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The what and where in visual masking.
Haluk Ogmen1, Bruno G Breitmeyer, Reginald Melvin
1Department of Electrical and Computer Engineering, University of Houston, N308 Engineering Building 1, Houston, TX 77204-4005, USA. ogmen@uh.edu <ogmen@uh.edu>
Vision Research
|May 14, 2003
Summary
Metacontrast masking affects target visibility but not reaction time (RT). This study rejects a single sensory-motor pathway, suggesting a dual-pathway model (RECOD) explains the dissociation based on stimulus timing.
Area of Science:
- Visual perception
- Psychophysics
- Cognitive neuroscience
Background:
- Metacontrast masking selectively suppresses target visibility without affecting reaction times (RT).
- The underlying neural mechanisms for this dissociation remain debated, with theories proposing either a masking-immune sensory-motor pathway or specific stimulus timing interactions.
Purpose of the Study:
- To investigate whether the metacontrast masking dissociation arises from a sensory-motor pathway unaffected by masking or from interactions within sustained and transient visual channels.
- To test the validity of a single sensory-motor pathway theory against a dual-pathway model.
Main Methods:
- Examined target visibility and RT under varying stimulus onset asynchronies (SOAs) using para- and metacontrast masking.
- Analyzed the contribution of contour-masking to RT across different SOAs.
Main Results:
- Both para- and metacontrast showed U-shaped functions for target visibility.
- RTs were largely unaffected by metacontrast masking across SOAs, while paracontrast showed reduced RT contribution at later SOAs.
- The dissociation between visibility and RT was observed in metacontrast but not paracontrast.
Conclusions:
- The findings reject the single sensory-motor pathway theory, as RTs were influenced by masking under certain conditions (paracontrast).
- The results support a dual-pathway model, such as RECOD (Rival Inhibitory Convolution of Energized Dampeners), where interactions between fast and slow processing channels, modulated by stimulus timing, explain the observed dissociation.