Is it true that the color red has a signaling and warning effect reflected in the brain?
Researchers at the Ernst Strungmann Institute for Neuroscience have investigated whether red triggers brain waves more in a certain area than other colors.
© esi/c. kernburger
People experience colors when certain light-sensing cells in the retina, called cones, are activated. They respond by converting light stimuli into electrical signals, which are then carried by nerve cells to the brain. The top row shows RGB color contrast and how the brain responds with varying degrees of gamma oscillations when the maximum number of chromatic colors in the RGB color space is selected. The bottom row shows colors that equally activate retinal cones, and then trigger equally strong gamma oscillations in the brain.
© esi/c. kernburger
If the traffic light is red, we stop. Ripe cherries on a tree stand out because of their color. A sign and warning effect is attributed to the red color. But is it also reflected in the brain? Researchers at the Ernst Strungmann Institute for Neuroscience have now examined this question. They wanted to know whether red triggers brainwaves in a certain area more than other colors.
at the center of research Benjamin J. stochAlina Peter, Isabel Ehrlich, Zora Nolte and ESI Director Pascal Fries The initial visual cortex stands out, also known as V1. This is the largest visual area of the brain. And first let’s get the input from retina. There, brain waves (oscillations) occur at a specific frequency, the so-called gamma band (30–80 Hz), when this range is stimulated by strong and spatially homogeneous images. But not all images produce this effect equally.
display a color effect
“Recently, many research projects have revolved around the question of which specific input drives the gamma waves,” said study first author Benjamin J. Stoch explains. “One trigger seems to be colored surfaces. Especially when they are red. Scientists have taken this to mean that there is something special to the visual system due to the red evolution, because fruits, for example, are often red.” But how can the effect of a color be scientifically proven? Or even refutation? It is difficult to define color objectively, as is comparing colors between different studies. Every computer monitor renders a color slightly differently, so red on one screen will not be the same as another. In addition, there are several ways to define color: on the basis of a single monitor or perceptual judgments, or on the basis of their arrival on the human retina.
Colors activate light-sensing cells
Because humans perceive colors when certain light-sensing cells in the retina, the so-called cones, are activated. They respond by converting light stimuli into electrical signals, which are then carried by nerve cells to the brain. To be able to recognize colors, we need a variety of cones. Each type of cone is particularly sensitive to a specific range of wavelengths: red (L cone), green (M cone) or blue (S cone). The brain compares how strongly the corresponding cones respond and uses this to determine the color impression.
It works in a similar way for all people. So one way to objectively define colors would be by how much they activate the different retinal cones. Scientific studies with macaques have shown that the early primate visual system had two color axes at the base of these cones: the LM axis comparing red to green, the S-(L+M) axis comparing yellow to purple. does from.
“We believe that a color coordinate system based on these two color axes is the correct way to define color when researchers want to find out the strength of gamma oscillations, as it directly defines colors based on how strong and in what way. “Activate the early visual systems,” is convinced Benjamin J. Stauch. Since previous work on color-related gamma oscillations was mostly done with small samples from a few primates or human subjects, the spectra of cone activation were genetically modified. As the form can vary from person to person, he and his team measured a larger sample in a now published paper individual (n = 30).
Same effect of red and green
They explore the question of whether red is really anything special. That is, whether this color triggers stronger gamma oscillations than green with comparable color strength (ie cone contrast). And a side question is this: can colour-induced gamma oscillations also be detected by magnetoencephalography (MEG), that is, by a method for measuring the magnetic activity of the brain?
They concluded that red is not particularly strong in terms of the intensity of the gamma oscillations that trigger it. Rather, with the same full LM cone contrast, red and green trigger equally strong gamma oscillations in the early visual cortex. Furthermore, with careful handling, colour-induced gamma waves can be measured in human MEG, allowing future research to explore 3R Principles for Animal Testing (Reduce/Reduce, Replace/Save, Refine/Improve) Can be performed on humans instead of non-human primates.
Colors that activate only the S-cone (blue) usually reveal weak neural responses in the early visual cortex. It is somewhat to be expected that the S cone is less common, evolutionarily older, and more dull on the primate retina.
Contribution to the development of the visual prosthesis
The results of this study by ESI scientists, understanding how the early human visual cortex encodes images, may one day aid in the development of visual prostheses that allow the visual cortex to function in people with impaired retinal Cah-like perceptual effects. Tries to activate. , However, this goal is still a long way off. More needs to be understood about the specific responses of the visual cortex to visual input.
