title: Anomalous Auditory Cortex Activations in Colored Hearing Synaesthetes: An fMRI-Study.
abstract: Color percept induction in synaesthetes by hearing words was previously shown to involve activation of visual and specifically color processing cortex areas. While this provides a rationale for the origin of the anomalous color percept the question of mechanism of this crossmodal activation remains unclear. We pursued this question with fMRI in color hearing synaesthetes by exposing subjects to words and tones. Brain activations in word condition accompanied by highly reliable color percepts were compared with activations in tone condition with only occasional color percepts and both contrasted to activations in normal subjects under the same stimulus conditions. This revealed that already the tone condition similar to the word condition caused abnormally high activations in various cortical areas even though synaesthetic percepts were more rare. Such tone activations were significantly larger than in normal subjects in visual areas of the right occipital lobe, the fusiform gyrus, and the left middle temporal gyrus and in auditory areas of the left superior temporal gyrus. These auditory areas showed strong word and tone activation alike and not the typically lower tone than word activation in normal subjects. Taken together these results are interpreted in favour of the disinhibited feedback hypothesis as the neurophysiological basis of genuine synaesthesia.
authors.affiliation: Leibniz Institute for Neurobiology, Magdeburg, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Gaschler-Markefski
authors.forename: Gregor R
authors.initials: GR
authors.lastname: Szycik
authors.forename: Christopher
authors.initials: C
authors.lastname: Sinke
authors.forename: Janina
authors.initials: J
authors.lastname: Neufeld
authors.forename: Udo
authors.initials: U
authors.lastname: Schneider
authors.forename: Frank
authors.initials: F
authors.lastname: Baumgart
authors.forename: Oliver
authors.initials: O
authors.lastname: Dierks
authors.forename: Ursula
authors.initials: U
authors.lastname: Stiegemann
authors.forename: Henning
authors.initials: H
authors.lastname: Scheich
authors.forename: Hinderk Meiners
authors.initials: HM
authors.lastname: Emrich
authors.forename: Markus
authors.initials: M
authors.lastname: Zedler
mesh_terms: D000328:Adult; D000368:Aged; D001303:Auditory Cortex / Q000502:physiology*; D001931:Brain Mapping; D003118:Color Perception / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009778:Occipital Lobe / Q000502:physiology; D010468:Perceptual Disorders / Q000503:physiopathology; D011601:Psychophysics; D013067:Speech Perception / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology; D055815:Young Adult