Two New Studies Explore the Neuroscience of Negative Emotions

We've all had experiences we'd prefer not to remember. That's especially true for people who have gone through a traumatic event such as childhood abuse, combat-related PTSD, or a bad accident. But there may be positive health applications for identifying, predicting, and retrieving negative emotions in the brain, according to two new studies.

In the first, Luke Chang, assistant professor of psychology and brain sciences at Dartmouth, identified a brain pattern under fMRI imaging that can predict a “neural signature of negative emotion.” In the study, recently published in PLOS Biology, Chang and his fellow researchers showed 183 participants pulled from the general population negative photos ranging from bodily injuries to human feces, as well as neutral photos. Thirty additional participants were subjected to painful heat. 

Researchers identified the different networks in the brain that all work together during a participant’s negative emotional experience, which they call a “brain signature.” Then, they used machine-learning algorithms to find global patterns of brain activity that best predicted the participants’ responses. “What we’re calling a 'brain signature' is basically a configuration—a brain pattern that is predictive of a state,” Chang tells mental_floss. He compares the process to the way that Netflix predicts who is watching a certain type of show based on the watcher’s choices in programming.

This brain signature was identical in all participants—an “exciting and surprising" finding, Chang says. “If you came in and saw these images, I could basically say which ones you would think were negative with about 100 percent accuracy without knowing anything about you."

Much of the neuroscience of emotion focuses on manipulating a single psychological state and then seeing which regions of the brain are activated. Chang believes that approach—trying to assign a specific brain region to a specific emotional state—is too reductive.“The regions that comprise the signature aren’t just one region, but distributed through many systems, which is counter to the way people think about emotion,” he notes.

Predicting negative emotional states could have applications for future treatment of mental illness, substance abuse, and trauma, Chang says. “From substance abuse to depression and anxiety and psychosis, most people agree that some sort of disruption in emotion processing is common in all mental health issues.”

MEMORIES CAUSED—AND LOST—BY TRAUMA

Many psychologists believe that in order for patients to recover from trauma, they often need to be able to recall what happened to them. The second study, published in Nature Neuroscience, investigated how the brain stores negative memories, known as “state-dependent learning.” The study, conducted in mice at Northwestern University’s Feinberg School of Medicine, suggests that negative memories caused—and then “lost”—by traumatic experiences may be retrieved by re-creating the state of the brain in which the memory first occurred.

Researchers injected the hippocampus of mice brains with gabaxadol, a benzodiazapene drug that stimulates extra-synaptic GABA receptors in the brain, which change the brain’s state from sleepy to alert, or aroused to inebriated. Essentially, they made the mice feel a little drunk. Then the mice were put in a box and given a mild electric shock. When the mice were put back in the box the next day, they moved freely and did not act afraid, suggesting that they did not remember the shock. But when scientists injected the drug again, and returned them to the box, they froze as though in fear of another shock.

The study suggests that in response to trauma, the brain activates this extra-synaptic GABA system, which appears to encode memories of fear-inducing events and hide them away from consciousness, rather than the glutamate system, which helps to store all memories, positive and negative. This research may provide a window into how to access these traumatic memories when needed for therapeutic reasons.