Neuroscientists have discovered a delicate balance between the positive and negative emotions by identifying two neuron populations that can encode happy and fearful moments. Our brain consists of a tiny structure named amygdala which is responsible for giving out positive emotions such as happiness and negative feelings such as fear.

According to Medical Express, a new study from MIT states both the positive and negative emotions are controlled by two populations of a neuron. They are genetically programmed to encode both the cheerful and painful memories. The study also suggests that an imbalance between these populations can cause depression and post-traumatic stress disorder.

In 2014, the lab of Susumu Tonegawa, Picower Professor of Biology and Neuroscience, identified a brain circuit that links memories with positive and negative memories. During the study, the researchers also portrayed that they could reverse a memory's association in mice. While the mouse was undergoing a happy moment, the researchers artificially activated the hippocampal cells which have been storing the negative moments. This weakened the fearful moment of the original memory and replaced it with a more positive feeling.

As per a report published by news.mit, Tonegawa's lab identified genetic differences which could be used to differentiate the fear-responsive and reward-responsive populations. After studying about all the genes turned on in BLA cells, they came up with one gene, present in the BLA cells, which can encode positive memories but not in cells that encode negative memories.

BLA is generally divided into two sections - posterior and anterior. In the study, the researchers have discovered that each population of neurons can inhibit the other. The brain continuously balances the activity between these two populations of a neuron. They also found out that the fear neurons extend to a part of the brain known as nucleus accumbens and the reward neurons extend to both parts of the brain - nucleus accumbens and amygdala.

The study was funded by the National Institutes of Health, the RIKEN Brain Science institute, JPB Foundation and the Howard Hughes Medical Institute.