PSYC 206 Lifespan Development Bilge Yagmurlu

Chapter Overview The Periods of Prenatal Development Environmental Conditions and Prenatal Development Teratogens: Sources of Birth Defects 2

The Period of Prenatal Development Divided into three broad periods: Germinal Period Embryonic Period Fetal Period 3

At the cellular level Cell division: These cells initially are all the same. Cell migration & Cell differentiation: Following division cells begin to migrate to different locations. and begin to differentiate both in terms of structure & function. For example, some become the neural tube forming the basis of the brain & the spinal cord. Cell death: The selective death of some cells.

Germinal Period Begins at conception Lasts until implantation Implantation: process by which the organism becomes attached to the uterus 8 to 10 days after conception Cell division 5

How does implantation occur? The First 14 Days implantation: The process beginning about 10 days after conception, in which the developing organism nestles in, and attaches to the placenta that lines the uterus. How does implantation occur? The Most Dangerous Journey Conception Zygote (single cell) Two-celled stage Fallopian tube Ova Sperm Ovum Implantation Ovary 6 6

Embryonic Period Begins at implantation Lasts until the 8th week Cell differentiation Organogenesis Placenta 7

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Placenta The placenta communicates with the developing human through the vessels of the umbilical cord. 9 9

Placenta When the fetus is born, its placenta begins a physiological separation for spontaneous expulsion afterwards (and for this reason is also called the afterbirth). 10 10

Fetal Period Begins at the 9th week Lasts until birth Growth in weight and length Brain and all organ systems increase in complexity Existing structures are refined By 15 weeks the fetus exhibits all movements observable at birth. 11

Fetal Period Movement promotes coordination and refinement of the nervous system Basic sensory capacities developing 12

Characterizing the fetus & its experience Movement ~ 5wks Sensory experience Smell: Amniotic fluid has odor of what mom ate; During fetal breathing, amniotic fluid comes into contact with olfactory receptors Hearing: Internally generated sounds (mom’s heartbeat, breathing, etc.); Externally generated sounds (mom’s voice and people talking to her); Fetus moves & shows heartbeat changes Touch: Grasping, sucking, rubbing, bumping walls of uterus Taste: Swallows amniotic fluid Fetus has a sweet tooth Sight: Negligible

Fetal Period Fetal learning Example: Sandman et al. (1997) experimental study Sample: 32 wk-old fetuses DV: Heart Rate IV: Old vs. new sounds. presented (via a loudspeaker near the mother’s abdomen) fetuses with a speech sound “babi”. 14

Fetal Period Fetal learning: Does learning survive birth? Example: work by DeCasper and Spence (1986) DV: sucking rate IV: “Cat in the Hat” vs. new story Conclusion: prefer the familiar 15

Stages of Prenatal Development Germinal period Zygote Embryonic period Embryo Fetal period Fetus Implantation to Organogenesis +6 weeks Organogenesis to Birth +30 weeks Conception to Implantation 2 weeks

Prenatal Brain Development Brain stem Hindbrain Neural tube (forms spinal cord) Forebrain (a) 25 days Midbrain Prenatal Growth of the Brain How does the brain grow during the periods, or stages, of prenatal development? (b) 50 days (c) 100 days (d) 20 weeks (e) 28 weeks 18 (f) 36 weeks (full term) 18

Environmental Conditions and Prenatal Development Maternal factors (age, nutrition, stress, disease, etc.) Teratogens: Environmental agents that increase risk of deviation in normal development, can lead to abnormalities or death 19

Teratogens Common Teratogens: Effects can vary considerably Drugs Including prescription drugs, caffeine, tobacco, alcohol, marijuana, cocaine, and heroin Infections (including rubella and HIV) Radiation or pollution at high levels Effects can vary considerably 20

Teratogens Dose-response relationship Effects are not uniform: significant individual differences in susceptibility Many harmful agents cause damage only if exposure occurs during a sensitive period Sleeper effects 21 21

