Brain development: How genes and experience make us who we are

Transcription

1 Brain development: How genes and experience make us who we are

2 Plan Genes and environment and their interaction Plasticity (ie effects of environment) and its limits (ie critical periods) Lifespan brain development Mechanisms Regional differences

3 Plan Genes and environment and their interaction Plasticity (ie effects of environment) and its limits (ie critical periods) Lifespan brain development Mechanisms Regional differences

4 Genes Behavior Experience

5 Genes and environment: the nature versus nurture debate "Give me a dozen healthy infants & my own specific world to bring them up in, & I'll guarantee to take any one at random & train him to become any type of specialist I might select - doctor, lawyer, artist, merchant, chef & yes, even beggar & thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors." - John B. Watson, 1924

6 Genes and environment: the nature versus nurture debate Compensatory education has been tried and it apparently has failed." - Jensen, 1969 The story of attempts to raise intelligence [by environmental enrichment] is one of high hopes, flamboyant claims, and disappointing results." - Hernstein & Murray, 1994

7 Behavioral genetics Partitions variance in a trait (eg IQ) into genetic variance and environmental variance Surprising range of traits show substantial heritability (IQ, vulnerability to most mental illnesses, personality, political orientation) Clever (but imperfect) methods Adoption studies Twin studies

8 Twin studies Workhorse of behavioral genetics Measure correlations of a trait between twins

9 Twin studies Workhorse of behavioral genetics Measure correlations of a trait between twins A B

10 Twin studies Workhorse of behavioral genetics Measure correlations of a trait between twins eg, at right, fairly high correlation in IQ A B

11 Twin studies The correlation depends on the kind of twins identical or fraternal Identical, monozygotic, share all genes Fraternal, dizygotic, share 50% of genes If a trait is strongly genetic, eg eye color, then If a trait is not genetic, eg language spoken, then

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13 Cortical thickness Schmidtt, Cerebral Cortex, 2008

14 Heritability estimates are not absolute they describe variances in a particular population Turkheimer (Psych Sci, 2003) twin study of intelligence, showing heritability as a function of socioeconomic status

15 Plan Genes and environment and their interaction Plasticity and its limits (ie critical periods) Lifespan brain development Mechanisms Regional differences

16 Gene-environment interaction Caspi, Science, 2002

17 Gene-environment interaction Caspi, Science, 2003

18 Plan Genes and environment and their interaction Plasticity and its limits (ie critical periods) Lifespan brain development Mechanisms Regional differences

19 More on environmental influences: I want to say one word to you, just one word: Plastics Plasticity

20 Plasticity Neuronal connections depend on neuronal activity Neurons that fire together wire together Small amount of neurogenesis as well Can actually change macroscopic size and shape of brain!

21 Plasticity Changes in brain as a result of experience Maguire, PNAS, 2000

22 Plasticity Changes in brain as a result of experience Draganski, Nature, 2004

23 Plan Genes and environment and their interaction Plasticity and its limits (ie critical periods) Lifespan brain development Mechanisms Regional differences

24 Limits on plasticity Critical periods, sensitive periods

25 Vision Critical periods

26 Critical periods Language Studies of second language acquisition

27 Critical periods Language Studies of second language acquisition First language acquisition

28 Plan Genes and environment and their interaction Plasticity and its limits (ie critical periods) Lifespan brain development Mechanisms Regional differences

29 Building a brain Much known about prenatal and postnatal events at the cellular level Generally hard to relate this level to psychological phenomena

30 Prenatal processes Cell birth Cell migration Cell differentiation Cell maturation Synaptogenesis Cell death and synaptic pruning Myelination

31 Postnatal development Synaptogenesis continues

32 Postnatal development Myelination continues Enhances neuronal conduction velocity Continues through young adulthood

33 Postnatal development Pruning continues

34 Plan Genes and environment and their interaction Plasticity and its limits (ie critical periods) Lifespan brain development Mechanisms Regional differences

35 Adolescent brain development Allstate Insurance advertisement

36 Adolescent brain development Two systems maturing at different rates

37 Key Points Genes and environment Both important interact Plasticity Ubiquitous, evident even at macroscopic scale but has its limits, some severe Lifespan brain development Cellular mechanisms and regional differences

38 Questions, comments?