Time-averaged T2*

Acquisition

• MRI data was acquired over 90 min on a 3 T Siemens Biograph mMR PET/MRI scanner.
  • T1 weighted magnetization-prepared rapid gradient-echo (MPRAGE) sequence
    • (TR, 2300 ms; echo time (TE), 2.98 ms; flip angle, 9°; inversion time (T1), 900 ms; voxel size, 1.0 × 1.0 × 1.0 mm)
• Functional images were acquired using blood oxygen level dependent (BOLD) signal from an echoplanar sequence
  • (TR, 1500 ms; TE, 30 ms; flip angle, 50°; voxel size, 2.3 ×2.3 mm in-plane resolution) with contiguous 2.3 mm – thick slices aligned to maximally cover the cortex and basal ganglia.

Processing

• Each volume was normalized to the whole-brain mean (z-score normalization
  • Coverage map created from all inputs for each participant
• The normalized signal was aggregated voxel-wise across all volumes using the median
• Resulted in one normalized T2* -weighted (nT2*w) image for each participant (nT2*w)
• High motion time points were identified as volumes containing frame-wise displacement (FD) > 0.3 mm were excluded
• nT2*w values were extracted separately across each basal ganglia region of interest (ROI) using the Harvard-Oxford subcortical atlas (Jenkinson et al., 2011)
  • Pallidum, nucleus accumbens (NAcc), putamen, and caudate nucleus

Inverse relation to Tissue Iron, proxy for Dopamine

• tat2 in LNCD Tools
• Contributions of dopamine-related basal ganglia neurophysiology to the developmental effects of incentives on inhibitory control