Allegra head scanner

Magnetic resonance imaging scanning was performed with a 3-Tesla Allegra head scanner (Siemens, Erlangen, Germany) and a one-channel head coil. Functional whole-brain images were acquired interleaved with a T2^∗-weighted gradient echo planar imaging (EPI) sequence (time-to-repeat, TR = 2 s; time-to-echo, TE = 30 ms; flip angle, FA = 90°) consisting of 34 transverse slices (voxel-size = 3 mm × 3 mm × 3 mm; field of view, FOV = 192 mm × 192 mm). In addition, we collected a high-resolution structural scan (160 sagittal slices each) with a T1-weighted, magnetization prepared rapid gradient echo (MP-RAGE) sequence (TR = 2.25 s, TE = 2.6 ms, FA = 9°, voxel size = 1 mm × 1 mm × 1 mm, FOV = 240 mm × 256 mm). The sequence was optimized for the differentiation of gray and white matter by using parameters from the Alzheimer’s disease Neuroimaging Initiative project².

A 3-Tesla Siemens Allegra Head Scanner (Siemens Inc., Erlangen, Germany) located at the University Medical Center Regensburg was used to record the imaging data. The scanner acquired echo-planar-imaging (EPI) sequences using fast gradients. During T2^* data acquisition, we recorded 32 axial slice in interleaved order with a Time-to-Repeat (TR) of 2.0 s, a Time-to-Echo (TE) of 0.95 s, a flip angle of 90°, a Field of View (FoV) of 192 x 192 mm and a voxel size of 3 × 3 × 3 mm. A total of 767 functional images were recorded in the entire experiment.
A structural image was recorded from every subject at the end of functional data acquisition. These T1-weighted images were obtained using a MPRAGE (Magnetization Prepared Rapid Acquisition Gradient Echo) pulse sequence (TR = 2.25 s, TE = 0.026 s, TI = 0.9 s, FoV = 256 mm), scanning 160 slices with voxel size of 1 × 1 × 1 mm³.
The entire scan session lasted approximately 35 min.

All MRI experiments were performed on a 3-Tesla Allegra head scanner (Siemens, Erlangen, Germany). Conventional anatomical MRI was first performed covering the whole brain using a 3D MPRAGE pulse sequence with the following parameters: repetition time (TR) = 1.4 s, echo time (TE) = 2.5 ms, inversion time (TI) = 800 ms, flip angle = 8°, field of view = 25.6 × 25.6 × 17.6 cm³, 256 × 256 imaging matrix in-plane, and 176 contagious sagittal slices. Blood-oxygen-level-dependent (BOLD) images were then collected for tf-fMRI using a single-shot echo-planar-imaging (EPI) pulse sequence with the following parameters: TR = 2 s, TE = 26 ms, field-of-view = 20.5 × 20.5 cm², 104 × 104 imaging matrix, and 28 contiguous 3 mm thick axial slices. The total duration of tf-fMRI was 8 min with eyes closed at rest. Diffusion tensor MRI was acquired covering the whole brain using spin-echo diffusion-weighted EPI sequences with the following parameters: 12 diffusion gradient directions at diffusion weighting factor (b) = 850 s/mm² and one b = 0 s/mm² (b₀), TR = 5.2 s, TE = 80 ms, field-of-view = 20.5 × 20.5 cm², 104 × 104 imaging matrix, and 38 axial slices at 3 mm thickness. We used landmarks based on anatomical MRI and the human brain atlas to ensure consistent localization of tf-fMRI and diffusion tensor MRI measurements across subjects.