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Researchers may have caught a glimpse of what sadness looks like in the brain.
A study of 21 people found that for most, the feeling associated with increased communication between brain areas involved in emotions and memory, a law from the University of California, San Francisco reported on Thursday in the magazine Cell .
"There was a network that would tell me again and again if they felt happy or sad," said Vikaas Sohal, an Associate Professor of Psychiatry at UCSF.
The discovery can lead to a better understanding of mood diseases and perhaps new ways of treating them.
Previous research has shown that sadness and other feelings include amygdala, an almond mass found on each side of the brain. And there was also evidence that hippocampus, associated with memory, could play a role in emotion.
But Sohal and the other researchers were curious about what these and other brain areas do when someone's mood changes.  "We really wanted to know when you feel satisfied or feel happy, what exactly happens in the brain at these moments," says Sohal.
You can not get that information from brain scans, which does not detect changes that occur in fractional portions of a second. Then the team studied 21 people in hospital waiting for brain surgery for serious epilepsy.
Before surgery, doctors put small threads in the brain and monitor their electrical activity for up to a week.
Sohal says the team hoped that these recordings would help answer a basic question: "When patients sit there or watch TV or talk to their family or wait or worry, what regions of the brain are talking to each other? "
Patients agreed to keep an ongoing log of their mood. And the team saw that some moods coincided with communication within specific brain networks.
The researchers thought they could find networks similar to a couple of people. But they were "really surprised" to learn that 13 of the 21 patients shared the same network, "says Sohal.
But it is meaningless that communication between areas involved in memory and emotion would be associated with sadness. "Maybe you feel down and then you start to remember times in your life when bad things have happened, or you start to remember those experiences and that's what makes you feel down," he says.
The study could not confirm it. It could also not show whether the increase in communication was the result of a mood change or the cause of one.
Still, Sohal says that the discovery can provide comfort to people with depression.
"As a psychiatrist, it's incredibly powerful to only say to patients," Hi, I know something happens in your mind when you feel down. ""
In the same way, the new study only confirms the results of early research on animals, says Dr. Joshua Gordon, Head of the National Institute of Mental Health.
"There is a circuit, part of the brain that we already knew was involved in mood – it's less than the wow part," he says. "The wow part is that it's in humans."
The study also provides a detailed map of what is happening in human brain, which is what doctors and researchers need to look for better treatments for patients with mood disorders.  "It's really important that we find the circuits that are behind the mood so we can learn more about them and treat them with tools we develop that focus on circuits." These tools include transcranial magnetic stimulation, which uses pulses of energy delivered through the skull to change the activity of the brain circuits.
The study also shows the value of the BRAIN initiative, launched by President Obama in 2013, says Gordon.
"The goal of the BRAIN initiative is to develop tools we can use to get unprecedented access to and understanding of the brain," said Gordon. "This study does both."
The research group's funding was part of the Defense Research Institute for Defense Research, a major supporter of the BRAIN initiative.