New York, Jan 5 (IANS): If you happen to witness fear and trauma in the life of your loved ones or even strangers, chances are that a change may occur in the information flow in your brain and lead to post-traumatic stress disorder (PTSD), researchers have said.

PTSD is an anxiety disorder that can develop in some people after they experience a shocking, scary, or dangerous event.

However, it does not stop at direct victims of illness, injury, or a terrorist attack, the researchers said.

"It can also affect their loved ones, caregivers, even bystanders the people who witness or learn about others' suffering," said lead author Alexei Morozov, Assistant Professor at the Virginia Polytechnic Institute and State University (Virginia Tech) in Roanoke, US.

The findings showed that prefrontal cortex the part of the brain responsible for empathising and understanding the mental state of others physically changes after witnessing fear in another.

To test this, the team measured transmission through inhibitory synapses that regulate strength of the signals arriving in the prefrontal cortex from other parts of the brain in mice who had witnessed a stressful event in another mouse.

The results showed that "observational fear physically redistributes the flow of information".

"...And this redistribution is achieved by stress, not just observed, but communicated through social cues, such as body language, sound, and smell," Morozov said.

This shift may potentially enable more communications via the synapses in the deep cellular layers of the cerebral cortex, but less so in the superficial ones.

It is not yet clear exactly how the circuits have altered, only that they have indeed changed, Morozov noted.

"Once we understand the mechanism of this change in the brain in the person who has these experiences, we could potentially know how something like PTSD is caused," Morozov said.

The results were published online in the journal Neuropsychopharmacology.