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Synesthesia Jasmine Wong
Synesthesia: Seeing Sound and Hearing Colours
Jasmine Wong (Year 10, Keller)
Imagine a world where colours flash before your eyes when you hear a sound. Imagine a world where every single letter of the alphabet had a specific colour attached to it. Surprisingly, a minority of us don’t need to imagine this, as this phenomenon happens to a very unique 4% of the world’s population.
We all probably remember Skittles’ 2009 commercial slogan ‘Taste the Rainbow’. When looking at the Skittles, you might imagine the red Skittles tasting like strawberries and the yellow ones tasting like lemons. But according to a neuropsychologist, Don Katz, Skittles are in fact the same flavour. Be that as it may, this does not make you a synesthete because Skittles are scented to make you believe they are flavoured. This plays with a person’s senses by tempting them to ‘taste the rainbow’ rather than visualising it.
Synesthesia is a perceptual phenomenon where you experience one sensory or cognitive pathway that leads to involuntary experiences in a second sensory or cognitive pathway. It is a rare neurological condition in which sensory modalities are crossed, for example, a sense of smell in response to a certain visual stimuli, and it is believed to be polygenic (involving many genes). Contrary to the word ‘anesthesia’, which means a loss of sensation, the word ‘synesthesia’, translated from greek, means joined sensations: ‘syn’ means together and ‘esthesia’ means sensation or to feel.
There are over 60 types of synesthesia. The most common form of synesthesia is grapheme-colour synesthesia in which people who associate letters and numbers with specific colours, genders or even personalities. Dr Cytowic describes synesthetes as ‘seeing the similar in the dissimilar.’ To some synesthetes, the number 3 may be a boy who is athletic and fun, but to others it could be a girl who is studious and quiet. Other forms of synesthesia involve seeing or feeling musical notes as colours or textures (sound synesthesia). In addition, when synesthetes hear different phonemes they may experience different taste in words. This is a very rare type of synesthesia called lexical-gustatory synesthesia: to them, the words ‘college’ or ‘passage’ could taste like a sausage as the words have similar endings.
Figure 1: An example of what a person with grapheme-colour synesthesia may see
It is important to note that synesthesia is more of a trait than a disorder. Disorders such as delusions and schizophrenia are tested positive or negative whereas synesthesia is not. Once synesthetes establish a colour association to letters or numbers in childhood, they typically remain fixed for life. These childhood influences involve imprinting memories through exposure to cultural artifacts such as calendars, food names, musical notes and time units. A single nucleotide change in the sequence of one’s DNA as a result of this exposure can alter perception; therefore, there may be some subjective differences. In other words, exposure to influences during childhood can change the colour synesthetes associate words with.
HOW DOES IT WORK?
There are 4 lobes of the brain that are roughly divided up by function (fig 2). The frontal lobe is responsible for controlling important cognitive skills in humans such as emotional expression, problemsolving, impulses and more. The occipital lobe participates in vision processing and is responsible for analysing content such as shapes and colours. The parietal lobe is in charge of movement and sensation. Finally, the temporal lobe helps us speak, hear and understand the complicated combinations of speaking and listening. The exact mechanism of synesthesia is not agreed on by all neuroscientists, however most believe that the regions of the brain responsible for listening to words and processing them are next to each other.
Figure 2: A basic diagram of the cerebral cortex
THE DIFFERENT THEORIES OF SYNESTHESIA
There are several different theories for the cause of synesthesia:
1. Areas of the brain have anatomical names, but we refer to them as the Brodmann number. The Broadman number was identified in 1909 by a German Neurologist, Korbinian Broadmann, based on cytoarchitectonics (the study of the cellular composition of the nervous system’s tissue which can be seen under the microscope). Of the 52 regions in the cerebral cortex, it is believed that area 37, known as the fusiform gyrus, is part of the colour processing area in the occipital lobe, but it is also a part of the auditory processing which is controlled by the temporal lobe. This theory hypothesises that in synesthetes, neurons and synapses (microscopic gaps/junctions between nerve cells which impulses pass across via diffusion) that are part of one sensory system cross paths with another sensory system.
It is unclear why this occurs, however scientists believe that these cross-connections are present in everyone at birth as it is an inherited biological process, but some people may lose them due to maturation processes, whereas others retain them because of their different genetic composition. Studies by multiple synesthesia experts, such as Carolyn Johnson Atwater, show that coloured-hearing synesthetes (ones who see colour in an auditory stimulus) display activity in several areas of the visual cortex when
they hear certain words, so areas of the visual cortex associated with processing colour are activated automatically when synesthetes hear words.
2. Richard Cytowic’s research shows that the limbic system (a set of structures in the brain that deal with emotions and memory), which includes several brain structures predominantly responsible for regulating our emotional responses, is primarily responsible for synesthetic experiences.
3. Scientists at Baylor University have demonstrated that a specific region of DNA on chromosome 16 is the reason for the grapheme-colour synesthesia (or coloured sequence synesthesia).
4. Other scientists theorise that we are born with our senses mixed up but then over time the neural bridges between our senses shut down, hence we normally experience our everyday senses separately. In this theory, synesthetes’ neural bridges may not have shut down fully, causing them to experience different senses simultaneously.
