Emotions are vital for human survival, yet scientists are still uncovering how they truly arise in the brain. A new study published in Science, led by Karl Deisseroth at Stanford University, has revealed brain-wide activity patterns that occur at the exact moment an emotion begins.
The researchers discovered that emotions are not only immediate reactions but can also last well beyond the event that triggers them. To explore this, they designed an experiment in which participants received short puffs of air to one eye at irregular intervals. This harmless but slightly uncomfortable stimulus caused participants to feel mild annoyance.
High-speed cameras captured their blinking and facial expressions, while some participants — epilepsy patients with implanted brain electrodes — provided detailed brain activity recordings. The data showed two distinct responses: a rapid reflex and a slower, longer-lasting emotional reaction linked to annoyance.
To separate reflex from emotion, the researchers administered ketamine to some participants. Under its influence, reflexive blinking remained the same, but the slower emotional response faded more quickly. Interestingly, participants no longer found the air puffs unpleasant, describing them instead as a tickle.
The study was then repeated in mice, with similar results. The initial reflex involved the thalamus, a midbrain region that processes sensory input, while the slower emotional phase engaged the limbic system and frontal cortex. The thalamus acted as a bridge, connecting quick sensory alerts to longer-lasting emotions.
Researchers concluded that the timing of brain activity directly shapes how we experience emotions. If signals fade too quickly, the brain may fail to learn from negative events. If they last too long, they might contribute to disorders such as depression, OCD, or PTSD.
This groundbreaking work offers a rare look into the very first seconds of emotion formation and could pave the way for targeted treatments for emotional disorders, providing deeper insight into how the brain transforms simple sensations into com.
