September 17, 2018Behavior
Responding appropriately to aversive or rewarding stimuli is essential for survival. This requires fine-tuned regulation of brain systems that enable rapid responses to changes in the environment, such as those involved in sleep, wakefulness, stress, and reward-seeking. These same brain systems are often dysregulated in addiction and other psychiatric conditions. According to an article published in Nature Neuroscience (August 2018), previously unknown brain pathways have been identified in mice for reward-seeking and avoidance behavior. These results should have relevance for mental health and addiction research. These study results may help untangle multiple psychiatric conditions, including alcohol use disorder, anxiety disorders, insomnia, and depression in humans.
For the study, the authors looked at the extended amygdala, a brain region involved in fear, arousal, and emotional processing and which plays a significant role in drug and alcohol addiction. They then focused on a part of this structure known as the bed nucleus of stria terminalis (BNST), which connects the extended amygdala to the hypothalamus, a brain region that regulates sleep, appetite, and body temperature. The hypothalamus is also thought to promote both negative and positive emotional states, and that a better understanding of how the BNST and hypothalamus work to coordinate emotion-related behavior could shed light on the emotional processes dysregulated in addiction.
To map the brain circuitry between the BNST and the hypothalamus, the authors exposed mice to rewarding and aversive stimuli, and then visualized and manipulated the activity of neurons using fiber optic techniques. The study identified two distinct subpopulations of neurons in the BNST that connect to separate populations of neurons in the lateral hypothalamus. These parallel circuits drove opposing emotional states: avoidance (aversion) and approach (preference). Different neurotransmitters were linked to aversion and preference within these neurocircuits - corticotropin releasing factor was involved in aversion, while cholecystokinin played a role in preference.
According to the authors, the discovery of the unique and opposing influences of these specific BNST to LH circuits may be broadly relevant to the fields of neuroscience and mental health, and that future studies of the BNST to LH pathways will inform the development of improved therapeutic approaches for psychiatric disorders.