Study reveals emotions trigger generation of neurons

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JUNE 15, 2011

A tantalizing twist in the understanding of how emotions impact memory formation was revealed in a study published Tuesday by a team of UC Berkeley neuroscientists.

In the study, published in the journal Molecular Psychiatry, researchers were able to explain that the brain’s center for processing emotional information  — called the amygdala — triggers the brain’s center for memory creation — called the hippocampus — to generate new neurons.

These neurons, in turn, create pivotal impressions that the brain remembers when it is reintroduced to an environment that, for example, it recognizes as a place of fear.

Along with graduate student Elizabeth Kirby, the lead author of the study, graduate student Aaron Friedman and others, Daniela Kaufer, a UC Berkeley assistant professor of integrative biology, used rats to monitor the influence of fear on the body — fear being a “robust emotion” and one of the easier emotions to monitor, according to Friedman. Researchers were able to see how rats reacted to an environment they recognized but that they feared.

The rate at which new neurons were created, they discovered, was greatly increased based on the rats’ reaction to fear.

“We monitored a rat’s response based on how they reacted to being in the environment they were afraid of,” Friedman said. “The research suggests that these new neurons that are formed as a result of being afraid play a role not only in the formation of memory but also in helping to create the emotional context of memory.”

Kirby and Kaufer’s finding comes on the heels of brain researcher Fred Gage’s research which demonstrated that the formation of new memories is linked to increased activation of newly formed nerve cells in the hippocampus that are derived from adult stem cells.

Gage, a researcher at the Salk Institute for Biological Studies in La Jolla, Calif., revealed that adult stem cells appear to differentiate continually into new nerve cells, and if they are highly activated —  such as in learning new complex information — more of them could likely survive and help in establishing new memories in the brain.

“The new angle with the study (at UC Berkeley) is to totally highlight this new role for adult stem cells in the brain,” Kaufer said. “We can now say new neurons directly get input from the amygdala, and we now know there is an emotional response such as fear or stress and how those emotions create interactions with new neurons.”

The findings from the study have implications on how to better understand post-traumatic stress disorder and other problems caused by faulty regulation of emotional memory.

Going forward, the team of researchers now plans to try to find out whether other negative stimuli, such as stress and anxiety, similarly cause amygdala activity to formulate or alter the formation of neurons in the hippocampus.

“We’re not necessarily interested in the initial fear but the memory of the fear and the way we kind of relive fear or other emotions in our memory,” Friedman said. “The challenge is to really understand how neurogenesis affects human health.”

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JUNE 17, 2011