The human brain has 100 – 200 billion neurons at birth. During the first two years, fibers from these form synaptic connections at a rapid rate and some neurons die as a result.
Experience determines brain development. Neurons not stimulated lose their synaptic connections. Neurons often stimulated strengthen connections by growth of new dendrites
Glial cells multiply rapidly during the first two years. (About half the brain’s volume) Glial cells produce myelin to coat neuron axons. Myelination improves the efficiency of neural transmission.
The order in which cortical regions develop corresponds to the order in which capacities emerge in the growing child.
In the first year, there is a burst of synaptic growth in the auditory and visual areas. Areas supporting language show dramatic growth during toddlerhood. One of the last regions to develop are the frontal lobes.
Rapid frontal lobe growth at ages 3-6 Myelination of cerebellum-cortex links, reticular formation, corpus callosum
Specialization of functions in the two hemispheres of the cortex is called lateralization. For most people, language, logic and positive emotion are processed by the left hemisphere. Spatial and wholistic tasks and negative emotions are right hemisphere. Lateralization is very plastic.
Brain growth spurts, as measured by weight, size and EEG, occur: 3 to 4- months – reach for objects 8 months – crawl, search for objects 12 months – walk years – talk Ages 9, 12, 15, 18-20
Results in deficits in: Concentration Attention Anger and other impulse control
Does not result in geniuses. May cause infant withdrawal. May lead to disappointed parents. May cause strain between infants and parents.
Reward and pleasure centers (limbic system) mature before judgment centers (pre-frontal cortex) do. Baird & others (1999) found that year olds process emotional information using the amygdala, year olds use the frontal lobe.
Production of new neurons throughout life Growing new dendrites through the 70’s Brains rewire themselves – functional plasticity Myelination between cortex & limbic system in 40’s & 50’s Decrease in lateralization
Early-life idea density at 22 linked to fewer incidences of mild cognitive impairment Positive emotions linked to longevity Teachers showed more moderate intellectual declines Sisters with high folic acid levels showed little Alzheimer-like damage
Normal age related cell death in the brain does not lead to loss of ability to engage in everyday activities. Dementia: a set of disorders occurring almost entirely in old age and leading to impairment of many aspects of thought and behavior
Alzheimers: most common form Close to 50% of people over age 80 are affected Starts with memory loss, faulty judgment, anxiety, aggressive outbursts, reduced initiative, social withdrawal, depression Later purposeful movement may degenerate, may lose speech, lapse into a coma
Neurofibrillary tangles: twisted threads from collapsed neural structures Amyloid plaques: deposits of deteriorated protein surrounded by clumps of dead nerve cells Lowered levels of acetylcholine and serotonin (Drugs limiting acetylcholine breakdown reduce dementia symptoms.)
Familial: early onset, rapid progress Genes on chromosomes 1, 14, and 21 Dominant Related to Down syndrome Sporadic: no obvious family history Abnormal gene on chromosome 19 leads to excess ApoE4 blood protein that carries cholesterol and is linked to amyloid formation Some have no known genetic markers
Toxic substances Viruses Defects in the blood-brain barrier Vitamin and mineral deficiencies Excess dietary fat Cardiovascular disease Head injury Elevated aluminum levels
Vitamin C and E Anti-inflammatory drugs (aspirin, ibuprofen) Education Active lifestyle
5 to 10% of cases Series of small strokes leaves areas of dead brain cells Risks include high blood pressure, cardiovascular disease, diabetes Also smoking, heavy alcohol use, high salt intake, very low dietary protein, obesity, inactivity, and stress In most cases caused by atherosclerosis
Subcortical dementia Involves dopamine-producing neurons in the substantia nigra of the brain Symptoms include muscle tremors, slowed movements, and partial facial paralysis Drug treatment is partially successful
Depression Prescription drugs Surgery Environmental changes Social isolation
Sensation is detection Perception is organization & interpretation
Newborns are sensitive to touch and to pain. Facial expressions show that they distinguish sweet, sour and bitter. Newborns like the smell of bananas, vanilla,strawberry & chocolate, but dislike rotten eggs & fish. 6-day olds (but not 2-day olds) prefer the smell of their mother’s breast pad Infants prefer the sounds of human speech, recognize mom’s voice. Vision is the least developed sense at birth.