5. This theory states that synesthesia is caused by neurochemistry. It proposes that instead of being located in its assumed part of the brain, synesthetes have neurotransmitters (chemicals which enable the transmission of nerve impulses and overall functioning of the brain) located in a different region. It also states that a reason for this change of location could be that synesthetes may lack chemicals called inhibitors, which usually prevent this from occurring.
6. Simon Baron-Cohen studies and researches synesthesia at the University of Cambridge and suggests that synesthesia is a result of an overabundance of neural connections in areas of the brain such as V4 (the third cortical area in the ventral stream, receiving strong feedforward input from V2).
Figure 3: Comparison of the hyperconnectivity in the brain between a typically developing child and a child with synesthesia (Source: Cell Reports, Keown et al)
7. A psychologist at Naropa University in Colorado named Peter Grossenbacher believes that synesthesia happens when a single sense area of the brain gets feedback from multisensory areas. This information gets jumbled up unlike in a regular brain, where information from multisensory areas return only to the appropriate single-sense area.
DRUGS AND SYNESTHESIA
Genuine synesthesia is a consistent, predictable and quantifiable phenomenon. Drugs can bring about some aspects of synesthesia where the brain is affected by the drug, but this is completely different from the genuine phenomenon. Since the psychedelic drug LSD was discovered by Albert Hofmann in the 1930s, there have been numerous anecdotal reports about LSD triggering synesthesia. However, initial studies had a number of methodological problems, causing researchers to remain uncertain about LSD’s potential to induce real synesthesia. A group of scientists from the University of London recruited nine men and one woman for a study on LSD and synesthesia. They were all deemed to be physically and psychologically healthy. In the initial testing session, they were all injected with a saline solution to act as a placebo before completing psychological tests to measure synesthesia experience. 7-10 days
later, all participants were invited back. But this time they injected 40-80 micrograms of LSD. This resulted in 2 verified tests of grapheme-colour synesthesia and sound-colour synesthesia. This is because it temporarily alters the subject's neurochemistry. Nonetheless, it does not meet the consistency and specificity requirements of genuine synesthesia.
CONCLUSION
There is still so much more about synesthesia and the way our brains function that we can explore. Although synesthesia can cause many problems in a synesthete’s daily life such as the distracting flashing coloured lights and the mixing up of numbers, scientists believe that synesthesia can reveal something about human consciousness, for example solving the 'Binding Problem', which is how a human mind can bind all of our perceptions together and observe the same thing.
Without synesthesia, many of our favourite pieces of art and music would not exist: Van Gogh would have never produced his famous Starry Night, nor would the hit song ‘Bad Guy’ by Billie Eilish and her brother Finneas O'Connell have existed. All of these artists have chromesthesia (when they hear a sound, they see colour) and used this phenomenon to their advantage to produce something wonderful for the world to see and hear.
BIBLIOGRAPHY
[1] Wikipedia contributors. "Synesthesia." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 10 Apr. 2020. Web. 15 Apr. 2020. https://en.wikipedia.org/wiki/Synesthesia
[2] SciShow. “Hearing Colors, Seeing Sounds: Synesthesia” Youtube, 31 July. 2012, https://www. youtube.com/watch?v=vEqmNX8uKlA
[3] Kate Kershner "How Synesthesia Works" 22 June 2007. HowStuffWorks.com. 15 April 2020 https://science.howstuffworks.com/life/inside-the-mind/emotions/synesthesia.htm
[4] Mayim Bialik. “Do You Hear in Color?! Explaining Synesthesia | Mayim Balik feat. Life Noggin“ Youtube, 31 August. 2017.https://www.youtube.com/watch?v=0e4zSrGpGt0
[5] Eric W. Dolan “ Does LSD induce genuine synesthesia - or something different?” PsyPost. 17 May, 2016. https://www.psypost.org/2016/05/lsd-induce-genuine-synesthesia-something-different-42812
[6] Melissa Lee Phillips “Synesthesia” Neuroscience for Kids http://www.neuroanatomy.wisc.edu/ selflearn/Synesthesia.htm
[7] Dr. Veronica Gross “The Synesthesia Project” https://www.bu.edu/synesthesia/faq/
[8]Alina Bradford “What is Synesthesia” Live Science. 18 October, 2017 https://www.livescience. com/60707-what-is-synesthesia.html
[9] Richard E. Cytowic “What color is Tuesday? Exploring synesthesia - Richard E. Cytowic” Ted-Ex. Youtube. 10 June, 2013, https://www.youtube.com/watch?v=rkRbebvoYqI
[10] Richard E. Cytowic “ Synesthesia” (MIT Press Essential knowledge series) Page 27.
[11] Brainemy “The Brain Explained | Cerebral Cortex - Frontal Lobe - Parietal Lobe”. Youtube. 11 July, 2018 https://www.youtube.com/watch?v=gGeZaEABacE&t=85s
[12] Dr, Sayan Adhikari “Synesthesia - The blending of senses” Good Morning Science. Bio-Sci, Health Science. 16 June, 2018. https://gmsciencein.com/2018/07/16/synesthesia-blending-senses/
