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Training Synesthetic Letter-color Associations by Reading in Color
Published on: February 20, 2014
Metacontrast masking is processed before grapheme-color synesthesia
Michael Patrick Bacon1, Bruce Bridgeman, Vilayanur S Ramachandran
1Department of Psychology, Social Sciences 2 UCSC, Santa Cruz, CA 95064, USA.
Attention, Perception & Psychophysics
|November 29, 2012
Summary
Grapheme-color synesthesia involves experiencing colors when seeing letters or numbers. This study used metacontrast masking to show synesthesia occurs after visual processing, not during it.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Sensory Perception
Background:
- Grapheme-color synesthesia is a neurological phenomenon where individuals perceive colors associated with letters or numbers.
- Metacontrast masking is a visual illusion used to study visual processing.
- Previous research suggests metacontrast masking is a cortical process.
Purpose of the Study:
- To investigate the neural processing stage of grapheme-color synesthesia.
- To compare visual processing in synesthetes and non-synesthete controls using metacontrast masking.
- To determine if synesthetic color perception influences metacontrast masking effects.
Main Methods:
- Utilized a metacontrast masking paradigm with grapheme stimuli.
- Employed dichoptic presentation to isolate cortical processing.
- Compared monochromatic (same color target/mask) and dichromatic (different color target/mask) masking conditions.
- Ensured equiluminance of target, mask, and background for all participants.
Main Results:
- Both synesthetes and controls exhibited stronger U-shaped metacontrast masking in monochromatic conditions compared to dichromatic conditions.
- Optimal masking occurred at a stimulus asynchrony of approximately 66 ms for both groups.
- The difference in masking between monochromatic and dichromatic conditions was less pronounced in synesthetes than controls, but still significant.
Conclusions:
- Metacontrast masking is a cortical phenomenon influenced by visual processing.
- Synesthetic color perception does not alter the fundamental metacontrast masking effect.
- The findings suggest that grapheme-color synesthesia is processed at a later stage than the visual mechanisms underlying metacontrast masking.
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