Synesthesia

I have decided that I might as well get some use out of my old papers from undergrad/grad school so I will slowly be going back and posting them to my blog after I quickly review and make any necessary revisions.   This is the first in the series of old papers.  This particular paper is from 2008.

        Synesthesia is best described using a translation from its Greek parts “syn” meaning “together” and “aesthesis” meaning “sensation” or as Cytowic(2002) translates it “a union of the senses”.  Synesthesia is truly a union of at least two senses in those with the condition.  Synesthesia has many accepted forms and they can be “bewildering in their variety: sounds can evoke colors; tastes can evoke shapes; colors can evoke smells; pain or sexual orgasm can evoke colors, and so on.”(Robertson and Sagiv, 2005) , because of this great diversity some have adopted a specific format for listing the type of synesthesia a person experiences.  Typically, the stimuli experienced is listed first and then the additional experience is listed second.  For example grapheme-color synesthesia describes a version of the condition in which a person perceives a particular grapheme which triggers an extra perception of color not associated with the physical world in any empirical way.  An interesting point raised in Fundamentals of Human Neropsychology is that almost everyone knows what it is like to truly feel sound.  Consider the intense physical reaction many have when confronted with the sound of fingernails on a blackboard.  People with a form of synesthesia in which they feel particular everyday sounds can sometimes experience similar sensations, although the extrasensory perceptions experienced by those with synesthesia are not necessarily adverse.

        Synesthesia can initially be broken down into two categories.  Congenital synesthesia and synesthesia that is brought about due to drug use, seizure, blindness/deafness,  or occasionally injury.  The fact that synesthesia like perceptual changes and hallucinations can occur while under the influence of multiple drugs has unfortunately lead to the assumption by many that those with synesthesia have been heavy drug users at some point.  The DSM-IV-TR actually lists synesthesias under its diagnostic criteria for hallucinogenic intoxication and “Essentials of Psychiatry” lists synesthesia related perceptions as a method to distinguish between PCP psychosis and LSD psychosis.  While these drugs do in fact replicate some forms of synesthesia “the idea that synaesthesia is a result of drug use is only applicable to a few people, and seems to occur only during the ‘trip’. One explanation of this is that certain drugs might pharmacologically mimic the same physiological mechanisms that underlie genetically based synaesthesia.”(Ramachandran & Hubbard, 2001) Furthermore, because not all who use drugs associated with synesthesic events(LSD, mescaline, marijuana) have a synesthesic experience it could very well be that “only those with a genetic predisposition will experience synaesthesia under the influence of psychoactive drugs.” (Ramachandran & Hubbard, 2001) A good example of psychedelic induced synesthesia is the French poet, Baudelaire, “whose drug experimentation was well known”.  Baudelaire wrote about the color of vowels: ““A noir, E blanc, I rouge, U vert, O bleu” (i.e., A = black, E = white, I = red, U = green, and O = blue).” (Fatemi and Clayton, 2008)

        Grapheme-color synesthesia is thought to be the most common, although while there is existing literature to back this assertion it is the “tremendous volume of unsolicited, anecdotal accounts we have received from synesthetes” (Robertson et al. 2005) that gives this position it a lot of its strength.  Studies have indicated that among this type of synesthesia people can generally be broken down into two categories.  “Associator synesthetes are the most common type of colorgraphemic synesthete, and they typically report that they experience synesthetic colors in their “mind’s eye.” Projector synesthetes, on the other hand, account for just 5 or 6% of all color-graphemic synesthetes, and they report experiencing synesthetic colors as colored overlays bound to the graphemes.” (Robertson and Sagiv, 2005)

Interestingly, synesthesia appears to have some interaction with hypnotic color blindness.  Once under hypnosis and made blind to the color red a particular individual was noticed to have lost “conceptual values and meanings for the word three and its corresponding numeral”(Erikson 1943).  A second instance of synesthesia noticed through hypnotic color blindness also involved the color red.  Once made blind to this color the subject reported a “a feeling of unfamiliarity for that number[7] despite its recognition”(Erikson 1943).  Uppon further investigation the subject was found to have associated certain sounds with the color red.  While blind to red the subject reported that “these sounds lost their chracteristics of warmth and familiarity and in some instances she failed to recognize them, especially in connection with music.”(Erikson 1943)

