Dr's Casebook: How the brain reacts to surprising events

Time capsule being lowered into the well at Sandal Castle

A few weeks ago some guides and brownies lowered a time capsule into the well at Sandal Castle.

Dr Keith Souter writes: When it is retrieved and opened in 50 years’ time, the people who read the newspaper cuttings, letters and messages may be very surprised at the strange and turbulent times that we are currently living through.

Brexit, the Covid pandemic and the Ukraine war have all been surprising enough, but we continue to be hit by a barrage of surprises in politics, sport and on the international front on an almost daily basis. At times it can be hard to take it all in.

How the brain reacts to surprising events is a subject of great scientific interest.

Indeed, research on mice from the USA has shown that a specific part of the brain called the locus coeruleus is involved in this reaction, and that it floods the brain with noradrenaline, one of the natural chemicals called neuromodulators. This is of importance, because it allows the brain to learn from surprising outcomes.

Neurotransmitters are natural chemicals that transmit information between brain cells.

Neuromodulators on the other hand are released over large areas of the brain, flooding it to produce a more general effect. It is thought that these neuromodulating effects are important for survival and brain state regulation.

The researchers trained mice to push a lever when they heard a high-frequency tone, but not when they heard a low-frequency tone.

When the mice responded correctly to the high-frequency tone, they received water, but if they pushed the lever when they heard a low-frequency tone, they received an unpleasant puff of air.

Effectively, the locus coeruleus pumps out noradrenaline when the mouse receives signals that indicate it will get a reward.

However, when they mixed things up, for example by giving a negative puff of air instead of water, the locus coeruleus pumped out greater amounts of noradrenaline. Subsequently, the mouse would be come wary of pressing the lever to get a reward.

It seems that the excess bursts that are pumped out and flood the brain when a surprise occurs spread the noradrenaline to the prefrontal cortex, the part of the brain associated with planning and cognitive functioning.

Surprises are part and parcel of life and each one is a potential learning experience.