Scientists at the Sainsbury Wellcome Center have discovered a brain mechanism that enables animals to overcome instinctive fears. The research, published in Science, found that the ventrolateral geniculate nucleus (vLGN) of the brain plays a crucial role in suppressing fear responses.
When mice were exposed to an expanding shadow that mimicked an approaching aerial predator, they initially sought shelter. However, with repeated exposure and no actual danger, they learned to remain calm instead of escaping. The researchers mapped out how the brain learns to suppress these instinctive responses through experience.
The study revealed two key components in this learning process: specific regions of the visual cortex are essential for learning to stop fearing a visual threat, and the vLGN stores memories of previous experiences with threats. If the cerebral cortex is inactivated, animals fail to learn to suppress their fear responses. However, once they have already learned to stop escaping, the cerebral cortex becomes unnecessary.
The researchers also uncovered the cellular and molecular mechanisms behind this process. Learning occurs through increased neural activity in vLGN neurons triggered by the release of endocannabinoids, brain-internal messenger molecules that regulate mood and memory.
This discovery could help advance our understanding of what is going wrong in the brain when fear response regulation is impaired in conditions such as phobias, anxiety, and PTSD. The researchers hope to develop new treatments for maladaptive fear responses and anxiety disorders by targeting vLGN circuits or localized endocannabinoid systems.
Source: https://medicalxpress.com/news/2025-02-scientists-brain-mechanism.html