Today's Topics

  • Wrap-up on evolution
  • The development of the nervous system

Prenatal brain development

Insemination

  • 3-4 days before or up to 1-2 days after…
    • Ovulation

Fertilization

  • Within ~ 24 hrs of ovulation

Implantation

  • ~ 6 days after fertilization

Early embryogenesis

Formation of neural tube (neurulation)

  • Embryonic layers: ectoderm, mesoderm, endoderm
  • ~18-26 days
  • Failures of neural tube closure
    • Spina bifida
    • Anencephaly
  • Neural tube becomes
    • Ventricles
    • Central canal of spinal cord

Neurogenesis and gliogenesis

  • Neuroepithelium cell layer lines neural tube
  • Neural stem cells
    • Undergo symmetric & asymmetric cell division
    • Generate glia, neurons, and basal progenitor cells

Zika and microcephaly

Radial glia

Cell migration

Radial unit hypothesis

Migration

Migration

Glial migration

Axon growth cone

Axons follow

  • Chemoattractants
    • e.g., Nerve Growth Factor (NGF)
  • Chemorepellents
  • Receptors in growth cone detect chemical gradients

Differentiation

  • Neuron vs. glial cell
  • Cell type
  • NTs released
  • Where to connect

Differential gene expression in PFC vs. other

Infancy & Early Childhood

Synaptogenesis

Proliferation, pruning

  • Early proliferation
  • Later pruning
  • Rates, peaks differ by area

Apoptosis

  • Programmed cell death
  • 20-80%, varies by area
  • Spinal cord >> cortex
  • Quantity of nerve growth factors (NGF) influences

Apoptosis and cortical expansion

Synaptic rearrangement

Synaptic rearrangement

  • Progressive phase: growth rate >> loss rate
  • Regressive phase: growth rate << loss rate

Myelination

Myelination

  • Neonatal brain largely unmyelinated
  • Gradual myelination, peaks in mid-20s
  • Non-uniform pattern
    • Spinal cord before brain
    • Sensory before motor

Gyral development

Structural development

Postnatal patterns of synaptogenesis

Myelination across human development

Networks in the brain

Functional connectivity

The "development" of developmental connectomics

Myelination changes "network" properties

Synaptic rearrangment, myelination change cortical thickness

(Gogtay et al., 2004)

(Shaw et al., 2008)

(Shaw et al., 2008)

(Shaw et al., 2008)

Changes in brain energetics

Gene expression across development

Summary of developmental milestones

Prenatal

  • Neuro- and gliogenesis
  • Migration
  • Synaptogenesis begins
  • Differentiation
  • Apoptosis
  • Myelination begins
  • Infant gene expression ≠ Adult

Postnatal

  • Synaptogenesis
  • Cortical expansion, activity-dependent change
  • Then cubic, quadratic, or linear declines in cortical thickness
  • Myelination
  • Connectivity changes (esp within networks)
  • Prolonged period of postnatal/pre-reproductive development (Konner, 2011)

How brain development clarifies anatomical structure

3-4 weeks

4 weeks

~4 weeks

6 weeks

~6 weeks

Beyond

Organization of the brain

Major division Ventricular Landmark Embryonic Division Structure
Forebrain Lateral Telencephalon Cerebral cortex
Basal ganglia
Hippocampus, amygdala
Third Diencephalon Thalamus
Hypothalamus
Midbrain Cerebral Aqueduct Mesencephalon Tectum, tegmentum

Organization of the brain

Major division Ventricular Landmark Embryonic Division Structure
Hindbrain 4th Metencephalon Cerebellum, pons
– Mylencephalon Medulla oblongata

From structural development to functional development

Next time…

  • Perception

References

Baumann, N., & Pham-Dinh, D. (2001). Biology of oligodendrocyte and myelin in the mammalian central nervous system. Physiological Reviews, 81(2), 871–927. https://doi.org/10.1152/physrev.2001.81.2.871

Cao, M., Huang, H., & He, Y. (2017). Developmental connectomics from infancy through early childhood. Trends in Neuroscience, 40(8), 494–506. https://doi.org/10.1016/j.tins.2017.06.003

Chi, J. G., Dooling, E. C., & Gilles, F. H. (1977). Gyral development of the human brain. Ann. Neurol., 1(1), 86–93. https://doi.org/10.1002/ana.410010109

Gogtay, N., Giedd, J. N., Lusk, L., Hayashi, K. M., Greenstein, D., Vaituzis, A. C., … Thompson, P. M. (2004). Dynamic mapping of human cortical development during childhood through early adulthood. Proc. Natl. Acad. Sci. U. S. A., 101(21), 8174–8179. https://doi.org/10.1073/pnas.0402680101

Götz, M., & Huttner, W. B. (2005). The cell biology of neurogenesis. Nat. Rev. Mol. Cell Biol., 6(10), 777–788. https://doi.org/10.1038/nrm1739

Hagmann, P., Sporns, O., Madan, N., Cammoun, L., Pienaar, R., Wedeen, V. J., … Grant, P. E. (2010). White matter maturation reshapes structural connectivity in the late developing human brain. Proceedings of the National Academy of Sciences, 107(44), 19067–19072. https://doi.org/10.1073/pnas.1009073107

Irimia, A., & Van Horn, J. (2014). Systematic network lesioning reveals the core white matter scaffold of the human brain. Frontiers in Human Neuroscience, 8, 51. https://doi.org/10.3389/fnhum.2014.00051

Johnson, M. H. (2001). Functional brain development in humans. Nat. Rev. Neurosci., 2(7), 475–483. https://doi.org/10.1038/35081509

Kang, H. J., Kawasawa, Y. I., Cheng, F., Zhu, Y., Xu, X., Li, M., … v Sestan, N. (2011). Spatio-temporal transcriptome of the human brain. Nature, 478(7370), 483–489. https://doi.org/10.1038/nature10523

Knickmeyer, R. C., Gouttard, S., Kang, C., Evans, D., Wilber, K., Smith, J. K., … Gilmore, J. H. (2008). A structural MRI study of human brain development from birth to 2 years. J. Neurosci., 28(47), 12176–12182. https://doi.org/10.1523/JNEUROSCI.3479-08.2008

Konner, M. (2011). The Evolution of Childhood. Belknap Press of Harvard University Press. Retrieved from http://www.hup.harvard.edu/catalog.php?isbn=9780674062016

Kuzawa, C. W., Chugani, H. T., Grossman, L. I., Lipovich, L., Muzik, O., Hof, P. R., … Lange, N. (2014). Metabolic costs and evolutionary implications of human brain development. Proc. Natl. Acad. Sci. U. S. A., 111(36), 13010–13015. https://doi.org/10.1073/pnas.1323099111

Petrican, R., Taylor, M. J., & Grady, C. L. (2017). Trajectories of brain system maturation from childhood to older adulthood: Implications for lifespan cognitive functioning. Neuroimage. https://doi.org/10.1016/j.neuroimage.2017.09.025

Rakic, P. (2009). Evolution of the neocortex: A perspective from developmental biology. Nature Reviews Neuroscience, 10(10), 724–735.

Shaw, P., Kabani, N. J., Lerch, J. P., Eckstrand, K., Lenroot, R., Gogtay, N., … Others. (2008). Neurodevelopmental trajectories of the human cerebral cortex. Journal of Neuroscience, 28(14), 3586–3594. https://doi.org/10.1523/JNEUROSCI.5309-07.2008