2.2. Data acquisition

MRI data collection took place at CCHMC. All subjects were imaged during natural sleep on a 3T Philips Ingenia scanner with a 32‐channel head coil between 39‐ and 44‐weeks postmenstrual age (PMA). Infants were fed 30 min prior to imaging, fitted with silicone earplugs to dampen scanner noise (Instaputty, E.A.R. Inc, Boulder, CO), and swaddled in a blanket and vacuum immobilization device (MedVac, CFI Medical Solutions, Fenton, MI). A 68 direction dMRI acquisition was performed in the axial plane with full brain coverage. Of the 68 directions, 61 had b‐values of 2,000 s/mm² and 7 had b‐values of 0 s/mm², with the b0s uniformly distributed throughout the acquisition (to allow for subsequent intrascan motion correction). The dMRI was acquired posterior to anterior. An additional six b0 images were acquired with anterior to posterior phase encoding in a separate acquisition. Parameters common to both acquisitions were: 88 ms echo time; 5,073 ms repetition time, flip angle 90°, field of view 160x160 mm², 80 × 78 matrix, 2.0 mm slice thickness; 6:27 min scan time; multiband factor = 2; and SENSE factor = 2.