Protomap (neuroscience) explained

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. The protomap is a feature of the ventricular zone, which contains the principal cortical progenitor cells, known as radial glial cells.^{[1] [2]} 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.^{[3] [4] [5]} 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.^[6] 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.^{[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

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

Notes and References

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