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Infant Slide and Child Development
Chapter 5
Tuesday 25th, 2007
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Announcements:
Response Paper #1 is due Today by noon Ch 5, skip sections on adolescence (pgs 141145, 152-153, 156-157, 159, 165-171)
Ch 6 for Friday- motor, sensory, and perceptual development Exam 1- a week from Today...
Review sheet posted later today Exam details...
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5--Physical Development in Infancy
Body Growth and Change The Brain
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Primacy of Infancy
The paths first traveled will be the most significant for later development
"As the twig is bent, so grows the tree."
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Changes in Body Proportions
At birth, head is 70% of adult size and accounts for 25% total body length Legs at birth are not much longer than their heads; by adulthood, legs account for about half of total height Result in lowering the center of gravity
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Body Growth and Change
Infancy and Childhood
Infancy
Newborns double their birth weight by the age of 4 months and nearly triple it by their first birthday Growth slows in the second year; by age 2, children average 32 to 35 inches in height--nearly half their adult height!
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Size and Shape
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Body Growth and Change
Infancy and Childhood
Early Childhood (2-5 yrs)
Girls are only slightly smaller and lighter than boys Body fat declines slowly during preschool years; girls have more fatty tissue than boys and boys have more muscle tissue than girls Growth patterns vary due to heredity and environmental experiences.
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Environmental Conditions Influence Growth Rate
Babies born in Malawi face conditions such as widespread malnutrition, chronic poverty, disease, and a rising HIV/AIDS infection rate. As a result, Malawian infants grow at a slower rate than their American counterparts.
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Body Growth and Change
Infancy and Childhood
Middle and Late Childhood (Ages 6 to 11)
Slow, consistent growth averaging 2 to 3 inches a year. Muscle mass increases; body fat decreases. Improved muscle tone and strength. Bones continue to harden.
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The Brain: Primacy of Infancy
The paths first traveled will be the most significant for later development
"As the twig is bent, so grows the tree."
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How is the brain developing compared to the rest of the body?
First lets refresh our memories on the structure and function of the brain...
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The Brain
Brain Physiology
The brain has two hemispheres. The forebrain, or top portion, is covered by a layer of cells called the cerebral cortex
responsible for 80% of the brain's volume critical in perception, thinking, language, and other functions.
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The Brain
Four Lobes of the Cortex:
Frontal lobes: Voluntary movement, thinking, personality, and intentionality or purpose. Occipital lobes: Vision Temporal lobes: Hearing, language processing, and memory. Parietal lobes: Spatial location, attention, and motor control.
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The Brain
Brain Physiology (continued)
Limbic System
Hypothalamus (monitors eating, drinking, and sex) Pituitary gland (controls growth, regulates other glands) Amygdala (governs emotions) Hippocampus (governs memory and emotion)
Pituitary Gland
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The Brain
Brain Physiology (continued)
Neural circuits are clusters of neurons that work together to handle particular types of information. The neural circuit for attention and working memory uses the neurotransmitter dopamine and lies in the prefrontal cortex. Memories are created like footpaths through the grass
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The Brain: Infancy
Brain development occurs extensively in utero. of Because the extensive brain development during infancy, the infant's head must be protected. Fontanels Shaken baby syndrome: Damage to brain from shaking a baby, includes brain swelling and hemorrhaging.
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The Brain: Infancy
Changing Structures
2 months: development of motor control centers allow reaching and grabbing (parietal lobe) 4 months: neural connections for depth perception begin to form (occipital lobe) 7 - 9 months: Rapid growth of frontal cortex (used in integrating information)
Prefrontal area -> important for the development of voluntary behavior (e.g., impulse inhibition)
12 months: speech centers ready to produce language (temporal lobe)
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The Brain: Infancy
Changing Neurons
Myelination- begins prenatally and continues through middle childhood
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The Brain: Infancy
Changing Neurons (continued)
Increase in synaptic connections (synaptogenesis)
Blooming and pruning
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The Brain: Infancy
Synaptic Density in the Human Brain from Infancy to Adulthood
Visual Blooming
Auditory and Prefrontal Blooming
Visual Pruning Auditory and Prefrontal Pruning
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Second-Year Changes
Accelerated myelination
Within cerebral cortex Between brain stem and cortex Leads to new self-awareness, emotional responses, better problem solving, voluntary control of behavior, enhanced analysis of visual and auditory input, and language acquisition
Neuron branching close to adult magnitudes
Each neuron has multiple connections with others, usually numbering in the thousands!
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Rats Raised in Enriched Environments
Experiment
What would happen if you raised rats in dull vs. enriched environments? Would their brains look different?
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Rats Raised in Enriched Environments
Experiment
Increased rates of learning in standard laboratory tasks (i.e. mazes) Increased overall weight of the cerebral cortex (the part that integrates sensory information) by 5%! Increased amounts of acetylcholinesterase, a brain enzyme that enhances learning Larger neuronal cell bodies and glial cells More synaptic connections
Rosenzweig, 1984
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Active Interaction with the Environment
Experiment Rats were raised with an enriched environment but were housed singly in small cages so that could do no more than observe what was going on around them The learning capacity of these rats did not differ from that of the animals that were housed in individual cages away from the enriched environment What might this imply for child-rearing or teaching?
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The Brain: Infancy
Early Experience and the Brain
Depressed brain activity has been found in children who grow up in a deprived environment (Cicchetti, 2001), and it's possible the effects are irreversible. Neuroscientists believe that what wires the brain is repeated experience: Before birth, genes direct wiring patterns. After birth sensory and environment input shape neural connections.
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The Brain: Infancy
Early Deprivation and Brain Activity (PET scans)
Typical child
Romanian Orphan
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Review and Reflect:
Describe how the brain changes
Review
What is the nature of brain physiology? How does the brain change in infancy? What characterizes the development of the brain in childhood? What role does experience play in cortical development?
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Imagine that you are the director of a community program to improve the early experiences of children living in a poor community. Based on what you know of early brain development, what activities would you promote in your program? Include why in your answer.