Sensitive periods for teratogens

What are the risks at different stages of development? Birth Defects from Teratogens: Time of Exposure and Effect on Major Organs Germinal Period Main Embryonic Period (in weeks) Fetal Period (in weeks) 1 2 3 4 5 6 7 8 9 16 32 38 Common site(s) of action of teratogens Highly critical period Less critical period Central nervous system Neural-tube defects Mental retardation Learning disabilities Heart Arms Legs Lips Cleft lip Ears Low-set malformed ears and deafness Eyes Cataract, glaucoma Teeth Enamel staining Palate Cleft palate Sex organs Masculinization of female genitalia Teratogens often prevent implantation Major congenital anomalies Functional defects and minor anomalies 23 23 Source: Adapted from K.L. Moore & Persaud. 2003

Teratogens Fetal Alcohol Syndrome (FAS) A set of symptoms that includes an abnormally small head and underdeveloped brain, eye abnormalities, congenital heart disease, joint anomalies, and malformations of the face 24

Teratogens: immediate vs. sleeper effects Alcohol Fetal alcohol syndrome (FAS) Low IQ Poor attention Hyperactivity Slow physical growth If no FAS Attention-deficit hyperactivity problems Cigarettes Low birth weight Less attentive to sounds Lower IQ Cancer Illegal Drugs Prematurity Low birth weight Physical defects Breathing problems Addicted at birth Difficult to care for

Gene-environment interactions Individual differences in susceptibility

Teratogens: Environmental Sources of Birth Defects Cranio-facial abnormality Cerebral cortex size

Alcohol crosses the placental barrier and can stunt fetal growth or weight, create distinctive facial stigmata, damage neurons and brain structures, and cause other physical, mental, or behavioral problems. The main effect of FAS is permanent CNS damage, especially to the brain. Developing brain cells and structures are underdeveloped or malformed by prenatal alcohol exposure, often creating an array of primary cognitive and functional disabilities (including poor memory, attention deficits, impulsive behavior, and poor cause-effect reasoning) as well as secondary disabilities (e.g., mental health problems, and drug addiction). The risk of brain damage exists during each trimester, since the fetal brain develops throughout the entire pregnancy.

Individual differences in susceptibility Romitti et al., 1999 DV: Oral cleft defects Predictors: Child’s genes Mother’s smoking & alcohol consumption Incidence 1 in 1000 live births Smoking-alcohol increases incidence at least 2-3 fold Genetic markers and smoking-alcohol increases incidence 3-6 fold

Teratogens Six general principles apply to all teratogens: The susceptibility of the organism depends on its developmental stage. A teratogen’s effects are likely to be specific to a particular organ. Individuals vary in their susceptibility to teratogens. The mother’s physiological state influences susceptibility. The greater the concentration of a teratogenic agent, the greater the risk. Teratogens that have little or no effect on the mother can seriously affect the developing organism

The Newborn’s Condition Assessing the Baby’s Vitality The Apgar Scale Physical condition Brazelton Neonatal Assessment Scale Behavioral condition Primary Goal: Screen for infants at risk Secondary Goal: Predict aspects of future development 31

Physical Condition The Apgar Scale Assesses physical condition Factors rated: Heart rate Respiratory effort Muscle tone Reflex responsivity Color A low score requires immediate medical attention 32

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Behavioral Condition Brazelton Neonatal Assessment Scale Assesses subtle aspects behavior Includes tests of: Reflexes Motor capacities Muscle tone Responsiveness to objects and people Control of own behavior 34

Problems and Complications Prematurity Birth before the 37th week Immature lungs, digestive, or immune systems Low Birth Weight Below 2500 grams Intrauterine growth restrictions 35 35

Closing Thoughts From what you discovered about prenatal development in these slides, what examples can you cite to support the statement, “The most dramatic and extensive transformation of the entire life span occurs before birth?” 36