In a recent study, published in the journal of Nature Neuroscience, the researchers trained mice to fear the smell of cherry blossom using electric shocks before allowing them to breed. The offspring produced showed fearful responses to the odor of cherry blossom compared to a neutral odor, despite never having encountered them before. The following generation also showed the same behavior. This effect continued even if the mice had been fathered through artificial insemination.
The researchers found the brains of the trained mice and their offspring showed structural changes in areas used to detect the odor. The DNA of the animals also carried chemical changes, known as epigenetic methylation, on the gene responsible for detecting the odor. This suggests that experiences are somehow transferred from the brain into the genome, allowing them to be passed on to later generations.
The researchers now hope to carry out further work to understand how the information comes to be stored on the DNA in the first place.
They also want to explore whether similar effects can be seen in the genes of humans.
Prof. Marcus Pembrey, a paediatric geneticist at University College London, said the work provided "compelling evidence" for the biological transmission of memory. He added: "It addresses constitutional fearfulness that is highly relevant to phobias, anxiety and post-traumatic stress disorders, plus the controversial subject of transmission of the ‘memory’ of ancestral experience down the generations.
"It is high time public health researchers took human transgenerational responses seriously. "I suspect we will not understand the rise in neuropsychiatric disorders or obesity, diabetes and metabolic disruptions generally without taking a multigenerational approach.”
Prof. Wolf Reik, head of epigenetics at the Babraham Institute in Cambridge, said, however, further work was needed before such results could be applied to humans. He said: "These types of results are encouraging as they suggest that transgenerational inheritance exists and is mediated by epigenetics, but more careful mechanistic study of animal models is needed before extrapolating such findings to humans.”
Another study in mice has shown that their ability to remember can be effected by the presence of immune system factors in their mother's milk. Dr Miklos Toth, from Cornell University in New York, found that chemokines carried in a mother's milk caused changes in the brains of their offspring, affecting their memory in later life.