Content area
Full Text
ARTICLES
http://www.nature.com/natureneuroscience
Web End = Bilateral olfactory sensory input enhances chemotaxis behavior
http://www.nature.com/natureneuroscience
Nature Publishing Group
200 8
Matthieu Louis1, Thomas Huber2, Richard Benton1,3, Thomas P Sakmar2 & Leslie B Vosshall1
Neural comparisons of bilateral sensory inputs are essential for visual depth perception and accurate localization of sounds in space. All animals, from single-cell prokaryotes to humans, orient themselves in response to environmental chemical stimuli, but the contribution of spatial integration of neural activity in olfaction remains unclear. We investigated this problem in Drosophila melanogaster larvae. Using high-resolution behavioral analysis, we studied the chemotaxis behavior of larvae with a single functional olfactory neuron on either the left or right side of the head, allowing us to examine unilateral or bilateral olfactory input. We developed new spectroscopic methods to create stable odorant gradients in which odor concentrations were experimentally measured. In these controlled environments, we observed that a single functional neuron provided sufcient information to permit larval chemotaxis. We found additional evidence that the overall accuracy of navigation is enhanced by the increase in the signal-to-noise ratio conferred by bilateral sensory input.
The general principles governing orientation in chemical gradients have long been studied in various organisms, from the bacterium Escherichia coli to mammals17. The signaling pathways involved in directional sensing have been thoroughly investigated in prokaryotic and eukaryotic cells, such as E. coli8, the budding yeast9 and Dictyostelium discoideum10. Although most bacteria navigate using indirect random locomotion that is biased in the direction of the chemical gradient, certain unicellular organisms are able to locally extract directional information about the gradient11. Mathematical models can explain how signaling networks achieve sensing and amplication of external signals, noise ltering and locomotion12,13.
These models guided experiments that showed that Caenorhabditis elegans navigates toward chemical attractants according to an improved random-walk strategy14.
Chemotaxis involves direct navigation toward attractive chemicals and away from aversive chemicals. In contrast with the indirect biased random-walk strategies adopted by E. coli, this process requires computing odorant gradients locally and directing motion along, or against, the direction of steepest concentration change. The gaseous nature of the atmosphere in which most insects and mammals evolved makes this detection problem potentially more complicated than in liquid phase. It may therefore require sophisticated data integration that is supported by...