NIEER

Policy Recommendations:• Government and business should support prenatal and well-child health care, good nutrition,efforts to eliminate children’s exposures to harmful pollutants and toxins, and high-qualitypreschool programs in striving to support healthy early brain development.

• Early prevention is better and less expensive than later remediation. Health care services,early intervention programs, and preschools should ensure that they provide early hearing,vision, language, cognitive, and behavioral screenings, and link children to necessary services.

• Sensitive interactions with adults do more to promote brain development than any toy, CD, orDVD. Preschools should deliver services that enable adults to have rich interactions with children.

• Preschools should embrace educational approaches that encourage child-oriented discoveryover adult-directed instruction.

• Since social-emotional and cognitive development are intertwined, preschool programsshould recognize and focus on both.

• Exposure to chronic early stress is harmful. Mental health experts can help preschool staffwork with children with behavioral problems and learn to identify and refer children andfamilies to other services as needed.

What We Know:• The most significant advances in brain architecture occur prenatally.

• Brain development is life-long, hierarchical, cumulative, and integrated.

• The brain incorporates experience into its architecture.

• Critical periods are exceptional, not typical, in brain development.

• The developing brain’s flexibility declines over time, but some plasticity endures.

• The young mind is astonishingly active, capable, and self-organizing.

• Developmental neuroscience provides much greater insight into the hazards to avoidin brain development than opportunities for enrichment.

December 2008, Issue 17

Pres

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lPol

icy

Brie

f

Policy Brief series edited byEllen C. Frede, Ph.D., andW. Steven Barnett, Ph.D.

National Institute forEarly Education Research

www.nieer.org

The past decade has seen an upsurge in public understandingof early brain development. News reports, statements bypolicymakers, and commercial marketing of productsfor infants and young children have all contributed toa widespread understanding of the explosive growthof the brain in the early years and that stimulation actsas a catalyst to brain growth. Beyond this, however,most people are unsure what to make of this newknowledge about brain development.1

This policy brief summarizes what is known aboutearly neurobiological development and corrects some ofthe common misunderstandings and misrepresentationsof the research.

Connecting Neurons,Concepts, and PeopleBrain Development and its Implicationsby Ross A. Thompson, Ph.D.

Acknowledgement: Ross Thompson isgrateful to Deanna Gomby for her finecontributions to this brief as an editorand consultant.

2

The study of human brain develop-ment is still in its infancy. New tech-nologies—electroencephalogram(EEG), positron emission tomogra-phy (PET), functional magnetic reso-nance imaging (fMRI)—are nowpermitting more direct examinationof brain functioning than olderapproaches that relied on studiesof animals or behavioral studies ofhumans who had experienced braindamage. Still, the new methods, whichare less invasive and can produceimages of the brain’s activity, are bestused with older children and adultswho can sit still for the examination,and they cannot capture completelyall the simultaneous processes ofgrowth and change that happen soquickly in young children. As a con-sequence, our understanding of thedeveloping brain is based on multiplesources of still-evolving knowledgeand is likely to change in the nextdecade.

The following summarizes themain principles of early brain devel-opment, based on the science at thistime.2 Together, these principles revealthat brain development is the productof an ongoing complex interplaybetween the child’s active mind andthe environment, in the context ofstrong genetic guidance.3

1. The most significantadvances in brain architectureoccur prenatally.During pregnancy, the child’s braingrows more significantly in size andfunction than at any subsequent stageof development. While the fetus is inthe womb, neurons are produced atan astonishing rate (this process iscalled neurulation)—more than250,000 per minute during someperiods.4 The neurons migrate totheir eventual destinations within thebrain and begin to form axons anddendrites to enable the process ofsynaptogenesis, which is the processby which neurons make connections

with other neurons through the cre-ation of electrochemical junctions.

