Prenatal Development: Key Stages and Processes

• Chapter 2: Birth and Prenatal Development

Vocabulary

• Conception occurs when sperm joins with an egg.
• A Zygote is a fertilized egg that moves down the fallopian tube and attaches to the uterine wall.

Womb Terminology

• The germinal period spans from 1-2 weeks, involving the zygote and blastocyst.
• The embryonic period lasts from 3-8 weeks, during which the embryo develops.
• The fetal period extends from 9 weeks until birth, during which it is called a fetus.
• Cephalocaudal development proceeds from head to tail, with areas closer to the head developing first.
• Proximodistal development occurs from near to far, with areas closer to the body's center developing first (e.g., heart, lungs).

Important Processes of Cells

• Division involves rapid multiplication, forming inner cell mass.
• Migration happens when cells change location in the inner cell mass.
• Differentiation is when location determines cell specialization.
• Cell death or Apoptosis happens when unneeded cells are discarded

Fetal Cognition

• Habituation is the fetus's response to sounds that diminishes over time.
• Learning occurs within the womb as newborns prefer familiar sounds like their mother's voice.

Fetal Movement

• Movement starts at 5-6 weeks, initially uncoordinated but improves with practice.
• Sleep-wake cycles stabilize during the second half of pregnancy.
• Near the end of pregnancy, fetuses spend most (3/4) of their time sleeping

Fetal Perception

• Some light reaches the womb.
• Touch occurs through infant movement and touching objects.
• Smell and taste are present via amniotic fluid.
• Infants can hear and respond to sounds from outside the womb.

Timeline of Development

• At 2 weeks, the zygote implants in the uterine wall and cells differentiate.
• At 4 weeks, the head and face develop, the heart beats, and blood circulates
• At 5.5-8 weeks, facial features begin to form.
• At week 9, eyes and ears form, internal organs, fingers/toes appear and movements occur
• At 12 weeks, the heart is fully formed, spine, ribs, and the brain are visible.
• At 16 weeks, lower body areas develop rapidly, movement is pronounced, some reflexes are present, and gender can be observed.
• At 20 weeks, facial movements and expressions are present, and the fetus spends most of its time upside down.
• At 28 weeks, the brain and lungs are developed enough for birth, REM and brainwaves are similar to newborns, and the auditory system is active.
• The fetus develops for ~38 weeks before birth.

Newborns

• Newborns sleep about 2/3 of the time, half of which is active (REM) sleep in short increments.
• Newborns communicate mainly through crying, which can reflect hunger, pain, frustration, etc.

DeCasper & Spence, 1986

• Researchers tested newborns' preferences for familiar passages.
• Mothers read stories to fetuses prior to birth.
• Testing used sucking rate to determine if a familiar or novel passage would be read.
• Results showed that infants preferred the familiar passage, demonstrating infant hearing, recognition, and preference, which shows infant cognition.

The Birth Process

• Birth occurs after roughly 38 weeks, signaled by uterine contractions 4-5 minutes apart.
• During dilation, the cervix widens to about 10cm.
• The baby becomes visible and is pushed out through the birth canal, followed by the placenta.
• Infant head plates are not fused, allowing for skull flexibility and longer development in utero.

Terminology

• Teratogens are environmental factors that can harm the fetus like diseases, drugs, or hormone levels.
• The fetus is more vulnerable during critical or sensitive periods.
• Different organs are vulnerable at different times, and harm depends on when teratogen exposure occurs.
• There is a relationship between a teratogen dose and response.

Common Teratogens

• Sexually transmitted diseases can infect infants, and breast milk can transmit infections.

• Thalidomide, a drug from the 1960s, could cause defects like missing limbs if taken during the 2nd month of pregnancy and heroin intake can cause addiction, low birth weight, prematurity or death to the infant

• Marijuana is a drug that can cause slow growth and memory impairment in infants.

• Cocaine usage can cause cognitive delays, birth defects, and irritability.

• Alcohol consumption can lead to fetal alcohol syndrome, causing physical and cognitive deficits.

• Smoking decreases oxygen to the fetus, which may lead to motor development and learning disabilities.

• Radiation (e.g., X-rays) can damage the eyes or CNS while Mercury can cause Minamata disease.

• Pollution and lead are environmental hazards.

• Older parental age - Women giving birth after their mid-thirties have increased risk of Down syndrome, stillbirth, and preterm babies while older paternal age can increase the likelihood of learning disabilities and mental disorders.

• Rubella is a dangerous disease for the infant and if a woman catches Zika during pregnancy, the infant can be born with microcephaly.

