The time-course of cortico-limbic neural responses to air hunger

• This is the first report of the time-course of dyspnea related neural activity.
• Sub-regions of neural circuitry relate to early and late dyspnea components.
• The length of dyspnea stimulus used is more pertinent to clinical dyspnea.
• Our findings may explain discrepancies in previous dyspnea brain mapping studies.

Several studies have mapped brain regions associated with acute dyspnea perception. However, the time-course of brain activity during sustained dyspnea is unknown. Our objective was to determine the time-course of neural activity when dyspnea is sustained. Eight healthy subjects underwent brain blood oxygen level dependent functional magnetic imaging (BOLD-fMRI) during mechanical ventilation with constant mild hypercapnia (∼45 mmHg). Subjects rated dyspnea (air hunger) via visual analog scale (VAS). Tidal volume (VT) was alternated every 90 s between high VT (0.96 ± 0.23 L) that provided respiratory comfort (12 ± 6% full scale) and low VT (0.48 ± 0.08 L) which evoked air hunger (56 ± 11% full scale). BOLD signal was extracted from a priori brain regions and combined with VAS data to determine air hunger related neural time-c