fMRI acquisition and analyses
A 3-T MRI scanner (Signa PET/MR, ver. 26, GE Healthcare, Milwaukee, WI) with a standard 8-channel head coil was used. Functional images were corrected with a T2*-weighted gradient-echo echo-planar imaging sequence to produce 40 whole-brain, continuous, transaxial slices (slice thickness, 3.5 mm with a 0.5-mm gap, repetition time [TR], 2500 ms; echo time [TE], 25 ms; flip angle [FA], 80°; field-of-view [FOV], 192 mm; 64 × 64 matrix; voxel dimension, 3.0 × 3.0 mm). A T1-weighted anatomical scan was also acquired using a fast spoiled-gradient recalled imaging sequence (TR, 8.46 ms; TE, 3.24 ms; FA, 11°; FOV, 256 mm; 256 × 256 matrix; 172 slices; voxel dimension, 1.0 × 1.0 × 1.0 mm).In image data processing, for MRI signal equilibrium, the first four volumes were discarded from the analysis. The remaining 240 images were pre-processed and analyzed using the Statistical Parametric Mapping software (SPM ver.12, Wellcome Trust Center for Neuroimaging, London, UK) implemented in MATLAB R2019b (MathWorks, Natick, USA). Following slice-timing correction and spatial realignment, T1-weighted anatomical images were co-registered to functional images and segmented using a new segmentation algorithm with the DARTEL technique (Ashburner, After pre-processing, we first performed individual analyses to identify task-related activity. In this analysis, a design matrix containing two regressors of interest (ToM and GeN conditions) was created. Each condition was modelled with a general linear model, by using a 30-s box-car function convolved with the canonical hemodynamic response function, high-pass filtered at 1/128 Hz to minimize low-frequency artefacts. Six motion parameters were also included as nuisance regressors. Then, two contrast images (ToM and GeN) were obtained for each participant.For group analyses, the two contrast images corresponding to the ToM and GeN conditions generated in the individual analysis were chosen. To investigate the effect of PT, between- and within-group differences (PT/non-PT vs. [Time 1/Time 2]) were analyzed using repeated-measures analysis of variance (ANOVA) within the framework of the SPM flexible factorial design.Due to the small sample size, the following analyses were conducted, based on previous studies (Baumeister et al., Subsequently, to identify the expected intervention effect in the PT group, we conducted a within-subject SPM one-way ANOVA for separate comparison of the activities within the PT and non-PT groups under both conditions. The statistical threshold was set at 