| Evidence for two speed signals: a coarse local signal for segregation and a precise global signal for discrimination. | |
| | |
MedLine Citation:
|
PMID: 7660577 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
|
In calculating the precise speed of an object, the visual system must integrate motion measurements across time and space while keeping motion measurements from different objects separate. We examined whether an initial coarse estimate of local speed may be used to segregate the motions of different objects prior to a precise calculation of object speed. Our stimuli consisted of 256 dots that moved upward at two speeds. In Expt 1, each dot alternated between the two speeds every 133 msec. When the speed alternations were asynchronous across dots, subject saw two transparent surfaces moving at different speeds and their ability to discriminate changes in the slow speed were unaffected by the presence of the fast speed. This experiment suggests that before integration, motion measurements may be segregated according to speed. We sought more conclusive evidence for this claim in Expts 2 and 3. In Expt 2, dots with 33 msec lifetimes were used to generate the two speeds. Although individual dots permitted only crude speed discrimination, subjects perceived this stimulus as two surfaces moving at different speeds and they precisely judged the slower speed. Apparently, the coarse local signals generated by the slow dots were segregated from those of the fast dots and then separately integrated to produce a precise speed signal. In Expt 3, the dots again moved at two speeds, but each speed was generated by a range of spatial and temporal displacements. Once more, subjects saw two surfaces and precisely judged the speed of the slower surface, demonstrating that segregation may be based solely on differences in local speed.(ABSTRACT TRUNCATED AT 250 WORDS) |
| | |
Authors:
|
M J Bravo; S N Watamaniuk |
Related Documents
:
|
20829997 - Use of moving interference fringes for holographic recording onto a moving storage medium. 19726727 - Surround motion silences signals from same-direction motion. 19451377 - Connectedness affects dot numerosity judgment: implications for configural processing. 10336057 - Receptive field characteristics of neurons in the nucleus of the basal optic root in pi... 17645017 - Scale-dependent variation in coral community similarity across sites, islands, and isla... 10664757 - The peripheral drift illusion: a motion illusion in the visual periphery. |
Publication Detail:
|
Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S. |
Journal Detail:
|
Title: Vision research Volume: 35 ISSN: 0042-6989 ISO Abbreviation: Vision Res. Publication Date: 1995 Jun |
Date Detail:
|
Created Date: 1995-10-02 Completed Date: 1995-10-02 Revised Date: 2006-11-15 |
Medline Journal Info:
|
Nlm Unique ID: 0417402 Medline TA: Vision Res Country: ENGLAND |
Other Details:
|
Languages: eng Pagination: 1691-7 Citation Subset: IM; S |
Affiliation:
|
Smith-Kettlewell Eye Research Institute, San Francisco, CA 94115, USA. |
Export Citation:
|
APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
|
Differential Threshold
/
physiology Female Humans Male Motion Perception / physiology* Psychophysics Time Factors |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
Previous Document: Perceptual learning in parafoveal vision.
Next Document: Contour integration across depth.