• Chapter 3: Genetics

Chromosomes and Genetics

• Sperm and egg each carry 23 chromosomes, combining to form 23 pairs (46 total).
• The new arrangement creates a unique human being.
• The first 22 chromosomes are autosomes, responsible for personality.
• The last two (X and Y chromosomes) are sex chromosomes.
• Egg carries an X, while sperm carries X or Y; XX = female, XY = male.
• Gender is determined by sperm.
• Chromosomes contain DNA, the genetic blueprint.
• DNA contains genes, patterns in DNA.
• There are about 21,000 genes per person.
• Alleles are varying types of the same gene, with two of each, one from each parent.
• Genotype is the set of genes inherited, a person's genetic blueprint.
• Phenotype is the expression or outcome of the genotype, which is influenced by environment and specific alleles.
• Phenotype is determined by allele pairs.
• Homozygous means two of the same type of alleles.
• Heterozygous is two different alleles.
• Dominance determines expression when heterozygous.
• Dominant takes precedence of the trait expressed while recessive is secondary.

Genotype, Phenotype, and Environment

• Nature vs. Nurture is a classic debate; both factors are important.
• Parents' genotypes contribute to the child's genotype.
• The child's genotype contributes to their phenotype.
• The child's environment contributes to their phenotype.
• The child's phenotype contributes to their environment.
• The child's environment contributes to their genotype.

Behavioral Genetics

• Behavioral genetics studies the inheritance of behavioral and psychological characteristics.
• Behavior and psychology are complicated, so is their inheritance.
• Polygenetic inheritance: phenotype is determined by patterns across multiple genes rather than one pair.
• In behavioral genetics, twin studies are often used to isolate genetic contributions.
• Psychological traits in identical twins are compared.
• Adoption studies are used as well, where children are compared to their adopted and biological families.

Brain Development

• A newborn's brain is less than 1/4 its adult size, tripling in size by the 1st birthday.

• Neurogenesis is the creation of new brain cells with about 100 million neurons (created before birth).

• Axon extension consists of axons branching out toward connection points.

• Arborization is the branching of dendrites, which increases neuronal ability to form new connections.

• Myelination is the formation of myelin around axons, beginning before birth and continuing through adolescence.

• Different brain areas myelinate at different times related to infant abilities.

• Synaptogenesis is the generation of new neuronal connections which form trillions of them.

• Synaptogenesis occurs in different areas at different times.

• Hyperconnectivity is when the brain over-connects itself, connections form between unrelated areas, possibly causing synesthesia.

• Synaptic pruning is when unused connections are removed; 40% of connections are pruned away.

• Plasticity is the brain's ability to adapt to the environment and requires less information to be encoded in genes.

• Experience-expectant plasticity consists of neural connections formed based on input your brain expects based on being human.

• Unused brain areas are repurposed for other functions.

• Experience-dependent plasticity involves neural connections that form based on input from personal experience.

• Chapter 5: Seeing, Thinking, Doing

Testing Infants

• The High amplitude sucking paradigm measures the rate at which infants suck on special pacifiers
• Infants suck faster when interested and slower when bored.
• The access to a preferred stimulus can be made dependent on the sucking rate.
• Looking time- This is the ability when infants look at things they like or think are interesting or surprising.
• Preferential looking- Infants will look at the thing they find more interesting.
• Habituation is a method used to demonstrate infant learning, followed by increased attention to a new stimulus.
• Faster habituation may be a predictor for a higher adult IQ.
• Brain responses can be measured to stimuli.

Perception

• An infant's vision is worse than an adult but improves as they get older.
• Infants are extremely near-sighted/myopic at birth, and vision is best 6-9 inches away at birth
• This preference disappears after 8 months when vision sharpens
• Color vision is also poor until about 3 months because their cones are the wrong shape and length,and are less densely packed at the fovea.
• Object segregation: identification of different objects in the visual field.
  • Ability isn't innate, but is learned quickly.
• Perceptual constancy: perceiving an object as unchanging even when viewed under varying conditions.
  • It is inborn as objects seem unchanged even when the distance between you and the object changes.

Motor Development

• It starts with reflexes, including sucking, rooting, grasping, stepping, the Babinski reflex, the Moro reflex, and the tonic-neck reflex.
• Motor milestones consist of individual advantages that lead to independence, increased exposure, and learning.
• At 1 month, infants can lift their chins.
• At 2 months, infants can push themselves up with their hands.
• At 4-5 months, infants can sit with support.
• By 15 months, they can walk by themselves.
• Cultural differences in exposure to movement lead to small the way the infant develops.
• Infant motor skills develop in different stages and have to be adapted to different movements.

