Psychology of InfancyDefining development, prenatal development,

brain development

D. Messinger, Ph.D.

Questions (single essay format)

Define development. Argue for why you believe development does or does not have an endpoint. Describe genetic and experiential factors in brain development referring to experience expectant and experience dependent factors. Give examples of how prenatal sensory experience impacts sensory development. Describe similarities between the brain development of the postnatal child and differences in the brains of adult humans and macaque monkeys?Is it is all over after age 3? What are some basic patterns of synaptic and brain development in infancy? How they are influenced by experience? What can go wrong in this pattern?Provide examples from Nelson.What is the take-home message of Thursday's reading, The Seductive Allure of Behavioral Epigenetics?

Development defined

Development defined

Individual change that is, normative, non-reversible, relatively stable, and sequential. Normative process

Everyone’s doing it

Non-reversibleReorganization of the entire person

Relatively stableYou can’t go back,

Sequential changeCrawl before you walk

Examples

Is development

Increasing functionality in all things?

Loss of perceptual acuity in non-native languages between 6 & 12 monthsOld-age

Is development

Headed toward a goal?Development has normative outcomes, but time goes forwardprior events cause subsequent events

not the opposite

What does Thompson (2001, p. 21) mean?“A drive to development is inborn, propelling the human infant toward learning and mastery.”

Three models

In class assignment:What would a cross-tab of the transactional model look like?

What does individual development look like?

Individuals Group

Prenatal brain development

Overview of brain growth

Subcortical areas responsible for reflexes develop first

E.g. spinal cord

Followed by cortical areas in a specific progression

What is most human develops last

Most but not all neurons present at birthSynapses developMyelin develops

Cortical Expansion

Similar patterns of cortical expansion between infants and adults as between macaque monkeys and adults“The pattern of human evolutionary expansion is remarkably similar to the pattern of human postnatal expansion”

(Hill et al., 2010)

Bell

Postnatal cortical surface expansion.

Hill J et al. PNAS 2010;107:13135-13140

©2010 by National Academy of Sciences

Fig. 1. Postnatal cortical surface expansion. Maps of postnatal cortical surface expansion on the standard mesh average inflated term infant surfaces for both hemispheres, shown in lateral (A), medial (B), dorsal (C), and ventral (D) views. The absolute expansion scale indicates how many times larger the surface area of a given region is in adulthood relative to that region’s area at term. The relative expansion scale indicates the difference in proportion of total surface area at term birth and adulthood.

Comparison of evolutionary and postnatal cortical surface expansion. (A) Map of regional

evolutionary cortical expansion between an adult macaqueand the average human adult PALS-B12 atlas (right hemisphere only).Evolution expansion scale indicates how many times larger the surface area isin humans relative to the corresponding area in the macaque. (B) Map of human postnatal cortical expansion (combined left and right hemispheres)for comparison (detailed in Fig. 1 legend). (C) Correlation map comparingpostnatal to evolutionary cortical surface expansion.

Different regions, different ratesRegions responsible for lower cognitive functioning develop more rapidlyRegions responsible for higher cognitive functioning develop more slowly

They may have selection pressure to remain immature:

To facilitate the development of regions more crucial for early surivalTo limit overall brain size at birth by focusing on areas most necessary for early survival and keeping the head small (birth canal)

Bell

Writing assignment

What processes do Tierney and Nelson discuss under the concept of Early Stages of Brain Development? Define three of these process.

Overview:http://www.youtube.com/watch?v=YXTA0lUBZW4 1:20-2:19

Increasing differentiation of areas of cortexInfant is born during height of brain developmentTertiary sulci develop from 1 month before to 12 months after birth

Four levels of brain development

From Nelson, 1999

Creation of a tube

Synapses are connections between neurons

Neural migration

Many elements of initial neural migration specified geneticallyBy 20 weeks gestation, 100 billion neurons! 50,000 – 500,000 neurons per minute

Neurons follow path of glial cells outward from ventricles

To form 6 layers of cortex

Proliferation & migration of neurons

General pattern of brain development genetically specified

By 20 weeks, most neurons present3rd - 16th prenatal week most crucialAt 8 weeks, head is half of fetus

But specific connections depend on generic growth processes and sensory-motor stimulation

Trillions of connections still formingTrimming of these connections is developmental task

Neural development: Synaptogensis

Once in place, synapses are overproduced somewhat haphazardly

1 year old has 150% more synapses than adult

These are pruned (diminish) during developmentRepetition of sensory-motor patterns create more specific set of experience dependent synaptic linkages

Time lapse sequences of radial migration (also known as glial guidance) and somal translocation

neurite outgrowthhttp://www.youtube.com/watch?v=n_9YTeEHp1E&NR=1

Typical and Atypical http://www.youtube.com/watch?v=GBIa8G3gBH0&feature=related

Neuron migration

Increase in complexity of neural connections

Like a growing forest

How do the correct synapses form?

