Self-Assembled Circuits

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Science  02 Jul 2010:
Vol. 329, Issue 5987, pp. 14
DOI: 10.1126/science.329.5987.14-b

The mammalian brain develops as growth factors and transcription factors define fields of morphogenesis, with some types of neurons migrating outward from deep generative zones and other types of neurons migrating along the surface from distant generative zones. The result might be compared to a geopolitical map supported by an infrastructure of shipping, communication, and regulatory networks. Zhou et al. used a mouse mutant in which the neocortex had been disconnected from the rest of the brain in order to analyze the development of the surface map. In normal mice, a few weeks of postnatal development complete the brain's organization; the mutant mice survive during this phase but die at about 3 weeks of age. During these weeks, the mutant mice, despite having disconnected brains, display a variety of behaviors: eating, drinking, walking, and swimming. Some aspects, such as circadian rhythms of activity, are noticeably disrupted. Interneurons are present at normal densities, although reduced numbers reflect the generalized atrophy of their brains. Projection neurons seem particularly susceptible to attrition, and layer 4 of the cortex seems particularly dependent on its connections. Otherwise, the disconnected mouse brain shows a considerable ability to organize itself.

J. Neurosci. 30, 7928 (2010).

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