The spatial limit for motion detection in noise depends on element size, not on spatial frequency.
When a random spatial noise pattern is displaced for a short distance it seems to move coherently, but when the displacement exceeds a certain value, the direction of motion cannot be clearly perceived. We measured the displacement limit (Dmax) for a two-frame sequence and found that it depended on the size of the elements comprising the random pattern, even when low spatial frequencies were removed from the pattern by spatial band-pass filtering. Dmax depended strongly on contrast for the filtered patterns, but less so for the unaltered patterns. The data support a model for low level motion detection in which the maximum motion displacement that can be detected is determined by the mean separation of pattern elements, following a stage of low-pass spatial filtering, and in which the upper spatial displacement depends upon the pattern statistics, not upon the size of detectors in the visual system.
Morgan
M J
MJ
Department of Visual Science, Institute of Ophthalmology, London, U.K. m.j.morgan@ucl.ac.uk
Perry
R
R
Fahle
M
M
D005374:Filtration; D006801:Humans; D008959:Models, Neurological; D009039:Motion Perception / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011594:Psychometrics; D012684:Sensory Thresholds / Q000502:physiology; D012858:Size Perception / Q000502:physiology*; D013997:Time Factors