Influence of relationship between facial expression and facial color on brain activity

<Overview>

A research team consisting of the Cognitive Neurotechnology Unit and the Visual Perception & Cognition Lab of the Department of Computer Science and Engineering, Toyohashi University of Technology, showed that certain combinations of facial expressions and facial colors increased the event-related potential P3. The human brain emits weak electrical signals (electroencephalogram, EEG), and the event-related potential P3 is a positive amplitude potential that reflects selective attention and is observed in the EEG around the parietal and center at 300–500 ms after stimulus perception. This study showed that the P3 amplitudes for red angry faces are higher than those for red neutral faces, and that the relationship between facial expression and facial color, that is, an angry face and red, changed brain activity reflecting selective attention. The results of this study were published online in the journal eNeuro on January 10, 2025.https://doi.org/10.1523/ENEURO.0419-24.2024

<Details>

The face is an important feature for identifying individuals, and as suggested by the expression, “kaoiro wo ukagau” (Look at the complexion; i.e. be sensitive to someone’s mood, read someone’s countenance), facial color plays an important role in reading someone’s emotions. Previous studies have shown that facial color can change how we judge facial expressions, such as a redder face more likely to be perceived as an angry face, even for the same face. However, these studies have not clarified whether selective attention and its associated brain activity differ depending on the relationship between facial expression and facial color.

　Therefore, the research team focused on the event-related potential P3, which is a brain wave that reflects selective attention, and conducted an EEG measurement experiment using facial image stimuli with different facial expressions and facial colors. In the experiment, participants were asked to conduct an oddball task in which they were asked to count the number of times a low-frequency facial image was presented among a series of high-frequency facial images, during which time their EEG was recorded. The experiment involved the use of two facial expression images (angry, neutral) with three different facial colors (original, red, green), and participants responded to the number of times a specified facial expression was presented in the oddball task. We reduced the effects of ambient noise by conducting the experiment in a magnetically shielded room with constant controlled brightness.

 The results confirmed that the P3 amplitude for the red angry face was higher than that for the red neutral face (figure). This result was attributed to the participant directing stronger selective attention to the red angry face. These results supported previous research reports stating that red enhanced the response to an angry face in terms of EEG.

  Yuya Hasegawa, who is a first-year doctoral student in the Department of Computer Science and Engineering and is the first author of this study, explained, “Stronger selective attention is known to be directed to angry faces. And making an angry face redder is also known to make it more likely for the anger to be perceived. In that case, does selective attention also increase with a red angry face? If stronger selective attention is directed to a red angry face, then its associated brain activity might also change, which is what inspired this study.”

<Future prospects>

These results were the first to show that the relationship between facial expression and facial color enhanced brain activity reflecting selective attention (P3). Activity in the amygdala and other areas is known to contribute to facial reactions. Hence, in the future, the research team will investigate which brain regions are responsible for the enhanced response owing to the relationship between facial expression and facial color and will seek to understand the deeper mechanisms of brain activity.

<Acknowledgments>

This study was supported by JSPS KAKENHI JP22K17987, JP20H05956, JP20H04273, JP23KK0183, and JST SPRING JPMJSP2171.

<Paper information>

Hasegawa, Y., Tamura, H., Nakauchi, S., & Minami, T*. (2025). Interaction between facial expression and color in modulating ERP P3. eNeuro, 12(1) ENEURO.0419-24.2024; https://doi.org/10.1523/ENEURO.0419-24.2024

*Corresponding author.