HANGZHOU, Jan. 5 (Xinhua) -- Chinese scientists have discovered two types of neurons that can arouse or suppress innate fear induced by odor.

Innate fear, which include things like fear of height and insects, is a basic animal instinct to avoid danger, but in excess it can lead to anxiety and even mental disease. Understanding its neuron mechanism can benefit therapy for fear-related disorders, said Duan Shumin with the Chinese Academy of Sciences.

By exposing mice to the odor of their predator's feces and recording fear-related responses such as frozen movement, shaking and accelerated heart rate, Duan's team studied how such fears were related to their somatostatin-positive neurons and parvalbumin-positive (PV) neurons.

When their PV neurons were inhibited, the mice remained bold and continued to act normally despite the threat of a predator, while activation of the somatostatin neurons produced the same effect, said Wang Hao from Zhejiang University, who also participated in the research.

"These neurons are like fear switches. Even without the odor, the neurons can generate a fear response in mice, such as fleeing, increased heart rate and incontinence," Wang said.

The study was published in the latest issue of Nature Neuroscience.