During this period of rapid devel-opment and extending throughoutearly childhood as development con-tinues, the brain is a vulnerableorgan. External hazards, such as viralinfection, drug or alcohol exposure,or ingestion of environmental hazards(such as chemicals found in pesticides,air, food, or water; mercury in fish; orlead exposure from peeling paint inold buildings) are associated with avariety of disorders in brain develop-ment when these harms are experi-enced prenatally or in the early yearsof postnatal life.5 Because of thedeveloping brain’s high need for ener-gy to fuel its growth, prenatal mater-nal malnutrition (particularly defi-ciency in folic acid, iron, and certainother vitamins and nutrients) orpostnatal child malnutrition can havedevastating effects on the developingbrain.6 In addition, chronic stressfor the mother during the prenatalmonths and/or for young children areboth associated with the infusion ofstress hormones in the central nerv-

ous system that in some cases canhave damaging effects on children’sbrain growth.7

2. Neural connections developover an extended period oftime that varies for differentbrain regions.Synaptogenesis begins prenatally andcontinues most rapidly through adoles-cence, although synapses developthroughout life. It occurs earlier forbasic sensory and motor areas of thebrain (such as the areas associatedwith vision and hearing), later forbrain regions governing receptive lan-guage and speech production, and lat-est for the areas of the brain in theprefrontal cortex that are associatedwith higher cognitive functions suchas reasoning and planning.

The process of synaptogenesisinvolves two phases. The first is“blooming.” Under genetic control,an initial overproduction occurs ofsynapses distributed across broadregions of the brain. Blooming variesin timing by brain area but, by the

The Science of Early Brain Development

Preschool Policy Brief | December 2008

end of the child’s first year, the youngbrain is a very dense organ. The sec-ond phase is “pruning.” In this phase,a progressive retraction of synapsesoccurs based partly on experience,which helps determine which synapticconnections are activated and reacti-vated. Multiple activations help tostrengthen and consolidate synapticconnections, while the synapses thatare activated less frequently are morelikely to be eliminated or reabsorbed.8

The timing of these developmen-tal processes parallels changes thatcan be observed in children’s behavioras they grow older. The most essentialbrain functions such as basic sensoryand motor capabilities are consolidat-ed earliest in life, language emergeslater in childhood, while higher cog-nitive processes continue to developinto adolescence. Simpler skills pro-vide the foundation for more sophis-ticated skills.

It is important to emphasize thathealthy brain development requiresboth overproduction and retractionof neural connections. Too many neu-ral connections would ultimately beinefficient, so efforts to increase thenumber of neural connections inyoung children through the provisionof potentially overstimulating earlyexperiences in highly enriched envi-ronments are inconsistent with whatis known about brain development.

3. The brain incorporatesexperience into its develop-ing architecture throughsynaptic overproductionand retraction.9

Synaptic overproduction and retrac-tion allows the human brain to adaptto the requirements of everyday lifeand to changing environmental con-ditions.10 Through experience, thebrain becomes a more refined, effi-cient organ as the neural connectionsrelevant to the skills, language, andcognition for everyday life arestrengthened. But the brain’s respon-siveness to experience also means thatduring times of rapid brain growthsuch as early childhood, negative

experiences (such as those associatedwith chronic, overwhelming stress)can become incorporated into thedeveloping architecture of the brainand possibly result in longer-termnegative consequences.11

While we know that chronic stressis bad for the developing brain, weunfortunately know little about theearly experiences that are essential tobrain development.12 We do knowthat early visual experience is neces-sary to organizing optical brain areasin the occipital cortex,13 and languageexposure is necessary to organizingbrain regions related to receptive andexpressive language.14 But we knowmuch less about the significance ofother kinds of experience, especiallyregarding experiences that might helpthe organization of brain areas rele-vant to thinking, problem-solving,and other higher cognitive functions.

