Linked Life Data

10814760

Source:http://linkedlifedata.com/resource/pubmed/id/10814760

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PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
13
pubmed:dateCreated
2000-8-4
pubmed:abstractText
In a series of experiments we compared orientation discrimination performance for Gabor stimuli in which the stimulus profile was either matched to the receptive field profile of single V1 simple cells ('simple'), or in which the carrier and envelope orientations were different ('tigertails'). In the first Experiment, using small, high spatial frequency, peripheral stimuli to minimise the number of detectors involved, we found that simple stimuli were more detectable than tigertails of the same contrast energy, and that orientation discrimination thresholds for simple stimuli were lower than for tigertails of equal detectability. In later experiments with larger stimuli we measured thresholds for detecting tilts of the envelope with the carrier fixed in orientation. Envelope thresholds were similar for different carrier orientations, but carrier orientation had a strong biasing effect upon perceived envelope orientation. When the orientation difference between envelope and carrier was small, the carrier orientation was attracted to that of the envelope; when the difference was large (>10 degrees ) repulsion was found. The biases were reduced by half-wave rectifying the stimuli, putatively making the envelope visible to a first-order filter (Experiment 2). Discrimination thresholds for envelope orientation were higher than those for carrier orientation, and this difference was greater for briefly-presented parafoveal stimuli than for long duration foveal stimuli (Experiments 3 and 4). We conclude from these results that there are separate mechanisms for envelope and carrier orientation discriminations for large stimuli, but that first- and second-order mechanisms are not independent in the discrimination of orientation.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:status
MEDLINE
pubmed:issn
0042-6989
pubmed:author
pubmed:issnType
Print
pubmed:volume
40
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1751-63
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2000
pubmed:articleTitle
Are there separate first-order and second-order mechanisms for orientation discrimination?
pubmed:affiliation
Institute of Ophthalmology, University College London, Bath Street, London, UK. m.j.morgan@ucl.ac.uk
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't