Synesthesia Abstract: Synesthesia is a condition in which a multiple sensory response is triggered by a particular stimulus, causing the synesthete, as people with this condition are called, to generate automatic reactions and coherent associations. Although synesthesia was originally considered an illegitimate condition, growing studies and the advancement of technology support the fact that synesthesia is a true neurological phenomenon. Furthermore, there is evidence to show that synesthesia has a genetic factor, and is also a beneficial trait, causing increased memory capacity and stimulating creativity in some individuals. The cases of Daniel Tammet, an autistic savant suffering from synesthesia, and Stephen Schwartz, a musical composer, help support this idea. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay “Taste the rainbow,” a popular slogan used by Skittles, is not as absurd as it might seem. In fact, those who suffer from synesthesia, appropriately called synesthetes, may have this ability. Synesthesia, as its Greek roots imply, refers to a “fusion of the senses” (Palmeri, 2006). A stimulus perceived by one sense is simultaneously perceived by another sense. Even so, for a given stimulus, the number of senses stimulated can be more than two. To illustrate, a visual image can elicit a sound; a sound can elicit a taste. Synesthetes experience this phenomenon consistently, meaning the same image can repeatedly elicit a specific sound. Although this illustration suggests a form of learning known as acquired association, the multiple sensory responses to a stimulus characteristic of synesthesia are involuntary. Synesthetes usually do not recognize that they have synesthesia, because they believe that their perceptions are real. Therefore, synesthetes are often diagnosed by other people, who note the extraordinary perceptions of synesthetes. In order to be diagnosed with synesthesia, specific clinical criteria must be met. Synesthetes' experiences of the intertwined senses must be involuntary and coherent. Various tests have been developed to diagnose different types of synesthesia. Many tests measure how quickly and accurately subjects respond to a stimulus based on the perceptions they say they have. To diagnose grapheme-color synesthesia, for example, subjects are first given a "color coherence test" in which they can select a color that matches what they experience when presented with different symbols, words, or numbers. After this initial step, subjects should then take a timed test displaying a grapheme and a color, and they should each respond as quickly as possible whether or not that color matches their original perceptions. People who truly experience synesthesia respond to this test much more accurately than non-synesthetes, demonstrating that a synesthete's perception of words associated with different colors is involuntary and automatic and is not memorized or learned through habit. (Cytowic, 1995). Since the first recorded cases of synesthesia, people have questioned the validity of synesthetes' experiences. Indeed, synesthetes often face stigma from skeptics, who claim that synesthetes simply have “overactive imaginations” (Palmeri, 2006). Understandably, the dismissal of synesthesia as a legitimate condition stems from the paucity of comprehensive research at the time. In 2001, hoping to provide evidence to support the legitimacy of synesthesia, Ramachandran and Hubbardpublished a paper in which they concluded that synesthesia, particularly grapheme-color synesthesia, in which numbers and letters also register as colors, was more of a sensory effect than a cognitive one. Ramachandran, 2001). They were able to conclude this based on five experiments with two synesthetes. In one of these tests, subjects were asked to find an embedded shape between 5 and 2 (see image #1). The mirror images of the 5 and 2 serve to distinguish synesthetes from non-synesthetes since synesthetes, with their distinct colors for distinct numbers, were expected to detect the image more easily than non-synesthetes. Indeed, after measuring the performance of both synesthetes and non-synesthetes, the two scientists found that synesthetes “were significantly better at detecting the embedded shape than non-synesthetes” (Ramachandran, 2001). As further evidence, functional magnetic resonance imaging scans (fMRI scans) of synesthetes and non-synesthetes show differences in brain activity between the two, indicating that synesthesia is in fact a real phenomenon (Kiederra, 2005). There are several types of synesthesia, the most common and well-studied being grapheme-color synesthesia, in which symbols or words are perceived as having different colors. Other less common types of synesthesia include lexical-gustatory synesthesia, in which words and colors have certain tastes associated with them, and linguistic-ordinal synesthesia, in which different personalities are given to sounds, symbols, tastes, or days of the week. With grapheme-color synesthesia, there is strong evidence to support a neural basis for the condition. Using neuroimaging methods, studies show that “cross-wiring” between certain brain regions causes an individual to experience different senses simultaneously. For a grapheme-color synesthete, a region of the visual cortex and the color area of ​​the fusiform gyrus have interconnected neural connections, which