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Lia Chen

on 31 May 2016

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Transcript of Synesthesia

What is Synesthesia?
Exploring Specific Types of Synesthesia
What is the Cause of Synesthesia?
Treatments for Synesthesia?
No definitive treatments since the
majority of synesthetes do not suffer from adverse ill effects
special gift/blessing
One sense is
perceived with one or more additional senses
The automatic joining of letters, shapes, numbers, names with a sensory perception such as smell, color or flavor
Can take
many forms...
A neurological phenomenon in which stimulation of
one sensory or cognitive pathway
leads to automatic, involuntary experiences in a
second sensory or cognitive pathway
The word "synesthesia" originates from two Greek words:

syn (union) + aisthesis (sensation)
Lia Chen
CTY 2013: JHU Neuroscience A Session 1
Association of individual letters/numbers with a specific color
The majority of color-grapheme synesthetes only "feel" or "sense" the colors
The 10% minority of these synesthetes physically perceive projected colors on each grapheme
Associations consistent over time
Grapheme-Color Synesthesia


History of Synesthesia Research
Current Research
Heard sounds automatically evoke an experience/visualization of colors
For certain people, the stimuli are limited, and only a few types of sounds will trigger a perception (ex: speech sounds)
However, there are cases wherein several different sounds trigger color visualizations.
Ordinal Linguistic Personification (OLP)
Ordered sequences (ordinal numbers, days, months and letters) are associated with human characteristics
One may characterize the letter "A" as rude, happy etc.
Lexical-Gustatory Synesthesia
These synesthetes experience different kinds of tastes when they hear certain words or phonemes.
One of the more rare and intriguing types of synesthesia
Associations between words and tastes are
only by foods that synesthetes have tasted early in life
Can you count how many
5's there are in this image?
Now try...
This is how
color-grapheme synesthestes
perceive numbers
No concrete origin
Synesthesia is idiosyncratic
no two synesthetes will share the same experiences
Several theories...
Possible Benefits/ Disadvantages of Synesthesia
One experimental case suggested that synesthetes have an advantage in visual search and episodic memory tasks.
The results of the experiment indicated that synesthesia (by itself) does not necessarily lead to any advantage in performance.
Rather, the superior performance of synesthetes observed may have been due to a selection bias or individuals who used their synesthesia to their advantage
If the synesthesia
prove to be problematic,
psychological treatment
may be of assistance __________________(hypnosis)_________________________
Common traits among synesthetes...
Common traits among synesthetes...
-creative, artistic, or musical
-very visual people
-generally have strong memory and memorization skills
-usually very kinesthetic
-Some are obsessive-compulsive
-tendency to isolate oneself
-ridicule from peers
-incompetent math abilities (OLP)
-Synesthesia is sometimes linked to autism (crossover similarities between the two conditions)
Theories about Synesthesia
Irregular sprouting of
new neural connections
within the brain
of the boundaries
that normally exist between the senses.
Vilayanur Ramachdran's theory of crossmodal perception: senses "cross-activatating" each other, causing the
additive experience
of perceiving color when seeing a letter or number
Subtypes of number-color synesthesia are caused by hyperconnectivity between color and number areas at different stages in processing
Charles and Daphne Mauer's theory: newborns infants begin life as synesthetes, born with
immature brains that are highly malleable.
Connections between different sensory parts of the brain exist that later
become pruned or blocked
as the infant matures.
Grapheme-color synesthetes merely their associations based on associations made at a young age (automatic connections made with environment)
Hereditary synesthesia genes
studies suggesting that the genes for synesthesia are dominant and located on the X-chromosome.
Certain psyhcedelic drugs/hallucinogens, such as LSD, psilocybin, mescaline, can also induce synesthesia in some individuals.
Richard Cytowic, notable neurologist, defines synesthesia as...

1. Involuntary and automatic sensations
2. Must be projected into an environment; must have sense of location
3. Sensations are consistent the same stimuli will produce similar sensations
4. Highly memorable sensations
5. Emotional experiences
2-4% of the population
1 out of every 25,000 people in the US
*Women are 6 times more likely to inherit synesthesia
How Common is Synesthesia?
Dr. Richard Cytowic estimates...
1 out of every 2,000 people in the UK
Effects on the
Nervous System
extraordinary perceptions of the world
The Results
The Future of Synesthesia?
Evolutionary significance of synesthesia
Neuroscientists David Brang and V. S. Ramachandran believe that synesthesia may have a "hidden agenda," one that
Improves the world's artistic legacy.

linkage to increased creativity
Natural selection
Awareness is growing
Ancient Greece: The interest in colored hearing (co-perception of color in hearing sounds or music)
17th Century: Physicist Isaac Newton tried to assume that musical tones and color tones have frequencies in common
19th century: American scientist Mary Calkins coined the term "synesthesia"
End of 20th century: Richard Cytowic's work
21st century: Currently a boom of fascination
experiments, statistical analysis
Thank you!

Physiology of Grapheme-Color Synesthesia
in the Brain
visual-grapheme area in the brain: located in the fusiform gyrus
adjacent to V4 (visual color area)
Lower Synesthestes: influenced by the visual appearance of a grapheme/number
ex: Roman numbers (I, II, III, IV, V) consistently do not evoke color only a number's appearance (not the abstract idea of a number)
Higher Synesthestes: perceive color with more abstract numerical concepts, sequence of numbers
Full transcript