Researchers have identified a brain circuit that causes mice to show signs of being afraid when high up, with a similar mechanism expected to also occur in people.
A brain circuit that mediates a fear of heights has been identified in mice, a discovery that could help improve treatments in people with an extreme reaction to such situations.
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| People standing on a glass floor at the Ostankino tower in Moscow, Russia Nosyrevy/iStockphoto/Getty Images |
A fear of heights, often accompanied by anxiety and dizziness, is thought to be an in-built physiological response that evolved to help prevent injuries from falling. But 3 per cent to 6 per cent of people have acrophobia, an intense version of this that can impact their quality of life.
To better understand why this occurs, Wei Shang at East China Normal University in Shanghai and his colleagues placed mice on a high, open platform, noting that they approached the edge cautiously before moving back or turning away, behaviour that is similar to people with acrophobia.
Further analysis revealed that exposure to heights activated neurons in the mice’s midbrain structure called the periaqueductal grey. When these cells were disabled by the researchers, the animals fearlessly explored the platform edge, even hanging from it and in some cases falling off.
Another set of experiments showed that these cells receive inputs from neurons in the lateral geniculate nucleus, a component of the visual system, and that silencing cells there also prevented the fear of heights.
In the next part of the study, Shang and his colleagues found that neurons in another midbrain structure, the superior colliculus, were activated after the mice were placed on the high platform, which helped to suppress their fear of heights. Silencing these neurons in another group of mice dramatically increased the animals’ fear.
Together, the results show that a brain circuit that connects the lateral geniculate nucleus and periaqueductal grey drives a fear of heights in mice by processing height information and that an additional pathway linking these structures to the superior colliculus can inhibit this fear response.
“Our long-term goal is to reveal how physiological fear of heights evolves into acrophobia and develop treatments for this condition,” says senior author Xiaobing Yuan.
“We plan to collaborate with psychologists to investigate whether these mechanisms also apply to humans, and to clarify the specific visual cue that triggers fear of heights and what brain circuitry detects height information to initiate the behavioural response.”
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