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Essay on Commonality of Synesthesia Induced by Serotonin

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The study of synesthesia has grown exponentially over the past few decades and as a result there is some level of ambiguity as to the scope of what defines it. Gail Martino and Lawrence Mark propose that synesthesia can be categorized into strong or weak. The former refers to those who experience “a vivid image in one sensory in response to stimulation in another”, whereas the latter is characterized as “cross-sensory correspondence[s] expressed through language, perceptual similarity and perceptual interactions during information processing” (Martino and Marks, 2001). This view implies that even the subtlest forms of cross-modal interactions that take place in the individual, albeit associating certain sounds to sight, deserve some…show more content…
Conversely, the administration of melatonin allowed for a subject to experience grapheme-color synesthesia, in which S1 activation was lowered allowing for the “dis-inhibit[ion] of S2a receptors leading to synesthesia” (p. 903). These conclusions thus support the notion that the uptake of serotonin in the S2a receptors has some correlation to synesthetic experience, yet it is unclear which S2a receptors were specifically looked at. Berit Brogaard recently conducted a study that looked at Brang and Ramachandran’s serotonin hypothesis across drug-induced and acquired forms of synesthesia. Brogaard states that “it has been shown in several studies that psychedelic hallucinogens that function primarily as serotonin agonists,” such as LSD, often induce “auditorial-visual synesthesia” . It is believed that this form of drug-induced synesthesia is a result of “an alternation of functional brain connectivity” caused by the binding of serotonin to S2a receptors (p. 5). In regards to acquired synesthesia following brain injury “research has shown that necrosis following tissue damage leads to local neurotransmitter flooding caused by an excessive release of serotonin and glutamate” (Brogaard, 2013). Damaged tissue requires the cells in the brain to shift to anaerobic glycolysis, which quickly depletes the ATP levels present and ultimately causes the “membrane-ion
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