How Surprises Impact the Brain

The brain has its own unique way of responding to a surprising event or situation. When the brain wants you to pay attention to something, it will make sure you are aware of it. According to a new study by MIT, one way the brain does this is by sending out a burst of noradrenaline. 

Neurotransmitters and the Brain

Noradrenaline is a neuromodulator that is produced by something called locus coeruleus. The locus coeruleus (LC) is a structure deep in the brain that can affect widespread parts of the brain. MIT researchers studied mice to see how their brains responded to noradrenaline. Their findings showed that norepinephrine, also known as noradrenaline, works with the brain to help it learn of surprising outcomes. Additionally, noradrenaline also focuses on behaviors that lead to a reward to encourage these behaviors. When there is a situation where gratification may be unclear, the brain may still produce noradrenaline. 

Scientists are still researching the impact of neurotransmitters such as dopamine, which controls reward pursuit. Less is known about noradrenaline. However, from previous research, scientists have determined that noradrenaline has been linked to arousal and boosts alertness. However, too much noradrenaline is believed to lead to anxiety.

The Study

To study this, researchers trained mice to push a lever when a high frequency note was played. When the mice heard the high frequency note and pushed the lever correctly, they would receive water. However, if the mice pushed the lever when they heard a low frequency note, they would receive an unpleasant burst of air. Over time, they learned when to push the lever correctly, but were still unsure about whether to push it or not when hearing a sound with lower frequency. This study suggests that the noradrenaline in the brain advises that the subject should complete the task in order to potentially receive an award when unsure about the results.

A second burst of noradrenaline was also spotted when the mice received an unexpected reward. The initial presence of noradrenaline was found when the mice were stimulated to complete the task. If the outcome of the trial was a surprise, there was shown to be a second burst of noradrenaline, and it was as big of a burst as the first one. Researchers were able to analyze that the “surprise-encoding function” of the locus-coeruleus was much more widespread throughout the brain than what was originally thought. This findings backs up the research because everything we do is driven by surprise and reactions as such.  

Why This Matters

Overall, the connection between the locus coeruleus and noradrenaline has shown that there is a large surprise element in the brain, and that it may sense more in the brain than what was originally thought. Scientists plan to further investigate this, and explore the synergy between noradrenaline and other neurotransmitters in new research. By looking at this, they are interested in exploring how dopamine plays a role too. For future trials, scientists hope to analyze how the prefrontal cortex stores short-term memory from the input of the locus coeruleus.


ScienceDaily. (2022, June 1). How the brain responds to surprising events. ScienceDaily. Retrieved July 7, 2022, from

Jenna Doran

Jenna Doran is a rising Senior at Temple University studying English and Psychology. She is very excited to be joining the HappyNeuron Pro team as the Content Marketing Intern this summer. Jenna has completed past internships and held leadership positions in extracurriculars dedicated to mental health and wellness programming and development. She is looking forward to utilizing these skills and working with the team!

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