The smell of fear

A ‘smell sensor’ in mice triggers fear of foxes, snakes and other predators. This suggests aversion to threatening stimuli is genetically hardwired in mice — and perhaps in humans as well.

A team co-led by investigators from the University of Tsukuba exposed mice to a chemical mutagen and then looked for offspring with diminished fear responses to two predatory cues: a potent derivative of a fox odorant and shed snake skin.

They found that mice with a mutant version of Trpa1, a protein receptor involved in relaying chemosensory signals to the brain, could still smell the scents but were no longer intuitively afraid of them.

By studying core fear pathways like this one in mice, the researchers hope to better understand the genetic basis of human anxiety disorders and other conditions linked to emotional processing.