Study finds role of mid-brain in integrating heart and respiratory response to exercise

WASHINGTON -- For almost one hundred years the brain’s “central command” system – whose charge includes controlling the body’s cardiorespiratory response to exercise – has been pursued. Animal experiments and functional imaging studies have provided clues to the location of this system, but the underlying electrophysiological activity has never been measured. Oxford University researchers recently examined several deep brain nuclei during exercise and have concluded that the periaqueductal grey area (PAG), the small-celled gray matter adjoining or surrounding the cerebral aqueduct and the third ventricle in the midbrain, contains the greatest number of neural changes in connection with anticipation of exercise. The findings provide direct evidence implicating the PAG as a key area of the brain’s circuitry’s affecting cardiorespiratory response to exercise.

The study, Identifying Cardiorespiratory Neurocircuitry Involved in Central Command During Exercise in Humans, was conducted by Alexander L. Green, Shouyan Wang, Sarah Purvis, Sarah L. F. Owen, John F. Stein, Abe Guz, Tipu Z. Aziz, and David Paterson, all affiliated with the Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford; and Peter G. Bain, with the Division of Neurosciences and Mental Health, Imperial College London, Charing Cross Campus, London, all in the United Kingdom. Dr. Paterson will discuss the team’s findings in detail during the 120th annual meeting of the American Physiological Society (APS; www.the-APS.org), part of the Experimental Biology (EB ’07) conference. More than 12,000 scientific investigators are attending the conference, being held April 28-May 2, 2007 at the Washington, DC Convention Center.

The Study: Methodology

The researchers set out to test the hypothesis that neural activity in subcortical structures recorded from humans who have deep brain stimulating electrodes chronically implanted is directly related to changes in heart rate (HR), arterial blood pressure (ABP) and pulmonary ventilation (VE) when they are altered by anticipation of exercise and actual exercise. They sought to establish whether the subcortical structures provide neural circuitry that is involved in the anticipatory cardiorespiratory response to exercise in humans.