It's not in your head, that mouse might really be smiling at you.

German scientists have recently made a rather startling discovery about mice and emotions. Researchers believe that this discovery may help doctors treat human patients with mood disorders.

Courtesy of GIPHY

A team of neurobiologists at the Max Planck Institute of Neurobiology studied emotive mice and put them through a series of tests to see if an emotional state was reflected in their facial expressions. They were able to determine five separate emotions—pleasure, disgust, nausea, pain, and fear.

For example, the mice were fed a bitter-tasting food to generate a reaction of disgust or something sugary to get a reaction of pleasure. During the tests, they observed that the mice did not all react the same to the stimulants, but instead, showed a varied range.

Using computer vision technology, the team was also able to get images from inside the mice’s heads. Using two-photon microscopy—a way of using light to stimulate neurons while getting images of the living tissue—they simultaneously recorded the mice's facial expressions.

Researchers were then able to discern that the same areas of the human brain, the anterior insular cortex, associated with emotion were also active in the mice during the stimulation.

"Individual neurons of the insular cortex reacted with the same strength and at the exactly same time as the mouse's facial expression. In addition, each individual neuron was linked to only one single emotion.

These results suggest the existence of "emotion neurons," each reflecting a specific sensation -- at least in the insular cortex. "By recording facial expressions, we can now investigate the fundamental neuronal mechanisms behind emotions in the mouse animal model," explains Nadine Gogolla the lead researcher on the study. "This is an important prerequisite for the investigation of emotions and possible disorders in their processing, such as in anxiety disorders or depression." Per summary published in Science Daily.

Through the information discovered in this study, more effective treatments for various emotional and mental health issues, such as anxiety and depression, can be found. Of course, this is all just a starting point, as the field will need a lot more research; however, this is still very exciting news.

The study’s results were published in the journal Science in early April.

Mood and mental health disorders affect around 450 million people, according to the World Health Organization. Research and treatment are lacking in many areas for these disorders, even though they are one of the most prominent and long-term issues in the world. So learning how the brain originates, process, and transports emotions is a great step in the process.

What do you think about all this? Give us the scoop in the comments.