Breathing rhythm can enhance memory recall, fear response

These effects on behaviour depend critically on whether you inhale or exhale and whether you breathe through the nose or mouth.

In the study, individuals were able to identify a fearful face more quickly if they encountered the face when breathing in compared to when breathing out. 

Individuals also were more likely to remember an object if they encountered it on the inhaled breath than the exhaled one. The effect disappeared if breathing was through the mouth, said the study published in the Journal of Neuroscience.

"One of the major findings in this study is that there is a dramatic difference in brain activity in the amygdala and hippocampus during inhalation compared with exhalation," said lead author Christina Zelano, Assistant Professor at Northwestern University Feinberg School of Medicine in Chicago, Illinois.

The scientists first discovered these differences in brain activity while studying a small number of patients with epilepsy who were scheduled for brain surgery. 

A week prior to surgery, a surgeon implanted electrodes into the patients' brains in order to identify the origin of their seizures. 

This allowed scientists to acquire electro-physiological data directly from their brains. 

The recorded electrical signals showed brain activity fluctuated with breathing. The activity occurs in brain areas where emotions, memory and smells are processed.

"When you breathe in, we discovered, you are stimulating neurons in the olfactory cortex, amygdala and hippocampus, all across the limbic system," Zelano said.

The findings imply that rapid breathing may confer an advantage when someone is in a dangerous situation.

"If you are in a panic state, your breathing rhythm becomes faster," Zelano said. 

"As a result you'll spend proportionally more time inhaling than when in a calm state. Thus, our body's innate response to fear with faster breathing could have a positive impact on brain function and result in faster response times to dangerous stimuli in the environment," Zelano noted.