Tag Archives: Roi Cohen Kadosh

Grapheme-colour synaesthesia and enhanced cortical excitability – I find this research quite exciting, but maybe that’s just me

“He found that neurons in the primary visual cortex were more active than expected.”

This is a quote about a study of some grapheme-colour synaesthetes. I’m a grapheme-colour synaesthete, and I’m wondering if this enhanced cortical excitability in the primary visual cortex which they wrote about in New Scientist last November is also an explanation for my superior face memory and the many other atypical visual perception experiences that I’ve had, and have described in this blog. It’s exciting research.

Hyperactive neurons build brains in synaesthesia. New Scientist. 23 November 2011 Issue 2840 p. 18.  http://www.newscientist.com/article/mg21228405.400-hyperactive-neurons-build-brains-in-synaesthesia.html

Thomson, Helen Hyperactive neurons build brains in synaesthesia. New Scientist. 17 November 2011  http://www.newscientist.com/article/dn21183-hyperactive-neurons-build-brains-in-synaesthesia.html

Enhanced Cortical Excitability in Grapheme-Color Synesthesia and Its Modulation. Current Biology. Vol 21 Issue 23 2006-2009, 17 November 2011. 10.1016/j.cub.2011.10.032 http://www.cell.com/current-biology/retrieve/pii/S0960982211011936

Free full-text journal papers about defining and redefining synaesthesia!

Thank you British Journal of Psychology. I find this stuff interesting. I hope my horribly neglected readers will also find the February 2012 issue interesting. It has Dr Julia Simner’s most interesting paper and two papers in response to it, one by the leading US synesthesia researcher David Eagleman and and another by synaesthesia researchers Cohen Kadosh and Terhune, plus Simner’s response to the responses. So if you still think synaesthesia is just crossed senses, do take a look.

For those of us with an interest in face recognition as well as synaesthesia, there is also a free paper titled “Integration of faces and voices, but not faces and names, in person recognition”. Happy reading!


What is, and what is not, synaesthesia?

Even though scientists have been studying synaesthesia for well over a century, the world of science still has not settled on a consensus on a scientific definition of synaesthesia. This does not reflect poorly on science or on synaesthesia research, in fact it shows that science is operating in the way that it is supposed to operate, with theoretical frameworks in place that order, drive and inform investigations, but also taking into account new information and reviewing these theoretical frameworks when necessary. I hope to find the time to finish a piece that I am writing about my own ideas on this subject.

Some recent journal papers about the definition of synaesthesia:

Cohen Kadosh, Roi and Terhune, Devin B. Redefining synaesthesia? British Journal of Psychology. Article first published online: 24 FEB 2011. DOI: 10.1111/j.2044-8295.2010.02003.x http://onlinelibrary.wiley.com/doi/10.1111/j.2044-8295.2010.02003.x/full

Simner, Julia Defining synaesthesia. British Journal of Psychology. 2010 Oct 12. [Epub ahead of print] PMID: 20939943 http://www.ncbi.nlm.nih.gov/pubmed/20939943

Prevalence rates of some interesting neurological conditions and disorders

Number form synaesthesia   ~12% (Ward, Sagiv & Butterworth 2009)

Dyslexia   5-10% English-speakers (Mitchell Feb 2011)

Dyscalculia   5-6% (Mitchell Feb 2011)

Congenital amusia (tone deafness)   4% (Mitchell Jan 2011) (Mitchell Feb 2011)

Day of the week -> colour synaesthesia   2.8% (Banissy et al 2009)

Prosopagnosia   1-2% (Mitchell Feb 2011)

Congenital prosopagnosia 2.5% (Mitchell Jan 2100) (This figure is inconsistent with the above figure as people with congenital prosopagnosia should be a sub-set of all people who have prosopagnosia)

Mirror-touch synaesthesia   1.6% (Banissy et al 2009)

Grapheme -> colour synaesthesia   1.4% (Banissy et al 2009)

ASD including autism   ~0.6% (Wikipedia)

So this means that, if the disorders besides autism listed above do not overlap in the people they affect, possibly almost a quarter of the population either can’t read, can’t do maths, can’t comprehend music normally, or can’t recognize faces adequately, while diagnosable autism is thought to only be found in less than a percent of people. So why so much hysteria and research funding about autism and so little funding for research into all the other issues?

The total number of synaesthetes in the population cannot be calculated by simply adding up the different types of synaesthesia listed above, because we know that individual synaesthetes often have a number of different types. Regardless, it is clear that synaesthetes make up a sizeable proportion of the population, and synaesthesia isn’t rare at all. So why is it that most teachers that I have spoken to have never heard of synaesthesia, a neurological condition (not disorder) that can directly affect learning (positively and on occassion negatively) and can affect the student’s sensory experience in the classroom?


Banissy, Michael J, Kadosh, Roi Cohen, Maus, Gerrit W, Walsh, Vincent, Ward, Jamie Prevalence, characteristics and a neurocognitive model of mirror-touch synaesthesia. Experimental Brain Research. (2009) 198:261–272. Published online: 3 May 2009. DOI 10.1007/s00221-009-1810-9 http://www.springerlink.com/content/26mh37152110617x/fulltext.pdf

Mitchell, Kevin The Neuroscience of Tone Deafness: The strange connection between people who can’t sing a tune and people who are “face blind”. Scientific American. January 18th 2011. http://www.scientificamerican.com/article.cfm?id=the-neuroscience-of-tone

Mitchell, K. J. Curiouser and curiouser: genetic disorders of cortical specialization.Current Opinion in Genetics & Development. 2011 Feb 4. [Epub ahead of print] http://www.ncbi.nlm.nih.gov/pubmed/21296568

Ward, Jamie, Sagiv, Noam and Butterworth, Brian The impact of visuo-spatial number forms on simple arithmetic. Cortex. Volume 45 Issue 10 Pages 1261-1265 (November 2009). http://www.cortexjournal.net/article/S0010-9452(09)00213-5/abstract