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• Mitosis produces 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

The Blastula• 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- 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

Benefogens

• 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)

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 DevelopmentPostnatal 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

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 EmpiricismNativism 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?

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 ResearchMethods of Perceptual ResearchMethods of Perceptual ResearchMethods of Perceptual Research

• Visual Preference (Fantz)

• Visual Cliff (E. Gibson & Walk)

• Habituation-Dishabituation

• Operant Conditioning Procedures

Visual PreferenceVisual 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 - FantzLooking Chamber - Fantz

Visual CliffVisual 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. GibsonVisual Cliff - E. Gibson

Habituation-DishabituationHabituation-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 ProceduresOperant 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

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

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 ReflexesExamples of Reflexes

• Consummatory

• Defensive

• Social

Consummatory Reflexes(Watson (1920) eliciting rooting reflex)

Consummatory Reflexes(Watson (1920) eliciting rooting reflex)

• Search

Defensive ReflexesWatson (1920) eliciting Babinski reflex)

Defensive ReflexesWatson (1920) eliciting Babinski reflex)

How Do Reflexes Change?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 4End of Chapter 4