Chapter 4 Prenatal, Birth, and Postnatal Periods
A Remarkable Story • Transaction between special organism • Zygote • Unique genetic code • Specialized Environment • Species Typical • Fertilization in fallopian tube (oviduct) • Implantation in uterus • At birth- billions of specialized cells capable of surviving in complex environment
Three Prenatal Periods • Ovum-Germinal Period • ~ 2nd - 14th day • Embryonic Period • ~2nd-8th week • Fetal Period • 8th -38th week
Ovum-Germinal Period • Starts as Zygote in fallopian tube • Mitosisproduces duplication of cells • 32 cell ball called morula • Blastula (Blastocyst) differentiates into: • Embryoblast (Inner cell mass) – develops into the embryo • Trophoblast (Outer protective layer) • Becomes amnion, chorio, placenta, allantois (umbilical cord) • Ends at implantation in the uterus wall
Reproduction of Cells during Period of the Ovum • Duplication of undifferentiated cells • As cellular reproduction continues, differentiation begins • By the time it enters uterus, two distinct masses have formed
Embryoblast Inner cell mass becomes the embryo Trophoblast Outer layer of cells becomes fetal membranes amnion chorion allantois Blastula (or blastocyst)- the embryoblast & trophoblast The Blastula
The Blastula- Basic Structures
Implantation in Uterus • Hormones prepare uterine environment • Blastula sends out tendrils • Only 1/2 of zygotes implant • Phase shift in development • A Developmental Cusp • Marks end of Germinal Period • Marks the beginning of Embryonic Period
Implantation • Hormones prepare uterine environment Blastula sends out tendrils • Marks end of Germinal Period • Marks the beginning of Embryonic Period
Three Embryonic Layers • Endoderm • Innermost • Becomes digestive, respiratory, internal organs (pancreas & liver) • Mesoderm • Center Layer • Muscles, bones, circ. system • Ectoderm • Outermost • Hair, Skin, CNS
Period of the Fetus • Starts when all basic structures are complete • Period of refinement for survival in outside world
Laws of Developmental Direction • Cephalo-caudal • Head - tail (foot) • Proximo-distal • Near-far • Gross - fine • basic - refined
Teratogens • Substances or agents present prenatally that cause physical or psychological abnormalities • Laws of developmental direction mean that timing is important • Generally speaking, those having effects during embryonic development will have greater harmful outcomes
Coined term for agents present during prenatal development having a beneficial outcome E.G.: AZT (Zidovudine – ZDV) HIV infection Folic Acid Neural tube disorders (spina bifida) Benefogens
Teratogen Categories • Maternal Diseases • Drugs • Environmental Hazards • Maternal Characteristics
Maternal Diseases • Toxoplasmosis • Cytomegalovirus (CMV) • Rubella • Genital Herpes
Drugs • Cigarette Smoking • Alcohol Intake
Environmental Hazards • Radiation
Maternal Characteristics • Maternal Age • Malnutrition • Effect in Last Trimester • Nutritional demands of late fetus is greatest
Reproductive Risk versus Caretaking Casualty • Reproductive risks - pre & perinatal events • Impaired - unimpaired • Caretaking Casualty - postnatal events • nonfacilitative - facilitative environment • vulnerable - nonvulnerable organism
Postnatal Development The Remarkable Newborn
Assessing the Neonate • Apgar • Brazelton Neonatal Behavioral Assessment Scale • NBAS-R • 28 behavioral • 18 Reflexes • 7 Areas: • Habituation, social interaction, motor, state organization, state regulation, autonomic system, reflexes
The Ability to Respond to the Environment • Sensory Capability - Receptors • vision • hearing • smelling • tasting • feeling • Sensation - firing of receptors by stimulus • Perception - interpretation of sensory input
Nativism versus Empiricism • Nativism - innate - nature • Empiricism - experience - nurture • Behavioral Systems Approach – • Perception is due to both
How Do We Know the Sensory/Perceptual Capabilities of the Infant? • Common to all methods - Change in Behavior correlated with change in Stimulus
Methods of Perceptual Research • Visual Preference (Fantz) • Visual Cliff (E. Gibson & Walk) • Habituation-Dishabituation • Operant Conditioning Procedures
Visual Preference • Looking Chamber • Reflection of stimulus on cornea • The “Basic Problem” • Change in behavior - time gazing • Change in stimulus - different visual stimuli • Limitations - • The Coke vs. Pepsi Problem • There may be perception even though there is no preference
Looking Chamber - Fantz
Visual Cliff • Depth Perception • “Deep” vs. “Shallow” end • Mother entices the child to crawl • Limitations • Child or kid must be ambulatory • Overcome by monitoring heart rate of babies suspended over each end (Campos)
Visual Cliff - E. Gibson
Habituation-Dishabituation • Babies can’t suck & listen (watch) at same time. • Establish sucking response • Disrupt it with repeated stimulus (e.g., “Pa”) • With repetition of Pa, child habituates • sucking returns • A new stimulus (e.g., “Ba”) is introduced • If child perceives difference between Ba & Pa, sucking stops - Dishabituation
Operant Procedures • Behaviors which are reinforced become more frequent • Researcher reinforces response to one stimulus and not to another • If child perceives difference between stimuli than will respond more to reinforced stimulus
Operant Conditioning Procedures • Perception • Responses: e.g., head turning, sucking, kicking • Reinforcers: e.g., mother’s voice, milk, visual stimuli, heartbeat. • Memory & Cognition • Kicking mobile in presence of an X produces conjugate reinforcement • In later testing immediate kicking when X is present shows recall of contingency (remembering)
Operant Conditioning Procedures • Early Perception • Dr. Seuss passages read by mothers in last trimester. • Infants suck to produce mother-read passages. • Early Socialization • Infant social referencing.
Perceptual Abilities as Universal Behaviors • Some abilities are hard wired • Examples • Detect light from dark • Detect horizontal from vertical • Detect sound (phoneme) boundaries
Reflexes as Universal Behaviors • Hard - Wired • Present at birth • Do not need much experience • Unlearned thus “Unconditioned” • Reflex is not a behavior but stimulus-behavior relationship
Examples of Reflexes • Consummatory • Defensive • Social
Consummatory Reflexes(Watson (1920) eliciting rooting reflex) • Search
Defensive ReflexesWatson (1920) eliciting Babinski reflex)
How Do Reflexes Change? • 1. Reflexes May Stay the Same • 2. Reflexes May Disappear • 3. Reflexes May Be Elicited by New Stimuli - Respondent Conditioning • 4. Reflexes May be Elaborated into New Behaviors - Operant Conditioning
End of Chapter 4
