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PubMed · 6695505

Factors influencing velocity coding in the human visual system.

G A Orban·J de Wolf·H Maes
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Abstract

Differential velocity detection in the fovea was measured over a wide range of velocities (0.25-256 degrees/sec). Differential thresholds were minimum (about 6%) for intermediate velocities (4-32 degrees/sec). Velocity judgements were shown not to depend on duration judgments. The U-shaped curve relating differential velocity detection and velocity was preserved at different background levels and different contrasts. The physiological correlates of these observations are discussed.

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Differential ThresholdFovea CentralisHumansMacula LuteaMotion PerceptionPhotic StimulationTime FactorsVisual PerceptionJournal Article

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BibTeXRIS

G A Orban, J de Wolf, H Maes. 1984. Factors influencing velocity coding in the human visual system.. https://doi.org/10.1016/0042-6989(84)90141-x

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Two classes of models have been proposed to explain how the visual system processes texture modulations. In 'feature models', abstract representations of the featural properties of local texture regions (eg orientation, spatial frequency, contrast) are first generated, after which differences in individual feature properties across space are detected. In 'energy models', on the other hand, differences across space in the response energies of linear simple-cell-like filters are detected. This model thus processes the existing differences between texture regions directly without generating a full representation of the individual texture regions. We provide here direct evidence for the existence of the second, energy model, using an adaptation paradigm in conjunction with textures simultaneously modulated in two dimensions--orientation and spatial frequency. We found that the mechanism that processed the conjoint modulation was tuned to orientations and spatial frequencies that could not be predicted by any feature model, but which were precisely predicted by the energy model.

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