New study links human reaction times to breathing cycles

Imagine swimmers on starting blocks poised to dive at the sound of the starting horn or the driver of a car going 60 mph suddenly needing to brake to avoid a collision. A small fraction of a second in response time could make the difference between winning or losing and life or death.

Neuroscientists at Northwestern University have made the surprising discovery that response speed on an exhalation is faster than on an inhalation by an average of 41 milliseconds (1/25th of a second). Response speed during pauses between breaths is also faster than inhalation by 21 milliseconds.

The study is the first experiment to measure response speed during all phases of respiration including the pauses between.

The article, "Response speed is modulated by respiratory phase," will be published by Cell Press in the journal iScience at 12 p.m. CDT on Monday, Sept. 28. The study's senior author is Ken Paller, the James Padilla Professor of Psychology at Northwestern. The lead author is neuroscientist Erika M. Yamazaki, a former member of Paller's lab who has continued to partner on research since earning her Ph.D.

"By using a tangible and easy to understand task, we were able to show the relationship between respiration and cognition, which I hope people in a range of fields will find application for," Yamazaki said. "Study of the brain and body connection is still a new field of research, which makes the study findings all the more exciting."

Study participants completed a Psychomotor Vigilance Task (PVT), a widely used computer task in which subjects press the space bar as quickly as possible when spotting a red square turn yellow. The participants, 35 adults aged 18 to 33, performed the task while wearing a simple device under the nostrils to measure airflow. Each participant completed the task twice, once before and once after a nap or an eight-hour sleep in the lab.

This study documents an important link between respiration and the brain systems for responding to environmental events. We don't yet know exactly how they are linked, but we suspect neurophysiological efficiency, because other studies have shown that various brain oscillations are synchronized with the rhythms of one's breathing."

Ken Paller, the James Padilla Professor of Psychology, Northwestern University

Implications and next steps

Understanding sleep physiology in both the brain and the rest of the body, such as in linking respiration to brain oscillations, may yield new insights to help improve people's sleep and their next-day mental capacity.

Paller's lab is currently working on related research funded by the National Institutes of Health (NIH), and led by Yamazaki, focused on sleep apnea. The problem of harmful breathing pauses during sleep can be very detrimental for people's health and is often not adequately treated. It is also currently under-diagnosed.

The researchers hope that noninvasive strategies for improving sleep will counter some of the negative consequences of poor sleep, an approach that is sometimes called sleep engineering.