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Projectors, associators, visual imagery, and the time course of visual processing in grapheme-color synesthesia
Ben D Amsel1,2, Marta Kutas1,2,3, Seana Coulson1,2
1a Department of Cognitive Science , University of California , San Diego , CA , USA.
Cognitive Neuroscience
|July 13, 2017
Summary
Grapheme-color synesthesia involves seeing colors with letters/numbers. This study shows synesthetes
Area of Science:
- Neuroscience
- Cognitive Psychology
- Sensory Perception
Background:
- Grapheme-color synesthesia is a neurological condition where specific letters or numbers trigger color experiences.
- Understanding the neural mechanisms of synesthesia offers insights into sensory processing and cross-modal interactions.
Purpose of the Study:
- To investigate real-time word processing in grapheme-color synesthetes using event-related brain potentials (ERPs).
- To compare neural responses to visual contrast in synesthetes versus controls when processing color concepts.
Main Methods:
- Recorded ERPs from 15 synesthetes and 15 controls judging word pair validity under varying visual contrast.
- Utilized individually tailored achromatic grapheme strings to convey color concepts to synesthetes.
- Presented equivalent colored grapheme strings to control participants.
Main Results:
- Low visual contrast delayed visual ERP components (P1/N170) in both groups.
- Synesthetes showed delayed P1/N170 with achromatic grapheme strings conveying color, unlike controls where contrast modulated amplitude, not latency.
- Synesthetes exhibited enhanced N170 and P2 components across all stimuli, with N170 amplitude correlating with synesthesia type and visual imagery.
Conclusions:
- Color induction in synesthetes differs from standard color perception in controls.
- Immediate cross-activation between visual areas processing color and shape is prominent in projector synesthetes.
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