First, most neurons which are linked by long-distance connections are born around the same time and early on, suggesting the possibility of early contact or interaction between connected neurons during development. Second, early-born neurons are more highly connected (tendency to form hubs) than later born neurons. This indicates that the longer time frame available to them might underlie high connectivity. Both outcomes are not observed for random connection formation. The study finds that around one-third of electrically coupled long-range connections are late forming, raising the question of what mechanisms are involved in ensuring their accuracy, particularly in light of the extremely invariant connectivity observed in C. elegans.
In conclusion, the sequence of neural network development highlights the possibility of early contact or interaction in securing long-distance and high-degree connectivity.
The article reporting these results is currently in press (Varier and Kaiser, 2010). Earlier work on C. elegans (Kaiser and Hilgetag, 2006), neural network development (Kaiser et al., 2009), and neural network analysis (Kaiser, 2007) is listed below for further reference. Both the current article and the data sets showing the network at different developmental stages will be made available on www.biological-networks.org upon publication (within the next couple of weeks).
Kaiser M and Hilgetag CC. (2006). Nonoptimal component placement, but short processing paths, due to long-distance projections in neural systems. PLoS Comput. Biol. 2:e95.
Kaiser M, Hilgetag CC, and van Ooyen A. (2009). Random outgrowth and spatial competition generate realistic connection length distributions and filling fractions. Cereb. Cortex 19, 3001-3010.
Kaiser M. (2007). Brain architecture: a design for natural computation. Phil. Trans. R. Soc. A, 365, 3033-3045.
Varier S, and Kaiser M. (in press). Neural development features: Spatio-temporal development of the C. elegans neuronal network. PLoS Comput. Biol. http://www.ploscompbiol.org/home.action
Articles submitted to the Worm Breeder's Gazette should not be cited in bibliographies. Material contained here should be treated as personal communication and cited as such only with the consent of the author.
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