A new study on lab mice has found a way to access traumatic memories. This may serve as a breakthrough on how to psychologically treat patients who have repressed memories of traumatic events such as childhood abuse.

The report, published in Nature Neuroscience, described two amino acids in the form of glutamate and GABA as the Yin and Yang of the brain which are normally balanced. Glutamate is the chemical that helps us store memories whereas GABA calms us and helps us to sleep.

There are two kinds of GABA receptors, one which balances glutamate to help us to remain calm, whereas the others are extra-synaptic GABA receptors which adjust brain waves and mental states. "Extra-synaptic GABA receptors change the brain's state to make us aroused, sleepy, alert, sedated, inebriated or even psychotic," said a press release for the report.

Scientists from Northwestern University found that these amino acids also help encode memories of a fear-inducing event and hide these memories away from the conscience. "The brain functions in different states, much like a radio operates at AM and FM frequency bands," said principal investigator Dr. Jelena Radulovic, the Dunbar Professor in Bipolar Disease at Northwestern University Feinberg School of Medicine.

"It's as if the brain is normally tuned to FM stations to access memories, but needs to be tuned to AM stations to access subconscious memories. If a traumatic event occurs when these extra-synaptic GABA receptors are activated, the memory of this event cannot be accessed unless these receptors are activated once again, essentially tuning the brain into the AM stations."

Testing on mice, the researchers infused the hippocampus – in the medial temporal lobe of the brain - with gaboxadol, a drug that stimulates extra-synaptic GABA receptors. "It's like we got them a little inebriated, just enough to change their brain state," Radulovic said.

The mice were then placed in a box where they were given a small electric shock. They were then returned to the box the next day but seemingly didn't remember being shocked. However, they were then given gaboxadol which stimulated the GABA receptors and placed in again and froze with fear as they awaited an electric shock.

Radulovic said: "This establishes when the mice were returned to the same brain state created by the drug, they remembered the stressful experience of the shock." The findings suggest that some individuals react to a traumatic experience by activating the extra-synaptic GABA system and form inaccessible traumatic memories.

"The findings show there are multiple pathways to storage of fear-inducing memories, and we identified an important one for fear-related memories. This could eventually lead to new treatments for patients with psychiatric disorders for whom conscious access to their traumatic memories is needed if they are to recover."