Emotion, fragrance magically revive succession of memories

October 17th, 2008 - 1:42 pm ICT by IANS  

Washington, Oct 17 (IANS) An aroma wafts in from somewhere, magically reviving pleasant memories of long forgotten childhood or a family outing, or visits to the restaurant.In experiments with sleeping mice, Duke University Medical Centre researchers have shown that the part of the brain that processes scents is indeed a key part of forming long-term memories, involving other individuals.

“We can all relate to the experience of walking into a room and smelling something that sparks a vivid, emotional memory about a family member from years or even decades ago,” said Stephen Shea, co-author of the study. “This research sought to understand that phenomenon on a cellular level.”

Researchers examined how strong memories are formed by creating new memories in the minds of mice while under sedation and monitoring their response to a memory-inducing stimulus afterwards, when they were awake.

“Our work is unique because it allows us to examine the cellular make-up of a memory, evaluate how the neurons change when a memory is formed and learn how that memory affects behaviour,” Shea added.

Researchers created memories by stimulating the release of noradrenaline, a chemical present in the body during strong emotional events ranging from excitement to fear, according to a Duke University press release.

Previous studies have established a link between noradrenaline and the formation of enduring memories, especially during intense social events such as mating and childbirth. In mice and humans, the presence of noradrenaline also creates changes in the odour processing centre of the brain, called the olfactory bulb.

“When an animal forms a strong memory about another, it is reliant on odour cues and noradrenaline. Both need to be present at the same time in order for the memory to be formed,” Shea says. “Long-term memories created under these conditions often result in a permanent change in behaviour.”

The Duke team administered anaesthesia to a mouse and stimulated the release of noradrenaline with an electrode while wafting the scent of either food or the urine of another mouse under the nose.

“We wanted to see if these two elements - noradrenaline and odour - present at the same time were the key ingredients needed in the recipe for creation of memory - this is a concept that had not been directly tested before this study,” Shea said.

What they saw was an approximate 40 percent reduction in neuron activation after triggering the noradrenaline release - suggesting that a memory of the odour had been formed.

A day later, after the mouse was awake, the team observed changes in behaviour in response to the scents, showing that they remembered the smells from when they were asleep.

The report has been published in The Journal of Neuroscience.

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