Fear in the genes?

Scientists claim to have found a previously unrecognised layer of gene regulation associated with fear extinction, a finding which may have implications in conditions such as phobias and post-traumatic stress disorder.

An international team, led by University of Queensland, says that this is an inhibitory learning process thought to be critical for controlling fear-related behaviour when the fear response is no longer required.

Lead researcher Dr Timothy Bredy said the findings shed new light on the processes involved in loosening the grip of fear-related memories.

The research, published in the 'Nature Neuroscience' journal, explores how fear-related memories are formed, updated and extinguished at the molecular level.

It also provides fresh understanding of the actual function of genes expressed at the time of retrieval of fear memories, and how they are regulated to facilitate fear extinction, say the scientists.

"This is the first demonstration of how small non-coding RNAs contribute to the formation of fear extinction memory, and highlights the adaptive significance of activity dependent microRNA expression in the adult brain," Dr Bredy said.

Dr Bredy said that the extinction of fear-related memories occurred in the face of a competing memory process called reconsolidation, which saw memories potentially undergo modification every time they were retrieved.

"Contrary to popular belief, fear-related memories are not set in stone. Extinction learning involves retrieval and expression of the original fear memory, which naturally permits either the restabilisation of the original trace, or new extinction learning.

"And in order for new memories to be firmly established, the genes associated with the original fear memory trace must be transiently inhibited, so that the fear extinction process can proceed," he said.