Synesthesia: Imagined or Reality
First, please note that the info on this page is not all from me. If you decide to use any of it for part of your research for a paper, it would be very wise to try and find the information in my list of references. :)
The idea from this page came from having to do a project in one of my classes on synesthesia. It is a very interesting disorder and I hope to enlighten some people on what it is. Enjoy!!!
What is Synesthesia?
The word synesthesia means "joined sensation." It denotes the rare capacity to hear colors, tast shapes, or experience other "mixes" of the senses. Someone with synesthesia might describe the color, shape, or even flavor of your voice for expamle. The experience is usually projected outside of the body, not in the mind like most would think. They estimate that around 1 out of 25,000 people have synesthesia, but Cytowic (the leader in understanding this disorder) believes this estimate is far too low. There is such thing as drug induced synesthesia caused by psychoactive drugs such as LSD, mescaline, and psilocin.
General Features of Synesthesia
All synethetes declare that the sensory associations stay the same throughout their life. For example, if at age four, "Gina" sees red flashes when someone says the word "Hello", she will see the exact same red flashes to the same word even when she is forty! Synesthesia runs in families in a pattern consistent with either autosomal or x-linked dominant transmission. So far, no male to male transmission has been found. Women synethetes dominate 3:1 in the US and 8:1 in the UK. Synethetes have also been found to be predominantly right handed. All synethetes would be considered "normal" if you met them anywhere. Clinically, those with synesthesia seem mentally balanced. Their MMPIs are remarkable and standard neurological exams are normal. Many synethetes have very good memories and their spatial location (remembering the exact placing of things in a room even when in a different one) is very good. As far as the Wechsler Memory Scale, synesthetes perform in the superior range. They have found that some synesthetes can have uneven cognitive skills, low mathematical skills, right-left confusion, or a poor sense of direction. A first degree family history of dyslexia, autism, and ADD is present in about 15%.
The History of Synesthesia
Synethesia has been known medically for nearly 300 years! Interest peaked between 1860 to 1930, then disappeared after that. There are ten possible pairings of the five senses. The pairing is usually uni-directional. This means that in one person, sound may induce touch, but (in that same person) touch will not induce sound. Get it? This fact actually turns the 10 possiblities of pairings into 20 possible pairings!! It has also been found that it is rare for taste and smell to be the trigger or the response. Richard Cytowic has only found one case (see the case of VE) in which sight evokes smell and one case (see the case of MW) where taste and smell actually evoked a widespread tactile experience. There is one case of audiomotor that has been documented, which is actually quite strange. It is a 14 year old boy who when introduced to certain sounds actually distorted his body in different ways to each sound. A group went back a few years later to see if anything had changed (possibly to also make sure he was not faking it), and found that he made the exact same distortions to the exact sounds as he did the last time!!
Neurology
Synesthesia depends only on the left brain hemisphere and is accompanied by large metabolic shifts away from the neocortex that result in relatively enhanced limbic expression. Some cortical areas are expected to "light up" during a synesthestic experience, but they actually found that cortical metabolism plummets during an experience. This is impossible for regular humans to obtain...even with drug administration. MW's cortical levels dropped so low during an experience that he should have been blind, paralyzed, or shown some other form of a lesion, but his thinking and neurological exams showed no impairment!!
It has also been requested that the hippocampus should be a focus of testing. Seizure discharges in the hippocampus of the limbic system produce synesthesia in people who do not have it otherwise. Synesthesia is experienced in 4% of limbic seizures. Those that remain confined to the hippocampus produce an elementary experience (meaning the experience is not quite to the extreme as a realy synesthesia experience). Only when seizures spread to the cortex of the temporal lobe does the perception become more specified and elaborated.
Diagnosis of Synesthesia
Richard Cytowic suggests that there are 5 features for diagnosing synesthesia:
1) The experience is involuntary but elicited - This means that the experience cannot be called
up at will
2) Synesthesia is projected - The experience is not in the mind but actually projected outside
the person's body
3) Perceptions are durable (the perception does not change throughout the persons life),
discrete (each person's perception has unique qualities, no one person's experience is
the same as another's), and generic (not highly complex)
4) Synesthesia is memorable (sensations are easily and vivdly remembered)
5) Synesthesia is emotional and noetic - During the beginnings of their life, synesthetes
do not realize that they are reacting to their environment any differently than anyone
else. Although they eventually realize that the perceptions are not shared by everyone
else, they do know that what they experience is very real and very vivid.