4. Critical periods areexceptional, not typical,in brain development.Critical periods are specific episodesin development when exposure to aparticular environmental influence isrequired for healthy development tooccur. Although critical periods havebeen identified for other animalspecies, and in humans there are criti-cal periods for some basic sensoryfunctions like sight, the complexity ofhuman brain and behavioral develop-ment plus the extended periods ofsynaptogenesis suggest that “sensitive”rather than critical periods are morecommon. In sensitive periods, the rel-evant time periods for environmentalstimulation are broader and moreflexible.15 The concept of sensitiveperiods is more consistent than criti-cal periods with existing knowledgeconcerning the importance of earlylanguage stimulation in organizingrelevant brain regions, and withbehavioral evidence concerning thegrowth of cognitive functions16 andsocial-emotional development.17 The“window of opportunity,” therefore,for stimulating brain growth is widerather than narrow.

Preschool Policy Brief | December 2008 3

The science of brain

development provides an

unprecedented opportunity

to enhance public aware-

ness and generate support

for public policy initiatives

that can benefit young

children and their families,

but such support will

quickly disappear if the

public concludes that

the importance of the

developing brain was

oversold or the science

was misapplied.

5. Brain function is enhanced asneural circuits are myelinated,a process beginning prenatallyand extending throughadolescence.Myelination is the process by whichportions of the neuron become coatedwith a protein that improves insulationand speeds neural transmission.18 Likesynaptogenesis, myelination occursearliest for basic sensory and motorprocesses, and much later for areasgoverning sophisticated cognitiveskills. The influence of myelinationcan be observed in infancy, whensmoother and more coordinated armmovements replace the jerky swipes ofearlier months as myelination enablesmore efficient neural control of motormovement. In other words, at the sametime that blooming and pruning isoccurring, neural connections arefunctioning more efficiently becauseof myelination.

6. Brain development islife-long.Brain development begins prenatallyand continues into early adulthood,particularly in the development ofhigher cognitive functions in the pre-frontal cortex and elsewhere. Thebrain has tremendous adaptive flexi-bility,19 and neuroscientists have alsodiscovered that new neurons continueto be produced in certain areas of theadult brain,20 and new synapses areforged throughout life as a productof experience.

7. The developing brain’sflexibility declines over time,but some plasticity endures.The immature brain is a highly plastic(i.e., flexible and adaptive) organ,capable of incorporating a greatervariety of experiences and influencesthan at later ages.21 The infant brainhas many more neurons and synapsesthan does the mature brain, and manyhave not yet become integrated intobroader circuits or specialized func-tions. This gives the young brain con-siderable functional potential.

As neural connections becomerefined and consolidated throughexperience and as sensitive periodschannel brain growth in specificdirections, the brain’s plasticitydeclines. For example, newborninfants are capable of discriminating

the speech sounds of all of the world’slanguages, but this potential is gradu-ally lost as brain regions relevant tolanguage become progressively organ-ized to perceive the speech sounds ofthe language the child hears at homeand will eventually learn.22 Withincreasing age, therefore, the brainbecomes organized and functionallyadapted to exercise particular skillsand, as a consequence, much of itsearlier potential is lost.

An important implication ofdeclining brain plasticity is that it isbiologically more efficient to preventdifficulties from arising in brain func-tioning than it is to try to remediateproblems that have already devel-oped.23 The potential efficacy of earlyinterventions is increased by thegreater plasticity of the young brainto adapt positively to such interven-tions. By contrast, it may be moredifficult to remedy problems afterthey have developed, as the brain’sfunctional organization has becomeconsolidated around early deficien-cies. Indeed, the interventions thatmay be necessary to remediate laterproblems are likely to be much morecostly and prolonged than early pre-ventive interventions. For example,some language-related delays are besttreated early in life before languagepathways in the brain have beenconsolidated.24

Preschool Policy Brief | December 2008

The immature brain is a highly plastic (i.e., flexible

and adaptive) organ, capable of incorporating a

greater variety of experiences and influences than

at later ages.

4

8. Brain development isintegrated.The public understands that the brainhas functionally specialized areas.What is perhaps less well understood,however, is that the brain is also ahighly integrated organ. Many brainregions, for example, are involved inperceiving, interpreting, and respond-ing to emotional cues,25 and multiplecircuits are associated with the forma-tion and retrieval of memories.26 Theinterconnections among brain areascontribute to the brain’s functionalefficiency.

