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(D) SYNAESTHESIA 1. News 2. People 3. Overview 5. Funders 6. Publications 7. Links 8. Contact
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NEUROGENETICS & PSYCHIATRIC DISORDERS: Neurodevelopmental and Neurological Disorders Group Professor Anthony P. Monaco - Group Head
SYNAESTHESIA RESEARCH GROUP
- MAIN PAGE
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Dr Julian Asher |
jasher@well.ox.ac.uk |
3. Overview
What is Synaesthesia?
Synaesthesia is a neurodevelopmental condition affecting 0.05-1% of the population.
The word synaesthesia comes from the Greek syn (union) and aesthesis (sensation), and the symptoms are often described as a ‘mixing of the senses'. It was first described by Sir Francis Galton in the journal Nature in 1880.
Synaesthesia is characterised by altered sensory perception. In many cases, a sensation in one sensory modality triggers an automatic response in a different modality, as in auditory-visual synaesthesia, where sound triggers the perception of colour.
For other synaesthetes, the synaesthetic response may occur in a different facet of the same sensory modality, as in visual grapheme-colour synaesthesia where reading black text triggers the perception of colour. Each sensory trigger is paired with a unique response, which remains consistent throughout the synaesthete’s lifetime – if middle-C = blue, it will always be that particular shade of blue.
Synaesthetic perception occurs simultaneously with ordinary perception, and can theoretically involve any pair of senses – however, almost all synaesthetic responses are visual. These percepts are most commonly described in terms of colours, but often involve visually salient texture, movement, and a particular layout in the synaesthete’s visual field.
As normal and abnormal percepts occur simultaneously, synaesthesia often results in perceptual and cognitive dysfunction. Cognitive interference from the synaesthetic percepts leads to difficulty with numerical and linguistic processing; numerical cognition is particularly affected. In extreme cases, synaesthetes may find their percepts overwhelming, necessitating isolation from the outside world to avoid sensory overload.
Interestingly, synaesthesia has also been implicated in ‘positive’ cognitive variations, including enhanced recall and absolute (perfect) musical pitch.
FURTHER INFORMATION on synaesthesia from the UK Synaesthesia Association.
Is synaesthesia genetic?
The tendency of synaesthesia to occur in families was first noted by Francis Galton in 1883.
Reports from people with synaesthesia indicate that 36-45% of synaesthetes have at least one first degree relative with synaesthesia. This most likely represents an underestimate, as a recent study involving systematic screening of the first-degree relatives of people with synaesthesia revealed ‘non-synaesthete’ relatives to be synaesthetes with a different form of synaesthesia.
What are our goals?
Synaesthesia offers valuable insight into normal cognitive development. Patterns observed in synaesthetic sound-colour and grapheme-colour pairings have also been observed to a lesser extent in non-synaesthetes, implying that synaesthesia stems from mechanisms common to all humans.
The study of the genetics of synaesthesia is in its infancy, and we are in the first stages of unravelling the genetic substrates underlying the disorder.
Although there is strong evidence that synaesthesia has a genetic component, we do not know which genes cause synaesthesia or how they contribute to the development of the condition.
Working in collaboration with other groups in the field, we aim to identify and characterise genes that may make people more susceptible to developing synaesthesia and to further clarify the role of genes in human cognition and perception.(1)
4.1 The genetics of Synaesthesia
Previous familiality studies indicate a strong genetic component, and several independent pedigree analyses support the theory that synaesthesia is a single-gene (Mendelian) disorder with a dominant mode of inheritance.
However, in the course of our study we have uncovered evidence that the genetics of synaesthesia are more complex than they appear.
More here on complex genetic disorders
4.2 Initial studies
As existing diagnostic tests were not adequate to meet the demands of a genetic study, an improved diagnostic instrument (the Revised Test of Genuineness, TOG-R) was developed as the first phase of this project. (2)
Computer simulations confirmed that our sample had more than adequate power to detect a major locus.
We are in the process of identifying and characterising candidate regions that contribute to susceptibility to synaesthesia using a complete-genome scan.
These candidate regions will then be studied in more detail to identify candidate genes.
4.4 Collaborators
We work closely with Professor Simon Baron-Cohen at the University of Cambridge, one of the founders of modern synaesthesia research.
5. Funders
The Synaesthesia project is funded by grants from the following funders:
Dr Julian Asher received an Overseas Research Student Award by the Higher Education Funding Council for England (HEFCE), and also received a grant from The Cambridge Overseas Trust, Trinity College, University of Cambridge
6. Publications
Most recent Publications (from 2006):
2007
Barnett KJ, Newell FN, Finucane C, Asher JE, BargaryG, Corvin AP and Mitchell KJ. Familial patterns and the origins of individual differences in synaesthesia. Cognition June 2007. [PubMed record] [Abstract from journal]
Guillochon RMA and Asher JE. What is synaesthesia? British Medical Journal (Student Edition) (in press).
2006
(1) Baron-Cohen S, Bor D, Billington J, Asher JE, Wheelwright S and Ashwin C. Savant memory in a man with number-shape synaesthesia and Asperger Syndrome. Journal of Consciousness Studies (in press).
(2) Asher JE, Aitken MRF, Farooqi N, Kurmani S, and Baron-Cohen S. Diagnosing and phenotyping visual synaesthesia: the Revised Test of Genuineness. Cortex 42(2), 137-46 (2006). [PubMed abstract] [Link to publisher]
List of all publications: CLICK HERE
7. Links
See also:
Further information for scientists:
See the section 'positive cognitive variations' in the following paper (1), which details a case study of a man with autism, synaesthesia, and eidetic memory:
8. Contact
All enquiries should be directed to Dr Julian Asher: jasher@well.ox.ac.uk
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Page last updated on Mon Dec 3 14:40:19 2007 |