The identification of the locus coeruleus as a brain region involved in traumatic memory formation provides a promising new entry point, especially for drug developers, for fighting mental illnesses like PTSD. Its unusual blue color is what initially drew people to study this region.
It turns out that the neural cells of the locus coeruleus are blue because they make and release a specific kind of chemical signal, or neurotransmitter, called noradrenaline. Noradrenaline is a stress signal, released by the locus coeruleus when an animal is experiencing fear and stress.
When noradrenaline is released in the brain, it triggers the physical and behavioral responses to stress. Because the locus coeruleus sends noradrenaline to most parts of the brain, it is like an on-guard soldier that keeps the brain more reactive, and thus ready for challenges in our life, by making the brain more responsive to stress.
When noradrenaline excites the memory-forming parts of the brain, it can make an animal form a memory much more quickly. Since the locus coeruleus is activated by stressful situations Figure 1 , researchers wanted to know how it is involved in the formation of unpleasant memories of those stressful situations, like those formed in PTSD.
To study this, Akira Uematsu and colleagues performed experiments similar to those that Pavlov did with his dogs, but they used rats. To do this, the researchers either activated or blocked the activity of the locus coeruleus and looked at what happened to other brain regions. Previous work had shown that the locus coeruleus is involved in the formation of fearful memories because it is connected to the fear center of the brain.
Uematsu and colleagues observed that the locus coeruleus is also connected to other areas of the brain with different functions and wondered what happens to those brain areas when animals form fearful memories.
They found that some of the neural cells within the locus coeruleus communicate with a brain region called the prefrontal cortex. This shows that the locus coeruleus can both promote and inhibit the formation of traumatic memories just like a balance Figure 2B. This finding helps us to answer a long-standing question about one of the most commonly prescribed class of drugs to treat mental illness.
SNRIs serotonin and noradrenaline reuptake inhibitors are medications prescribed to treat mental illness such as, depression, anxiety and PTSD. SNRIs elevate the levels of noradrenaline, and another neurotransmitter, serotonin , in the brain. Since serotonin is a neurotransmitter commonly associated with happiness, it is easy to see why increasing serotonin leads to improved mood.
Rather than acting as an alarm button for stress hormones, it actually plays a very understated but significant role on the learning process — and an impact on behavior and mental health that we are just beginning to understand. Mriganka Sur, the Newton Professor of Neuroscience at The Picower Institute for Learning and Memory and a professor at the department of brain and cognitive sciences at the Massachusetts Institute of Technology, who co-authored the study.
After analyzing their data, the researchers found that the LC appeared to be synchronizing the response of various sensory inputs and regulating the internal cognitive states throughout the brain to correctly time releases of norepinephrine, sending doses toward the motor cortex to provide a chemical signal for when to act after processing visual information. For their test subjects, the researchers are training mice in basic learning tasks in which they are given signals with sounds projected at different pitches and volumes.
The mice are conditioned to hear a high-pitched tone and press a lever that will reward them with a food pellet. If the tone is a low-pitched sound, they learn to avoid it, as pressing the level releases an intrusive air puff. Post-publication activity Curator: Susan J.
Sara Contributors:. Nick Orbeck. Douglas Nitz. Sponsored by: Eugene M. Categories : Neuroscience Multiple Curators. Namespaces Page Discussion. Views Read View source View history. Contents 1 Anatomy 2 Physiology 3 Influence on target neurons and behavior 4 Functions of the locus coeruleus 5 References 6 See also. Izhikevich , Editor-in-Chief of Scholarpedia, the peer-reviewed open-access encyclopedia.
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