The best-known example of brainintegration is the integration of thecerebral hemispheres. It has longbeen known that right and left cere-

bral hemispheres of the brain arespecialized for somewhat differentpsychological processes, but the cere-bral hemispheres are functionallyintegrated through the part of thebrain called the corpus callosum.27

Similarly, scientists are now learn-ing that as children grow older, cer-tain areas within their brains becomebetter integrated with one anotherand changes in children’s behaviorresult. For example, as areas of theprefrontal cortex mature, beginningin early childhood and extendingthrough adolescence, they becomeprogressively integrated with earlier-developing brain regions associatedwith memory, emotion, attention, andother cognitive functions. This results

in improved problem-solving skills,learning, behavioral self-control, andemotion regulation through thegrowth of higher-order skills (called“executive functions”) influenced bythe prefrontal cortex.28 These executivefunctions help to regulate memory,attention, and behavior, such asmentally holding and manipulatinginformation in the mind, ignoringirrelevant information to focus atten-tion on the relevant, and inhibitingan initial response in favor of asecondary response. In other words,as their brains develop and becomemore integrated, children becomemore proficient at using their memory,attention, behavior, and emotions instrategic, planful ways.

5Preschool Policy Brief | December 2008

The integration of brain functionsand interconnectivity in brain archi-tecture have practical implications.For example, when stressful experi-ences activate specific neurobiologicaland hormonal systems within thebrain, other systems, including thoseassociated with learning and memory,may also be impaired.29 Consequently,young children who experiencechronic stress may have difficultieswith learning in the classroom. Theimplication: fostering children’s emo-tional well-being will help promotetheir cognitive development andmental achievement.

9. The young mind isastonishingly active, capable,and self-organizing.The developing brain is not an emptyvessel, passively waiting to be filledwith knowledge, but rather an activeorgan that grows through its own

activity. The experiences that pro-mote growth are those that provokethe brain’s activity, often through thechild’s interest and engagement.

There are at least two implicationsof this principle. One is that theexperiences that are developmentallyprovocative will change as the brainmatures. Early in life, for example,an immature brain is influenced bygeneral features of environmentalstimulation (e.g., familiarity or expo-sure to language) but with greatermaturity, more specific and detailedfeatures of the environment becomemore important. If a young child isexposed to influences that are devel-opmentally inappropriate or irrele-vant (e.g., identifying letters to ababy) these influences will not havetheir beneficial effects. Likewise, ifpreschoolers are expected to exertgreater self-control than their brainsare capable, both children and adults

are likely to become frustrated. Inother words, the environments thatfacilitate learning and growth will dif-fer significantly for children of differ-ent ages. A high-quality learning envi-ronment for a fourth-grader is muchdifferent than a high-quality learningenvironment for a 4-year-old becauseof differences in brain development.

Another implication is that inter-action with appropriately responsivesocial partners is one of the most devel-opmentally provocative experiences forthe growing brain. Regardless of thechild’s age, interaction with a sensitiveadult offers much more than anycommercial toy or DVD by providingstimulation that is active and respon-sive, calibrated to the child’s readinessfor new learning, individualized,multimodal, and very engaging.30

There is as yet no mechanical substi-tute for lively interchanges withanother human being.

6 Preschool Policy Brief | December 2008

10. Developmentalneuroscience providesmuch greater insight intothe hazards to avoid inbrain development thanopportunities for enrichment.Developmental neuroscience hashighlighted a broad variety of hazardsto avoid to ensure healthy braindevelopment. Many of these are asso-ciated with poverty, and most are pre-ventable. As described earlier, thesehazards include malnutrition of themother during prenatal growth andof the child during the early years,inadequate health care, and exposureto dangerous chemicals, viruses, envi-ronmental toxins, and chronic stressduring the prenatal and early child-hood years. Prenatal alcohol expo-sure, early sensory deficits that

remain untreated (such as strabismicamblyopia, commonly known as “lazyeye”), accidents (especially thoseinvolving head injury), and extremeneglect or abuse also constitute haz-ards to healthy brain development.