The fetus can hear even before birth. DeCasper & Spence, 1986 – Cat in the Hat research Newborns need more volume, are less pitch sensitive, not as good at sound localization, and have auditory preferences
Newborns like the smell of banana, vanilla, & strawberry & dislike the smell of rotten eggs & fish. 6-day olds (but not 2-day olds) prefer the smell of their mother’s breast pad
Research adding saccharin to amniotic fluid showed greater swallow & potential taste sensitivity in fetuses At 2 hours of age, babies make different faces to sweet, sour, salty & bitter
Birth, vision is 20/400 – 20/600 1 year – 20/20 visual acuity By 2 months can focus on objects and discriminate colors as well as adults Eye movements also under control for scanning and tracking
2-3 months – sensitive to binocular cues 6-7 months sensitive to pictorial (monocular) depth cues Crawling promotes 3-dimensional understanding (affordance of falling )
The Ecological View (Gibson) The purpose of perception is for us to adapt to and interact with the environment. All objects have affordances or opportunities for interaction that fit with out abilities to perform activities.
3-4 months, can relate moving lips to speech sounds 7 months, can relate a happy or angry voice to a facial expression Babies will not learn matches of sights and sounds that do not go together
Visual preference – length of time the infant looks; reflection in the eyes; Franz looking chamber Habituation & dishabituation Decreased responsiveness (looking, sucking, heartrate, respiration) Orienting & tracking Turning head or tracking with eyes Equipment videotape, computer, recording heart rate, etc.
Newborns prefer patterned to plain stimuli As infants develop contrast sensitivity they prefer more complex patterns. Infants first respond to parts of a pattern, then to the whole pattern. By 12 months, they have the perceptual property of closure.
Newborns prefer simple drawings of faces with features arranged naturally. 2-5 months they prefer a complex face to other complex patterns 2 months, look longer at mother’s face 3 months, discriminate photos of two strangers
Infants look for stable or invariant features of the environment Over time, the baby differentiates or detects finer and finer stable features Some theorists believe that in some sense, the infants impose meaning on the patterns that they perceive.
Infants form expectations about what they are going to see as early as 3 months Spelke at 4 months infants recognize the solidity & continuity of objects At 6-8 months, (but not 4), they perceive gravity & support
Perceptual/Cognitive Development Baby Mathematics –Shown a numerically impossible outcome, infants stare longer (Wynn, 1992) 1. Objects placed in case. 2. Screen comes up. 3. One object is removed. 4. Possible outcome: Screen drops, revealing one object. 4. Possible outcome: Screen drops, revealing two object.
All of the sensory systems with the possible exception of touch experience gradual decline as a person ages. Vision Hearing Taste Smell
Middle Adulthood Presbyopia, loss of accommodation (ability to adjust focus at different distances) between ages 40 and 59 50’s & 60’s – blood supply to eye declines, need more light, smaller visual field
Late Adulthood Dark adaptation is more difficult Glare sensitivity increases Continuation of degeneration of function from Middle Adulthood Possible retinal degeneration
Cataracts – 30% of people by age 70 Glaucoma – pressure from fluid buildup in the eye damages the optic nerve; 1% in 70’s, 10% in 90’s; treated with eye drops Macular degeneration – deterioration of retina; 1 in 6 people 75+; leading cause of blindness in older adults
Can start decline by age 40, high-pitched sounds first 15% of people over 65 legally deaf due to cochleal degeneration 75% of those over 75 have hearing problems
Ability to taste appears to start decline in the 60’s, leading to a preference for spicy and junk food Older adults (60 +) lose some of their sense of smell and may enjoy food less