Highlights of Human brain development from conception through adulthood.[1]

Conception

Day Event Reference
33posterior commissure appearsAshwell et al. (1996)[2]
33medial forebrain bundle appearsAshwell et al. (1996)[2]
44mammillothalamic tract appearsAshwell et al. (1996)[2]
44stria medullaris thalami appearsAshwell et al. (1996)[2]
51axons in optic stalkDunlop et al. (1997)[3]
56external capsule appearsAshwell et al. (1996)[2]
56stria terminalis appearsAshwell et al. (1996)[2]
60optic axons invade visual centersDunlop et al. (1997)[3]
63internal capsule appearsAshwell et al. (1996)[2]
63fornix appearsAshwell et al. (1996)[2]
70anterior commissure appearsAshwell et al. (1996)[2]
77hippocampal commissure appearsAshwell et al. (1996)[2]
87.5corpus callosum appearsAshwell et al. (1996)[2]
157.5eye openingClancy et al. (2007)[4]
175ipsi/contra segregation in LGN and SCRobinson & Dreher (1990)[5]

Studies report that three primary structures are formed in the sixth gestational week. These are the forebrain, the midbrain, and the hindbrain, also known as the prosencephalon, mesencephalon, and the rhombencephalon respectively. Five secondary structures originate from these in the seventh gestational week. These are the telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon; the lateral ventricles, third ventricles, cerebral aqueduct, and upper and lower parts of the fourth ventricle in adulthood originated from these structures.[6] The appearance of cortical folds first takes place during 24 and 32 weeks of gestation.[7]

Childhood and adolescence

Cortical white matter increases from childhood (~9 years) to adolescence (~14 years), most notably in the frontal and parietal cortices.[8] Cortical grey matter development peaks at ~12 years of age in the frontal and parietal cortices, and 14–16 years in the temporal lobes (with the superior temporal cortex being last to mature), peaking at about roughly the same age in both sexes according to reliable data. In terms of grey matter loss, the sensory and motor regions mature first, followed by other cortical regions.[8] Human brain maturation continues to around 20[9] to 25[10] and even up to 30[11] years of age and beyond. Although it is worth noting that there is no actual evidence suggesting that impulse control only finishes developing in humans in the twenties. It is a common misconception that the brain only fully develops by 25, as the number comes from two particular studies, one on psychosocial maturity, where greater than 50% of people being tested only reached a plateau in impulse control by the age of 25. However, some people were recorded to have reached adult-levels by mid-teens, and some had not reached it even after 30. It is worth noting that the majority of countries showed that people's impulse control linearly improved with age, suggested that most cutoffs are somewhat arbitrary. It is also believed to have originated from a study by Jay Giedd based on MRI data, scanning the brains of people aged up to 21 or 25 years and no participants that were older. Years of research and testing seem to indicate that the brain is functioning in full adult capacity by the time youths reach high school, or roughly the age range of 14-16. Though it is a controversial psychometric, adult IQ also begins to be tested around this age range, with the Raven's Progressive Matrices test beginning at age 14 and the Wechsler Adult Intelligence Scale test beginning at age 16, though scores between 14 and 16 on the Weschler test have differences so small that they are considered unreliable. This may bring into question the effectiveness of brain development studies in treating and successfully rehabilitating criminal youth.[12]

