Functional subdivision of the human periaqueductal grey in respiratory control using 7Â tesla fMRI

- 7 T MRI was used to image the brainstem during respiratory and motor tasks.
- Breath holds caused deactivation in the lateral and dorsomedial PAG.
- RETROICOR and hypercapnic noise correction techniques were employed.
- We demonstrate the potential of 7 T fMRI to investigate human brainstem respiratory control.

The periaqueductal grey (PAG) is a nucleus within the midbrain, and evidence from animal models has identified its role in many homeostatic systems including respiration. Animal models have also demonstrated a columnar structure that subdivides the PAG into four columns on each side, and these subdivisions have different functions with regard to respiration. In this study we used ultra-high field functional MRI (7 T) to image the brainstem and superior cortical areas at high resolution (1 mm3 voxels), aiming to identify activation within the columns of the PAG associated with respiratory control. Our results showed deactivation in the lateral and dorsomedial columns of the PAG corresponding with short (~ 10 s) breath holds, along with cortical activations consistent with previous respiratory imaging studies. These results demonstrate the involvement of the lateral and dorsomedial PAG in the network of conscious respiratory control for the first time in humans. This study also reveals the opportunities of 7 T functional MRI for non-invasively investigating human brainstem nuclei at high-resolutions.