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Published on: July 21, 2020
Detection of first- and second-order coherent motion in blindsight
Andrea Pavan1, Iona Alexander, Gianluca Campana
1International School for Advanced Studies, SISSA, Cognitive Neuroscience Sector, Via Bonomea 265, 34136 Trieste, Italy. apavan@sissa.it
Experimental Brain Research
|August 16, 2011
Summary
Blindsight patients struggle with second-order motion perception. Even with V5/MT(+) stimulation, individuals with blindsight cannot reliably detect artifact-free second-order motion, indicating distinct processing pathways.
Area of Science:
- Neuroscience
- Visual Perception
- Cognitive Science
Background:
- Blindsight patients exhibit unconscious visual processing, detecting stimuli in their blind field despite lacking subjective experience.
- Distinctions exist in neural substrates for first-order (luminance-defined) and second-order (contrast-defined) motion processing.
- The perception of second-order motion in blindsight remains under-investigated.
Purpose of the Study:
- To investigate the ability of blindsight patients to detect first- and second-order motion stimuli.
- To assess the roles of V5/MT(+) and V3(+) in coherent motion processing using repetitive transcranial magnetic stimulation (rTMS).
Main Methods:
- Two blindsight patients (GY, MS) and four controls performed a two-interval forced-choice task on first- and second-order motion stimuli.
- Repetitive transcranial magnetic stimulation (rTMS) was applied over V5/MT(+) and V3(+) to disrupt neural activity.
- Stimuli included textured squares defined by luminance or contrast modulation.
Main Results:
- Patient MS, with extensive ventral pathway damage, could not process second-order motion.
- Patient GY could process high-contrast second-order motion, potentially due to artifactual luminance cues.
- rTMS over V5/MT(+) impaired both first- and second-order motion detection in controls; rTMS over V3(+) had no effect on controls but impaired GY's first-order motion detection.
Conclusions:
- Neither blindsight patient could detect artifact-free second-order motion, suggesting its processing is impaired.
- Findings support distinct neural mechanisms for first- and second-order motion perception.
- V5/MT(+) appears crucial for both first- and second-order motion detection, while V3(+) may play a role in first-order motion and artifact-laden second-order motion.
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