User:Lisa Diez/sandbox

Lead
(Chromesthesia or sound-to-color synesthesia is a type of synesthesia in which sound involuntarily evokes an experience of color) *add: shape, and movement.

* Remove: With sounds inducing color concurrently, chromesthesia is sound-color synesthesia. (Not backed up and redundant).

* Add: Chromesthesia can be induced by different auditory experiences, such as music, phonemes, speech, and/or everyday sounds.

History (New section)
"For History of Synesthesia: History of synesthesia research"The terms synesthesia and chromesthesia have developed and evolved considerably throughout history. The first documented synesthete was Georg Tobias Ludwig Sachs in 1812. Although he did not give a specific name to his experience, in a medical dissertation regarding his albinism (written in Latin), he mentioned obscure ideas and described how colored ideas appeared to him. Even earlier than Sachs, however, Johann Gottfried Herder discussed similar ideas in his Treatise on the Origin of Language in 1772. He talked about how people, "through a sudden onset immediately associate with this sound that color".

The first concrete term associated with chromesthesia was given by Charles-Auguste-Édouard Cornaz in an eye disease dissertation in 1848. Color blindness was a common condition known as chromatodysopsia and, since Cornaz saw chromesthesia as the opposite, he named it hyperchromatopsia or perception of too many colors.

In 1881, Eugen Bleuler and Karl Bernhard Lehmann were the first to establish six different types of what they called secondary sensations or secondary imaginations. The first, which was the most common, was sound photisms. They described it as "light, color, and form sensations which are elicited through hearing". Their book was reviewed by an Austrian newspaper, where the term colored hearing, still commonly used today to describe chromesthesia, first appeared.

Research on synesthesia in the United States began in 1892. And, since 1895, the term finally expanded from pure sound-to-color experiences (chromesthesia) to a wide range of phenomena, including grapheme-color synesthesia, mirror-touch synesthesia, and lexical-gustatory synesthesia. The rise of behaviorism between 1920 and 1940 resulted in a considerable decline in interest for synesthesia, as it was seen as "little more than a learned association". The number of scientific papers on the topic rebounded around 1980 and exponentially increased in the 21st century, where substantial progress has been made to study it empirically and understand the mechanisms at work.

Drug-induced chromesthesia (New section)
Chromesthesia can be transiently induced with chemical agents through the manipulation of neurotransmitters. These substances can also modulate existing synesthesia. Psychoactive drugs including LSD, mescaline, psilocybin, and ayahuasca are non-selective serotonin agonists that elicit spontaneous synesthesia, specially sound-to-color.

The first to report drug-induced chromesthesia was Théophile Gautier in 1845. Under the influence of hashish, he described: "My hearing was developed extraordinarily; I heard the noise of colors. Green, red, blue, yellow sounds reached me in perfectly distinguishable waves". Gautier made a sketch of Gustave Moreau playing the piano, where he depicted his chromesthetic experiences as lines of color above the instrument.

Recent scientific studies, with enhanced methodologies, suggest that drug-induced synesthesia is substantially different from congenital synesthesia. Psychoactive substances "affect ongoing streams of transmission rather than causing stimulus-induced activation". The most common type of synesthesia elicited with chemical agents is chromesthesia. Still, frequent inducers include auditory and visual stimuli, especially music - which could explain the prevalence of sound-to-color synesthesia over other types of synesthesia.

Heinrich Klüver categorized recurring geometric shapes under the influence of peyote in the 1920's. He called these the form constants: Tunnels, Spirals, Honeycombs and Gratings, and Cobwebs. These also apply to both drug-induced and natural hallucinations, which appear in near-death experiences, sensory deprivation, waking up or falling asleep, and during migraines. According to Klüver, all hallucinations consist of shapes in one of these categories and 'atypical' hallucinations are simply variations. The form constants are common in chromesthetic experiences.

[I couldn't find a diagram of Klüver's form constants under the correct license to include. So, I created one using the information I read and other diagrams and pictures]

Psychedelics greatly enhance suggestibility, so it is fairly common to mistaken hallucinations with chromesthesia; especially considering that all measures of color perception including brightness, saturation, luminance, contrast, and hue are affected due to chemical agents. Drug-induced chromesthesia, as opposed to congenital chromesthesia, is not consistent or automatic. Furthermore, bottom-up processing is responsible for experiences under drug influence, so external stimuli and context are not as critical.