By contrast, beyond recommend-ing attention to health and responsivecare, developmental neuroscience hasmuch less to offer concerning strate-gies for improving the typical courseof brain development. Many of thedevelopmental processes discussedabove unfold on a maturationaltimetable that is largely controlled byour genetics, and so it is not clear thatinterventions can indeed accelerate orimprove the course of typical braingrowth. In addition, the environmen-tal experiences that have been identi-fied to date as important for braindevelopment (e.g., early exposure to

light and sound; hearing language)are hardly exotic interventions. Giventhat, it appears likely that otherimportant environmental catalystswould be commonplace occurrences,and not linked to specially-designedtoys or DVDs.

However, for children experienc-ing cognitive delays and difficulties inlearning, developmental neuroscienceoffers some potential avenues forhelpful intervention.31 Enlisting dev-elopmental neuroscience to createinterventions to assist children at riskof academic delay is one of the moreexciting areas of research in this field.For example, the Tools of the Mindcurriculum is a promising brain-based program that helps youngchildren develop executive functionand self-regulatory skills.32

Preschool Policy Brief | December 2008 7

Sensitive interactions with

adults do more to promote

brain development than

any toy, CD, or DVD that

purports to promote brain

development. Government

regulations should require

and preschools should

deliver services that enable

adults to have rich interac-

tions with children.

Preschool Policy Brief | December 20088

Any brain development findingsshould be interpreted against the richbackdrop of scientific understandingthat already exists concerning children’sbehavioral growth and development.We should expect, in other words,that what we learn from studies of thedeveloping brain will be consistentwith what we already know about thegrowth of cognitive, social, emotional,and other behavioral capacities inchildren.

And indeed it is so.33 Newbornscrave novel stimulation and becomebored with familiarity in a mannerthat is precisely what we would expectto see if the brain were significantly

expanding with new neural connec-tions. Infants acquire proficiency insensory and motor abilities beforethey acquire skill in language or inproblem-solving skills, and thoseearlier skills equip them with essentialcompetencies on which more advancedskills can be built. In addition, thegrowth of children’s self-regulatorycapacities—from sitting still at familygatherings, to playing “red light-greenlight,” to controlling emotional out-bursts—is consistent with what devel-opmental neuroscience concludesconcerning the progressive matura-tion of the prefrontal cortex.

If we forget to connect brain

science with the science of behaviorand development, we run the riskof moving too quickly to embraceservices or programs that do notmake sense for children.34 For example,it is from a narrow focus on specific(sometimes poorly designed) studiesthat misleading conclusions concern-ing the influence of a Mozart sonataor an infant education curriculumon brain development can emerge.

Interpreting Developmental Neuroscience

Preschool Policy Brief | December 2008

Recommendations

• Healthy brain development beginswith good maternal and child healthand nutrition. Government andbusiness should support prenataland well-baby health care as well asprenatal and early childhood nutri-tion programs, sponsor public infor-mation efforts to reduce prenataldrug or alcohol exposure, and workto eliminate children’s exposures toindoor and outdoor pollutants andtoxins that can affect brain develop-ment. Preschool programs shouldmake sure that they provide bal-anced, nutritious diets to childrenenrolled in their programs and thattheir environments are free fromlead and other toxins.

• Because brain plasticity and flexi-bility declines throughout an indi-vidual’s lifetime, early prevention isbetter and less expensive than laterremediation. Health care agencies,early intervention programs, andpreschools should ensure that theyprovide early hearing, vision, lan-guage, cognitive, and behavioralscreenings, and that they link chil-dren to necessary services. Depend-ing on children’s needs, high-qualitypreschool environments may beable to provide the necessary reme-diation (especially with well-trainedproviders), but children with specialneeds should be linked as early aspossible with Part C early interven-tion programs in their communitiesto make sure that they are offeredthe full range of services that mightbe helpful to them. In addition, ifbilingualism is a goal, then earlyintroduction of a second languageduring children’s preschool years isbeneficial.

