Lecture 04: Brain Development and Sensation and Perception

What percentage of zygotes successfully complete the germinal stage of development?

a) 0%

b) 25%

c) 50%

d) 75%

e) 100%

25%

Which of the following is/are incorrect?

a) Lanugo is a white, cheesy covering that helps prevent chapped skin.

b) Vernix is a fine layer of body hair to help the lanugo cover the body.

c) The age of viability is between 22 and 28 weeks.

d) The fetus’ movement may be felt by the mother for the first time in the 4th to 6th months of pregnancy.

e) Two of these options are incorrect.

f) All of these options are incorrect.

• Two of these options are incorrect.

  • A and b (definitions are mismatched)

Roxanne is heterozygous for sickle cell anemia. If she has offspring with a homozygous partner who does not have sickle cell anemia, what is the likelihood that Roxanne’s offspring will have sickle cell anemia?

a) 0%

b) 25%

c) 50%

d) 75%

e) 100%

• 0%

• No homozygous recessive children (sickle cell anemia is recessive) none of the children will have sickle cell disease

• They will have sickle cell trait (different than sickle cell disease) but thats not what the question is asking

Germinal stage

• 1st stage of prenatal development

• 0-2weeks (conception until implantation to the uterine wall)

The embryonic stage

• occurs from 3-8 weeks gestation.

• During this stage, rapid development occurs.

• Major organs develop! In fact, all major organs are formed and the heart begins to beat!

• During this stage, the embryonic disk differentiates into three cell layers:

  • Ectoderm

  • Mesoderm

  • Endoderm

Ectoderm

• becomes nervous system, skin & hair.

• Outside layer of embryonic disk

Mesoderm

becomes the muscles, bones and circulatory system.

Endoderm

becomes the digestive system, lungs, urinary tract, and other vital organs.

The Neuron

• are the basic units of the brain.

• Transmit electrical and chemical signals across synapses (space between the dendrites).

• Most formed by end of second trimester (end of 6th month).

Structure of the neuron

Brain Growth Spurt

• Beginning 7 months gestation and lasting to 2 years of age.

• Brain weight increases dramatically from 25% of its adult weight (at birth) to 75% of its adult weight (by age 2).

What accounts for brain growth?

1. Myelination

2. Synaptogenesis

Glia cells

• are a type of nerve cell and major contributor to brain growth.

• more numerous than neurons.

• serve supportive functions, including:

  • Nourishing cells.

  • Facilitating transport.

  • Managing debris and waste removal.

Oligodendrocytes

• a type of glia cell

• encases neurons in insulating sheets called myelin.

Myelinization:

• process of coating neurons with myelin sheath.

• Myelin sheath acts as an insulator to speed the transmission of neural impulses along the axon of the neuron.

• Allows brain to communicate more efficiently with the rest of the body

• Sensory pathways to brain myelinated at birth.

• Frontal cortex is not fully myelinated until adolescence or early adulthood

  • At 25

  • Also part of the reason why toddlers get distracted or bored with one thing very quickly

• Ex. If you asked a 1 year old vs 2 yr old “what’s 2+2” the 1 yr old will take more time to answer partly because they don’t have as much myelinization, meaning it takes longer to process info

• Increased myelination = enhanced motor ability, attention span, information processing

Which direction does myelination occur

• cephalocaudal

• proximal distal

cephalocaudal

• “Top to bottom”

• Things at top of head get myelinated before things further away from head

proximal distal

Myelination will occur first at things at centre of body before things further away from body

Synaptogenesis

• Recall, neurons transmit information via synapses.

• Synaptogenesis (formation of synaptic connections) proceeds rapidly.

  • Infants when born will have more neural connections than adults do

  • So half of neurons that are formed when child is young also die when child is young

• Brain plasticity—the brain is shaped by experience.

• E.g., Synaptic pruning (refers to the refinement and elimination of neurons).

  • Getting rid of neurons that are not used

  • Starts at time of birth and ends at sexual maturation

• Neurons and synapses that are most often stimulated continue to function.

  • If you don’t use it, you’ll loose it

Perceptual Narrowing

• Babies are very good at discriminating different stimuli

• Babies are born as “citizens of the world” and become culture bound perceivers.

  • Babies can be born anywhere in the world and learn the language of that place no matter their ethnicity

  • Can’t do that with an adult

• Perceptual Narrowing: increased sensitivity to frequently encountered stimuli and reduced sensitivity to infrequently encountered stimuli.

  • We will be good at stimuli we frequently increase

• Synaptic pruning may lead to perceptual narrowing

What path does perceptual narrowing follow?

