Monday, February 20, 2012
What can we conclude about the genuineness of Daniel Tammet's synaesthesia based on the 2007 fMRI study? - some papers of interest
Bor, D, Billington, J, Baron-Cohen, S. (2007) Savant memory for digits in a case of synaesthesia and Asperger syndrome is related to hyperactivity in the lateral prefrontal cortex. Neurocase. 2007 Oct;13(5):311-9.
[Unfortunately this revealing paper remains behind a paywall. Daniel Tammet is definitely the subject of this study, named “DT” in this paper. On page 314 in the text are listed visual brain regions of interest which were studied in a ROI analysis comparing Tammet with non-synaesthete controls. Region V4/8, left and right cuneus, calcarine sulcus, fusiform gyrus and lingual gyrus are listed. Table 1 lists “Areas of significantly greater activation for DT compared with controls for the contrast: encoding minus delay”. All of the brain areas listed here are in the frontal lobes, except for the “Subcortical Cerebellum”. None of the visual ROIs listed on page 314 are found in this table.]
Rouw, Romke, Scholte, H. Steven and Colizoli, Olympia (2011) Brain areas involved in synaesthesia: A review. Journal of Neuropsychology. (2011), 5, 214–242.
Neufeld J, Sinke C, Dillo W, Emrich HM, Szycik GR, Dima D, Bleich S, Zedler M. (2012) The neural correlates of coloured music: A functional MRI investigation of auditory-visual synaesthesia. Neuropsychologia. Volume 50, Issue 1, Pages 1-204 (January 2012).
[Behind paywall. Includes discussion of the various parts of the brain involved with vision that have been found to have been associated with synaesthesia, in an exploration of a finding of no significant group-differences detected in area V4 in this fMRI study of auditory-visual synaesthetes and controls reporting no synaesthesia. The role of the left inferior parietal cortex (IPC) as a sensory nexus involved with synaesthesia is discussed. It appears that this area is pretty much the same as the inferior parietal lobule and Brodmann areas 39 and 40, but I’m certainly no brain anatomist. The IPC was apparently not studied in the fMRI study of Tammet, who reported having an elaborated type of grapheme-colour synaesthesia. One needs to keep in mind that although it appears that the IPC is involved in a number of types of synaesthesia, this study is of coloured music synaesthesia and the exact pattern of activation found in this study is probably different to the situation in other types of synaesthesia.]