Do you know which part of the brain gets alarmed first when you recognise a fear and what other parts of the brain are responsible to avoid danger in the future?

Researchers Bo Li, Associate Professor and post doctorate fellow Mario Penzo from Cold Spring Harbor Laboratory (CSHL), and Jason Tucciarone from Stony Brook University, have a clear perception on that and their study sheds some light on this question. Their finding titled, ” The paraventricular thalamus controls a central amygdala fear circuit ” was published in the journal Nature.

Jason Tucciarone of Stony Brook University’s Department of Neurobiology and Behavior
Jason Tucciarone of Stony Brook University’s Department of Neurobiology and Behavior. | Credit: Stony Brook University

To identify which part of the brain is responsible for recognizing and remembering threats, as well as activating the brain to respond to danger, the team used mouse model. First, they looked at thalamus, the part of the brain that relays sensory information and acts as a center for pain perception; but in particular, they focused on the paraventricular nucleus of the thalamus (PVT), an area that is readily activated by both physical and psychological stressor.

As a part of the experiment, the researchers used footshock to simulate danger. Using genetically modified mice, the researchers study the role specific parts of the circuit play in protecting the mice from danger and confirmed that the PVT was indeed highly sensitive to threats.

Later, they looked at the neurons in the posterior PVT (pPVT) that were communicating with the lateral division of the central amygdala (CeL), where neuroscientists say is a site of fear memories. After that, the researchers conducted different experiments and found that some of the experiments were suppressing communications coming from these neurons. Hence they found that the pPVT plays an important role in conditioning the mice to fear certain situations and to remember those fears. Yes, the PVT in the brain recognizes danger and the neurons in the posterior PVT (pPVT)  avoid the danger or fear in the future.  They also demonstrated that this knowledge was “hard-wired” into the neuronal synapses.

The researchers hypothesized that the chemical messenger, the pPVT neurons send off to deliver this information to their cousins in the CeL, might be brain-derived neurotrophic factor (BDNF), a protein known to regulate synaptic functions. To test this hypothesis, they created mice without the gene to produce BDNF or without a BDNF receptor. Both kinds of mice shows an impaired ability to recognize danger. The researchers also tested the effect of BDNF on mice that had not been genetically altered by infusing their brains with BDNF, causing a “robust” response to danger.

The team concluded that the communications transmitted by BDNF produced in pPVT neurons and picked up by CeL receptors facilitate not only the formation of stable fear memories but also the expression of fear responses. [Stony Brook University via newswise]

Well, you might also want to take a look at how fear can be controlled through DNA modification.

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