Biology:Human brain development timeline

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

Conception

Day Event Reference
33 posterior commissure appears Ashwell et al. (1996)[2]
33 medial forebrain bundle appears Ashwell et al. (1996)[2]
44 mammillothalamic tract appears Ashwell et al. (1996)[2]
44 stria medullaris thalami appears Ashwell et al. (1996)[2]
51 axons in optic stalk Dunlop et al. (1997)[3]
56 external capsule appears Ashwell et al. (1996)[2]
56 stria terminalis appears Ashwell et al. (1996)[2]
60 optic axons invade visual centers Dunlop et al. (1997)[3]
63 internal capsule appears Ashwell et al. (1996)[2]
63 fornix appears Ashwell et al. (1996)[2]
70 anterior commissure appears Ashwell et al. (1996)[2]
77 hippocampal commissure appears Ashwell et al. (1996)[2]
87.5 corpus callosum appears Ashwell et al. (1996)[2]
157.5 eye opening Clancy et al. (2007)[4]
175 ipsi/contra segregation in LGN and SC Robinson & 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. PMID 19794405. 
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 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. ↑ 3.0 3.1 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. 
  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. 
  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. ↑ "Three-dimensional sonographic evaluations of embryonic brain development". J Ultrasound Med 27 (1): 119–24. January 2008. 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. doi:10.1038/srep05644. ISSN 2045-2322. PMID 25008163. Bibcode: 2014NatSR...4E5644B. 
  8. ↑ 8.0 8.1 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. 
  9. ↑ "Adolescent maturity and the brain: the promise and pitfalls of neuroscience research in adolescent health policy". J Adolesc Health 45 (3): 216–21. 2009. doi:10.1016/j.jadohealth.2009.05.016. PMID 19699416. 
  10. ↑ "Maturation of the adolescent brain". Neuropsychiatr Dis Treat 9: 449–61. 2013. doi:10.2147/NDT.S39776. 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. PMID 25449739. 
  12. ↑ Icenogle, G.; Steinberg, L.; Duell, N.; Chein, J.; Chang, L.; Chaudhary, N.; Di Giunta, L.; Dodge, K. A. et al. (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. PMID 30762417. 

External links

  • Translating Time — a website providing translation of brain developmental times among different species



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