Competition is a driving force in topographic mapping

Triplett, J. W., Pfeiffenberger, C., Yamada, J., Stafford, B. K., Sweeney, N. T., Litke, A. M., Sher, A., Koulakov, A. A., Feldheim, D. A. (November 2011) Competition is a driving force in topographic mapping. Proceedings of the National Academy of Sciences of the United States of America, 108 (47). pp. 19060-19065. ISSN 00278424

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DOI: 10.1073/pnas.1102834108


Topographic maps are the primary means of relaying spatial information in the brain. Understanding the mechanisms by which they form has been a goal of experimental and theoretical neuroscientists for decades. The projection of the retina to the superior colliculus (SC)/tectum has been an important model used to show that graded molecular cues and patterned retinal activity are required for topographic map formation. Additionally, interaxon competition has been suggested to play a role in topographic map formation; however, this view has been recently challenged. Here we present experimental and computational evidence demonstrating that interaxon competition for target space is necessary to establish topography. To test this hypothesis experimentally, we determined the nature of the retinocollicular projection in Math5 (Atoh7) mutant mice, which have severely reduced numbers of retinal ganglion cell inputs into the SC. We find that in these mice, retinal axons project to the anteromedial portion of the SC where repulsion from ephrin-A ligands is minimized and where their attraction to the midline is maximized. This observation is consistent with the chemoaffinity model that relies on axon-axon competition as a mapping mechanism. We conclude that chemical labels plus neural activity cannot alone specify the retinocollicular projection; instead axon-axon competition is necessary to create a map. Finally, we present a mathematical model for topographic mapping that incorporates molecular labels, neural activity, and axon competition.

Item Type: Paper
Uncontrolled Keywords: ephrin A1 animal cell animal experiment article brain mapping cell count competition computer model controlled study entropy mathematical model molecular interaction mouse nerve fiber nerve projection nonhuman priority journal retina ganglion cell superior colliculus topographic mapping wild type
Subjects: organs, tissues, organelles, cell types and functions > tissues types and functions > neural networks
organs, tissues, organelles, cell types and functions
organs, tissues, organelles, cell types and functions > tissues types and functions
organs, tissues, organelles, cell types and functions > tissues types and functions > visual cortex
CSHL Authors:
Communities: CSHL labs > Koulakov lab
Depositing User: Matt Covey
Date: 22 November 2011
Date Deposited: 07 Feb 2013 14:40
Last Modified: 02 Jan 2018 21:36
PMCID: PMC3223436
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