Increased Intrinsic Network Connectivity in Grapheme-Colour Synaesthesia

Introduction: It has been hypothesized that synaesthesia, a condition in which stimulation of one sensory modality leads to additional abnormal perceptions, is caused by an increased connectivity between relevant brain regions. Support for increased structural connectivity in grapheme-colour synaesthetes is provided by diffusion tensor imaging studies. However, an investigation (with functional magnetic resonance imaging, fMRI) of coherent neuronal activity, i.e. functional connectivity in synaesthesia, is lacking to date. Methods: Twelve grapheme-colour synaesthetes and twelve control subjects (matched for age,…