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Lecture 6

PSYC23H3 Lecture Notes - Lecture 6: Memory Consolidation, Synapse, Ring Signature


Department
Psychology
Course Code
PSYC23H3
Professor
David Haley
Lecture
6

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Agenda:
Review midterm
Infant stress, learning, memory
End of last lecture on stress in
preterm infants
Contingency learning at 3 months
at day 1
Contingency learning at 3 months
after 24 hours
Delayed imitation (i.e. memory)
after 15 min and after 24 hours
Midterm review:
** The questions are all in the ppt
Early stress: preterm infants
Separated from parents
Invasive procedures
All during a period of rapid brain growth
I. Preterm populations
Early Stress in preterm infants
5 to 7% born prematurely (<36
weeks)
Stressful events in the Neonatal
Intensive Care Unit (NICU)
Greater variation and impairment in cognition
in preterm vs. full-term populations
Slower information processing (e.g.
habituation, contingency detection,
deferred imitation)
Brain mechanisms underlying cognitive
differences remain unknown
Neurological vulnerabilities
Alterations in the development of
stress system
Steroids in preterm infants
Mothers at risk of premature
delivery receive steroids
Decrease mortality
Accelerate lung maturation
Stress and/or steroids alter HPA-axis
Down regulate GC receptor
expression
Dampen cortisol responses in
neonates
Alterations in HPA-axis
Physical health
Mental health
Cortisol at 3, 6, 8, and 18 months
Cortisol levels are lower in preterm infants
than in full-term infants at 3 months
Normal developmental decline in cortisol
levels from 3 to 18 months is altered in
extremely premature infants
I. Summary of early stress
Exposure to prenatal steroids and early
stress have independent effects on
dampening HPA activity in extremely
premature infants in the neonatal period
Normal development of HPA axis appears
altered in preterm infants in the first year of
life, which suggests a reprogramming of
stress physiology that may contribute to the
development of brain differences

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II. Stress and Learning: how does stress affect
learning?
Contingency learning
Contingency is exciting
Infant learns and remembers
association between leg and mobile
movement
Termination is frustrating
Violation of expectation
Stress and learning
Information processing is slower in preterm
infants
Habituation (Rose)
Contingency learning and memory
(Gekoski)
Delayed imitation (Barr)
Yerkes-Dodson law (1908)
Arousal is related to learning
Too little or too much arousal =
interference with learning
A little arousal = best for learning
Impaired stress regulation in high risk infants
Hyper- and hypo- responses to
novelty
Low inhibition of response
(Field, 1980; Tronick, 1990; Mayes, 2000)
Porges polyvagal theory (1995)
Components of autonomic nervous system
linked to behavioral and physiological
strategies
Structure and function evolved hierarchically
Stage
Autonomic
component
Purpose
I
Unmyelinated vagus
Homeostatic
processes
II
Sympathetic-adrenal
system
Mobilization for
challenge
III
Myelinated vagus
Social communication,
self-soothing, inhibits
sympathetic-adrenal
influences
Here is Porges Polyvagal Theory which
provides a springboard for considering why
regulation of physiological responses, such
as vagal regulation and other components
that influence the regulation of the autonomic
nervous system are related to the infant’s
social and cognitive processes.
In this model, specific components of the
autonomic nervous system are hierarchically
organized, with older primitive components
retained and inhibited by the newer and
more complex components.
Each component exerts an action in the
regulation of autonomic output and is
thought to support a behavioral strategy that
helps the organism adapt and survive. In this
slide, the older and more primitive
components of the ANS are the
unmyelinated vagus and the
sympathetic-adrenal system, which promote
homeostasis and mobilization of energy
resources, respectively, whereas the newer
component is the myelinated vagus, which
promotes social behavior, self-soothing. The
newer smarter vagus generally inhibits
autonomic output but when withdrawn
provides a very fast way for the organism to
respond to changes in the environment.
Parasympathetic and sympathetic nervous systems
Hypotheses
Hypothesis 1
Based on the impaired stress
regulation perspective, we expected
that preterm infants would show
slower rates of contingency learning
and greater sympathetic activation
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to contingent stimulation than
full-term infants
Hypothesis 2
Based on previous work, we
expected faster
contingency-learning infants would
show better stress regulation (lower
sympathetic activation, higher basal
vagal tone, greater regulation of
vagal tone, and lower negative
affect) than slower
contingency-learning infants
Kicking
Visual attention
Full terms more engaged in task
Negative affect
No differences until the end; preterms get
upset near extinction
Heart rate
Preterms learning well are more aroused
Vagal tone
Getting aroused is adaptive for learning
At baseline, full terms that learn well have
high levels of vagal tone
Which means their sympathetics
are in check
Parental responsiveness
For the full-term infants, faster learning
infants had higher levels of responsivity than
slower learning infants
For slow preterm infants, greater parent
responsiveness was associated with
decreases in negative affect and vagal tone
responses to contingency learning (r’s = -.60
and -.56)
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