Brain’s ‘reward’ center responds to bad experiences too

WASHINGTON - Scientists have found that the so-called reward center not only responds to good experiences but also to bad ones.

The finding may help explain the ‘thrill’ of thrill-seeking behavior or maybe just the thrill of surviving it, according to scientists at Georgia Health Sciences University and East China Normal University.

Eating chocolate or falling off a building-or just the thought of either-can evoke production of dopamine, a neurotransmitter that can make the heart race and motivate behavior, said Joe Z. Tsien, Co-Director of GHSU’s Brain and Behavior Discovery Institute.

Scientists looked at dopamine neurons in the ventral tegmental area of the mouse brain, widely studied for its role in reward-related motivation or drug addiction.

They found essentially all the cells had some response to good or bad experiences while a fearful event excited about 25 percent of the neurons, spurring more dopamine production.

Interestingly neuronal response lasted as long as the event and context was important, said Tsien.

Scientists used a conditioned tone to correlate a certain setting with a good or bad event and later, all it took was the tone in that setting to evoke the same response from the dopamine neurons of mice.

Tsien noted that genetics can impact the number of cells activated by bad events - and while interpretation of the findings needs more work - they could help explain inappropriate behaviors such as drug addiction or other risky habits.

In another study, Tsien and his colleagues at Boston University have provided more insight into how brains decide how much to remember good or bad. Inside the hippocampus, where memory and knowledge are believe to be formed, recordings from hundreds of mouse brain cells in a region called CA1 showed all are involved in sensing what happens, but not in the same way.

They found among most cells a big event, such as a major earthquake, evoked a bigger sensory response than a mild earthquake. But slightly less than half the cells involved logged a more consistent neural response to all events big and small. These are called invariant cells because of their consistent firing regardless of event intensity.

Tsien said these cells are critical in helping the brain remember those events.

The findings have been published in the journal PLoS One. (ANI)