Some anti-anxiety drugs are either not effective or have unwanted side effects. Understanding how the brain processes fear and nervousness could offer another way of developing better treatments for anxiety disorder.
Neuroscientists from the University of Bristol's School of Physiology, Pharmacology, and Neuroscience identified novel brain mechanisms responsible for anxiety and fear behaviors, such as freezing. It is a key pathway in the brain that offers a potential new drug target to alleviate the symptoms of anxiety and other related psychological disorders.
Fear Processing in the Brain
According to the World Health Organization (WHO), around 3.6% of the world population, or equivalent to 264 million, live with anxiety disorder. It is often comorbidity with depression, mania, and substance use disorders, which are psychological disorders that induce irrational fear and excess worry due to everyday stress.
Anxiety is a normal feeling when the brain reacts to stress, particularly fear that starts in the brain and ends up throughout the body. Smithsonian magazine explained that fear could either elicit fight or flight reactions. It begins in the amygdala's brain region, which is the almond-shaped set of nuclei in the temporal lobe responsible for emotional salience.
Threats, like the sight of a predator, trigger a fear response from the amygdala that activates areas involved in prepared motor functions in the fight and flight reactions. It triggers the release of stress hormones from the sympathetic nervous system that cause bodily changes.
These changes include pupil and bronchi dilation, breath acceleration, increase in heart rate and blood pressure, and decrease in gastrointestinal activity.
Novel Brain Mechanisms for Fear Processing
The team from Bristol sought to investigate who cerebellum influences activity on the periaqueductal grey (PAG), a brain region that coordinates survival mechanisms, including fear-evoked coping responses, Science Daily reported. They fitted animal models with electrodes to record its activity and applied a conditioning task to elicit the formation of fear memory and freezing.
In the study, titled "Cerebellar Modulation of Memory Encoding in the Periaqueductal Grey and Fear Behavior" published in eLife, researchers showed that a subset of brain cells have increased responsiveness to the conditioned tone within the PAG area that is consistent with encoding a fear memory.
On the other hand, the subsequent timing of fear-related neuronal activity in the PAG became less precise and the duration of freezing was increased when cerebellar output was changed during the conditioning.
Daily Express reported that this confirms that cerebellar PAG interactions contribute to the fear conditioning processes. More so, the study showed that this pathway cause impairment in fear-conditioned freezing and ultrasonic vocalizations.
Study lead authors Dr. Charlotte Lawrenson and Dr. Elena Paci explained that the findings of their study showed that the cerebellum is part of the survival network in the brain that regulates fear memory processes. Ultimately, the study offers a novel target for treating psychological conditions like PTSD and anxiety disorder.
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