• Sensitive interactions with an adultare better than any manufacturedtoy, CD, or DVD that purports topromote brain development. Paidfamily leave for new parents andfamily-friendly employer policiescan help give parents the flexibilitythey need to spend time with theiryoung children. Government regula-tions should require and preschoolsshould deliver services that enableadults to have rich interactions withchildren. This means, for example,that every preschool classroomshould have a high teacher-to-childratio, small class sizes, and well-qualified and trained teachers whoknow how to best promote chil-dren’s development. Public aware-ness campaigns and direct serviceprograms to help parents under-stand the importance of rich,responsive social interaction forearly brain development are alsoimportant.

• For most typically developing chil-dren, no special interventions beyondattention to health and responsivecare are likely to be needed to pro-mote brain development. Nonethe-less, because experience affects braindevelopment and because children’sengagement helps determine howmuch they gain from their environ-ments, preschools should embraceeducational approaches that encour-age child-oriented discovery, socialinteraction, language use, activelearning, and appropriate self-regulatory expectations. In suchapproaches, children choose activi-ties based on what captures theirinterests, rather than being drivensolely by adult-directed curricula.

• Social-emotional and cognitivedevelopment are intertwined andpreschool programs should recog-nize and focus on both, especiallyif they are concerned with schoolreadiness. Instructional approachesshould foster children’s social-emo-tional and self-regulatory skills,which are essential for group learn-ing and exercising the brain’s devel-oping capacities, just as much asthey concentrate on early languageor cognitive development.

• Exposure to chronic early stress isharmful, so community-based pro-grams designed to address childabuse and neglect, domestic violence,and parental mental illness areimportant. Because preschool staffencounter families daily, they areoften the first to notice when fami-lies are in crisis (usually becausechildren act out or are unable tocontrol their emotions in class).Preschool staff should therefore betrained and supported to identifychildren and families who are expe-riencing stress and to refer familiesto other community-based servicesas needed. Mental health consulta-tion to preschool staff can help staffwork with children who have beenexposed to chronic stress and havedeveloped behavioral problems.

Preschool programs should make sure that they provide

balanced, nutritious diets to children enrolled in their

programs and that their environments are free from lead

and other toxins.

9

Preschool Policy Brief | December 200810

Conclusion

Understanding developmental neuro-science and its implications for par-enting, practice, and policy remainsa significant challenge more than 10years after the I Am Your Child cam-paign brought early brain develop-ment to public attention. The unset-tled professional opinion about thisissue is reflected in a comparison oftwo articles. The first, published oneyear after the public engagementcampaign, highlights the varietyof educational implications of theemerging brain research and itsimportance to practitioners.35 Theother, appearing 10 years later, reportson an international conference ofdevelopmental scientists and edu-cators who issued a declarationindicating, among other things, that“[n]euroscientific research, at thisstage in its development, does notoffer scientific guidelines for policy,

practice, or parenting.”36 These dis-cordant views reveal that at a timeof remarkable new insights into theprocess of brain development, scien-tists are still debating the broader sig-nificance of this new knowledge. Still,program administrators, policymakers,

and today’s young children andfamilies cannot wait until scientificknowledge is complete. This briefrecommends the most reasonablesteps based on the current state ofour knowledge of early brain andbehavioral development.

Preschools should embrace

educational approaches

that encourage child-

oriented discovery over

adult-directed instruction.

