Popping the hood on synaesthesia – what’s going on in there?
by Dr Kevin Mitchell
Wiring the Brain.
November 3rd 2013.
"With this as background, we designed a neuroimaging study aimed at probing the functional involvement in the synaesthetic experience of areas with structural differences. What we found surprised us."
"When we looked more closely at the responses in these areas we found something really surprising. Two of them showed a clear difference in response to letters, but this was driven by a very strong reduction in activity in synaesthetes."
"Actually though, this finding is not completely novel – cortical deactivations were previously reported in response to synaesthesia-inducing stimuli in a PET study, some in the same areas we observe. Whether they have occurred in other fMRI studies is a little hard to know – experimental designs focusing on specific regions or looking specifically for positive differences may have missed these kinds of effects."
This Irish neuroscience and synaesthesia researcher was surprised to find deactivation in his synaesthesia study? If that's the case, he'd have to have a major gap in his knowledge of early synaesthesia research and also a major gap in his knowledge of popular writing on the subject. The pop psychology book The Man Who Tasted Shapes by Dr Richard Cytowic was I think the first book in the genre about synaesthesia and is a widely read book. The centrepiece of the book is a single case study, of Michael Watson, who is the synaesthete man who tasted shapes. The most exciting part of the book is the account of the "CBF" brain study by Dr Cytowic and Dr David Stump, of Mr Watson experiencing synaesthesia. What they found surprised them.
"....the average blood flow in Michael's left hemisphere dropped to three times below the lowest acceptable limit of an average person's!" (Cytowic 1993 p.150)
"....the most important point is that instead of an increase in metabolism, which is what I expect with any kind of activation, your brain shows a profound decrease in cortical metabolism during synesthesia." (Cytowic 1993 p.151)
The appropriate time for a synaesthesia researcher being surprised about finding a localized decrease in brain activity associated with synaesthesia ended twenty years ago, in 1993. Dr Mitchell has never read the book? In 2013 Dr Mitchell should not have been particularly surprised by the results of his synaesthesia study. When a leading researcher in a field of study shows a basic lack of knowledge about the area that he specializes in, and it appears that other researchers in the field don't bother to even look for what is possibly a most distinctive and striking characteristic of the subject of their study (deactivation in synaesthesia) it really is time to ask questions about the quality of neuroscience research today.
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