White matter microstructure throughout the brain correlates with visual imagery in grapheme-color synesthesia

Area of Science:

• Neuroscience
• Cognitive Science
• Psychology

Background:

• Synesthesia involves experiencing one sense through another, like seeing colors for letters.
• Previous research suggests structural brain differences in synesthetes, but direct behavioral correlations are less understood.

Purpose of the Study:

• To investigate the relationship between neuroanatomy and behavioral metrics in grapheme-color synesthesia.
• To explore if white matter microstructure differences in synesthetes correlate with visual imagery vividness.

Main Methods:

• Diffusion tensor imaging (DTI) was used to measure white matter microstructure in 20 grapheme-color synesthetes and matched controls.
• Fractional anisotropy and diffusivity metrics were analyzed.
• Correlation analysis was performed between neuroimaging data and visual imagery vividness scores.

Main Results:

• Synesthetes exhibited lower fractional anisotropy and higher perpendicular diffusivity compared to controls, indicating altered white matter microstructure.
• These microstructural differences were associated with more crossing white matter pathways in synesthetes.
• Lower fractional anisotropy and higher perpendicular diffusivity in synesthetes correlated negatively with their reported visual imagery vividness.

Conclusions:

• Synesthesia is associated with specific neuroanatomical differences in white matter microstructure.
• These brain differences are linked to behavioral measures, specifically visual imagery vividness.
• Synesthetes represent a population with both continuous variation and categorical neuroanatomical distinctions.