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Inside a synesthete's head: a functional connectivity analysis with grapheme-color synesthetes
C Sinke1, J Neufeld, H M Emrich
1Clinic for Psychiatry, Social Psychiatry and Psychotherapy, Hannover Medical School, Carl-Neuberg-Straße 1, 30625 Hanover, Germany. christopher.sinke@gmail.com
Neuropsychologia
|September 25, 2012
Summary
Grapheme-color synesthesia involves letters perceived with color. This study found altered brain connectivity in synesthetes, particularly in the parietal lobe and visual cortex, suggesting a broader network than previously understood.
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Psychology
Background:
- Grapheme-color synesthesia is a neurological condition where individuals perceive letters or numbers with associated colors.
- Existing models suggest involvement of higher-level visual and association areas in synesthesia.
Purpose of the Study:
- To identify brain regions and analyze functional connectivity associated with grapheme-color synesthesia.
- To investigate the neural underpinnings of the synesthetic experience using fMRI.
Main Methods:
- Event-related fMRI was used to compare brain activation and functional connectivity in 18 synesthetes and 18 controls.
- Stimuli included letters and pseudo-letters presented in black and color.
- Beta series correlation analysis was employed to assess functional connectivity between identified regions of interest.
Main Results:
- Activation differences were observed in the left and right inferior parietal lobule (IPL, BA7), right BA 18, and BA 40 between synesthetes and controls.
- Synesthetes showed increased functional connectivity between the left IPL and primary/secondary visual areas (BA 18).
- Enhanced connectivity was also noted between the right BA 7 and visual areas (BA 18) in synesthetes.
Conclusions:
- The parietal lobe plays a significant role in grapheme-color synesthesia.
- Information flow in synesthetes is modulated earlier than previously thought, potentially at the primary visual cortex level.
- Current models need refinement to include a more extended neural network involved in synesthetic experiences.
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