Optogenetic Slowing of Breathing Rate Reduces Fear Behaviors in Mice, Study Finds

Mice trained to slow their breathing rate displayed less fear-related behaviours in standard tests of mouse anxiety, according to research presented at the Embodied Minds Summit in Los Angeles on 3 May. Jack Feldman, a neuroscientist at UCLA, showed that the effect occurs even though mice lack any expectation that slow breathing should calm them.

“It’s not a placebo effect because the mice don’t know it’s supposed to calm them down,” Feldman stated.

He added that slow breathing doesn’t have to be a deliberate choice to induce calm. The study builds on Feldman’s 1991 discovery that the pre-Bötzinger Complex is the master pacemaker of breathing rate in mammals. This brainstem region mostly operates automatically, adjusting respiration according to the body’s needs.

In humans the pre-Bötzinger Complex is connected to cortical brain regions involved in decision-making, enabling people to intentionally override breathing rhythm to talk, laugh and sing. Mice do not share the human skill set that enables intentional override of breathing rhythm. To manipulate their breathing rate, Feldman and his team used optogenetics.

They inserted a light-sensitive protein into neurons of the pre-Bötzinger Complex that inhibit inhalation and lengthen exhalation. Pulses of light slowed the mice’s breathing rate up to 70 per cent. After four weeks of daily optogenetic stimulation, the mice’s breathing rates slowed during sessions and between them, indicating the animals had been trained to breathe more slowly.

Three days after their last training bout, trained mice were less likely to freeze in a stressful situation than control mice. Trained mice spent more time exploring open spaces while control mice stuck to dark corners. Andrea Zaccaro, a neuroscientist at the “G.

D’Annunzio” University of Chieti-Pescara in Italy, said the study isolates a low-level or bottom-up component of the breathing–emotion relationship. 627565. @NewScientist reported that while the findings demonstrate physiological benefits of slow breathing without conscious involvement, Zaccaro noted that mindful attention to the breath could plausibly amplify those effects.