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  On the Elementary Mechanism Underlying Secondary Motion Processing

Zanker, J. (1996). On the Elementary Mechanism Underlying Secondary Motion Processing. Philosophical Transactions of the Royal Society of London, Series B: Biological Sciences, 351(1348), 1725-1736. doi:10.1098/rstb.1996.0154.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0005-E6DA-2 Version Permalink: http://hdl.handle.net/21.11116/0000-0006-0EF7-5
Genre: Journal Article

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Zanker, JM1, 2, Author              
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1Max Planck Institute for Biological Cybernetics, Max Planck Society, Spemannstrasse 38, 72076 Tübingen, DE, ou_1497794              
2Former Department Structure and Function of Natural Nerve-Net , Max Planck Institute for Biological Cybernetics, Max Planck Society, Spemannstrasse 38, 72076 Tübingen, DE, ou_1497803              

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 Abstract: The movement of luminance-defined targets can be easily extracted by elementary motion detectors (EMDs) of the correlation type which often are referred to as Reichardt-detectors. In contrast to such ‘primary motion’, in ‘secondary motion’ the moving target is defined by more complex features, like changes in texture, flicker, or local contrast. Such stimulus attributes have to be extracted from the retinal intensity distribution by some nonlinear preprocessing, before they are fed into motion detectors. An intriguing case is the perception of the movement of the motion signal, as is present in theta motion, where an object moves in a different direction than the texture on its surface. A two-layer model of hierarchically organised EMDs has been postulated to account for such motion extraction. Other than for the first layer, the computational nature of the mechanism underlying motion processing in the second layer so far is a matter of speculation, and is therefore characterized here by means of computer simulations and psychophysical experiments. Random dot kinematograms were generated in which sinusoidally m odulated vertical dot motion defined gratings, and coherence thresholds were measured for the direction discrimination of a horizontally travelling modulation function. This was done for a variety of spatial frequencies and speeds of the modulation sinusoid. Thresholds turn out to be lowest not for a particular speed, but for a fixed temporal frequency of the modulation function (about 1 cycle per second), when various combinations of fine and coarse, and fast and slow secondary gratings are tested. This result favours a correlation-type mechanism over a gradient-type scheme which should lead to a speed-optimum independent of spatial frequency.

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 Dates: 1996-12
 Publication Status: Published in print
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 Identifiers: DOI: 10.1098/rstb.1996.0154
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Title: Philosophical Transactions of the Royal Society of London, Series B: Biological Sciences
Source Genre: Journal
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Publ. Info: London : Royal Society
Pages: - Volume / Issue: 351 (1348) Sequence Number: - Start / End Page: 1725 - 1736 Identifier: ISSN: 0962-8436
CoNE: https://pure.mpg.de/cone/journals/resource/963017382021_1