Several studies, both direct (intentionally trying to induce synesthesia) and indirect (participants respond to a set of questions, including one about synesthetic experiences), suggest that the induction of synesthesia with chemical agents is possible. Nevertheless, most studies "suffer from a large number of limitations including a lack of placebo control, double-blinds, and randomized allocation".

Research
[During an art class an experiment was conducted in which the participants were asked to create paintings while listening to songs from different genres every 20 minutes. The use of the colour mustard yellow was observed in most of the paintings. There was no hypothesis offered for the specific use of that colour. Some participants chose the same colours and the paintings were observed to be more abstract or messy. Music which was more loud or "rock" induced the participants to paint with more abrupt or rigid strokes. When a more traditional/cultural song was played most people painted what they associated with that culture, e.g. colours symbolising patriotism for the country or sites/scenery in the country.] -> not cited, remove

I'm going to remove two subsections from the Research section: Cross-activation theory and Disinhibited feedback model. It would be better to have a new, separate section for both because they are the two most prevalent and accepted theories of what the mechanisms of chromesthesia are.

Mechanisms (New section with existing - improved - information)
Synesthesia is established in early childhood when the brain is most plastic. There is a genetic predisposition for the condition but the specific type is determined by environment and learning, and that is why "mappings differ across individuals but are not strictly random". Furthermore, it manifests as the dominant process in distributed systems, or neural networks, which are dynamic, auto-assemble and self-calibrate. That is what is understood so far, but the specific mechanisms by which synesthesia occurs are still unclear and a general consensus has not yet been reached. There are two main hypotheses: Cross-activation theory and Disinhibited feedback model.

Cross-activation theory
Improve existing information: [The cross-activation theory of synesthesia was formulated by V.S. Ramachandran and E.M. Hubard, based on converging evidence from studies of synesthesia that sensory areas for processing real and synesthetic information tend to be neighboring brain regions. This is most apparent in grapheme-color synesthesia, because the brain regions for color processing and visual word form processing are adjacent. Individuals with sound-color synesthesia (replace with chromesthesia) show activation of brain areas involved in visual processing, such as V4, immediately after the auditory perception, indicating an automatic linking of sounds and colors. The reason for this cross-activation is unclear, but one hypothesis is that the increased connectivity between adjacent brain regions is due to a reduction in the pruning of neuronal networks during childhood.]

Add:

Neonates have increased connectivity between different brain areas but these hyper-connections are cut back during development. (Move here: The reason for cross-activation is unclear, but one hypothesis is that the increased connectivity between adjacent brain regions is due to a reduction in the pruning of neuronal networks during childhood. ) Another hypothesis is that unusual branching of neurons causes more numerous synaptic connections and cross-activation. These hypotheses align with Daphne Maurer's neonatal hypothesis, which states that all newborns are synesthetes but the condition disappears at around the age of three months.

Cross-activation may occur at the fusiform gyrus in projector synesthetes (who perceive photisms in external space), and at the angular gyrus in associator synesthetes (who perceive photisms, which come from learned associations, in their mind).

One problem with the cross-activation theory is that synesthesia should be present from birth but is only evident from mid-childhood.

Disinhibited feedback model
Improve existing information: [The disinhibited feedback model is an alternative to the cross-activation theory. The disinhibited feedback model rejects the assumption of increased connectivity in synesthetes and proposes that the cross-activation is due to a decrease of inhibition in the networks present in the normal adult brain. Disinhibited feedback could account for the fact that sound-color synesthesia (replace with chromesthesia) can be acquired by damage to the retino-cortical pathway (add: or transiently induced, through chemical agents, sensory deprivation, meditation, etc.).

(Add: In all brains, there are anatomical cross-connections where inhibition and excitation are counterbalanced. However, excitation prevails in synesthetes and this disinhibits other structures "to elicit sensory sensations in a second sensory area" . One theory explaining how this occurs is neurotransmitter-mediated inhibition. Local inhibitory networks are supposed to confine cortical firing to a specific region but, when these networks are blocked by bicuculline, it leads to a spread of cortical firing. )

Forward feeding connections in the brain that receive converging signals from multiple pathways are reciprocated by feedback connections. In most people, feedback connections are sufficiently inhibited to avoid synesthetic induction of a concurrent perception. In synesthetes, it is suggested that feedforward signaling in the inducer pathway could activate neurons to which both inducer and concurrent pathways converge, and that feedback signaling is capable of propagating down the concurrent pathway to activate the concurrent representation. In this mechanism, feedforward activity from the inducer leads to feedback activation of the concurrent representation.]

