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