• X axis :

  • prenatal (before birth )development is left of dotted line

  • Postnatal (after birth) development is right of dotted line

• y axis: how good is relative discriminability (perceptually between different stimuli)

3 theories for perceptual narrowing

• Universal theory

• Attunement theory

• Perceptual learning theory

Universal theory

• Thought to be the answer when it was proven that infants are actually outperforming adults ability to discriminate between different stimuli

• Perception discrimination abilities are fully developed prenatally, and after birth we need exposure to maintain abilities

• If we don’t get exposure, abilities will be lost

Attunement theory

• Data today supports this theory the most

• We have partially developed perceptual discrimination, and after birth they can either be facilitated, maintained, or lost

• If we don’t have experience: lost

• If we have some experience: maintained

• Emerson and exposure : facilitation and enhancement of perceptual abilities

Perceptual learning theory

• When infants are born, they have underdeveloped perceptual ability

• Only through induction they will increase perceptual discrimination skills

• After birth they need exposure to strengthen this skill

• If they don’t get exposure, they won’t get perceptual discrimination ability

• Experience was the answer until it was proven that infants are actually outperforming adults ability to discriminate between different stimuli

  • Universal theory was born

Development of the Brain

• Not all parts of the brain develop at the same rate.

• At birth, the most highly developed areas are the subcortical brain centers.

  • Lower brain centres

  • Control reflex’s and biological function (digestion, respiration and elimination)

  • These brain structures located deep in brain and include pituitary gland, limbic structure and basal ganglia

• Surrounding structures are cerebrum and cerebral cortex (impacted by voluntary bodily movement, perception, higher intellectual activities like learning, thinking and production of language)

• The first areas of the cerebrum to mature are the primary motor areas (waving of arms) and primary sensory areas (vision, hearing, smelling, tasting)

  • Piagets first stage of cognitive development had to do with primary sensory areas because this is what they are good at birth and the first to develop

At 6 months newborn reflexes

• Disappear

• This is because the higher cortical centres of brain or getting control over more primitive more subcortical areas of brain

Frontal lobe

Decision making

motor cortex

Body movements

Sensory cortex

Body sensation

Parietal lobe

Perception

Occipital lobe

Vision

Wernickes area

Understanding spoken language

Cerebellum

Equilibrium coordination (balance and posture)

Spinal cord

Transmission of neural impulses to and from the brain

Auditory cortex

Hearing

Temporal lobe

Verbal memory

Broncos area

Speech production

Diagram of brain NEED TO MEMORIZE

The Anatomy of the Brain

• The cerebrum consists of 2 hemispheres connected by the corpus callosum (band of fibres)

• Each of the hemispheres is covered by a cerebral cortex.

  • Outer grey matter layer that controls sensoral and motor processes, perception and intellectual functioning

Left hemisphere

• Control right side of body

• centres for speech, hearing, verbal memory, decision making, language processing and expressing of positive emotion

Right hemisphere

• Controls left side of body

• Centres for visual and spatial processing, nonlinguistic sounds (music), touch sensation and expression of negative emotion

Cerebral lateralization

• is the specialization of brain functions in the left and right cerebral hemispheres.

• occurs during the prenatal period.

• What evidence do we have for this?→ preference for one side of body over the other)

  • Nero imaging tech

  • Some behavioural evidence: 2/3 fetuses end up positioned in womb with right ear facing outward. Gives them a right ear advantage and leads us to think that left hemisphere is for language processing

  • Speech sounds stimulate more brain activity in left hemisphere than right

  • Newborns turn to right then left when they lie on back. And later they will reach for objects with right hand

• By birth, the brain is not completely specialized.

• Specialization happens throughout childhood (e.g., handedness (right vs left) is established by 2 years of age).

  • 9/10 adults will be right handed

• 32% of preschoolers will prefer one side of body

• More than half of adolescence will rely on one side of body

A neonate is born with _____ % of an adult’s brain and develops to _____% by 2 years of age through the brain’s growth spurt.

a) 25; 75

b) 30; 60

c) 50; 75

d) 50; 100

e) 25; 50

a) 25; 75

Michael thinks that his baby is born with all of their discrimination abilities and will either maintain or loose these abilities based upon the input received. What theory does Michael believe discrimination abilities follow?

