For the first time, researchers from the Queensland Brain Institute have proven that mild stress is enough to trigger post-traumatic stress disorder (PTSD) in models of autism.
While recent studies in humans have highlighted the co-occurrence of autism and PTSD, the link between the disorders is often overlooked and remains poorly understood.
“We set out to determine the occurrence of traumatic stress in ASD, and to understand the neurobiological mechanisms underlying the reported predisposition to PTSD,” said Dr Al Abed.
Autism and PTSD share common features, including impaired emotional regulation, altered explicit memory, and difficulties with fear conditioning.
“We demonstrated in four mouse models of autism that a single mild stress can form a traumatic memory.”
“In a control population, on the other hand, PTSD is triggered by extreme stress.”
“We wanted to understand this unique perception of stress in autism that leads to the formation of PTSD.”
The prefrontal cortex is a highly specialised area in the front part of the brain that plays a crucial role in social cognition and behaviour.
According to Dr Dehorter, dysfunction in the prefrontal cortex has been linked to both conditions.
“We identified specific cortical circuit alterations that trigger the switch between the formation of a normal memory and a PTSD-like memory during stress,” said Dr Dehorter.
The prefrontal cortex contains specialised cells called interneurons, which are crucial for adapted fear memorisation and normal sensory function and play a key role in stress-related disorders.
The formation of PTSD-like memories is triggered by over-activation of the prefrontal cortex that is present in autism and throws out the balance of these cortical circuits.
The capabilities of interneurons to respond to stress is altered in autism. This alteration worsens autism traits following the formation of a traumatic memory.
“We didn’t anticipate that forming a traumatic memory would aggravate the social and behavioural difficulties in autism.”