SynesthesiaPatricia Averill, C. Dillon Martin Hall

Presentation Outline

• Description• Definition• Types, common and otherwise• Population prevalence

• Theories• Historical Theories• Neural correlates for Synesthesia

• Evidence for Synesthesia as an ASC• Neuroimaging• “Pop-out” Effects• Further Discussion

Synesthesia Defined

• A neurological condition where an observed stimulus in one sensory modality is involuntarily associated with a particular stimulus in another sensory modality

• For Example:

• 1 2 3 4 5 etc...

• Jan (11 o’clock), Feb (12), etc...

• Robert (apple pie), Jane (orange juice)

Types of Synesthesia

• Grapheme Color

• Letters/Numbers on a page appear to be shaded by or are associated with specific colors

• One of the more common forms

• No consistency for grapheme/color associations across synesthetes

Types of Synesthesia

• Grapheme Color

Types of Synesthesia

• Grapheme Color

• "I was sitting with my family around the dinner table and I don't know why I said it but I said, "The number five is yellow." There was a pause and my father said, "No, it's yellow-ochre." And my mother and brother looked at us like, 'this is a new game, would you share the rules?' I was dumbfounded. So I thought, "Well." At that time in my life I was having trouble deciding whether the number two was green and the number six blue, or the other way around. And I said to my father, "Is the number two green?" and he said, "Yes, definitely. It's green." Then he took a long look at my mother and brother and became very quiet.    Thirty years after that, he came to my house and said, "you know, the number four *is* red, and the number zero is white. And," he said, "the number nine is green." I said, "Well, I agree with you about the four and the zero, but nine is definitely not green!"

Types of Synesthesia

• Music Color

• Tones or other aspects of musical notes (key, timbre, etc.) are associated with specific colors

• Less common than G C

• Some consistency across synesthetes, as higher notes appear to be more brightly colored

Types of Synesthesia

• Music Color

Types of Synesthesia

• Music Color

• " The sounds of musical instruments will sometimes make me see certain colors, about a yard in front of me, each color specific and consistent with the particular instrument playing; a piano, for example, produces a sky-blue cloud in front of me, and a tenor saxophone produces an image of electric purple neon lights"

-SD

Types of Synesthesia

• Lexical Gustatory

• Words and names are associated with a taste or combinations of tastes

• Rare

• Rhyming and syntactic associations common enough to be occasionally predictable (e.g. Tony Macaroni, or Blue Inky flavor)

Types of Synesthesia

• Lexical Gustatory

Absolute -TangerinesGallery -White ChocolateRegister -Pork Pie FillingAcademy -Thin Chocolate BarRent -CabbageAccept -Egg Yolk, HardRequire -Milk, CondensedAcid -Acid DropsGate -Bacon, ColdReservations -Mars BarAcquire -Milk, CondensedGillian -TonguesReserve  -Mars Bar  Acrobat -Choc. biscuit thick Glad -Potato, SlicedAdams -Tomatoes, TinnedGlasgow  - MilkAdmit -SmartiesGlobal -Pear DropsReveal -Meat Jelly, ColdAdrian -Watery, IncompleteGo -Meat LoafReward -Turkish DelightAdventure -Mashed vegetablesGood -CustardRisk -MilkyAdvert -Beef BurgersGordon -DirtRobert -Jam SandwichesGrab -Bacon, ThickRobin -Jam SandwichesAdvice -CarrotsGreat -Grapes

Roger -

Pork Pie Filling

Aeroplane -

Chocolate, Dark

Greed -

Cabbage

Rope -

Bread Crust

Grimsby -

Fruit Gum, Horrible

Ross -

Cornflakes, mlk & sgr

Grip -

Grape Skin

Route -

Pickled Beetroot

Ago -

Meat Loaf

Group -

Grape

Agree -

Cabbage

Guess -

wafer biscuits

Safety -

Toast lightly butterd

?