Experience Broadens Perception

• Early experience dictates how infant learn.
• This can be displayed using the Visual cliff Experiment
• Novice crawlers didn't fear the cliff; experienced crawlers refused to cross the cliff, which shows a fear of heights develops with experience.
• Scale errors: errors related to sizing and interacting with objects.
  • Objects that are sized wrong tend to not be successfully interacted with because they aren't a proper fit.
• "Sticky mittens": Velcro gloves allow infants to pick up objects.
  • The experience increased interest in objects, object exploration, and reaching and interest in forming social partnerships.

Learning

• Operant Learning: infant learns their actions have outcomes.
• Contingency paradigm: reward is dependent on actions of infant.
• Observational Learning: Tongue protrusion study
  • Babies learn from imitation.
• Light box study: infants imitated the actions of an adult after a delay showing the proof of deferred imitation.
• Dumbbell study: 18-month-old babies watched an adult fail to pull apart a dumbbell toy.
  • When given the toy, children happily pulled it apart themselves.

Cognition

• Violation of Expectancy: Infants were habituated to a board rotating 180° back and forth.
• Object Permanence is a great indicator to see how infants reacted based on visual cues.
• Early social cognition displays that infants were more surprised to see somebody reach to the same location than just seeing the hand and toy together.
• The understanding of how babies react can be studied using social traits.

Piaget

• Chapter 4: Cognitive Development
• Jean Piaget theorized that Children learn about the world through acting on it (exploring, experimenting).
• Scheme: mental representation for acting on a specific object.
• Assimilation: a new aspect is added to an existing scheme.
• Accommodation: an original scheme is refined and expanded in response to a new object.
• Operation: a reversible action. (E.g., turning lights on/off).
• Piaget's Developmental Stages are sensorimotor, preoperational, concrete-operational, and formal-operational.
• Sensorimotor (ages from 0-2 years), children develop schemes for acting on objects.
• 6 substages represent smaller cognitive gains. -Substage 1:( 0-1 month); infants adapt reflexes to specific objects -Substage 2:(1-4 months); infants combine reflexes to form one action. -Substage 3:(4-8 months); infants shows an interest centered outside the self ; Children can't grasp object permanence -Substage 4: (8-12 months); infants search for hidden objects and display basic memory skills -Substage 5: (12-18 months);infants demonstrate curiosity and want to explore the environment around them.
• Substage 6: (18-24 months); infants display enduring mental representations.
• Children leave from the sensorimotor stage when they express object permanence

Preoperational Stage

• lasts from 2-7 years old where children can understand symbols to represent existing objects
• The stage is hallmarked with the tendency to view everything in the world only from the your own perspective which can make an infant a challenge. -Infants tend to emphasize their most obvious feature which can be misleading since the emphasis is on the more obvious features of the parent so everything outside the parent can be deemed irrelevant.
• Tests can be done using operation tasks .An operation is performed which changes only the appearance of the object. -Children overcome overcome Centration to graduate from the stage.

Concrete-Operational Stage

• From 7-12 years old; children have a good understanding of objects based on the surface, not appearance.
• They rely on trial and error rather than coming up with systematic solution.
• They are closely tied to their personal experience.

Formal-Operational Stage

• 12+; children are no longer tied to understanding experiences.

• They understand and use reasoning around how things work to develop theories of the the world.

• Piaget's work is important to understand but his theories of cognitive understanding can vary in consistence and his test underestimate the influence from the people around the child.

Sociocultural Theories

• Sociocultural perspective is the study of understanding social and cognition due to social interaction.
  • Culture can define the abilities of the infant and shape how to learn.
• Vgotsky came up with three phrases to describe the process. -First, directions come from the adults around us. - Second, directions gravitate from the crowd to to silent, private thoughts, -Third, the private speech changes to silent thought
• Intersubjectivity; mutual understanding people share during communication which helps learning. -Joint attention can be used to study communication and how others communicate.
• Social scaffolding: when initial help is given, but slowly removed as children become more independent.
• The state and environment helps when necessary.

Information Processing Theories

• These theories focus on how toddlers reason around themselves.
• Metaphor: the child as a computer system.
  • infants increase processing with the help of biological aids and the growth that increases processing speeds.
• Increased speed of infant ability depends heavily on brain maturation and the environment around them.
• Infants solve issues differently depending on the person that is trying to solve there problem.

Planning

• Children develop their planning abilities at 12 months and they become able to problem solve
• The infant develops with their problem solving skills over time. -Development isn't linear
• Interconnectivity is a factor that impacts many different abilities for an infant.