June 3, 2015, Updated July 5, 2015

After hitting her head in a swimming pool, Prof. Mouna Maroun, the head of the Sagol Department of Neurobiology at the University of Haifa, set out to disprove an assumed position that the brains of humans of all ages act similarly.

Brain trauma (Shutterstock.com)
Brain trauma (Shutterstock.com)

“It all began when I knocked my head while I was in a swimming pool – a mild form of trauma, but enough to persuade me not to go back into a swimming pool for a long time. But children who were in the pool and who knocked themselves worse than I did, didn’t think twice about jumping straight back into the water. When I saw this, I realized that this was something I needed to examine in the laboratory,” she says.

The new University of Haifa study shows that young people’s brains cope with stress in a completely different way to adults.

The study was performed on rats and shows that young rodents extinguished fear much faster than the adult rats. Professor Maroun explains that in terms of exposure to trauma and fear extinction, rats are a very close model for human behavior. Since exposure to stress after the learning of fear associations is known to delay fear extinction among adults – and therefore, according to conventional wisdom, also among children – the investigators also included this factor in the equation.

“Childhood is a period when the brain and the prefrontal cortex are still developing. Accordingly, there is no reason that the mechanism of action in adults and young people should be the same,” says Maroun, who conducted the study.

During exposure to a stress experience, two cerebral mechanisms enable us to respond efficiently to fear, on the one hand, but also to return to normality once the event ends.

During the event, a mechanism located in the amygdale effectively tells us that we are in a frightening situation and must act (fight, escape, freeze on the spot, etc.). After the event, a fear extinction process begins in the prefrontal cortex and effectively returns the body to its routine state. When the latter mechanism fails to function properly, we delay the fear extinction mechanism and continue to experience reactions of fear, leading to symptoms of anxiety and post-trauma.

In the study, young (postweanling) and adult rats were exposed to a mild traumatic event. The findings showed that the adult animals reacted as expected: strong fear responses were seen by comparison to the rats that were not exposed to trauma. The group that was not exposed to stress extinguished fear more rapidly than the group that was exposed to stress. But among the young rats the picture was completely reversed. The fear reactions of the rats exposed to trauma were much lower, and the fear extinction time was much shorter, than among the adult rats. Moreover, the young rats exposed to stress actually accelerated the return to routine and significantly reduced fear reactions.

“This implies that it’s wrong to claim that the mechanism in adults and young people is identical, and simply operates a little differently. The mechanism is actually completely different. We can therefore state that we are familiar with the fear extinction among adults, but that we still need to work out how the brain works to extinguish fear in young people.

“The immediate significance of this finding is that we really cannot continue treating child trauma victims with the same methods and drugs we use to treat adult victims,” says Maroun.



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