Preschool Policy Brief | December 2008 11

References1 See, e.g., Bostrum, M. (2002), Hearts souls and minds: An analysis ofqualitative research regarding communicating school readiness and otherchild development policies (http://www.frameworksinstitute.org/ecd.html)and other papers from the Frameworks Institute on early childhooddevelopment.2 For more detailed descriptions of brain development, consult: Johnson,M. H. (2005). Developmental cognitive neuroscience (2nd Ed.). Oxford,UK: Blackwell; Nelson, C. A., de Haan, M., & Thomas, K. M. (2006).Neuroscience of cognitive development: The role of experience and the devel-oping brain. Hoboken, NJ: Wiley.3 Nelson et al., (2006).4 Cowan, W. M. (1979). The development of the brain. ScientificAmerican, 241, 112-133.5 Shonkoff, J. P., & Phillips, D. A. (Eds.) (2000). From neurons to neighbor-hoods: The science of early childhood development. Washington, DC:National Academy Press.6 Morgan, B., & Gibson, K. R. (1991). Nutritional and environmentalinteractions in brain development. In K. R. Gibson & A. C. Petersen(Eds.), Brain maturation and cognitive development (pp. 91-106).New York: Aldine de Gruyter. Morgan, B. L. G., & Winick, M. (1985).Pathologic effects of malnutrition on the central nervous system. In H.Sidransky (Ed.), Nutritional pathology - Pathobiochemistry of dietaryimbalances (pp. 161-206). New York: Dekker.7 Center on the Developing Child at Harvard University. (2005). Excessivestress disrupts the architecture of the developing brain. Retrieved December 8,2007 from http://www.developingchild.harvard.edu.8 Nelson et al., (2006).9 Greenough, W. T., & Alcantara, A. A. (1993). The roles of experience indifferent developmental information stage processes. In B. de Boysson-Bardies, S. de Schonen, P. Jusczyk, P. McNeilage, & J. Morton (Eds.),Developmental neurocognition: Speech and face processing in the first year oflife (pp. 3-16). The Netherlands: Kluwer Academic Publishers. Greenough,W. T., & Black, J. R. (1992). Induction of brain structure by experience:Substrates for cognitive development. In M. R. Gunnar & C. A. Nelson(Eds.), Developmental behavioral neuroscience. The Minnesota Symposiaon Child Psychology, Vol. 24 (pp. 155-200). Hillsdale, N.J.: Erlbaum.10 Nowakowski, R. S. (1987). Basic concepts of CNS development. ChildDevelopment, 58, 568-595.11 Center on the Developing Child at Harvard University, (2005).12 Thompson, R. A., & Nelson, C. A. (2001). Developmental science and themedia: Early brain development. American Psychologist, 56, 5-15.13 Katz, L. C., & Shatz, C. J. (1996). Synaptic activity and the constructionof cortical circuits. Science, 274, 1133-1138.14 Newport, E. L., Bavelier, D. & Neville, H. J. (2001). Critical thinking aboutcritical periods: Perspectives on a critical period for language acquisition.In E. Doupoux (Ed.), Language, brain and cognitive development: Essays inhonor of Jacques Mehler (pp. 481-502). Cambridge, MA: MIT Press.15 Bornstein, M. H. (1989). Sensitive periods in development: Structuralcharacteristics and causal interpretations. Psychological Bulletin, 105,179-197.16 Nelson, C. A. (2000). Neural plasticity and human development: Therole of early experience in sculpting memory systems. DevelopmentalScience, 3, 115-130.17 Thompson, R. A. (2001a). Sensitive periods in attachment? In D. Bailey,J. T. Bruer, F. J. Symons, & J. W. Lichtman (Ed.), Critical thinking about

