Imagine a mouse exploring its surroundings with caution, its senses alert to any sign of danger. In one part of its environment, the mouse has experienced something unpleasant – a mild but startling shock. As it roams, it pauses near the spot where the shock occurred, its behavior changing noticeably. It stretches out, sniffs the air, and hesitates to step back into the area where it was hurt.
Researchers have mapped a brain circuit responsible for detecting immediate threats as well as creating lasting memories of those threats. This finding could help us better understand how animals – and by extension, humans – process fear and protect themselves from danger.
The study, led by Professor Newton Sabino Canteras, aimed to identify the brain regions involved in signaling fear and how these regions help animals recognize environments associated with physical or predatory threats. The team used a technique called fiber photometry to measure neural activity in specific brain regions, including the dorsal premammillary nucleus (PMd), which acts as a critical “threat detector.”
When a mouse approached the area where it had previously received shocks, the PMd became highly active. This activity dropped when the mouse moved away from the dangerous area or turned its back on it.
To further investigate the PMd’s role, the researchers used chemogenetic silencing to inactivate specific receptors in the PMd. When the PMd was silenced, the mice’ behavior changed dramatically – instead of avoiding the shock-associated box, they entered it without hesitation, as if they no longer perceived it as dangerous.
The study also explored how the PMd interacts with other parts of the brain, particularly the septo-hippocampal-hypothalamic circuit, which integrates environmental information, and the periaqueductal gray (PAG) in the brainstem and the ventral anteromedial thalamus (AMv) in the thalamus.
The findings suggest that the PMd is not only crucial for detecting threats but also essential for forming memories of those threats. The study’s implications extend beyond basic neuroscience, informing new treatments for anxiety and fear-related disorders, such as post-traumatic stress disorder (PTSD).
Source: https://www.psypost.org/brains-threat-detector-uncovered-new-study-reveals-neural-circuit-for-identifying-and-remembering-threats/