Associated cognitive traits
I am going to change the name of this section to: Music and Chromesthesia (this is a much more appropriate name since all of the existing information in this section is about music and composers).

[The proportion of synesthetes among artists is around twice as high as it is in the general population. Synesthetic artists tend to excel in arts in which they benefit the most from their form of synesthesia. Individuals with sound-color synesthesia are thus more inclined to play a musical instrument. Additionally these artists use their ability to compose music that expresses the colors they are envisioning. The colors vary between the artists but some artists often associate similar colors with the same key signature.]

The information above is not cited so I am going to remove it. I could not find a source that stated that in particular, but I did find some related information that I am going to include:

Music and chromesthesia (New section with existing - improved - information)
Individuals with chromesthesia are more likely to play musical instruments and be artistically inclined. Furthermore, "both the hobbies and occupations of synesthetes are skewed toward the creative industries". People with synesthetic propensities are more metaphorical since the same genes cause them to relate concepts and ideas and, thus, be more creative. This could explain the higher incidence of musicians who have synesthesia. Keep this info: [However, musical experience does not assist the ability to consistently match colors to tones. Against natural expectation, studies have found that possession of absolute pitch increased local variance in matching ability. One possible explanation for this is that because absolute pitch is subject to chance error, occasionally incorrectly inferred note names could compete with the pitch-induced color on particular trials. Another possibility is that people with absolute pitch can label tighter pitch recognition categories than normal, introducing a greater number of category boundaries to cross between distinct tones.]

Composers with chromesthesia
[This form of Synesthesia is thoroughly discussed but is harder to clarify for individuals who do not comprehend it. For the curious Individual, one can research and discover music by composers who have Synesthesia. There are famous composers who composed or even continue to compose music with this ability as an influence. Composers range from Olivier Messiaen, Scriabin, Sibelius and many more.] -> not cited, remove.

Olivier Messiaen was influenced by the color of musical keys for his compositions.

I am going to create a new subsection for Alexander Scriabin, since he is a very famous composer who made the clavier à lumières (which is often associated with chromesthesia and is, in fact, the only picture already included in the article). He is famously cited as a synesthete but there is a lot of controversy whether he had the condition or not.

Alexander Scriabin
"Main articles: Alexander Scriabin and Clavier à lumières" Alexander Scriabin was a Russian composer and pianist. He is famously regarded as a synesthete but there is a lot of controversy surrounding whether he had chromesthesia or not. Scriabin was a major proponent of Theosophy, which had a system associating colors to feelings and emotions. This influenced the musician, who distinguished "spiritual" tonalities (like F sharp major) from "earthly, material" ones (C major, F major). Furthermore, Alexander Scriabin developed a "keyboard with lights" or clavier à lumières, which directly matched musical notes with colors.

"Scriabin believed integration of colored light within a symphonic work would act as a 'powerful psychological resonator for the listener'". That is why he created the clavier à lumières for his color-symphony Prometheus: The Poem of Fire. This consisted of a color organ, which projected colors on a screen. The musicologist Sabaneyev first published a table of Scriabin's sound-to-color mapping in 1911 : Scriabin was friends with composer Nikolai Rimsky-Korsakov, who was a synesthete, and their sound-to-color associations were not the same. Specifically, Rimsky-Korsakov made a distinction between major and minor scales and his associations had a "more neutral, spontaneous character". Still, different individuals respond to some sounds and not others, and sound-to-color associations vary greatly between them. When the notes are ordered by the circle of fifths, the colors are in order of a spectrum, which casts doubt on whether Scriabin experienced chromesthesia : Whether Scriabin had chromesthesia or not, his work was greatly influenced by the particularities of this phenomenon. He created a system that associated colors to tones and aimed to create holistic sensory experiences with his compositions. Not only did he experiment with colors, but also with "the generation of scents and sensation of touch and taste".