Optimized fMRI Acquisition for Ventral Prefrontal Cortex

fMRI image acquisition has been described in detail previously [1 (link)]. Briefly, gradient-echo T2*-weighted images were acquired using a Siemens Avanto 1.5 Tesla MRI scanner employing a 32-channel head coil (this head coil improves signal-to-noise ratio up to 3.5 times compared to standard 8- or 12-channel coils [26 (link)]). We collected 36 slices per volume, slice gap 1 mm (2 mm slices; 50% distance factor) (see Table 1). The echo planar imaging (EPI) sequence was highly optimised to minimise ventral prefrontal cortex dropout (for extensive sequence details, see previous work [1 (link),25 (link),27 (link)]): echo time = 50 ms, repetition time/slice = 87 ms, slice thickness = 2 mm, in-plane resolution = 2 × 2 mm. One fieldmap per participant per day was acquired using identical parameters to the EPI scans; for each participant, we also acquired one magnetization-prepared rapid gradient-echo T1-weighted 1 mm isotropic anatomical scan.
We used Statistical Parametric Mapping (SPM12; Wellcome Trust Centre for Neuroimaging, London, UK, www.fil.ion.uck.ac.uk/spm) in Matlab R2015a (for the initial region-of-interest (ROI)-based analyses) and Matlab R2018a (for the PPI analyses). All data were slice-time corrected to account for the long repetition time (TR) (3.132 seconds). Preprocessing was identical to that described previously [1 (link)].