old 80% adult size
brain development
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Neurogenesis – proliferation of neurons
through cell division
• At peak, 250,000 cells “born” every minute
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Synaptognesis – formation of connections
• Each neuron forms thousands of connections
• Axons elongate towards specific targets
• Dendritic “tree” increases in size and complexity
• 6 mos have 2 x more synaptic connections
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Synaptic pruning – elimination of
excess synapses
• Streamlines neural processing
• Without synaptic pruning, children wouldn't
be able to walk, talk, or even see properly.
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Myelination – insulating sheath
• Happens at different rates into adolescence
• Certain areas are myelinated first
importance of experience
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Plasticity – brain’s ability to change w/
experience
Experience-expectant plasticity
(experiences present throughout
evolution)
• Economizes on material encoded in genes
• Development will occur within a normal
range of environments
• Level of vulnerability in timing
•Critical periods
importance of experience
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Experience-dependent plasticity
(experiences of individual)
• Brain sculpted by idiosyncratic experiences
• Brain responsive to richness of stimuli
• Important in development of expertise
•More brain resources dedicated to processing
•E.g. musicians’ cortical representation of hands
• Timing may be less important
•Sensitive periods
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Why are abusive environments so
damaging for children?
There are many reasons
Effect of deprivation
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REM sleep – critical for neural development
in brain, esp. for activity-dependent
development
• E.g. visual system
• Facilitates learning/memory
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Sleep deprivation linked with later problems
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Babies most at risk of disruption
• E.g. ADHD, behavior-problems
• Premature infants in IC units
• Erratic, abusive environment
What is attachment?
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Attachment refers to the close,
emotional bond between an infant and
his/her primary caregiver.
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Orbital-frontal cortex: connects
processing of incoming sensory
stimulation with internal emotional
experiences
Early views of attachment
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Psychoanalytic Theory (Freud)
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Behaviorist Perspective
• Driven by oral needs during the first year
• Emphasized early experiences on later outcomes
• Driven by the need for food
• Learns to associate contact with mother with food
• Mother’s closeness continually reinforced
Ethology
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Rooted in Darwin’s
Evolutionary Theory
Focused on the
adaptive value of
behavior
Bond necessary for
survival
Lorenz (1952) Imprinting
Primary criticism of these early
perspectives
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Love (i.e., attachment) seen as
secondary to instinctive or survival
needs
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Harlow believed that the love and
affection were central to attachment
• necessary for survival
Harlow’s Monkeys (1958)
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Early work with monkeys
Cloth & wire mother
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Both groups preferred cloth mother
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• Only one equipped with feeding apparatus
• Monkeys randomly assigned
• Observed for 5 months
24
Mean
hours
per
day
18
.
.
.
.
. .
.
12
.
.
6
0
Infant monkey fed on
cloth mother
Infant monkey fed on
wire mother
Hours per day spent
with cloth mother
Contact Time with
Wire and Cloth
Surrogate Mothers
.
.. . .. .. . Hours
per day spent with
wire mother
.
.
1-5
11-15
21-25
6-10
16-20
Age (in days)
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Violence papers:
• Incorporate my comments
• Expand to begin providing explanations
(using the frameworks we’ve discussed so
far)
•3-4 pages (double-spaced)
• Bring 2 copies (printed and stapled/clipped)
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http://www.youtube.com/watch?v=hsA
5Sec6dAI
http://www.youtube.com/watch?v=caM
4-f6ZZBE&feature=related
mirror neurons
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Found in the frontal and parietal lobes
Fire when you
• engage in an activity (reaching out one’s hand)
• observe someone else engaging in the same activity.
Fire more strongly when action has some
purpose or content
• reaching out one’s hand for a cup.
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MN’s play a clear role in learning/imitation.
May also play a role in “mind-reading”
• grasping intentions, goals, desires.
crying
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Crying – infant form of communication
• Response to distress
•Development of emotional self-regulation
•Mastery of environment – agency
•Biofeedback loop
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When an infant’s needs are met, they
are able to turn their focus to the world
around them and explore.
• Their brains take in and adapt to stimulation
from the external world.
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When they aren’t met, they become
fixated on trying to get their needs met
• They stop exploring and shut out other
stimulation from the external world.
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Prolonged crying expose the brain to high levels
of cortisol, adrenaline, and other damaging
chemicals.
• Damage to hippocampus
• Reduced levels of vasopressin and serotonin
• Reduced levels of emotional regulation
• Impaired memory
• Increased levels of aggression/violence/bullying
• Increased levels of anxiety disorders
stress and brain development
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Exposure to excessive stress hormones is bad for
brain development.
Early symptoms of PTSD
The brain can become incapable of producing
normal stress responses.
• Hyper-vigilance (Ghosts in the Nursery)
• Emotional flatness
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Physical/emotional abuse and neglect can be
equally damaging.
emotions and cognition: bi-directional
Emotional reactions
Limbic system
o
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amygdala/hippocampus link
Lead to learning that is essential
for survival
Influence how a situation is
perceived, interpreted, and
remembered.
o Improve memory of event
o Highlight issues of importance
o Make things personally relevant
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Create life-long positive/
negative associations
emotional self-regulation
Strategies learned for adjusting emotional state to a
comfortable (adaptive) level of intensity in order to
accomplish goals.
Sympathetic:
child more easily soothed,
more interested
more self-regulated
Non-responsive (wait to intervene):
child enters into rapid, intense distress
harder to soothe
doesn’t develop self-regulation
temperament
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Constitutionally based individual
differences in
• Emotion
• Motor function
• Attentional reactivity
• Self-regulation
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Influences the way that children develop,
display, and control emotions
Foundation for later personality
Temperament styles
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Types
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Differences in punishment/reward
Differences in sociability
Bi-directional issues
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• Easy
• Difficult
• “Slow to warm up”
• Gender
• Cultural differences
• Goodness of fit (with parents/environment)
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Neurotransmitters
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Hormones
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Adrenaline/Cortisol
• Serotonin
• Noradrenaline
• Testosterone
Gene/Environment Interaction
Two levels of environmental influence:
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Environment
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Genes: Genotype
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Genes: Phenotype
Gene/environment interactions
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Passive genotype-environment correlation.
Evocative genotype-environment correlation.
Each child’s genes elicit other people’s responses,
and these responses shape development.
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In other words, a child’s environment is partly the result
of his or her genes.
Active genotype-environment correlation.
Children, adolescents, and especially adults
choose environments that are compatible with
their genes (called niche-picking),
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thus genetic influences in adulthood increase.