Event-related fMRI adaptation paradigm on real and synesthetic colors

Jean-Michel Hupé (1) , Cécile Bordier (2) , Michel Dojat (2)

1 CERCO - Centre de recherche cerveau et cognition
2 GIN - Grenoble Institut des Neurosciences

The subjective experience of color by synesthetes when viewing achromatic letters and numbers supposedly relates somehow to real color experience. Using fMRI, we tried to specify the degree of coactivation by real and synesthetic colors, by evaluating each color center individually and applying adaptation protocols across real and synesthetic colors. Indeed, fMRI activation of the same voxels by real and synesthetic colors would not be enough to prove that the same neurons are involved, given the relatively weak anatomical resolution of the BOLD signal (≈ 3mm). We therefore performed fMRI event-related adaptation protocols on 10 synesthetes in order to measure possible cross-adaptation effects when mixing real and synesthetic colors. However, to start with, we did not find any region that was activated both by real and synesthetic colors. We did not observe any clear adaptation for synesthetic colors in color ROIs, but we also did not observe any systematic color adaptation in retinotopic V4 or in color ROIs, so we could not test rigorously our hypothesis of adaptation across real and synesthetic colors. This technical report should be read in complement to "The neural bases of grapheme-color synesthesia are not localized in real color-sensitive areas", by Jean-Michel Hupé, Cécile Bordier & Michel Dojat, published in Cerebral Cortex 2011; doi:10.1093/cercor/bhr236.

Domaines: Neurosciences [q-bio.NC]

Jean-Michel Hupé, Cécile Bordier, Michel Dojat. Event-related fMRI adaptation paradigm on real and synesthetic colors. 2011. ⟨hal-00623554⟩