Prevalence of Synesthesia

• Early Data

• between “1 in 20” and “1 in 20,000”

• Questionable collection methods relying on self-reporting

• Recent Data

• Prevalence of “1 in 23” suggested by random population study

• Simner et al

Prevalence of Synesthesia

• Tends to cluster in families

• Strongly suggests genetic origin

• Likely “X-linked”, as no father-to-son transmission ever recorded

• Slightly more common in women than in men

• 1.1 : 1 ratio, Simner et al

Historical Theories about Synesthesia

• Is it learned?

• once suggested that colored fridge magnets caused a learned association

• doesn’t explain forms other than Grapheme Color

• Doesn’t explain historical accounts before the prevalence of colored fridge magnets

Historical Theories about Synesthesia

• Is it just an overly vivid imagination?

• As with all ASCs, difficult to tell apart from actual subjective experience

• Test- retest reliability

• Synesthetes: 90% over one year

• Non-synesthetes: 30-40%

• Stroop Effect

Two Main Types Of Synesthesia

• Lower Level

• Fusiform Gyrus

• Higher Level

• Angular Gyrus

Lower Level Synesthesia

Higher Level Synesthesia

Low Level Synesthesia: Pop-Out Effects

Low Level Synesthesia: Pop-Out Effects

Other Effects

• Lower the Contrast

• Colorblind Synesthetes

• Roman Numerals (A Concept)

• Higher level synesthetes will see 5 in the same color as the Roman numeral V

• For lower level synesthetes, the Roman numeral will not appear in color

5 and VFor Example:

Fusiform GyrusThe Cross Activation Hypothesis

Angular GyrusConcept & Metaphor

Booba Kiki Experiment

Synesthesia as an Altered State?

• Lack of Pruning (Selectively or Globally)

• Artists and Poets

• Greater prevalence among them

• Relation to metaphor?

• Schizophrenics

LSD

• The threshold dosage level for an effect on humans is of the order of 20 to 30 µg (LSD is extremely potent)

• Doses can be as high as 1,200 µg but higher doses come with the increased risk of “bad trips”

• LSD affects a large number of the G protein coupled receptors, including all dopamine receptor subtypes, all adrenoreceptor subtypes and most serotonin receptor subtypes

• Initially used for psychotherapy

Sensory Effects of LSD

• Users experience Synesthesia

• “LSD does not produce hallucinations in the strict sense, but instead illusions and vivid daydream-like fantasies.”

• Visual Effects

• movement of static surfaces (walls breathing)

• geometric patterns and an intensification of colors and brightness

• Schizophrenics do not experience the effects of LSD

Alternate States and Additional Questions

• Could LSD be the gateway to the synesthesiac experience/consciousness?

• Are synesthetes experiencing the world at a level of consciousness different from the rest of us?

• Do we all have synesthesia at some level?

• Booba/Kiki

• Metaphor

• What about schizophrenics…

• they lack the ability to comprehend metaphor

• they do not experience the synesthesic effects of LSD

Sources• Ramachandran, V. S. & E. M. Hubbard (2001), "Synaesthesia: A window into

perception, thought and language", Journal of Consciousness Studies 8(12): 3-34

• Simner, J.; C. Mulvenna & N. Sagiv et al. (2006), "Synaesthesia: The prevalence of atypical cross-modal experiences", Perception 8(35): 1024-1033

• Wannerton, J. I., “The World of Synaesthesia”, http://www.wannerton.net/

• Synesthesia - Wikipedia, http://en.wikipedia.org/wiki/Synesthesia

• Ramachandran, V. S. and Hubbard, Ed (2003), Hearing Colors, Tasting Shapes, Scientific American, Vol 288 Issue 5 (May 2003), 42-49.

• Ramachandran, V. S. and Hubbard, E.M. (2001). Psychophysical investigations in to the neural basis of synaesthesia. Proceedings of the Royal Society, 268, 979-983.

• Ramachandran, V. S., Lecture, http://www.nyas.org/ebriefreps/ebrief/000500/presentations/ramachandran/player.html

• Duffy, P. L. (2001). Blue Cats and Chartreuse Kittens: How Synesthetes Color their Worlds. New York: Henry Holt & Company