a) Attunement Theory

b) Universal Theory

c) Perceptual Learning Theory

d) Perceptual Narrowing Theory

b) Universal Theory

Newborn Reflexes

• Survival Reflexes

• Primitive Reflexes

• Indication of brain development

Survival reflexes

• Needed for basic function

• Breathing , sucking and swallowing

• Rooting reflex

Rooting reflex

• Side of check stroked, baby turns head to direction of stimulus

• Great for feeding purposes. Help infant search for food and find something to suck on

sucking and swallowing Reflex

• Pressure at top of infants mouth, they will suck

• Good for feeding, when nipple or bottle enters their mouth they know to suck at get food

• Also positive reinforcement for caregiver who sees baby soothed, and helps with bonding process

Primitive reflexes

• No adaptive or survival important

• Remnants of evolutionary history that were useless at one point in time, not anymore

• Controlled by subcortical part of brain

• Gradually disappear at 1 yrs old especially at 6months, sign of higher brain development

• Grasping or babinski reflex

Babinki reflex

• Stoke bottom of baby foot, the toes will fan out and curl back

• Not sure why this exists or was once useful

Grasping reflex

• Put your finger in babies palm, they will grasp finger

• Not sure why this exists or was once useful

How are reflexes connected to brain development

• By 6 months, reflexes have disappeared indicating that higher cortical centers are assuming proper control over the more primitive subcortical areas of the brain.

• Lingering of primitive reflexes is a sign of problem

If you stroke the bottom of a baby’s foot, what do you expect to happen and what is this reflex called?

a) The baby’s toes will curl; Babinski reflex.

b) The baby’s toes will bend back; Rooting reflex.

c) The baby’s toes will fan out; Babinski reflex.

d) The baby’s leg will kick; Rooting reflex.

e) The baby’s toes will be tickled.

c) The baby’s toes will fan out; Babinski reflex.

Sensation

• Information received by the sense organs

• i.e., brain receives input from the eyes

Perception

• Interpretation of the information received from the sense organs

• i.e., brain makes sense of the input received from the eyes

Sensation & Perception: Illusions

• Example 1: we all see the same picture, but some people perceive dancer spinning clockwise, counterclockwise or both

• Example 2: we all see same picture (sensation) but some people perceive young lady, old lady or both

Jen sees this image as a grey and green shoe, whereas John sees it as a white and pink shoe. This is an example of differences in their _____ of the shoe.

A. Sensory understanding

B. Sensation

C. Visual processing

D. Perception

D. Perception

Early Controversies

• Nature vs nurture

• Enrichment vs differentiation

  • Is reality simply “out there” to be detected by our senses? OR Do we construct our own interpretations of reality based on our experiences?

Nurture

• William James

• Newborn as a blank slate (tabula rasa)

• Learn to interpret sensations

Nature

• Descartes and Immanuel Kant

• Perceptual abilities are innate

• i.e., Born with an understanding of spatial relations (objects far away look smaller and get bigger as they move closer)

Enrichment Theory

• Cognition enriches sensory experience

• Our knowledge helps construct meaning from sensory stimulation

• We have to use cognitive schemas that we already have to make sense of world

• Ex. People that can identify the song after one or two notes. They use the already existing schema (or memory of that song) to answer correctly

Differentiation Theory

• Detecting distinctive features allows for discrimination between experiences

• Everything is already there in object, but we have to take features from that object to help us understand how it is different from another object

• All information we need is present in sensory environment, all we have to do is detect distinctive features

• Ex. When children use the word”dog” to refer to every small furry creature. As they grow older they can differentiate between different animals (bunny and dog)

Development of Perception: Timeline (order in quickest to slowest to mature)

1. taste, smell, touch

2. Hearing

3. Vision

Taste

• Highly developed at birth (even in utero)

• Taste preferences at birth - sweet tooth

  • Newborns found to suck faster and longer for liquids that are sweet opposed to other tastes

• Elicits different facial expressions (even in infants at 2 hrs old)

  • Sweet → pleasant expression

  • Sour → pleasant expression

Smell

• Present very early

• Facial expressions of disgust

• Preference for the odor of milk to that of amniotic fluid as early as 4 days after birth

• Discriminates own mother from other women at 1-2 weeks old based off the smell of mother’s breast and armpits

Touch

• Developed in the womb

• Grasping of umbilical cord, thumb sucking

• Therapeutic benefits of touch → lower stress level and help promote healthy neural activity

• Develops earliest around mouth, then palm of hands, and soles of feet to explore environment

• Sensitive to temperature and pain (even 1 day old infant will cry to needle)

• Benefits of skin-to-skin contact Reduces infant crying by 82% in response to pain like needle

Hearing

• 1st few hours of life, baby hearing is as good as an adult’s with a cold. Could be because of fluids that got in ear during birth

• Newborns can discriminate sounds that differ in:

