Posts tagged synaesthesia
Articles and news from the latest research reports.
Experiencing letters as colours: new insights into synaesthesia
Scientists studying the bizarre phenomenon of synaesthesia – best described as a “union of the senses” whereby two or more of the five senses that are normally experienced separately are involuntarily and automatically joined together – have made a new breakthrough in their attempts to understand the condition.
V.S. Ramachandran and Elizabeth Seckel from the University of San Diego studied four synaesthetes who experience colour when seeing printed letters of the alphabet. Their aim was to determine at what point during sensory processing these ‘colours’ appeared.
To do this, the researchers asked their synaesthetes – as well as a control group – to complete three children’s picture puzzles in which words were printed backwards or were not immediately visible.
When the results were processed, Ramachandran and Seckel discovered that the synaesthetes were able to complete the puzzles three times faster than the control subjects, and with fewer errors. The synaesthetes also revealed that they saw the obscured letters in the puzzles in the same colour as they would the ‘normal’ letters. This process effectively clued them in to what the letters were, and allowed them to read the distorted words much more quickly than the controls could.
Although it was just a small study, Ramachandran and Seckel’s work, published in the current issue of Neurocase, ‘strongly supports the interpretation that the synthetic colours are evoked preconsciously early in sensory processing’. The four synaesthetes had an advantage in completing the puzzles because the ‘extra’ information they received when looking at the letters was then sent up to ‘higher levels of sensory processing, providing additional insight for reading the distorted and backwards text’: a fascinating and important insight into a condition those of us who see letters as just letters find simply baffling.
Synaesthesia is more common in autism
People with autism are more likely to also have synaesthesia, suggests new research in the journal Molecular Autism.
Synaesthesia involves people experiencing a ‘mixing of the senses’, for example, seeing colours when they hear sounds, or reporting that musical notes evoke different tastes. Autism is diagnosed when a person struggles with social relationships and communication, and shows unusually narrow interests and resistance to change. The team of scientists from Cambridge University found that whereas synaesthesia only occurred in 7.2% of typical individuals, it occurred in 18.9% of people with autism.
On the face of it, this is an unlikely result, as autism and synaesthesia seem as if they should not share anything. But at the level of the brain, synaesthesia involves atypical connections between brain areas that are not usually wired together (so that a sensation in one channel automatically triggers a perception in another). Autism has also been postulated to involve over-connectivity of neurons (so that the person over-focuses on small details but struggles to keep track of the big picture).
The scientists tested – and confirmed – the prediction that if both autism and synaesthesia involve neural over-connectivity, then synaesthesia might be disproportionately common in autism.
The team, led by Professor Simon Baron-Cohen at the Autism Research Centre at Cambridge University, tested 164 adults with an autism spectrum condition and 97 adults without autism. All volunteers were screened for synaesthesia. Among the 31 people with autism who also had synaesthesia, the most common forms of the latter were ‘grapheme-colour’ (18 of them reported black and white letters being seen as coloured) and ‘sound-colour’ (21 of them reported a sound triggering a visual experience of colour). Another 18 of them reported either tastes, pains, or smells triggering a visual experience of colour.
Professor Baron-Cohen said: “I have studied both autism and synaesthesia for over 25 years and I had assumed that one had nothing to do with the other. These findings will re-focus research to examine common factors that drive brain development in these traditionally very separate conditions. An example is the mechanism ‘apoptosis,’ the natural pruning that occurs in early development, where we are programmed to lose many of our infant neural connections. In both autism and synaesthesia apoptosis may not occur at the same rate, so that these connections are retained beyond infancy.”
Professor Simon Fisher, a member of the team, and Director of the Language and Genetics Department at Nijmegen’s Max Planck Institute, added: “Genes play a substantial role in autism and scientists have begun to pinpoint some of the individual genes involved. Synaesthesia is also thought to be strongly genetic, but the specific genes underlying this are still unknown. This new research gives us an exciting new lead, encouraging us to search for genes which are shared between these two conditions, and which might play a role in how the brain forms or loses neural connections.”
Donielle Johnson, who carried out the study as part of her Master’s degree in Cambridge, said: “People with autism report high levels of sensory hyper-sensitivity. This new study goes one step further in identifying synaesthesia as a sensory issue that has been overlooked in this population. This has major implications for educators and clinicians designing autism-friendly learning environments.”
(Source: eurekalert.org)
A longitudinal study of grapheme-color synaesthesia in childhood
What colour is H? Is 4 brighter than 9? For most people these questions might seem baffling, but not for people with grapheme-color synesthesia.
In the first long-term childhood study on grapheme-color synesthesia, researchers followed 80 children to determine when and how associations between graphemes and colors develop. The latest results are published in the open-access journal Frontiers in Human Neuroscience.
Grapheme-color synesthesia is a harmless, alternative form of perception caused by subtle differences in the brain – possibly, stronger connections between centers for language and color – that give letters and numbers their phantom colors. It is passed down from parent to child in around 1 to 2% of the population.
In the present study, a group of synesthete children was tested three times between 6 and 10 years old. Each child was presented with 36 graphemes – the letters A to Z and digits 0 to 9 – and asked to choose the ‘best’ of 13 colors for each.
Children with grapheme-color synesthesia had already developed strong associations for around 30% of graphemes at 6 years old. At 7 years old, the same children had associations for around 50% of graphemes, and this increased to 70% of graphemes at 10 years old. The synesthete children were consistent in their choices over this 4-year period. Three children who were synesthetes at ages 6 to 7 were no longer so at 10 years old, indicating that the condition spontaneously disappears in some children as they grow older.
"This repeated testing of child synesthetes in real time allowed us to see for the first time that synesthetic colours emerge slowly during childhood, building up an incremental inventory of colorful letters and numbers," says Dr. Simner, a cognitive neuropsychologist who specializes in synesthesia, from the University of Edinburgh, UK.
The researchers’ next challenge is to determine how changes in the intensity of synesthesia - as strengthening or loss with increasing age - can be explained from changes in the organization of the brain.
(Image: Shutterstock)