BRAIN & PERCEPTUAL DEVELOPMENT

Feldman Modules 3-2 & 3-3 Santrock Chapters 3 & 4

• At birth, the brain is at about 30% of it’s adult weight.

• At age 2, the brain is at about 70% of its adult weight.

• Brain reaches 90% of adult weight by age 6

BRAIN DEVELOPMENT

Prenatal : neurogenesis – 2nd trimester, fetal period

Post Natal (after birth) (cycle) Synaptogenesis – dendrite formation

Synaptic pruning

Myelination

BRAIN DEVELOPMENT

SYNAPTIC TRANSMISSION

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.

BRAIN DEVELOPMENT - SYNAPTOGENESIS

Experience determines brain development.

Neurons not stimulated lose their synaptic connections.

Neurons often stimulated strengthen connections by growth of new dendrites

BRAIN DEVELOPMENT – SYNAPTIC PRUNING

BRAIN DEVELOPMENT – GLIAL CELLS AND MYELINATION

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.

CEREBRAL CORTEX

The order in which cortical regions develop corresponds to the order in which capacities emerge in the growing child.

CEREBRAL CORTEX

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.

BRAIN DEVELOPMENT

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.

CEREBRAL CORTEX – LATERALIZATION & PLASTICITY

• 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 1.5 -2 years – talk Ages 9, 12, 15, 18-20

BRAIN DEVELOPMENT – SENSITIVE PERIODS

• Results in deficits in:

Concentration

Attention

Anger and other impulse control

BRAIN DEVELOPMENT - UNDERSTIMULATION

• Does not result in geniuses.

• May cause infant withdrawal.

• May lead to disappointed parents.

• May cause strain between infants and parents.

BRAIN DEVELOPMENT - OVERSTIMULATION

BRAIN DEVELOPMENT IN ADOLESCENCE

Reward and pleasure centers (limbic system) mature before judgment centers (pre-frontal cortex) do.

Baird & others (1999) found that 10-18 year olds process emotional information using the amygdala, 20-40 year olds use the frontal lobe.

BRAIN CHANGES IN ADULTHOOD

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

MANKATO NUN STUDY

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

MENTAL DISABILITIES IN OLDER ADULTHOOD

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

DEMENTIAS

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

ALZHEIMER 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.)

ALZHEIMER RISK FACTORS 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

ALZHEIMER RISKS Toxic substances Viruses Defects in the blood-brain barrier Vitamin and mineral deficiencies Excess dietary fat Cardiovascular disease Head injury Elevated aluminum levels

PROTECTIVE FACTORS

Vitamin C and E Anti-inflammatory drugs (aspirin,

ibuprofen) Education Active lifestyle

CEREBROVASCULAR DEMENTIA 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

PARKINSON DISEASE 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

REVERSIBLE DEMENTIA

Depression Prescription drugs Surgery Environmental changes Social isolation

SENSORY & PERCEPTUAL DEVELOPMENT

Sensation is detection Perception is organization &

interpretation

THE NEWBORN – SENSORY CAPACITY

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.

HEARING – PRENATAL & INFANT

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

SMELL - INFANT

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

TASTE - INFANT

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

VISION

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

DEPTH PERCEPTION

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 VISUAL CLIFF

SENSORY & PERCEPTUAL DEVELOPMENT

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.

SENSORY & PERCEPTUAL DEVELOPMENT – RESEARCH METHODS

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.

PATTERN PERCEPTION

• 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.

FACE PERCEPTION

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 – PERCEPTUAL CONSTANCY

Size constancy ( 3 mos. – 11 years)

Shape constancy ( 3 mos.)

By 12 months, perceptual property of closure

DIFFERENTIATION THEORY

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.

VISUAL EXPECTATIONS

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.

SENSES IN ADULTHOOD

All of the sensory systems with the possible exception of touch experience gradual decline as a person ages.

Vision Hearing Taste Smell

VISION IN ADULTHOOD

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

VISION IN ADULTHOOD

Late Adulthood Dark adaptation is more difficult Glare sensitivity increases Continuation of degeneration of function

from Middle Adulthood Possible retinal degeneration

DISEASES OF THE EYE

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

TASTE & SMELL

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