  • Loudness, duration, detection & frequency

• Hearing improves in 4-6 months

• Newborns can discriminate mother’s voice

  • Prenatal learning influencing neonatal preferences

  • Baby will suck faster to hear recording of their mothers voice as opposed to voice of another women

  • Baby will also suck faster when mother repeats a passage that she read to baby while pregnant

• At birth, more developed than visual ability

• Can be disrupted by otitis media

otitis media

• Bacterial infection in middle ear may produce mild to moderate hearing loss that can last months

• 6 months - 3 yrs old hit the hardest

• Mostly found in infants and preschoolers in canada

• 75% of children affected at least once, reoccurrence is common

• Developmentalists thought reoccurring infections will affect child’s ability to understand another persons speech Which will further harm their ability for their overall language development and social and cognitive skills

Vision

• Least matured sense at birth

  • However sensitivity to light

  • Can track stimulus with eyes if it moves slowly enough

• Visual acuity of 20/400 → legally blind

• Have trouble bringing stimuli into focus

• Reaches adult level at 12 months old

• More likely to track with eyes and head stimuli of faces than other objects

• Newborn preference for their mother’s face

• 2-3 months -> basic colour discrimination

• 4 months -> grouping shades into colour categories

  • Light blue and royal blue are both blue

How Can We Study Infant Perception?

• Preference method

  • Video coding

  • Eye tracking

• Habituation Method

  • Discriminable stimuli

• High Amplitude- Sucking Method

  • Preference abilities

Preference Technique

• Preference for one stimuli over another

  • Are the two stimuli discriminable? (Can they tell stimuli apart)

  • Is one stimuli preferred more than the other?

• Fantz’ Looking Chamber (1956)

• Video coding, eye-tracking (used today)

  • Video coding : record baby face when they look at stimuli, human watches recording and sees which stimuli baby looked at for longer

  • Eye tracker : live tack pupil movement and tell us where child was looking

Fantz’ Looking Chamber

• Infants placed on back and shown 2 stimuli

• Observer hovering over and recording how much time infant spent looking at each stimuli

• If they looked at one stimuli over the other, that stimuli was more favourable

• Faces looked at longer than other stimuli

Preference Technique: Sounds

• Record their looking time to pictures for audios that play different sounds

• Infant directed-speech (how you talk to baby→ baby voice) versus adult-directed speech (normal voice)

• Infants looked at picture that corresponded with Infant directed-speech longer showing favour ability

Shortcoming with using Preference Technique

If baby showed no preference to stimuli, we don’t know if thats because they failed to discriminate stimuli or if they found both stimuli to be equality interesting

Habituation

Less and less attention directed to a stimulus that has become familiar through repetition

Dishabituation

Increase in attention that occurs when a stimuli changes

Habituation Method

• Baby is repeatedly shown same stimuli over and over and then interest in that stimuli decreases because they are familiar with that object

• Interest in object measured by head or eye movements, change in respiration or change in heart rate

• Baby recognizes that they’ve seen something before, and so they have less interest or attention towards that

• Researcher do this by

  1. Show baby same object a lot until they show decreased interest (habituation)

  2. Then introduce new stimulus

  3. if infant can discriminate between the 2, they will dishabituate when looking at new stimulus (show interest and increased attention)

Willow is a 6-month-old infant, she is shown a blue-coloured card repeatedly. If the colour of the card is now changed to green, and Willow displays increased interest, what can we infer?

A. Willow is not able to perceive the difference between the two cards.

B. Willow can perceive the difference between the two cards.

C. Willow prefers the green card to the blue card.

D. Willow prefers the blue card to the green card.

B. Willow can perceive the difference between the two cards.

High-Amplitude Sucking Method

• Examining infant discrimination and preference abilities

• Birth – 4 months old

• Based on variation in the rate of sucking on a special pacifier

• Special pacifier has some electric circuitry

• Researchers need to determine baseline sucking (what rate does baby normally suck at)

• Then when baby sucks faster, the pacifier will introduce a new stimuli

• If baby find this stimuli interesting they can make it last longer by displaying bursts of high speed sucking

• When baby is no longer interested, sucking will return to baseline, and stimuli from projector will go away

• Ex. High amplitude triggers mothers voice, low amplitude triggers stranger women voice. If baby continues to engage in high amplitude sucking, we can infer they prefer their mother’s voice

• Usually only used for sound stimuli because at 4 months vision is not as developed

Ensemble perception

• Ability to extract summery information from complex scenes

• Reduces cognitive load because it would be lots of effort to notice every emotion

• We can extract what the average emotion is, for example in this pic, average emotion is confused, even though there are a few happy faces