Brain Bee Chapter 7 - Infant, Child, and Adolescent Brain

average brain-weight of a newborn

370 grams (13 ounces)

average adult brain weight

3 pounds

number of neurons in adult brain

86 billion

growth rate of an infant’s brain

1% per day immediately after birth
0.4% per day 3 months after birth

fastest growing brain region

cerebellum (also has the most neurons)

first 3 months of life, number of neurons in cortex increases by

23-30%

synaptogenesis

formation of synapses

oligodendrocytes

myelination

synaptic pruning

depend on toddler’s experience

critical period

period of development where genes and environment exert strong influences
coincide with high rates of learning

second critical period

during adolescence (teenage years)
increase in white matter volume
synaptic pruning

MRI

magnetic resonance imaging
shows white matter vs gray matter
brain volume

diffusion tensor imaging

DTI - shows quality of white matter

fMRI

measures brain activity

alcohol abuse in teenagers

MRI + DTI - reduced gray matter volume, reduced white matter integrity
fMRI - lower brain activity, less sustained attention, poorer working memory

neurodevelopment

continues until 30

gray matter changes

generally decreases into adulthood (but increases in left temporal lobe = memory and language)

white matter changes

frontal and parietal neocortices become more myelinated closer to age 30
late maturation / myelin development in frontal lobe

neuroplasticity / plasticity

ability of brain to modify itself and adapt to the environment
experience-expectant
experience-dependent
(important for critical periods)

experience-expectant plasticity

common or universal environmental experiences necessary for shaping development
ex: finches must hear adult songs before sexual maturation to be able to sing well

experience-dependent plasticity

changes in the brain as a result of unique life experiences
ex: skills that develop throughout life, with no critical or optimal period → violin players show greater cortical development in left-hand control

two-photon imaging

allows for observation of living neurons in animals and their growth → neuroplasticity