BRAIN & PERCEPTUAL DEVELOPMENT
 Feldman
Modules 3-2 & 3-3
BRAIN DEVELOPMENT
•
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
SYNAPTIC TRANSMISSION
BRAIN DEVELOPMENT SYNAPTOGENESIS
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 – SYNAPTIC
PRUNING



Experience determines brain
development.
Neurons not stimulated lose their
synaptic connections.
Neurons often stimulated strengthen
connections by growth of new dendrites
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
CEREBRAL CORTEX –
LATERALIZATION & PLASTICITY
•
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 DEVELOPMENT – SENSITIVE
PERIODS
•
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 UNDERSTIMULATION
•
Results in deficits in:
Concentration
Attention
Anger
and other impulse control
BRAIN DEVELOPMENT OVERSTIMULATION
•
Does not result in geniuses.
•
May cause infant withdrawal.
•
May lead to disappointed parents.
•
May cause strain between infants and
parents.
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
 Starts
to 50% of people over age 80 are affected
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


Orienting & tracking


Decreased responsiveness (looking, sucking, heartrate,
respiration)
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)
4. Possible outcome: Screen
drops, revealing one object.
1. Objects placed
in case.
2. Screen
comes up.
3. One object
is removed.
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