Tuesday, 11 August 2015

How the Brain Purges Bad Memories

PTSD

Researchers Identified Neuronal Circuit – To Purge Bad Memories

Researchers have now identified a neuronal circuit – a brain circuit which is responsible in the brain’s ability to purge bad memories. The brain is proficient in knowing when startling or threatening stimulus tends to turn out to be resolved or harmless. However at times, this method fails resulting in unpleasant association arising, a malfunction presumed to be at the root of post-traumatic stress disorder –PTSD and the researchers finding could have effects in treating PTSD as well as other anxiety disorders.

The brain is extremely good in alerting us to dangers such as noxious smells, loud sound, approaching raiders and send electrical impulses down the sensory neurons to our brain’s fear circuitry and to some extent giving rise to either fight or flee from the situation. Similar to most of the emotions, fear is said to be neurologically complicated though earlier work has been constantly connected with two specific areas of the brain in contributing and regulating fear responses.

The two small arcs of brain tissue deep below our temple, the amygdala, is responsible in emotional reaction and tends to flare with activity whenever one experiences fear. If a certain threat tends to become harmless, the region in the brain behind the forehead known as the prefrontal cortex takes over and the fright diminishes. The potential to extinguish painful recollections is said to involve some kind of synchronized effort between the amygdala and the prefrontal cortex.

Working between Two Brain Region – To Eliminate Fear

Andrew Holmes, latest study at the National Institutes of Health, approves that a connection of working between the two brain regions is essential to eliminate fear. For instance, mice usually listening to repeated sound which has been connected with mild foot shock, will learn that on its own the tone is harmless and they tend to stop being afraid.

With the use of optogenetic stimulation technology, or adjusting certain neurons and animal behaviour using light, authors observed that unsettling the amygdala, - prefrontal cortex connection, prevented the mice from disabling the negative connection with the benign tone and in neurobiology speak, memory `extinction’ fails to take place. Besides this, they also observed that stimulating the circuit resulted in the increased extinction of memories of fear.

Till now the investigator was not sure if the amygdala – prefrontal cortex communication pathway could control fear extinction on its own. Both the structures tend to interact with several other brain regions and in isolating their effects on behaviour would be challenging. The discovery was possible due to optogenetics enabling the NIH group to accurately evaluatein real time, only the connection between the two brain regions, providing an accurate connection between neuronal activity and behaviour.

Two Main Hubs – Amygdala & Prefrontal Cortex

Holmes envisages the amygdala and prefrontal cortex as two main hubs in an intricate communication network. In the case of impaired fear extinction such as PSTD, it is just a single connection between the two regions which is damaged and not the hubs.

Holmes explains that `to regulate fear extinction it would be better to isolate and fix that particular line of communication opposed to trying to re-engineer the hubs themselves and it is their job to carry several lines of communication for all types of brain functions most of which are perhaps working fine’. Considering the similarities in case of fear circuitry between humans and rodent, the new study could enlighten the research into new satisfying approaches to anxiety disorders inclusive of mediation which tend to act on the fear circuit.

He believes that healthy fear extinction depends on neural plasticity, which is the brain’s capabilities of making new neuronal connection, which is in part inclined by the brain’s own cannabinoids compounds which tend to regulate neurotransmitters.Drugs which tend to alter the cannabinoid system provide a way in modifying the fear circuit and probably improve anxiety.

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