Can you see the music, taste the colors or feel the color?

Synesthesia is a condition in which stimulation of one sensory modality causes unusual experiences in a second, unstimulated modality (Hubbard and Ramachandran, 2005). This condition It occurs in approximately 2% to 4% of the population (Simner et al., 2006).

The association between one modality and another can cause a synesthete to perceive flavors when seeing certain shapes or colors when seeing letters. Thus, there are different types of synesthesia that present themselves in many ways, covering a wide range of sensory interactions, both cross-wise and within a single modality (Novich et al.2011).

Neural basis of synesthesia

The neurological basis of synesthesia has been studied in depth in grapheme-color synesthesia (in which numbers and letters evoke colors) using psychophysical tests and functional imaging. Several research groups have found that simple achromatic graphemes activate both grapheme regions and color area V4 in the brains of synesthetes (Brang and Ramachandran, 2011).

So that, The neural explanation underlying this condition is that of “cross activation.” (Ramachandran, 2011) between different areas of the brain. Ramachandran and Hubbard (2001a) argue that synesthesia is the product of an excess of neuronal connections between associated modalities, possibly as a consequence of a decrease in neuronal pruning between (typically adjacent) regions that are interconnected.

The cause of this connectivity could be a genetic mutation that causes defective pruning of the connections between brain maps. This mutation can be expressed selectively in the fusiform or angular gyri, which explains the existence of different types of synesthesia.

If expressed very diffusely, there may be extensive cross-wiring between brain regions that represent abstract concepts, which would explain the link between creativity, metaphor and synesthesia (Ramachandran and Hubbard, 2001b).

It is common for people with synesthesia to be more creative and have more memory because their brain has a greater number of connections.

Types of synesthesia

According to Day (2005) there are two general categories of synesthesia:

Cognitive synesthesia: induced by stimuli associated with symbolic meanings learned through culture (graphemes, phonemes, proper names, days of the week, etc.).Synesthesia itself: stimuli from one sensory modality are simultaneously and involuntarily perceived through another sensory channel.

Within these categories, more than 70 types of synesthesia can be found, some of which are more prevalent than others (Day, 2012). In this article we will only focus on the most common ones:

1. Grapheme-color synesthesia

It is estimated that around 61.26% of synesthetes have this type of synesthesia, which consists of relating words, letters and numbers with a specific colorfor example: an individual with grapheme-color, upon seeing the word typography, would perceive a certain color such as white, blue, yellow, etc.

2. time-color synesthesia

Within the different types of synesthesia, we find one that It is related to time units and color vision. It is estimated that, within the group of synesthetes, 22.96% have this connection.

A person with this type of synesthesia would see, for example, 10:00 am as yellow and 4:00 pm as sky blue.

3. Music-color synesthesia

This type of synesthesia is linked to the senses of hearing, specifically in the presence of music, and color vision. 18.05% of synesthetes see colors when listening to music.

When listening to a song, a person with music-color synesthesia perceives one or several colors throughout the entire musical sequence.

4. Sound-color synesthesia

Among the different types of synesthesia, it only occurs in 16.21% of synesthetes. This way of perceiving is very similar to that of music-color, but it occurs only with general sounds.

These individuals observe colors when hearing sounds (not just musical ones). For example, a person hearing a dog bark might see the color red.

5. Note-color synesthesia

It is present in 7.8% of the synesthetic population and, like the previous twois related to hearing and vision, but this time only with musical notes. Each tone of a note has a specific color when heard. A person with this type could see the color blue when hearing an Mi and green when hearing a Fa.

The variety of types of synesthesia is immense due to the different sensory modalities. We can find cross activation between touch and vision (color sensation synesthesia). In this experience, the person perceives a color as a consequence of an emotional sensation or touch.

We can also find spatial sequence synesthesia in which a person can perceive a relative spatial location for each day of the week (Novich et al.2011).

To conclude, although there are many types of synesthesia that relate the other senses, they all, in general, have a similar neuroanatomical basis. This condition is a path to understanding a little more about how the human brain works and how it creates reality. in which he operates daily.

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