[Synesthesia as a neuronal palimpsest]

Med Sci (Paris). 2012 Aug-Sep;28(8-9):765-71. doi: 10.1051/medsci/2012288019. Epub 2012 Aug 22.
[Article in French]


Synesthetes, a small fraction of the population, experience systematic, additional associations. For example, they may arbitrarily associate a specific color to each letter or number. Synesthesia has offered for the last ten years to cognitive science a unique opportunity to study the neural bases of subjective experience, drawing on individual differences just like in neuropsychology, but with healthy people. Here we review the current knowledge and propose a new theory, the "palimpsest hypothesis", a variant of the recycling hypothesis for reading. The neural development of written language expertise (a recent cultural invention acquired without any genetic modification) requires indeed the recycling of brain regions predisposed to expertise acquisition into reading regions. The palimpsest hypothesis supposes that for synesthetes recycling involves neuronal networks that were already specialized for color perception. Synesthetic colors would be the remains of this former expertise.

Publication types

  • English Abstract
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Brain Mapping
  • Cerebral Cortex / physiology
  • Color Perception / physiology
  • Feedback, Physiological
  • Humans
  • Individuality*
  • Models, Neurological*
  • Models, Psychological
  • Nerve Net / physiology
  • Neuronal Plasticity / physiology*
  • Perception / physiology*
  • Perceptual Disorders / physiopathology*
  • Perceptual Disorders / psychology
  • Psychological Tests
  • Reading
  • Synaptic Transmission