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Evidence for limbic system activation during CO2‐stimulated breathing in man.
Author(s) -
Corfield D R,
Fink G R,
Ramsay S C,
Murphy K,
Harty H R,
Watson J D,
Adams L,
Frackowiak R S,
Guz A
Publication year - 1995
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1995.sp020947
Subject(s) - brainstem , thalamus , hypercapnia , cerebral blood flow , medicine , ventilation (architecture) , cortex (anatomy) , neuroscience , gyrus , insular cortex , midbrain , cerebral cortex , anesthesia , anatomy , respiratory system , central nervous system , psychology , mechanical engineering , engineering
1. The role of supra‐brainstem structures in the ventilatory response to inhaled CO2 is unknown. The present study uses positron emission tomography (PET), with infusion of H2(15)O, to measure changes in relative regional cerebral blood flow (rCBF) in order to identify sites of increased neuronal activation during CO2‐stimulated breathing (CO2‐SB) in awake man. 2. Five male volunteers were scanned during CO2‐SB (mean +/‐ S.E.M.; end‐tidal PCO2, 50.3 +/‐ 1.7 mmHg; respiratory frequency, 16.4 +/‐ 2.7 min‐1; tidal volume, 1.8 +/‐ 0.2 l). As control, scans were performed during ‘passive’ isocapnic (elevated fraction of inspired CO2) positive pressure ventilation (end‐tidal PCO2, 38.4 +/‐ 1.0 mmHg; respiratory frequency, 15.5 +/‐ 2.2 min‐1; tidal volume, 1.6 +/‐ 0.2 l). With CO2‐SB, all subjects reported dyspnoea. 3. The anatomical locations of the increases in relative rCBF (CO2‐SB versus control) were obtained using magnetic resonance imaging. 4. Group analysis identified neuronal activation within the upper brainstem, midbrain and hypothalamus, thalamus, hippocampus and parahippocampus, fusiform gyrus, cingulate area, insula, frontal cortex, temporo‐occipital cortex and parietal cortex. No neuronal activation was seen within the primary motor cortex (at sites previously shown to be associated with volitional breathing). 5. These results suggest neuronal activation within the limbic system; this activation may be important in the sensory and/or motor respiratory responses to hypercapnia in awake man.