Emotions are essential to everyday life guiding decisions, shaping behavior, and helping us navigate the world. But when emotions linger too long or become inappropriate, they can lead to serious mental health issues. Despite extensive efforts, neuroscientists and psychiatrists still have much to uncover about how emotional states are generated and sustained in the brain.

A new study, published May 29 in Science and led by Stanford Medicine researchers, sheds light on this mystery by mapping brainwide activity associated with emotional responses to mildly unpleasant sensory experiences. The study reveals that humans and mice share remarkably similar patterns of neural processing in response to such stimuli, suggesting deeply conserved emotional circuits across mammals. These findings could help advance our understanding of neuropsychiatric disorders many of which are rooted in emotional dysregulation.

"Emotional states are central to psychiatry," said Dr. Karl Deisseroth, the study’s senior author and a professor of bioengineering and psychiatry. The research was part of Stanford's Human Neural Circuitry (HNC) program, which merges cutting-edge brain monitoring technologies with behavioral science in clinical settings.

Using a safe and reproducible stimulus brief puffs of air to the eye, similar to those used in eye exams researchers triggered mild discomfort in both human volunteers and mice. Participants described the sensation as “unpleasant” or “annoying,” and the emotional impact increased with repeated exposure. Importantly, the emotional response persisted even after the stimulus ended.

This persistence, researchers found, reflects a brainwide pattern of communication that integrates sensory input with broader behavioral context. Just as a piano’s sustain pedal prolongs the sound of a note, the brain seems to hold onto emotional signals, allowing them to influence actions and thoughts over time. Tuning this duration may be key to emotional health too short or too long a signal could underlie psychiatric symptoms.

By studying shared responses in humans and mice species separated by 70 million years of evolution the researchers identified fundamental emotional processing mechanisms that likely apply across the mammalian brain. Their results offer new insight into how brief experiences can spark lasting emotional states, and how those states might go awry in disorders like depression, anxiety, and PTSD.

As the team continues to investigate responses to positive stimuli, their findings may pave the way for improved diagnostics and treatments for emotional dysfunction.

Source: https://med.stanford.edu/news/all-news/2025/05/emotions-eye-puff.html