Individual differences among grapheme-color synesthetes: brain-behavior correlations

Neuron. 2005 Mar 24;45(6):975-85. doi: 10.1016/j.neuron.2005.02.008.


Grapheme-color synesthetes experience specific colors associated with specific number or letter characters. To determine the neural locus of this condition, we compared behavioral and fMRI responses in six grapheme-color synesthetes to control subjects. In our behavioral experiments, we found that a subject's synesthetic experience can aid in texture segregation (experiment 1) and reduce the effects of crowding (experiment 2). For synesthetes, graphemes produced larger fMRI responses in color-selective area human V4 than for control subjects (experiment 3). Importantly, we found a correlation within subjects between the behavioral and fMRI results; subjects with better performance on the behavioral experiments showed larger fMRI responses in early retinotopic visual areas (V1, V2, V3, and hV4). These results suggest that grapheme-color synesthesia is the result of cross-activation between grapheme-selective and color-selective brain areas. The correlation between the behavioral and fMRI results suggests that grapheme-color synesthetes may constitute a heterogeneous group.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Brain Mapping
  • Cerebrovascular Circulation / physiology
  • Color Perception / physiology*
  • Color Vision Defects / physiopathology*
  • Functional Laterality / physiology
  • Humans
  • Illusions / physiology*
  • Magnetic Resonance Imaging
  • Neuropsychological Tests
  • Observer Variation
  • Pattern Recognition, Visual / physiology*
  • Photic Stimulation
  • Visual Cortex / anatomy & histology
  • Visual Cortex / physiology*
  • Visual Pathways / anatomy & histology
  • Visual Pathways / physiology*