Heart Rate Breathing

Neural Control of Cardiorespiratory Responses to Environmental Change in Vertebrates

The goal of our research program is to determine why (and how) animals breathe the way they do under different conditions (at rest, sleep, exercise, altitude, dormancy, hibernation, diving, etc.).

Breathing is essential for gas exchange in almost all vertebrates but the mechanisms that produce the respiratory rhythm, and the manner in which the basic rhythm is modified to meet changing demands is not fully understood.

Work from our laboratory, and those of others, suggests that certain areas within the brain of all vertebrates (from fish to man) produce a respiratory rhythm but that this rhythm is not always expressed. The natural rhythm is modified by information from different sensory systems and from other areas in the brain, and this interaction determines if, when and how breathing occurs. This leads to the hypothesis that the wide variety of breathing patterns observed in vertebrate animals results from differences in the net balance of different inputs to a common system.

The many breathing patterns seen in vertebrates, including those which contain prolonged periods during which breathing ceases (apneas etc.), not only provide a challenge to this hypothesis, but also suggest that a mechanism that can explain the episodes where breathing stops in turtles and hibernating squirrels may also explain sleep apnea and SIDS in man.

Given this, one group of our studies examines the central pattern generators for ventilation in isolation (using brainstem-spinal cord and brain slice preparations). A second group of studies examines the sensory information that comes from the lungs and gills, and from the heart and blood vessels of different animals. A third group of studies examines the interaction of this sensory feedback with the central rhythm generator and such descending inputs as those associated with locomotion, changes in arousal state (such as sleep, dormancy and hibernation) and body temperature. A fourth group of studies tests the hypothesis that all breathing patterns are adaptive and optimally designed to reduce the work of breathing and increase gas exchange efficiency.

Using species differences (phylogeny), developmental changes (ontogeny) and genetic manipulations as tools, we ultimately hope to help determine the neural basis of respiratory pattern formation and the manner in which this has been shaped by evolution to meet the demands of animals living in different environments.