Until two years ago, I thought that Wednesdays are green and the number five and letter “S” are red for everyone. I presumed that for everyone, September is silvery and is located right in front of everyones’ left shoulder and it could be pointed at. I thought everyone would see the drift of shapes and colours when listening to Beethoven’s Pathétique sonata! However two summers ago, in the last minutes of a poem analysis session of an English literature course, I got introduced to this world that I have been living in for the last twenty years. The fantasy word to describe this characteristic would be Synesthesia (thanks to my English professor who mentioned it). In the world of neuroscience, it is a condition in which, stimulation of one sense will lead to involuntary stimulation of another sense. This is a genetically inherited trait and would be found in 2 to 5 percent of a general population.
There are two theories introduced so far in order to explain the physiological mechanism behind synesthesia. The first theory states that, communication between regions of the cerebral cortex in the brain that are not otherwise connected in non-synesthetes is responsible for the creation of such mixed senses. Based on this theory, the existing excess neural connections are typically removed during the brain development however in synesthetes, this cross-wirings remain intact and thus synesthetic neural pathways persist.
The other theory states that, in a normal brain there is a certain balance between inhibition and stimulation of neural pathways. However in syntesthetes’ brains, due to reduced inhibition of these normal existing neural pathways, excess communication between certain regions of brain causes the phenomenon synesthesia. This excess stimulation (or reduced inhibition) of neural pathways is believed to be due to the excess amount of the neurotransmitter serotonin S2A.
In the following video, Drs. Cytowic and Frakowiak will talk briefly about synethtesia and its different types among syntesthetes.
Grapheme->colour synesthesia. photo from the user whimperingpenguin: http://flic.kr/p/6yPN1a
Today, synesthesia is an active area of research focusing on finding any correlation between this genetic condition and other neuropsychological conditions such as Attention Deficiency Disorder (ADD), Autism and Schizophrenia due to its neurophysiological similarity to these conditions.
As the final word I would like to add Dr. Veronica Gross’s statement about people with synesthesia which explains that, synesthesia is a “condition” not a “disease” and it has its own benefits to those who have this condition:
“…Synesthesia is not a disease. In fact, several researchers have shown that synesthetes can perform better on certain tests of memory and intelligence… “
Synesthesia is a phenomenon that is largely a gift to those who experience it, since many synesthetes have an aptitude for the arts, a strong sense of creativity, and increased memory skills.
Here is a video summarizing the highlights of this characteristic:
-Shamim
