Eigengrau: The Hallucinatory Color We See When We Close Our Eyes
Close your eyes. Do you see? The first thing we probably respond to is nothing, or darkness. A darkness that we generally associate with blackness.
But let’s close our eyes again and look closely, is what we see really blackness? The truth is that what we see is more of a grayish color, the eigengrau which we are going to talk about in this article.
We call eigengrau color that we perceive when we keep our eyes closed or are in complete darkness said color being less dark than that which corresponds to black.
It is a dark gray color, close to black but curiously, despite being perceived in the absence of light, it is lighter than an object of the latter color in full light. The intensity of perceived gray may be slightly different depending on the person. In fact, the term in question means intrinsic gray or own gray in German. This term is considered to have been researched and popularized by Gustav Theodor Fechner, known for his important role in the genesis of psychophysics and the measurement of human perception.
Its perception is considered a phenomenon generated by the retina or its nervous connections with the brain, or a product of its action. However, it has been observed that the perceived color is not completely stable As time goes by and we keep our eyes closed, the gray gradually appears to become lighter or color perceptions may even appear.
Explanation of your perception when you close your eyes
The perception of the eigengrau color may seem strange if we take into account that in reality we should not be able to detect anything with our eyes closed or in complete darkness, with various explanations that have been tried to offer in this regard at a scientific level.
1. General interpretation
Since Fechner’s first research, it was suspected and considered that this perception arose as a kind of residue or background noise of neuronal activity. Even with the eyes closed, the different nerves remain active and discharge, generating neuronal activity in the absence of light that the brain is not able to separate from a true perception of luminosity It would therefore be the product of nervous activity, something that is in fact true to a greater or lesser extent.
2. Isomerization of rhodopsin
Another theory that seeks to delve deeper into the cause of eigengrau perception links this perception to the isomerization of rhodopsin, the type of pigment linked not to color perception but to the perception of movement and luminosity allowing vision in the dark and in the twilight.
3. Neuromelanin
Finally, another of the main explanations links the perception of this grayish tone especially with the formation of neuromelanin It is a photosensitive pigment that is produced from the oxidation of dopamine and norepinephrine.
This production takes place in different areas of the brain especially in the substantia nigra, locus coeruleus, pons, or cranial vagus nerve.
Link with hallucinatory phenomena
The eigengrau and its perception have been linked to the existence of hallucinations, in fact being considered a hallucinatory phenomenon of a biological, physiological and non-pathological type The reason for this consideration is the fact that deep down we would be perceiving something that does not really correspond to an external reality.
Some authors also link the perception of this color with a different hallucinatory phenomenon: the appearance of hallucinations. hypnagogic and hypnopompic
In both cases we would be faced with perceptions without an object and of variable complexity that usually occur in moments of transition between different states of consciousness, specifically the transition from wakefulness to sleep (hypnagogic hallucinations) or vice versa (hypnopompic hallucinations), and which are not considered pathological but rather product of imbalances between the activation and deactivation of different processes and networks in the process of falling asleep and waking up (also called physiological hallucinations).
