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Fearful memories can be passed down genetically, study shows

December 2, 2013 2:51pm
One of the central ideas in Frank Herbert's Hugo and Nebula award-winning Dune saga is that memories can be passed down genetically from one generation to the next.
"Genetic memory" is a tantalizing science fiction concept that provides a plausible explanation for past-life experiences and reincarnation—but there may be a hint of truth to it after all.
Two scientists from Atlanta's Emory University have shown that it's possible for mice to pass down the fear of a certain smell—essentially the memory of a bad experience—down to their offspring for up to two generations.
Neurobiologist and psychiatrist Kerry Ressler and his colleague, Brian Dias, trained laboratory mice to fear the smell of acetophenone: the sweet cherry-like food flavoring was presented to male subjects along with a mild electric shock.
The mice quickly learned to associate the smell with pain, and would react in fear to acetophenone even if the shock was no longer being administered.
Curiously enough, the children and even grandchildren of these mice exhibited similar fearful reactions even if they had never been trained to fear acetophenone.

'Epigenetic' memory
Scientists have long known about "epigenetics": changes in gene activity that aren't caused by genetic mutation, such as predisposition to certain diseases in a harsh environment.

Epigenetics is the reason why identical twins with the exact same genes aren't exactly the same: the environment and other factors come into play that affect what the genes do.

For example, one twin may get cancer while the other one doesn't, even if both are genetically disposed to the disease:

However, it's only now that epigenetics has been shown to affect behavior across generations—but the mechanism behind this phenomenon has yet to be found and understood.

In the case of Ressler's and Dias' study, DNA methylation has been posited as the epigenetic cause for heightened sensitivity to acetophenone but it remains unclear why succeeding generations would also be fearful of the chemical.
"How the association of smell with pain influences sperm remains a mystery," said Scientific American's Ewen Callaway of Ressler's and Dias' study

The human connection

According to Callaway, Ressler believes that similar behavior-changing epigenetic changes might also be found in humans.

He said that Ressler became intrigued by epigenetic inheritance after working with poor people living in inner cities, where cycles of drug addiction, neuropsychiatric illness, and other problems often seem to recur in parents and their children. 
"(Ressler believes that) a parent’s anxiety could influence later generations through epigenetic modifications to receptors for stress hormones. But (he) and Dias are not sure how to prove the case, and they plan to focus on lab animals for the time being," Callaway explained. 
"Unfortunately, (finding a molecular explanation is) probably going to be complicated and it's probably going to take a while," Ressler was quoted as saying. — GMA News
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