15,000 synapses for every cortical neuron

1.8 million per second in first 2 years!Cerebral cortex triples in thickness in 1st year

Sensory and motor neurons must extend to correct brain are and form correct synapses This quantity of information cannot be genetically micro-managed

Two types of experience in brain development

Experience-expectant

Experience dependent

Experience-expectant

“How common early experiences provide essential catalysts for normal brain development”

Early visual stimulation, hearing, exposure to language, coordinating vision and movement,

“The developing brain “expects” and requires these typical human experiences, and relies on them as a component of its growth.”

Experience-dependent

“How individual experience fosters new brain growth and refines existing brain structures” “Can be unique to an individual”

ReadingSinging, music

Neural Darwinism (Edelman)

Use it or lose itWhat is not used, is prunedWhat is used, develops stronger connections

Organism & environment are system that shapes brain

Brain development is guided by environment

Brain enables behavior which shapes brainSynaptic development is not teleological

The fetus as constructing its own development

Fetal behavior impacts physical development

In chicks prevented from moving, cartilage turns to bone

Fetal sensory experience impacts sensory development

Mice whose tongues were anesthetized had malformed cleft palates

Prenatal sensory experience impacts sensory development

Hearing typically develops before sightRats, ducklings, and quail chicks exposed to visual stimulation prenatally

before they normally would

lose hearing ability at birth

Normal sensory development contingent on extra-fetal environment

Differences in the timing of augmented prenatal stimulation led to different patterns of subsequent auditory and visual responsiveness following hatching. When augmented tactile and vestibular stimulation coincided with the onset of auditory function (Days 9-14), embryos subsequently failed to learn a species-typical maternal call prior to hatching.

No effect on normal visual responsiveness to species-typical maternal cues when exposure to tactile and vestibular stimulation coincided with the emergence of visual function (Days 14-19)When exposure took place after the onset of visual functioning (Days 17-22), chicks displayed enhanced responsiveness to the same maternal visual cues.

Honeycutt, H. & R. Lickliter (2003). Developmental Psychobiology 43: 71-81. The influence of prenatal tactile and vestibular stimulation and visual responsiveness in bobwhite quail: A matter of timing

“Promoting early brain development”?

Re-discovery of importance of early experience

“How brain connections grow and change as a result of stimuli from the environment. How early stress can be harmful to the developing brain. Principle of "use it or lose it" Seven ways to support brain development:

http://www.pitc.org/

“Considerable misunderstanding of early brain development occurs when neurons and synapses are considered independently of the development of thinking, feeling, and relating to others.”

Thompson, 2001, p. 29

Is it all over after 3?

Is the course of development set in infancy? Early experience is importantBut, with some exceptions, human beings remain open to the positive effects of additional experience

The same is true for the impact of experience on brain development

How important is it to ‘stimulate your child’s brain’?

Implications for Policy and Programs Sensitive periods & NeuroplasticityFinancial paybackEarly identification and intervention

Fernandez

Abecedarian Intervention Project

• Children who participated in the early intervention program had higher cognitive test scores from the toddler years to age 21.Academic achievement in reading and math was higher from the primary grades through young adulthood. Intervention children completed more years of education

more likely to attend a four-year college.

Intervention children were older when their first child was born. Mothers whose children participated in the program achieved higher educational and employment status than mothers whose children were not in the program.

Results especially pronounced for teen mothers.

Enhanced language development appears to have been instrumental in raising cognitive test scores.

