The shape of DNA in the brain affects how well mice can ‘unlearn’ previously acquired fear memories, a finding that could lead to new treatments for post-traumatic stress disorder and other psychiatric conditions.

A team led by scientists at the University of Queensland showed that, during fear learning, anti-clockwise helices of DNA form in the mouse prefrontal cortex — the short-term memory centre of the brain.

During fear extinguishing, when mice were exposed to safe stimuli in similar environments, an enzyme known as ADAR1 latched onto the reverse-twisted DNA and converted the helix shape back to its normal, clockwise spiral.

Without ADAR1, the DNA got stuck in its backwards configuration and mice were unable to form non-fearful memories. The results thus provide a link between DNA flexibility and cognitive flexibility.