Good versus bad and how the brain remembers
24 Apr 2011 by Evoluted New Media
The brain’s reward centre is also geared towards bad behaviour, evoking production of neurotransmitters say scientists who have also shown how the brain remembers events.
The brain’s reward centre is also geared towards bad behaviour, evoking production of neurotransmitters say scientists who have also shown how the brain remembers events.
|
Dopamine neurons also respond to bad behaviour |
Researchers from Georgia Health Sciences University and East China Normal University found the brain’s reward centre responds to bad experiences as well as good. Their work may explain the ‘thrill’ of thrill-seeking or the thrill of surviving it.
Scientists studied dopamine neurons in the ventral tegmental area of the mouse brain – widely studied for its role in reward-related motivation and drug addiction. They used a conditioned tone to correlate a certain setting with a good or bad event. Later, just the tone in that setting evoked the same response from the dopamine neurons.
“We have believed that dopamine was always engaged in reward and processing the hedonic feeling,” said Dr Joe Z Tsien, co-director of GHSU’s Brain & Behaviour Discovery Institute. “What we have found is that dopamine neurons are also stimulated or respond to negative events.
All the cells had some response to good or bad experiences, while a fearful event excited around 25% of the neurons, spurring more dopamine production. The neuronal response lasted as long as the event and the context was important.
Exactly how good or bad events induce dopamine production remains a mystery, said Tsien – it’s just the way the brain is wired, but he believes genetics could impact the number of cells activated by bad events and help explain inappropriate behaviours.
Tsien and colleagues at Boston University have also provided insight into how the brain decides to remember the good and bad. Recordings from mouse brain cells in the CA1 region of the hippocampus showed that all cells are involved in sensing what happened, just in different ways.
During a big event, most cells evoke a large sensory response, but slightly less than half the cells involved logged a more consistent neural response to big and small events. These cells are known as invariant cells because of their consistent firing regardless of intensity.
Invariant cells are critical in helping the brain remember those events – some keep replaying specific memories, while the majority focus on the more general features of the event. Tsien believes genetics plays a role in an individual’s specific ratio of cells involved in encoding general versus detailed memories.