        When discussing synesthesia one must consider the case of S.V. Shereshevkii, who is usually referred to just as S. in most literature.  As discussed in Foundations of Cognitive Psychology by Daniel J. Levitin, “He seemed to have the exceedingly rare ability, known as synesthesia, to conjure up vivid images of light, color, taste, and touch in association with almost any sound. These images also helped him to remember new information.”  When looked at from a cognition point of view, having synesthesia should help a particular person have a far more detailed memory of most of their experiences due to the shear number of additional cues stored with their perceptions.  Having so many cues with which to draw from makes it easier for one to set off a chain reaction in their memory.  This lends credence to the reports of some with synesthesia who describe their memory, particularly memory regarding numerals, being similar to walking an imaginary landscape that just seems to contain the information they are looking for.   This is very similar to how a high school reunion seems to have a cascading effect on ones memory in which one persons voice, story, or mannerisms sets of a chain reaction among those within range of perception. 

        In the case of S., his exceptional memory eventually lead to his being noticed and informed of his differences from the general population.  S. was a newspaper reporter and “the fact that he never took notes at briefings as  other reporters did brought him to the attention of his employer, who questioned him on the matter.  S. responded by repeating verbatim the transcript of the briefing they had just attended”(Kolb and Wishaw 2003) Furthermore, as S. discussed his abilities he revealed that he “did not consider himself unusual, although he wondered why other people relied so much on written notes.”(Kolb and Wishaw 2003)  S.’s employer eventually convinced him to get in contact with a psychologist.  This lead him to A.R. Luria who studied his remarkable abilities over the following 30 years.

        Luria provides an account of these studies in his book, The Mind of a Mnemonista particularly interesting experiment that was performed to study S.’s synesthesia was conducted in the Laboratory on the Physiology of Hearing at the Neurological Institute, Academy of Sciences.  When “presented with a tone pitched at 20 cycles per second and having an amplitude of 100 decibels, S. states that her saw a strip 12-15 cm. in width the color of old, tarnished silver.”  When the stimuli was changed to  a ton set to 50 cycles per second at an amplitude of 100 decibels, S. reported “a brown strip against a dark background that had red, tongue-like edges” as well as reporting a “sense of taste he experienced was like that of sweet and sour borscht”.  One last example from this experiment is of when the stimuli was adjusted to 500 cycles per second and to an amplitude of 74 decibels S. reported that he “saw a dense orange color which made him feel as though a needle had been thrust into his spine.”  Understanding that many would discount S.’s reports as being made up as he went along, Luria decided to retest the stimuli over multiple days and found that “invariably the same stimuli produced identical experiences”

        Synesthesia is an intriguing condition and definitely one that merits further study. Hopefully one day the discoveries made from studying synesthesia can help lead to breakthroughs in memory that will not only improve quality of life for those suffering from conditions that degrade memory but also improve the abilities of everyday people.  When the abnormal is understood completely the chance for the normal to become extraordinary increases exponentially. 

Kolb, B, & Wishaw, I (2003). Fundamentals of Human Neuropsychology.W H Freeman & Co.

Robertson, L, & Sagiv, N (2005). SYNESTHESIA Perspectives from Cognitive Neuroscience.New York: Oxford.

Cytowic, R.E. (2002). Synesthesia: A Union of the Senses. (2nd ed.). New York: MIT Press. As cited in (Robertson and Sagiv, 2005)

(2000). Diagnostic and Statistical Manual of Mental Disorders. Washington DC: American Psychiatric Association.

Ramachandran, V.S., & Hubbard, E.M. (2001). Synaesthesia—A Window Into Perception, Thought and Language. Journal of Consciousness Studies. 8, 3-34.

Fatemi, S, & Clayton, P (2008). The Medical Basis of Psychiatry.Humana Press.

Erickson, M. (1943). Hypnotic investigation of psychosomatic phenomena: Psychosomatic

interrelations studied by experimental hypnosis. Psychosomatic Medicine, 5,

51-58.

Levitin , D Foundations of Cognitive Psychology .

Luria, A.R. (1963). THE MIND OF A MNEMONIST. New York / London: Basic Books, Inc.

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