Protomap (neuroscience)

Map of the functional areas of the mammalian cerebral cortex during early embryonic development

The Protomap is a primordial molecular map of the functional areas of the mammalian cerebral cortex during early embryonic development, at a stage when neural stem cells are still the dominant cell type.[1] The protomap is a feature of the ventricular zone, which contains the principal cortical progenitor cells, known as radial glial cells.[2][3] Through a process called 'cortical patterning', the protomap is patterned by a system of signaling centers in the embryo, which provide positional information and cell fate instructions.[4][5][6] These early genetic instructions set in motion a development and maturation process that gives rise to the mature functional areas of the cortex, for example the visual, somatosensory, and motor areas. The term protomap was coined by Pasko Rakic.[1] The protomap hypothesis was opposed by the protocortex hypothesis, which proposes that cortical proto-areas initially have the same potential,[7][8] and that regionalization in large part is controlled by external influences, such as axonal inputs from the thalamus to the cortex.[9] However, a series of papers in the year 2000 and in 2001 provided strong evidence against the protocortex hypothesis, and the protomap hypothesis has been well accepted since then.[5][10][11] The protomap hypothesis, together with the related radial unit hypothesis, forms our core understanding of the embryonic development of the cerebral cortex. Once the basic structure is present and cortical neurons have migrated to their final destinations, many other processes contribute to the maturation of functional cortical circuits.[12]

## See also

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* Radial unit hypothesis
* Neural stem cell
* Stem cell
* Neurogenesis
* Cellular differentiation
* Cortical patterning
* Gyrification

## References

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1. ^ a b Rakic P (July 1988). "Specification of cerebral cortical areas". Science. 241 (4862): 170–6. doi:10.1126/science.3291116. PMID 3291116.
2. ^ Noctor, SC; Flint, AC; Weissman, TA; Dammerman, RS; Kriegstein, AR (8 February 2001). "Neurons derived from radial glial cells establish radial units in neocortex". Nature. 409 (6821): 714–20. doi:10.1038/35055553. PMID 11217860. S2CID 3041502.
3. ^ Rakic, P (October 2009). "Evolution of the neocortex: a perspective from developmental biology". Nature Reviews. Neuroscience. 10 (10): 724–35. doi:10.1038/nrn2719. PMC 2913577. PMID 19763105.
4. ^ Grove, EA; Fukuchi-Shimogori, T (2003). "Generating the cerebral cortical area map". Annual Review of Neuroscience. 26: 355–80. doi:10.1146/annurev.neuro.26.041002.131137. PMID 14527269. S2CID 12282525.
5. ^ a b Fukuchi-Shimogori, T; Grove, EA (2 November 2001). "Neocortex patterning by the secreted signaling molecule FGF8". Science. 294 (5544): 1071–4. doi:10.1126/science.1064252. PMID 11567107. S2CID 14807054.
6. ^ Sur, M; Rubenstein, JL (4 November 2005). "Patterning and plasticity of the cerebral cortex". Science. 310 (5749): 805–10. doi:10.1126/science.1112070. PMID 16272112. S2CID 17225116.
7. ^ O'Leary, DD (October 1989). "Do cortical areas emerge from a protocortex?". Trends in Neurosciences. 12 (10): 400–6. doi:10.1016/0166-2236(89)90080-5. PMID 2479138. S2CID 9371858.
8. ^ Cognitive Neuroscience of Development (Studies in Developmental Psychology). East Sussex: Psychology Press. 2003. ISBN 978-1-84169-214-2.
9. ^ Sun T, Walsh CA (August 2006). "Molecular approaches to brain asymmetry and handedness". Nature Reviews Neuroscience. 7 (8): 655–62. doi:10.1038/nrn1930. PMID 16858393. S2CID 12208186.
10. ^ Bishop, KM; Goudreau, G; O'Leary, DD (14 April 2000). "Regulation of area identity in the mammalian neocortex by Emx2 and Pax6". Science. 288 (5464): 344–9. doi:10.1126/science.288.5464.344. PMID 10764649.
11. ^ Mallamaci, A; Muzio, L; Chan, CH; Parnavelas, J; Boncinelli, E (July 2000). "Area identity shifts in the early cerebral cortex of Emx2-/- mutant mice". Nature Neuroscience. 3 (7): 679–86. doi:10.1038/76630. PMID 10862700. S2CID 20047258.
12. ^ Ackman, JB; Burbridge, TJ; Crair, MC (11 October 2012). "Retinal waves coordinate patterned activity throughout the developing visual system". Nature. 490 (7419): 219–25. doi:10.1038/nature11529. PMC 3962269. PMID 23060192.

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