MRI data were acquired on a 3‐tesla Skyra VD13 (Siemens Healthcare, Erlangen, Germany). During the BOLD MRI sequence, the CO2 stimulus was modulated by a computer‐controlled gas blender with prospective gas targeting algorithms (RespirAct, Thornhill Research Institute, Toronto, Canada).
18 (link) Details about BOLD MRI acquisition and data processing can be found in DataS1 .
The CVR calculation
19 (link) included voxel‐wise temporal shifting for optimal physiological correlation of the BOLD signal and CO2 time series. CVR, defined as the percentage BOLD signal change/mm Hg CO2, was then calculated from the slope of a linear least square fit of the BOLD signal time course to the CO2 time series over the range of the first baseline of 100 seconds, the step portion of the protocol (80 seconds) and the second baseline of 100 seconds on a voxel‐by‐voxel basis.
19 (link),
20 (link)
18 (link) Details about BOLD MRI acquisition and data processing can be found in Data
The CVR calculation
19 (link) included voxel‐wise temporal shifting for optimal physiological correlation of the BOLD signal and CO2 time series. CVR, defined as the percentage BOLD signal change/mm Hg CO2, was then calculated from the slope of a linear least square fit of the BOLD signal time course to the CO2 time series over the range of the first baseline of 100 seconds, the step portion of the protocol (80 seconds) and the second baseline of 100 seconds on a voxel‐by‐voxel basis.
19 (link),
20 (link)
