Linked Life Data

10615495

Source:http://linkedlifedata.com/resource/pubmed/id/10615495

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
19
pubmed:dateCreated
2000-1-24
pubmed:abstractText
We determined two-dimensional motion discrimination contours in the spatio-temporal frequency plane to characterize the mechanisms underlying velocity perception. In particular, we wanted to determine whether there exist mechanisms tuned specifically to velocity, rather than separable mechanisms tuned to spatial and temporal frequency. A 4-AFC paradigm was used to determine spatio-temporal frequency discrimination thresholds for moving sinewave gratings defined by luminance contrast. Three of the grating patches used were defined by the same spatial and temporal frequency (standard), the other (test) differed by a fixed proportional change in spatial and temporal frequency. Subjects had to indicate which grating differed most from the others and the thresholds determined for varying proportions of change in spatial and temporal frequency were used to trace out complete threshold contours in the plane spanned by these attributes. Some of the contours, primarily at speeds above 1 deg/s, were noticeably oriented along lines of constant velocity. To further isolate these mechanisms, spatio-temporal noise was added to the standard stimuli either along a line of constant velocity or in the direction orthogonal to it. When spatio-temporal noise of constant velocity was added to the standard stimuli, threshold contours became elongated only along the direction of the noise. The same amount of noise in the orthogonal direction produced an overall increase in thresholds without changing the shape of the contour, presenting clear evidence for velocity tuned mechanisms. In further experiments we discovered that velocity tuned mechanisms interact with separable mechanisms to produce optimal discriminability. Analogous experiments with isoluminant stimuli failed to exhibit evidence for velocity tuning, supporting the notion that the human color vision system is impaired in its coding of stimulus speed, despite excellent sensitivity to direction of motion.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0042-6989
pubmed:author
pubmed:issnType
Print
pubmed:volume
39
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
3267-85
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1999
pubmed:articleTitle
Velocity tuned mechanisms in human motion processing.
pubmed:affiliation
Max-Planck-Institut für biologische Kybernetik, Tübingen, Germany.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't