Saturday, August 30, 2014

Trauma-Induced Fear-Anxiety Circuits Turned Off In Mice

Scientists say they have found a way to "turn off" bad memories and divorce emotional association from stored neural materials, making it possible to "forget" traumatic events.
Scientists say they have found a way to "turn off" bad memories and divorce emotional association from stored neural materials, making it possible to "forget" traumatic events.

Alan: I once opposed the development-and-use of "Brave New World" techniques that impose happiness on people. Now, at age 67, I look back and see my opposition as misplaced idealism arising from sophomoric conviction that "will power" is much more capable than it is. Routinely, trauma is so life-shattering -- and so durably destructive -- that I now welcome every advance in brain science that promises to "erase" trauma and "put Humpty together again" - however incompletely.
Bad memories of trauma need not leave people emotionally scarred for life, according to neuroscientists who claim it is possible to erase feelings of fear or anxiety attached to stressful events.
In a breakthrough for the treatment of depression or post-traumatic stress, researchers at the Riken-MIT Centre for Neural Circuit Genetics in the U.S. have pinpointed the brain circuits that attach emotions to memories, and crucially, learned how to reverse the link.
They managed to “switch off” feelings of fear in mice that had been conditioned to feel anxious. It is likely that the same technique could be used in people.
“In our day-to-day lives we encounter a variety of events and episodes that give positive or negative impact to our emotions,” said Susuma Tonegawa, professor of biology and neuroscience at the centre. “If you are mugged late at night in a dark alley, you are terrified and have a strong fear memory and never want to go back to that alley. On the other hand if you have a great vacation, say on a Caribbean island, you also remember it for your lifetime and repeatedly recall that memory to enjoy the experience.
“So emotions are intimately associated with memory of past events. And yet the emotional value of the memory is malleable. Recalling a memory is not like playing a tape recorder. Rather it is like a creative process.
“The circuits seem to be very similar between humans and mice when it comes to memory formations and the emotions of memories. So a similar technology could be available for humans.”
Memories are made of many elements, that are stored in different parts of the brain. The context of a memory, such as the location and time that the event took place, is stored in cells in a different area of the brain than those cells that store the emotional response.
The team studied which brain cells were active when mice were experiencing a pleasant experience — a male mouse spending time with a female mouse — or a negative experience — a mild electrical shock.
They then showed that by stimulating the neurons associated with the opposite emotion they could reverse the response to the memory. Mice became more relaxed in situations where they had previously been anxious, and more fearful where they had previously been content.
“We found that we can dictate the overall emotion and the direction of the memory,” added Tonegawa. “We could switch the mouse’s memory from positive to negative and negative to positive.”
The brain cells are triggered by a technique called optogenetics which uses pulses of blue light to fire the neurons.
Tonegawa said the fact that the stimulation occurs on the surface of the brain makes it less invasive than previous methods.
Previous studies have shown that memories can change over time as recollections become more vague or entirely false memories appear.
Behavioural therapists often take patients back to a traumatic event and attempt to “rewire” their brains. But this is the first time that scientists have shown which brain circuits are responsible for emotions, and reversed them.
Richard Morris at the Centre for Cognitive and Neural Systems at the University of Edinburgh said: “Molecular engineering is shedding light on our understanding of the underlying physiological networks of memory.”
The study was published in Nature.

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