Fernandez

Implications for practice

It is important to provide a safe, warm, supportive, stimulating environment for infantsBut its never too late to improve developmental outcome for an individualAt any point, current conditions are as important as past conditions

Baby media

No flashcards…http://www.psychologicalscience.org/index.php/news/releases/do-babies-learn-vocabulary-from-baby-media-study-says-no.html

Brain Overgrowth in the First Year of Life in Autism

The clinical onset of autism appears to be preceded by 2 phases of brain growth abnormality: a reduced head size at birth and a sudden and excessive increase in head size between 1 to 2 months and 6 to 14 months. Abnormally accelerated rate of growth may serve as an early warning signal of risk for autism

Courchesne, Carper, Akshoomoff, (2003)

Why overgrowth?

Rate of head circumference growth as a function of autism diagnosis and history of autistic regression.

Webb, Sara Jane; Nalty, Theresa; Munson, Jeff; Brock, Catherine; Abbott, Robert; Dawson, Geraldine Journal of Child Neurology, Vol 22(10), Oct 2007, 1182-1190. doi: 10.1177/0883073807306263

Midwifery – the first profession

Birth Process

Prenatal to PostnatalPreparation for Birth

-Braxton Hicks contractions-Hormonal activities (e.g. progesterone -> estrogen = muscle activity)

Stages of Birth1. From womb to birth canal. Longest stage, uterine

contractions (enables mother’s cervix to expand).2. From birth canal to outside. Pushing. 3. Afterbirth. Delivery of the placenta

Survival after Birth-Baby breathes on its own.-Change of blood circulation (oxygenation now occurs from the lungs not the placenta

Romero

Human birth – cephalo-pelvic proportionality

Are human beings evolving?

How might the rise in the rate of delivery by c-section be related to evolution?

Final project ideas

Prenatal maternal stressPrenatal infectionPrenatal behaviorImpact on outcomes (after birth)Embryology: www.ehd.org

www.ehd.org

"In nonhuman primates, the fetus usually emerges with its face toward that of its mother. She may then reach down and pull it up toward her along the normal flexion of its body.

"In humans, however … the close equivalence of cephalopelvic dimensions has resulted in … infant being born facing away from its mother.

In this position, the use of her own hands to assist delivery before the shoulders have emerged could result in pulling the infant against the normal flexion of its body, again with the risk of injury particularly to the nerves of the neck." Wenda R. Trevathan, Human Birth, (New York: Aldine de Gruyter, 1987), p. 89-92

Human birth – a social process

Human birth – graphic content

More medical, ‘produced’ videohttp://video.google.com/videoplay?docid=-7170052415220169972&q=birth+videos

Just video of birthevtv.com

NPR segment on birth process

Messinger

Prenatal development is usually divided into three main periods.

Zygote - covers the first two weeks after conception

ends when the zygote implants into the wall of the mother's uterus.

Embryo - from two to eight weeks following conception

the major organs and bodily systems form

Fetusfrom eight weeks after conception until birth

grows tremendously in size and weight.

Messinger

Zygotic cell differentiation

Messinger

From zygote to embryo

Messinger

The question

The zygote grows through cell divisionMitosis - One for one copying of all 23 chromosomes

All cells contain the same genetic information in their nucleiBut qualitatively different types of cells develop in different parts of the bodyHow does this occur?

Messinger

General processes yield specific outcomes

Cells clump together as a sphereThis changes the extra-cellular environment of cells on the inside and outside of the sphereDifferences in environment impact cell’s genetic make-up to activate different proteins

Messinger

Genes in Environment

Environmental factors influence development from the start

Cells are environmentsThe uterus is an environment

The fetus participates in actively constructing its own development

it is not passively constructed

Messinger

What do you think?

Stem cell debateCloningAssistive reproduction technology

Messinger

Additional readings

Plomin, et al. The genetic basis of complex human behaviors.Plomin, R., & Rutter, M. (1998). Child development, molecular genetics, and what to do with genes once they are found. Child Development, 69(4), 1223-1242. Rutter. M. (in press [2002]. Nature, nurture, and development: From evangelism through science towards policy and practice. Child Development. Collins, W. A., Maccoby, E. E., Steinberg, L., Hetherington, E. M., & Bornstein, M. H. (2000). Contemporary research on parenting: The case for nature and nurture. American Psychologist, 55(2), 218-232.Sleigh, M. J., Columbus, R. F., & Lickliter, R. (1998). Intersensory experience and early perceptual development: Postnatal experience with multimodal maternal cues affects intersensory responsiveness in Bobwhite Quail Chicks. Developmental Psychology, 34(2), 215-223.