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Parallel discrimination of subjective contours defined by offset gratings
R Gurnsey1, G K Humphrey, P Kapitan
1Department of Psychology, Concordia University, Montreal, PQ, Canada.
Perception & Psychophysics
|September 1, 1992
Summary
Subjective contour detection can be reflexive, not always requiring selective attention. Early visual processing (V2) registers contours, but attention may be needed for conscious access.
Area of Science:
- Visual neuroscience
- Psychophysics
- Computational vision
Background:
- Physiological studies suggest early V2 encoding of subjective contours.
- Psychophysical data indicate a role for selective attention in contour detection.
- Reconciling these findings suggests reflexive registration with attentional access.
Purpose of the Study:
- Investigate the role of selective attention in subjective contour perception.
- Determine if subjective contours are processed bottom-up or require top-down attention.
- Explore the neural basis of subjective contour integration.
Main Methods:
- Visual search tasks with varying numbers of distractor subjective contours.
- Detection of horizontal/vertical subjective contours and curved forms.
- Discrimination of textured regions defined by subjective contours at brief durations.
Main Results:
- Contour detection was attention-independent when distractors were absent.
- Search asymmetry observed for curved forms, similar to feature search.
- Discrimination of textured contours depended on abrupt line terminations, supporting V1 cell integration.
Conclusions:
- Subjective contours can be registered reflexively, without attention.
- Selective attention may be necessary for conscious awareness of contours.
- Neural integration of V1 end-stopped cell responses likely underlies contour formation in V2.