PSYC 352 Study Guide - Midterm Guide: Phonological Awareness, Dentate Gyrus, Magnocellular Cell

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7 Sep 2020
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BRAIN DEVELOPMENT
Infant brains are big and develop fast
o Structures not so different from other animals, esp. non-human primates
o But size relative to rest of the body is very unusual among other animals
o Fetus’ brains not fully formed -> Develop a lot even after birth, a lot faster
than the rest of your development
Everything else develops at a much more protracted rate
Possible mechanisms of plasticity:
o Differentiation/synaptogenesis: neurons extend dendrites and axonal terminals, forming
synapses with other synapses, 3rd trimester through
adolescence
o Postnatal neurogenesis: new neurons develop in some parts of brain including dentate
gyrus of hippocampus and olfactory bulb, birth to adulthood
o Myelination: neurons become coated by fatty tissue that results in faster transmission of
nervous signals and reduction of interference, 3rd trimester to adulthood
o Selective cell death (apoptosis): neurons die, 3rd trimester to adulthood
o Synaptic pruning: number of synapses per neuron is greatest between 4 and 8 months of
life and decreases with age, infancy through adulthood
Pattern of changes in cortical thickness (gray matter, mostly neurons) observed over childhood
and adolescence varies with age and with level of IQ -> Difference especially pronounced in
frontal regions
o Negative correlation between cortical thickness and IQ in early childhood -> Children
with higher IQs had thinner cortices than children with lower IQs
Pattern reversed in late childhood and adolescence
o Children with exceptionally high IQs showed early acceleration of cortical growth
followed by accelerated thinning in early adolescence
Finding Function
Used to think that neural systems were "hard-wired" and that experience just "fine-tuned"
But that there is a much bigger role for experience, even in developing some of what we think is
relatively basic functioning in neural systems
o Experience-expectant: given a species-typical environment, all will develop a particular
organization
Like language area, where it has strong biological proclivity to develop in a
particular way, but they need the appropriate input to develop properly
o Experience-dependent: reflect the unique experiences of an individual
Some things can only be learned by being taught it i.e. reading
Common across species to have this skill, but only through cultural transmission
that we are able to read
Age-related changes in brain structure and function associated with changes in cognition and
behavior also observed in adolescence
o Changes occur in distribution of various neurotransmitters, with some decreasing
substantially in both the frontal cortex and limbic system, an area of the brain associated
with emotion
o Amount of gray matter decreases relative to childhood while white matter increases
(mainly due to increased myelination in frontal cortex) and different areas of brain
become increasingly connected
o Amygdala and other structures in limbic system reach adult levels before prefrontal lobes
o Changes likely adaptive, in that the emerging adult must seek independence from parents,
experiment with new environments, establish a place in their social group
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