Summary: According to research, brain chemicals have been found that help animals reduce their natural apprehensions when threats become safe over time.
They discovered that certain areas of the visual cortex are required for learning to supersede fear but not for maintaining memory using a visible threat model in mice. Instead, the ventrolateral geniculate nucleus (vLGN ) retains these learning-induced memories, regulating fear suppression. The process is driven by endorphins, which increase neuronal activity in vLGN cells to reduce fear responses.
These findings challenge conventional theories about memory store and show a clear connection between instinctual behaviors and mental understanding. Understanding this process could lead to new therapies for fear-related problems such as phobias, stress, and PTSD.
Important Information:
- Anxiety Suppression Memory: The vLGN, not the physical brain, shops learned fear reduction actions.
- Neurological Mechanism: Endocannabinoids control vLGN neurons, increasing action to reduce worry reactions.
- Medical Potential: Using vLGN wires or cannabinoids pathways to treat anxiety and PTSD could lead to novel treatments.
Origin: Sainsbury Wellcome Center
The precise brain mechanisms that help animals overcome instinctive fears have been discovered by researchers at the Sainsbury Wellcome Centre ( SWC ) at UCL.
Published today in , Science, the study in mice could have implications for developing therapeutics for fear-related disorders such as phobias, anxiety and post-traumatic stress disorder ( PTSD ).
The research group, led by Dr. Sara Mederos and Professor Sonja Hofer, studied how the mind learns to control messages to perceived threats that are later found to be safe.
” Humans are born with instinctive dread emotions, such as reactions to loud noises or fast-approaching things”, explains Dr Mederos, Research Fellow in the Hofer Lab at SWC.
” Nevertheless, we can override these instinctive reactions through practice, such as when kids learn to enjoy lights rather than their loud curls. We sought to understand how these kinds of mental processes are related to learning.
The team studied mice that were presented with an costs expanding shadow that resembled an approaching flying prey using an impressive exploratory strategy. First, the mice sought sanctuary when encountering this physical threat.
However, with repeated contact and no real harm, the mice learned to be quiet instead of escaping, providing researchers with a design to examine the reduction of fear responses.
The team was able to track knowledge of previous threat experience and make recommendations for previous work in the Hofer Lab regarding the ability of an area of the brain called the ventrolateral geniculate nucleus (vLGN ) to suppress fear reactions when it was active.
The researchers looked into whether this neural pathway had a role in learning to avoid fear a visual threat because the vLGN also receives significant input from visual areas in the cerebral cortex.
The study identified two crucial elements in the learning process: ( 1 ) specific regions of the visual cortex proved to be essential for the learning process; and ( 2 ) a brain called the ventrolateral geniculate nucleus (vLGN ) stores these learning-induced memories.
When particular cortical visual areas were inactivated, animals failed to learn to suppress their fear responses. However, once the animals had already learned to stop escaping, the cerebral cortex was no longer necessary”, explained Dr Mederos.
Our findings challenge conventional notions of memory and learning, according to Professor Hofer, study’s senior author.
We discovered that the subcortical vLGN and not the visual cortex actually stores these important memories, despite the cerebral cortex ‘ longstanding status as the brain’s primary center for learning, memory, and behavioural flexibility.
” This neural pathway can provide a link between cognitive neocortical processes and ‘ hard-wired’ brainstem-mediated behaviours, enabling animals to adapt instinctive behaviours.”
The researchers also found the molecular and cellular mechanisms underlying this process. Learning is facilitated by the release of endocannabinoids, a brain-internal messenger molecules that regulate mood and memory, in specific vLGN neurons, which are triggered by this increased neural activity.
This release lowers vLGN neurons ‘ inhibitory output, leading to increased activity in this area of the brain when the visual threat stimulus is encountered, which lowers vLGN neurons ‘ levels of inhibition. This results in a suppression of fear responses.
The effects of this discovery go beyond the lab.
Our findings may also help us better understand what is wrong with the brain when the regulation of the fear response is impaired in conditions like phobias, anxiety, and PTSD. The brain pathway we discovered exists in humans also, explains Professor Hofer, while instinctive fear reactions to predators may be less applicable for modern humans.
By focusing on vLGN circuits or localized endocannabinoid systems, this may open new avenues for treating fear disorders.
In order to find new, specific treatments for maladaptive fear responses and anxiety disorders, the research team intends to work with clinical researchers to study these brain circuits in humans.
Funding: This research was funded by the Sainsbury Wellcome Centre core grant from the Gatsby Charity Foundation and Wellcome ( 090843/F/09/Z ), a Wellcome Investigator Award ( 219561/Z/19/Z ), an EMBO postdoctoral fellowship ( EMBO ALTF 327-2021 ) and a Wellcome Early Career Award ( 225708/Z/22/Z ).
Concerning this news about neuroscience research and fear
Author: April Cashin-Garbutt
Source: Sainsbury Wellcome Center
Contact: April Cashin-Garbutt – Sainsbury Wellcome Center
Image: The image is credited to Neuroscience News
Original Research: Closed access.
By Sara Mederos and colleagues,” Overwriting an instinct: Visual cortex instructs learning to suppress fear responses.” Science
Abstract
Overwriting an instinct: Visual cortex instructs learning to suppress fear responses
Fast instinctive responses to environmental stimuli can be crucial for survival, but they are not always the best choice. The neural pathways that drive these ethologically relevant forms of learning are still unexplored, despite how animals can adapt their behavior and repress instinctive responses.
We discovered that a top-down pathway to the ventrolateral geniculate nucleus (vLGN ) leads to the development of posterolateral higher visual areas ( plHVAs ), which are necessary for learning to suppress escapes from innate visual threats. PlHVAs no longer are required after learning; instead, vLGN populations that have inhibitory control over escape responses are based on plasticity in the learned behavior.
Through endocannabinoid-mediated long-term suppression of their inhibitory inputs, vLGN neurons receiving input from plHVAs enhance their responses to visual threat stimuli during learning.
We thus reveal the detailed circuit, cellular, and synaptic mechanisms underlying experience-dependent suppression of fear responses.