critical periods (pp. 83-106). Baltimore, MD: Paul H. Brookes Publishing.18 Gibson, K. R. (1991b). Myelinization and behavioral development: Acomparative perspective on questions of neoteny, altriciality and intelli-gence. In K. R. Gibson & A. C. Petersen (Eds.), Brain maturation andcognitive development (pp. 29-63). New York: Aldine de Gruyter.19 Nelson et al., (2006).20 Gage, F. H. (2000). Mammalian neural stem cells. Science, 287, 14333-14338. Gould, E., & Gross, C. G. (2002). Neurogenesis in adult mammals:Some progress and problems. Journal of Neuroscience, 22, 619-623.21 Nelson et al., (2006).22 Kuhl, P. K. (2004). Early language acquisition: Cracking the speech code.Nature Reviews Neuroscience, 5, 831-843.23 Knudsen, E. I., Heckman, J. J., Cameron, J. L., & Shonkoff, J. P. (2006).Economic, neurobiological, and behavioral perspectives on buildingAmerica’s future workforce. Proceedings of the National Academy ofSciences, 103, 10155-10162.24 Merzenich. M. M., Jenkins, W. M., Johnston, P., Schreiner, C., Miller, S.L., & Tallal, P. (1996). Temporal processing deficits of language-learningimpaired children ameliorated by training. Science, 271, 77-81. Tallal, P.,Miller, S. L., Bedi, G., Byma, G., Wang, X., Nagarajan, S. J., Srikantan, S.,Schreiner, C., Jenkins, W. M., & Merzenich, M. M. (1996). Language com-prehension in language-learning impaired children improved with acousti-cally modified speech. Science, 271, 81-84.25 LeDoux, J. E. (1996). The emotional brain. New York: Simon & Schuster.26 Eichenbaum, H. (2003). Learning and memory: Brain systems. In L. R.Squire, F. E. Bloom, S. K. McConnell, J. L. Roberts, N. C. Spitzer, & M. J.Zigmond (Eds.), Fundamental neuroscience (2nd Ed). (pp. 1299-1327).New York: Academic Press.27 Bloom, F., Nelson, C. A., & Lazerson, A. (2006). Brain, mind, andbehavior (3rd Ed., Rev.). New York: W. H. Freeman.28 Nelson et al., (2006). Thompson, R. A., Lewis, M. D., & Calkins, S. D.(in press). Reassessing emotion regulation. Child Development Perspectives.29 McEwan, B. S., & Sapolsky, R. M. (1995). Stress and cognitive function.Current Opinion in Neurobiology, 5, 205-216.30 Thompson, R. A. (2001b). Development in the first years of life. TheFuture of Children, 11(1), 20-33.31 Noble, K. G., Tottenham, N., & Casey, B. J. (2005). Neuroscience per-spectives on disparities in school readiness and cognitive achievement.The Future of Children, 15, 71-89.32 Diamond, A., Barnett, W. S., Thomas, J., & Munro, S. (2007). Preschoolprogram improves cognitive control. Science, 318, 1387-1388.33 Thompson, R. A., (2001b).34 Thompson, (2001b).35 Burnes, J. P., & Fox, N. A. (1998). The educational relevance of researchon cognitive neuroscience. Educational Psychology Review, 10, 297-342.36 Hirsh-Pasek, K., & Bruer, J. T. (2007). The brain/education barrier.Science, 317, 1293. The quote is taken from The Santiago Declaration.The declaration also says, “Current brain research offers a promissory note,however, for the future. Developmental models and our understanding oflearning will be aided by studies that reveal the effects of experience onbrain systems working in concert. This work is likely to enhance ourunderstanding of the mechanisms underlying learning.” RetrievedDecember 8, 2007 from www.jsmf.org/declaration.

by Ross A. Thompson, Ph.D.Ross A. Thompson, Ph.D., is a professor of psychology at the University of California, Davis.

His work focuses on early personality and socioemotional development in the context of close relationships.

Acknowledgement:Ross Thompson is grateful to Deanna Gomby for her fine contributions to this brief as an editor and consultant.

Connecting Neurons, Concepts, and People: Brain Development and its Implicationsis issue 17 in a series of briefs developed by the National Institute for Early Education Research.

It may be used with permission, provided there are no changes in the content.

Available online at nieer.org.

This document was prepared with the support of The Pew Charitable Trusts. The Trusts’ Advancing Pre-Kindergarten for Allinitiative seeks to advance high quality prekindergarten for all the nation’s three-and four-year-olds through objective,policy-focused research, state public education campaigns and national outreach. The opinions expressed in this report

are those of the authors and do not necessarily reflect the views of The Pew Charitable Trusts.

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NATIONAL INSTITUTE FOREARLY EDUCATION RESEARCH