For the first time, neurobiology scientists at the Max Planck Institute in Germany have identified emotional facial expressions in mice.
Like humans, the facial expressions of mice change when they taste something sweet or bitter, as well as when they feel anxious.
In the new research, recently published in the scientific journal Science, the team of neurobiologists emphasizes that the changes detected in the mice are not reactions to the environment, but rather emotional expressions.
Using artificial vision, the scientists were able to reliably link five emotional states to the mice’s facial expressions: pleasure, disgust, nausea, pain, and fear were clearly distinct for the algorithms.
“Mice that licked a sugar solution when they were thirsty showed a much more joyful facial expression than satiated mice,” explained scientist Nadine Gogolla, who led the investigation.
Mice that tried a slightly salty solution, on the other hand, showed an expression of “satiated”, while those that tried a very salty solution showed a “disgusted” expression.
Based on this study, the scientists concluded that, dissociated from the sensory stimulus, facial expressions reflect the internal and individual character of an emotion.
“By recording facial expressions, we can now investigate the fundamental neuronal mechanisms behind emotions in the mouse animal model (…) This is an important prerequisite for the investigation of emotions and possible disorders in their processing, such as in anxiety disorders or depression,” concluded the specialist.