result in the experience of colors when seeing words and numbers (Ramachandran, 2001). An excess of neural pathways may be linked to problems that occur during the neurodevelopmental process, specifically involving synaptic pruning. Synaptic pruning is a regulatory process that occurs from infancy to late childhood, in which extra or unnecessary neural connections between brain regions are removed. This process plays a key role in early brain development and, in synesthetes, it is hypothesized that pruning does not occur normally or is inhibited, explaining the abundance of synaptic connections. (Synesthesia: opening the doors of perception, 2010). Furthermore, newborns have many interconnected brain regions due to incomplete pruning. At this age the senses are not yet very distinguishable, when you are exposed to a stimulus, such as a face, the visual cortex can be activated along with the auditory cortex or other parts of the brain, similar to synesthesia. Another explanation for the cause of synesthesia describes a disinhibition of already existing neural connections. While the cross-activation hypothesis describes that a person with synesthesia has more connections than a non-synesthete, disinhibited feedback suggests that a synesthete has no abnormal pathways but only a disinhibition of normally existing ones (Grossenbacher and Lovelace, 2001). This explanation would also mean that a non-synesthete has neural connections that link multiple senses, but they are inhibited across the processing areas of the brain. Synesthesia has been studied and found to run in families, with 40% of synesthetes reporting a close relative with the condition (Brang and Ramachandran, 2001), however the individual perceptions experienced vary fromperson to person. Furthermore, types of synesthesia also vary within a family of synesthetes, suggesting that the genetic basis is more general rather than specific (Ward, 2011). A genetic factor would also help support the cross-activation hypothesis that synesthesia occurs due to a disruption of regular synaptic pruning. A mutation of a gene that initiates this process can lead to these extra neural connections, but no clear gene has yet been found to explain this (Ward, 2011). Researchers studying the inheritance of synesthesia had previously thought it may be an X-linked chromosomal disorder, due to the high prevalence of female synesthetes, however this bias is less than previously suggested due to more recent testing conducted with larger populations of synesthetes (Simner et al., 2006). Other studies show that multiple genes on different chromosomes (2, 5, 6 and 12 instead of X) may be responsible for synesthesia (Asher et. al., 2009). True synesthesia is separate from learning associations, however there are different cases of acquired synesthesia. The loss of a sense, such as sight, led to the reorganization of neural connections between different sensory areas. As a result of synaptic plasticity, connections are rewired and further strengthened. Acquired auditory-visual synesthesia is often reported in people who have become blind, but only after a long period of time (usually after a year). (Ward, 2011) Phantom limb syndrome is another form of acquired synesthesia that is the result of plasticity and reorganized pathways. Visual cues or other forms of sensory reception might cause a patient (with an amputation) to experience sensations of pain where the limb used to be (Ramachandran, 1996). Acquired synesthesia can occur following damage to the spinal cord or brain, but these cases are generally rare. In one case, a 45-year-old man who suffered a posterolateral thalamic hemorrhage acquired both auditory and visual synesthesia (Schweizer et. Al., 2013). He developed synesthesia nine months after suffering a hemorrhagic stroke in the thalamus of his brain. He has acquired lexical-gustatory (color-taste) and ordinal linguistic (sound-emotion) synesthesia. For example, eating raspberries makes him think of a shade of blue, and seeing blue creates the taste of raspberries. The high-pitched instruments, and especially the “James Bond” theme song, give it a feeling of euphoria. He is also able to turn his synesthesia on and off. Finally, there are types of temporary synesthesia that can be induced by epileptic seizures and the use of antiserotonergic hallucinogens. However, these should be distinguished as pseudo-synesthetic experiences as there are fundamental differences between true synesthesia and these examples. This is mainly due to the fact that these perceptions are “inconsistent, non-automatic and highly dependent on the subject's current state” (Sinke et. al., 2012). Synesthesia is generally not considered a debilitating condition, so most who suffer from it do not require treatment. In fact, grapheme-color synesthetes tend to perform better in memory recall tasks due to the already existing associations between symbols and colors (Carriere et. Al., 2009). For example, many synesthetes explain that seeing colors with different letters helped them memorize names, phone numbers, or dates. An extreme case related to this is that of Daniel Tammet, a high-functioning autistic savant (a person with extremely prodigious abilities) who attributes the memorization of over 22,500 digits of Pi to his synesthesia. When he recites numbers, he visualizes landscapes with colorful shapes, 2013).