2.3.1. MRI

Structural MRI images were acquired with a 1.5 T GE EXCITE HG whole-body scanner (General Electric) with a high-resolution T1-weighted IR-FSPGR scan (TR = 8.5 s, TE = 3.75 ms, TI = 500 ms, flip angle = 10°, FOV = 240, 166 sagittal slices, 1.2 mm slice thickness, in-plane resolution 0.94 × 0.94 mm). Structural images were used to reconstruct each participant’s cortical surface (Dale et al., 1999; Fischl et al., 1999) which served to constrain inverse source estimates. The inner skull surface was used as a boundary element model of volume conductor in the forward calculations. For the purposes of intersubject averaging, the reconstructed surface was morphed onto an average brain representation (Fischl et al., 1999). The solution space was approximated by ~5000 free-rotating dipoles spaced ~7 mm apart.