MRI acquisition
All infants were scanned after receiving breast or formula feeding during natural sleep (no sedation used). At 33 weeks GA (time-point 1), preterm infants were scanned using a MR compatible incubator (Lammers Medical Technology, Lübeck, Germany) and monitored using a Philips MR patient monitor Expression MR400 and Philips quadtrode MRI compatible neonatal ECG electrodes. At term-equivalent age (time-point 2), infants were scanned using a vacuum mattress for immobilization. All infants, at both time points, were monitored for heart rate and oxygen saturation during the entire scanning time. MR-compatible headphones (MR confon, Magdeburg, Germany) were used to protect the infants from scanner noise.MRI acquisition at both time-points was performed on a 3.0 T Siemens MR scanner Siemens Magnetom (Siemens, Erlangen, Germany), using a 16-channel neonatal head coil. T2-weighted images were acquired using the following parameters: 113 coronal slices, TR= 4990 ms, TE= 160 ms, flip angle= 150°, matrix size= 256 × 164; voxel size= 0.8 × 0.8 × 1.2 mm