Detecting Noisy Gradients

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Science  17 Jul 2009:
Vol. 325, Issue 5938, pp. 247
DOI: 10.1126/science.325_247a

Growing neurons are faced with myriad cues as they try to find their designated target. The signals may be soluble or immobile, they may prompt attraction or repulsion, and they may deliver context-dependent messages. Last but not least, any single growth cone interprets its input via a variety of receptors spread across its surface; the growth cone may start or stall, grow quickly or slowly, turn right or left, or reverse course entirely. Mortimer et al. have developed a Bayesian model to explain how the growing tips of axons can identify the minute changes in noisy molecular gradients and then interpret them as guidance cues. The optimal strategy for a neuron gives more weight to feedback from receptors that are farther away from the center of the growth cone. Observations of explanted rat neurons facing constructed gradients of signaling ligands in collagen gels showed growth behaviors consistent with this interpretation.

Proc. Natl. Acad. Sci. U.S.A. 106, 10296 (2009).

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