See also

References

  1. ↑ Tau, G. Z.; Peterson, B. S. (2010). "Normal Development of Brain Circuits". Neuropsychopharmacology. 35 (1): 147–168. doi:10.1038/npp.2009.115. PMC 3055433. PMID 19794405.
  2. 1 2 3 4 5 6 7 8 9 10 11 Ashwell, K. W.; Waite, P. M.; Marotte, L (1996). "Ontogeny of the projection tracts and commissural fibres in the forebrain of the tammar wallaby (Macropus eugenii): timing in comparison with other mammals". Brain, Behavior and Evolution. 47 (1): 8–22. doi:10.1159/000113225. PMID 8834781.
  3. 1 2 Dunlop, S. A.; Tee, L. B.; Lund, R. D.; Beazley, L. D. (1997). "Development of primary visual projections occurs entirely postnatally in the fat-tailed dunnart, a marsupial mouse, Sminthopsis crassicaudata". The Journal of Comparative Neurology. 384 (1): 26–40. doi:10.1002/(SICI)1096-9861(19970721)384:1<26::AID-CNE2>3.0.CO;2-N. PMID 9214538. S2CID 38381685.
  4. ↑ Clancy, B; Kersh, B; Hyde, J; Darlington, R. B.; Anand, K. J.; Finlay, B. L. (2007). "Web-based method for translating neurodevelopment from laboratory species to humans". Neuroinformatics. 5 (1): 79–94. doi:10.1385/ni:5:1:79. PMID 17426354. S2CID 1806001.
  5. ↑ Robinson, S. R.; Dreher, B (1990). "The visual pathways of eutherian mammals and marsupials develop according to a common timetable". Brain, Behavior and Evolution. 36 (4): 177–195. doi:10.1159/000115306. PMID 2279233.
  6. ↑ Kim MS, Jeanty P, Turner C, Benoit B (January 2008). "Three-dimensional sonographic evaluations of embryonic brain development". J Ultrasound Med. 27 (1): 119–24. doi:10.7863/jum.2008.27.1.119. PMID 18096737.
  7. ↑ Budday, Silvia; Raybaud, Charles; Kuhl, Ellen (2014-01-01). "A mechanical model predicts morphological abnormalities in the developing human brain". Scientific Reports. 4: 5644. Bibcode:2014NatSR...4E5644B. doi:10.1038/srep05644. ISSN 2045-2322. PMC 4090617. PMID 25008163.
  8. 1 2 Blakemore, S.J. (June 2012). "Imaging brain development: the adolescent brain". NeuroImage. 61 (2): 397–406. doi:10.1016/j.neuroimage.2011.11.080. PMID 22178817. S2CID 207182527.
  9. ↑ Johnson SB, Blum RW, Giedd JN (2009). "Adolescent maturity and the brain: the promise and pitfalls of neuroscience research in adolescent health policy". J Adolesc Health. 45 (3): 216–21. doi:10.1016/j.jadohealth.2009.05.016. PMC 2892678. PMID 19699416.
  10. ↑ Arain M, Haque M, Johal L, Mathur P, Nel W, Rais A, Sandhu R, Sharma S (2013). "Maturation of the adolescent brain". Neuropsychiatr Dis Treat. 9: 449–61. doi:10.2147/NDT.S39776. PMC 3621648. PMID 23579318.
  11. ↑ Shafee, R.; Buckner, R. L.; Fischl, B. (2014). "Gray matter myelination of 1555 human brains using partial volume corrected MRI images". NeuroImage. 105: 473–485. doi:10.1016/j.neuroimage.2014.10.054. PMC 4262571. PMID 25449739.
  12. ↑ Icenogle, G.; Steinberg, L.; Duell, N.; Chein, J.; Chang, L.; Chaudhary, N.; Di Giunta, L.; Dodge, K. A.; Fanti, K. A.; Lansford, J. E.; Oburu, P.; Pastorelli, C.; Skinner, A. T.; Sorbring, E.; Tapanya, S.; Tirado, L. M.; Alampay, L. P.; Al-Hassan, S. M.; Takash, H. M.; Bacchini, D. (2019). "Adolescents' Cognitive Capacity Reaches Adult Levels Prior to Their Psychosocial Maturity: Evidence for a "Maturity Gap" in a Multinational, Cross-Sectional Sample". Law and Human Behavior. 43 (1): 69–85. doi:10.1037/lhb0000315. PMC 6551607. PMID 30762417.
  • Translating Time — a website providing translation of brain developmental times among different species
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