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This Article Full Text Full Text (PDF) All Versions of this Article: 102/2/797    most recent 91215.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Hofmann, M. H. Articles by Wilkens, L. A. PubMed PubMed Citation Articles by Hofmann, M. H. Articles by Wilkens, L. A.

Edge-Detection Filter Improves Spatial Resolution in the Electrosensory System of the Paddlefish

Center for Neurodynamics, Department of Biology, University of Missouri, St. Louis, Missouri

Submitted 15 December 2008; accepted in final form 12 May 2009

In many fishes, prey capture is guided primarily by vision. In the paddlefish, the electrosense can completely substitute for the visual system to detect tiny daphnia, their primary prey. Electroreceptors are distributed over the entire rostrum, head, and gill covers, and there are no accessory structures like a lens to form an image. To accurately locate planktonic prey in three-dimensional space, the poor spatial resolving power of peripheral receptors has to be improved by another mechanism. We have investigated information processing in the electrosensory system of the paddlefish at hind- and midbrain levels by recording single cells extracellularly. We stimulated with a linear array of electrodes that simulated a moving dipole field. In addition, global electric fields were applied to simulate the temporal component of a moving dipole only. Some stimulation were done with sinusoidal fields. The fire rate of cells in the hindbrain followed the first derivative of the stimulus wave form. In contrast, the response of tectal cells were similar to the third derivative. This improves spatial resolution and receptive fields of tectal units are much smaller than the ones of hind brain units. The principle is similar to a Laplacian of Gaussian filter that is commonly used in digital image processing. However, instead of working in the space domain, the paddlefish edge detection filter works in the time domain, thus eliminating the need for extensive interconnections in an array of topographically organized neurons.