Think about a time when you had to suddenly slam on the car brakes or got a long email from your boss first thing Monday morning.
That sense of panic or feeling of overwhelm eventually dissipates, at which point you begin to see the situation more clearly — the construction down the road that brought traffic to a stop or the list of tasks in your boss’s email you can start tackling one by one.
In the past, focusing in a high-stress situation may have meant the difference between life or death — the ability to outsmart and escape a charging predator, for example.
But until now, scientists didn’t know what caused the brain to switch from panic into focus. They thought the brain just needed some time for the neurotransmitter called noradrenaline — basically adrenaline for the brain — to dissipate.
Then, a new study of stressed-out mouse brains revealed something entirely surprising: a never-before-seen brain circuit that channels noradrenaline to special brain cells called astrocytes.
When the mice became stressed, the researchers observed that the astrocytes kicked into high gear. They helped the animals relax their brains and control the overexcited neuron floods which contribute to “fight or flee” stress responses.
Mouses brains differ from those of humans. Human brains contain astrocytes which may also function similarly.
If this brain circuit in humans is the same, then it may help researchers better understand attention disorders such as ADHD and to develop more effective treatments.
A new brain circuit
Researchers from the University of California San Francisco examined the brain activity of mice under acute stress and discovered that noradrenaline in the brain actually sends two messages — one to neurons to engage alertness and one to astrocytes to calm overactive neurons.
“I didn’t expect astrocyte activity to closely follow changes in the arousal states of animals,” said Kira Poskanzer , Senior author and associate professor of Biochemistry and Biophysics.
Astrocytes are star-shaped cells located between the brain’s neurons. They were understudied until recently because they were viewed as a supporting system rather than a main player.
But a new study shows that they are crucial in the activity of neurons.
“We learn more about the workings of the brain when we study elements like astrocytes that are often left out in traditional neuroscience research,” Poskanzer explained.
A better understanding of stress management and hyperactive disorders
People with hyperactivity disorders typically experience worsened symptoms under stress. They may find it difficult to relax and focus.
If researchers could identify the mechanisms that cause our brains relax, regain focus and perception, during times of stress, it would be possible to learn how to use it in order to help those who suffer from severe stress.
This was a mouse study, so researchers cannot say with certainty how these findings will translate to human beings.
Despite the fact that both humans and mice are mammals, the research “suggests human astrocytes could also play a role in regulating neuronal activities in the cortex”, Poskanzer explained.
And because the newly discovered brain circuit in mice helps control attention and perception, it could play an important role in treating attention disorders, and other neurological and psychological disorders, Poskanzer said.