3 tesla scanner

The fMRI session was conducted ten to twelve hours after each individual's wake up time that was determined by the MCTQ. Scanning was performed on a 3 Tesla scanner (Siemens, Erlangen, Germany) using standard gradients and a 12-channel phase array head coil. Participants lay in a supine position. Head movement was limited by foam padding within the head coil. To ensure optimal visual acuity, participants were offered MRI-compatible glasses if necessary.
The experimental runs comprised 223 whole-brain echo planar imaging (EPI) scans. These were preceded by three initial dummy scans allowing for signal saturation effects. Thirty-two slices (3 mm thickness, distance factor 40%) were positioned parallel to the AC/PC line. The following parameters were applied: matrix size 64 x 64; field-of-view (FOV), 200 mm x 200 mm; echo time (TE), 30 s; repetition time (TR), 1.94 s. For anatomical localization, a magnetization-prepared rapid gradient echo (MP-RAGE) sequence was acquired during the same imaging session (TR = 2250 ms; TE = 3.03 ms; ST = 1 mm; FOV = 256 x 256 mm; voxel size = 1.0 x 1.0 x 1.0 mm).

MRI data acquisition was performed on a 3-Tesla scanner (Siemens Medical Solutions, Erlangen, Germany). Foam padding and headphones were utilized to restrict head motion and reduce scanner noise. The 3D T1-weighted anatomical image was acquired with a magnetization-prepared rapid gradient echo (MPRAGE) method with the following parameters: repetition time (TR) / echo time (TE) / inversion time (TI) / flip angle (FA) = 1900 ms / 2.2 ms / 900 ms / 9°, acquisition matrix = 224 × 256 × 176, voxel size = 1 × 1 × 1 mm³.

MRI images were obtained on a Siemens 3 Tesla scanner. T1-weighted images were acquired for each participant using the following acquisition sequence parameters: 192 slices, 0.9 mm slice thickness, 0.8 mm x 0.8 mm in-plane resolution, TE = 2.59 ms, TR = 1900 ms, flip angle = 9°.

MRI data acquisition was performed on a 3-Tesla scanner (Siemens Medical Solutions, Erlangen, Germany). MRI data were collected the day after the subjects finished the cognitive testing. Sedation was forbidden during the MRI scanning. Foam padding and headphones were used to limit head motion and reduce scanner noise. The 3D T1-weighted anatomical image was acquired with a magnetization-prepared rapid gradient echo (MPRAGE) method in the following parameters: repetition time (TR)/echo time (TE)/inversion time (TI) / flip angle (FA) = 1900 ms/2.2 ms/900 ms/9°, acquisition matrix = 224 × 256 × 176, voxel size = 1 × 1 × 1 mm³. DTI parameters were: 12 non-linear directions (b-value = 1000 s/mm²) with 1 non-diffusion weighting acquisition, TR/TE = 6000 ms /85 ms, 30 axial slices, slice thickness = 5 mm, FOV = 256 × 256 mm², acquisition matrix = 128×128, number of averages = 4.

MRI brain scanning was performed on a 3-Tesla scanner (Siemens Medical, Erlangen, Germany). The head was immobilized in a standard head coil with foam pads. The following whole brain MRI datasets were acquired on each subject: 1) standard high-resolution sagittal images acquired with volumetric T1-weighted 3D-MEMPRAGE (TR = 2530ms, TE = 1.74ms/3.6ms/5.46ms/7.32ms, flip angle = 7º, FOV = 256×256mm, matrix = 256×256, slice thickness = 1mm); 2) BOLD-fMRI images acquired with gradient-echo echo planar imaging (EPI) sequence (TR = 1450ms, TE = 30ms, flip angle = 90º, FOV = 220×220mm, matrix = 64×64, thickness = 5mm, slice gap = 1mm) while the subject was at rest. The visual presentation of the crosshair, the physiological set-up for the sampling of PCO₂ and PO₂ in the MRI session were the same as those used in the TCD session. The gas analyzers were again calibrated to the barometric pressure on the day of MRI session and corrected for vapor pressure. ECG was measured using a Siemens physiological monitoring unit (Siemens Medical, Erlangen, Germany). Physiological changes including PCO₂, PO₂, ECG and respiration were measured simultaneously with MRI acquisition. All the physiological measurements, including those of PCO₂, PO₂ and ECG were synchronized using trigger signals from the MRI scanner. BOLD-fMRI images and physiological recordings were stored for offline data analysis.