Functional MRI localisation of central nervous system regions associated with volitional inspiration in humans

1. Functional magnetic resonance imaging (fMRI) provides a means of studyin g neuronal circuits that control respiratory muscles in humans with better spatial and temporal resolution than in previous positron emission tomograp hy (PET) studies. 2. Whole brain blood oxygenation level-dependent (BOLD) changes determined by fMRI were used to identify areas of neuronal activation associated with volitional inspiration in five healthy men. Four series of scans of each su bject were acquired during voluntary breathing (active task) and mechanical ventilation (passive task). Ventilation and end-tidal P-CO2 were similar b etween tasks. Scan data were re-aligned to correct for movement artefacts a nd cross-referenced breath by breath to respiratory data for selective aver aging of inspiratory and expiratory images. 3. Group analysis identified significant increases in the fMRI signal with volitional inspiration in the superior motor cortex, premotor cortex and su pplementary motor area at loci similar to those detected in earlier studies that used PET. Additional regions activated by volitional inspiration incl uded inferolateral sensorimotor cortex, prefrontal cortex and striatum (the se foci were only revealed by PET under significant inspiratory load). 4. This study represents the first synchronised breath-by-breath analysis o f respiratory-related neuronal activity with whole brain imaging in humans. Temporal resolution is sufficient to distinguish individual breaths at a n ormal breathing frequency.