|
|
|
|
Synesthesia:
Language in Color Synesthesia is defined as occurring when stimulation of one modality leads to an involuntary experience in another modality (Goldstein, 1999). The word synesthesia comes from the Greek words, "syn" meaning union and "aistesis" meaning sensation. Although it was first described as a psychological quirk, a lot has been learned since the first reference to synesthesia over 200 years ago (Cytowic, 1989). Synesthesia was first referenced in 1710, describing a blind man who perceived sound-induced colored visions. At some point during its history, synesthetes were seen as mentally defective or artistically gifted. For most, it was an embarrassment and for some it still is. Doctors and researchers were the only ones to publicly describe their symptoms for many years. Presently, those who experience synesthesia do not see it as an obstacle or something that hinders their functioning but some believe that they may be mentally ill. Today, it is predominantly found in women and is characterized as an international phenomenon, which occurs in less than one percent of people (Cytowic, 1989; Hornik, 2001). Synesthesia can combine any or all five of the senses. The most common combination is found with sight and sound, which is also referred to as colored hearing. For synesthetes with colored hearing, sound causes them to see moving colors and shapes that are externally projected. For these individuals, "I see what you are saying," can mean exactly that (Cytowic, 1989). As described by one synesthete, letters, numbers, names, and simply words in general cause her to see a flash of colors. When trying to remember someone’s name, she stated, "I knew the name was green. It started with ‘F’ and ‘F’ is green," (Hornik, 2001). She also said that the letter does not appear in color but rather there is a flash of color. The letters do not evoke the same color for everyone. Because of this color association, many synesthetes have described synesthesia as a memory aid. As with the coloring of names, a color is associated with them, which helps with recall. Synesthesia makes life richer according to one synesthete (Hornik, 2001). Feeling pain in color is another sensation which synesthetes experience. One synesthete had an accident where she tore a ligament. At the moment of the accident, her experience was that everything became orange and she felt as if she were wearing orange sunglasses. After another incident where she stubbed her toe, she yelled out in pain but all she could initially say to her husband was the word orange (Hornik, 2001). Synesthetes may see blobs, spirals, cross-hatching, and/or moving lines but color and geometric shapes are most described. They may also taste salty or metallic tastes and feel cold, prickly and/or rough textures (Cytowic, 1989). Synesthesia has been described as more than cross-modality; it is higher cortical functioning. It is defined by five criteria that separate it from basic imagery. The experience must be involuntary and it cannot be suppressed. The sensations also appear externally as being real and not imagined, not simply in the mind. The sensations are very few and are categorical or generic. They are highly memorable as well. Strong emotion and sense of conviction accompany the sensations. (Cytowic, 1989) In the past, it had been difficult to identify the pretenders from those who actually have synesthesia. (Hornik, 2001) Synesthesia can be categorized into idiopathic synesthesia and synesthesia whose etiology is already known to the medical world. Epileptic synesthesia which is related to seizures and drug-induced synesthesia stemming from use of hallucinogens such as LSD are accounts of synesthesia with a known etiology. It may also be experienced by electrical stimulation of the temporal cortex. Idiopathic synesthetes have normal neurologic exams and are of normal intelligence. The trait appears in childhood and because of this adult synesthetes are surprised to find that others do not have the same perceptions. Left-handedness or mixed dominance is commonly found in idiopathic synesthetes (Cytowic, 1989). Recently, there has been a surge of interest in studying synesthesia. This has not occurred because of an increased number of individuals declaring with experiences commonly described as synesthesia. Instead, due to the interest in the study of the brain, the interest in synesthesia has increased as well. Peter Grossenbacher, a researcher at the National Institute of Health, introduced one theory of the etiology of synesthesia. His theory suggests that input travels from single-sense modules along a pathway into a multi-sensory area. Grossenbacher adds that there also are pathways which exist that travel back again. For the majority of us, these backward paths are inhibited but for synesthetes, their feedback mechanism is unusually strong. The sensory connections appear normal but the usage of the connections is abnormal. Another theory suggests that we as infants all experience synesthesia until six months of age. After six months of age, generally, as the infant’s brain develops the multi-sensory connections die and the infant’s responses are divided. According to this theory, synesthetes do not have this division during infancy which results in cross-modality or synesthesia (Hornik, 2001). A study conducted in 1993 by Dr. Simon Baron-Cohen, a psychologist at Cambridge University, looked at using positron emission tomography and the cerebral blood flow and neural activity of synesthetes versus non-synesthetes. The participants were asked to listen to words recorded on tape. Non-synesthetes, the control group, listened to the tape and showed activity in the language areas. For the synesthetes, blood flow was increased in the visual cortex areas. The notion here is that even though the synesthetes did not see anything, visual information was being processed. In recent times, functional Magnetic Resonance Imaging affirmed these results. Interviews, sophisticated screening, and imaging techniques used to observe neural activity and measure the brain’s response to stimuli are other testing methods which are being used (Hornik, 2001). Other sources determine that the left-hemisphere is where the synesthesia is located and that the mechanism important for creating the parallel perception is the hippocampus. Evidence for this includes right-left confusion, difficulty with spatial relations, and a poor sense of direction (Cytowic, 1989). Currently, researchers are looking at the genetic factor of synesthesia (Hornik, 2001). Paulesu and co-workers in 1995 also conducted a study using positron emission tomography measuring the brain activity of six women. The women who experienced color-word synesthesia were presented pure tones with which there was an increase in brain activity in the auditory areas. A contrast was found when the participants were presented with words. Increased activity was then found in the language area and in some higher order visual areas (cited in Goldstein, 1999). A conclusion was made at the completion of this study that color-word synesthesias occur due to an interaction between the language and visual areas. Non-synesthetes can also draw associations between modalities using cross-modality matching. This technique involves adjusting a stimulus in one modality to match a stimulus in another modality, thus forming a relationship between the two. In a study providing evidence for this, the participants were presented with pieces of paper ranging from black to white and were asked to match them with a tone. It was found that squares that were lighter were associated with higher pitches (Goldstein, 1999). Synesthesia has come a long way since its description as a psychological quirk. As we learn more and more about the brain, we will also discover more about the experience of synesthetes. A better understanding of it will develop as we uncover more about neural activity in the brain and the sensation itself that is perceived through the many testing methods that have been introduced. Synesthesia may not seem to be advantageous and may seem like a burden to non-synesthetes but may actually be pleasurable and provide a new description of life not only with words but also with colors and shapes. "Although the senses are separated in many ways, they also share commonalties of experience" (Goldstein, 1999, p.344).
References Cytowic, R. E. (1989). Synesthesia and mapping of subjective sensory dimensions. Neurology, 39, 849-850. Goldstein, E. B. (1999). Sensation and perception (5th ed.). Pacific Grove, CA: Brooks/Cole. Hornik, S. (2001). For some, pain is orange. Smithsonian, 48-54.
|