Interoception refers to the processes through which the nervous system detects, interprets and integrates signals arising from within the body. These include heartbeat, breathing, hunger, fullness, visceral tension and certain digestive sensations.

Such signals do not always enter conscious awareness. Much of the body’s regulation takes place silently. Some changes nevertheless become perceptible: a racing heart, altered breathing, tightness in the throat, contraction in the belly, or a sense of emptiness or heaviness.

A brain-imaging study of heartbeat perception found that attending to internal signals recruits areas including the insula and the cingulate cortex. Activity in the right anterior insula was associated with how accurately participants perceived their own heartbeats. The study helped establish a connection between bodily perception, self-awareness and the intensity of emotional experience.

Uderochromatism takes shape within this passage: the point at which a physiological manifestation may become conscious experience and, subsequently, material for creation.

The internal organs continuously send information to the nervous system. A study in mice found that different signals arising from the viscera are represented by distinct groups of neurons within a region of the brainstem.

These findings cannot be translated directly from an animal model to human experience. They nevertheless show that visceral sensations have their own neural organisation and do not amount to undifferentiated bodily noise.

In humans, attending to the heart and attending to the stomach do not recruit exactly the same brain networks. An MRI study involving healthy participants observed different patterns of activation depending on whether attention was directed towards cardiac or gastric sensations.

Inner perception is therefore not a single, uniform ability. It also depends on the organ involved and on the kind of signal receiving attention.

This distinction resonates with the uderal approach. A sensation felt in the stomach, the intestines or across the abdomen may call for a different form, duration or intensity. The aim is not to establish a rigid anatomical map, but to recognise that visceral experience has multiple locations and qualities.

Emotion is not merely an idea identified by the mind after the fact. It is often accompanied by bodily changes: an altered heartbeat, shorter breathing, warmth, muscular tension, shivering, nausea or sensations in the abdomen.

In a series of experiments involving 701 participants, Lauri Nummenmaa and his colleagues asked people to mark on body silhouettes the regions in which they felt activity increase or decrease during different emotions.

The emotions produced statistically distinct maps of bodily sensation, with recurring patterns found in both European and Asian samples. These maps were based on self-reports rather than direct measurements of individual organs. They nevertheless show that emotions are spontaneously experienced and located within the body.

A more recent study used an ingestible capsule capable of measuring pressure, temperature and acidity in the digestive system while participants watched videos designed to evoke different emotions.

Scenes associated with fear and disgust were accompanied by reported gastric sensations, including nausea, as well as changes in certain digestive parameters. The authors nevertheless stress that the study does not yet establish a simple, universal gastric signature for each emotion.

These studies support an essential proposition of Uderochromatism: emotion may be approached through the way it moves through and alters the body. They do not demonstrate that every emotion originates in the belly, but they support the artistic decision to make it a privileged field of observation.

From a scientific perspective, it would be excessive to claim that the belly is the sole seat of emotion. Emotional experience arises through complex interactions between the brain, the autonomic nervous system, the viscera, hormones, memory, context and the environment.

Uderochromatism may nevertheless choose the belly as a poetic and perceptual centre. This choice is grounded in concrete experience: the belly is a region where many internal changes become noticeable before they can be clearly interpreted.

A contraction may be felt before a person knows whether it relates to fear, anticipation, desire or discomfort. An inner sensation does not necessarily carry a fixed emotional meaning. It must be understood through context, personal history and the person’s overall state.

This uncertainty is essential. It prevents Uderochromatism from becoming a rigid system in which every sensation would correspond to a specific emotion. The belly is not used as a diagnostic instrument. It becomes a space for questioning and translation.

Science does not describe emotion as an autonomous creature living within the viscera. This figure belongs entirely to the artistic realm.

It nevertheless finds support in the shifting and distributed nature of emotional experience. Internal signals change, circulate and interact with attention, memory and the environment. Emotion does not therefore always appear as a stable entity that could be isolated.

By giving emotion an imagined body, Uderochromatism does not claim to reveal a hidden biological structure. It invents a form through which what remains diffuse may be approached.

The creature may gather, fragment or move because it does not represent a real organ. It represents the variability of lived sensation. Its morphology is a sensory hypothesis, not a scientific illustration.

This distinction preserves the strength of the concept: science describes certain mechanisms of the body; art gives them a presence, a narrative and a shareable form.

Research into fetal perception shows that, during the second half of pregnancy, the fetus can respond to certain auditory and vibratory stimuli. Studies have observed changes in fetal heart rate in response to familiar and unfamiliar voices. Other work suggests that some forms of auditory learning begin before birth, particularly in relation to the maternal voice and the language heard in the womb.

These findings support the idea of prenatal sensitivity to rhythm, voices and certain vibrations. They do not, however, justify the claim that the fetus experiences its mother’s “joys” or “sorrows” as emotions identical to her own.

The mother’s physiological state can influence the environment in which the fetus develops. This influence operates through complex biological mechanisms and should not be understood as a direct, conscious transmission of emotion.

Within Uderochromatism, prenatal life may therefore be approached as one of the earliest environments of rhythm, vibration and bodily resonance. It should not be used as proof that a complete emotional memory is already inscribed in the belly.

Sound and light cannot be placed directly on a single shared scale. Sound is a mechanical vibration travelling through a medium, whereas light belongs to the electromagnetic spectrum. Their frequencies do not produce comparable perceptions through a simple numerical conversion.

Perceptual correspondences between hearing and vision do nevertheless exist. Experiments show, for example, that higher-pitched sounds are often associated with lighter forms or greater visual brightness. Other associations may involve pitch, timbre, saturation or brilliance, and can influence perceptual judgements.

These correspondences do not amount to a universal and unchanging language. Their strength varies with context, stimulus properties, learning and sometimes culture. Recent research suggests in particular that associations between pitch and colour may depend more strongly on brightness than on hue itself, and may shift according to the conditions in which they are presented.

Uderochromatism may therefore bring sound and colour together without claiming to uncover a physical equivalence or a universal chart of correspondences. Their relationship is created within the work, from a particular sensation and situation.

Sonified colour thus becomes an artistic translation: a way for intensity to circulate between the belly, the image, rhythm and sound.

Contemporary research provides reasonable grounds for saying that internal signals contribute to conscious and emotional experience; that gastric sensations have a perceptible reality and their own neural representations; that emotions are often accompanied by localised bodily sensations; that the fetus becomes responsive to certain sounds and rhythms before birth; and that perceptual correspondences may arise between particular auditory and visual properties.

It does not allow us to conclude that the belly is the sole origin of emotion, that emotion has an objective form, that a colour naturally expresses a particular affect, or that any sound-colour correspondence is universal.

These limits do not weaken Uderochromatism. On the contrary, they help define its proper territory.