Participants were told that they would participate in a study investigating ‘cognitive load’, all study information was given during debriefing. The TSST was used as stress intervention in the afternoon (3:15–7:00 PM) to minimize variance in diurnal cortisol secretion, and was performed as previously published (Kirschbaum et al., 1993). This specific intervention was chosen for its robust induction of a stress response (Narvaez Linares et al., 2020). Participants were randomly assigned to the stress condition or the control (no-stress) condition. The stress condition consisted of a five-minute job interview and a three-minute mental arithmetic task while facing a committee, the no-stress condition featured five minutes of free speech and a simple three-minute arithmetic task with the researcher in the same room but without a committee (Het et al., 2009). Three resting state functional scans were obtained, i.e. before (RS1), and 20 (RS2) and 90 min (RS3) after TSST onset. In between RS2 and RS3, an emotion processing and a reward task were performed inside the scanner, which was consistent across participants (van Leeuwen et al., 2018a, van Leeuwen et al., 2019b, van Leeuwen et al., 2019c). The cortisol response to the TSST was evaluated using the area under the curve related to cortisol-increase (cortisol-AUCi), meaning the area under the curve minus the area between zero and the first measurement, as previously described (van Leeuwen et al., 2018a, Pruessner et al., 2003). Additionally, the cortisol-AUCi was calculated based on the first four samples (from 10 before to 30 min after TSST onset) to reflect the acute cortisol increase. The area over the curve related to cortisol decrease was quantified using the last four samples (from 30 to 120 min after TSST onset) to reflect recovery-related cortisol depletion. Finally, a visual analog scale (VAS) was completed 10 min before, and 5 (i.e. during the TSST) and 20 min after TSST onset to assess subjective stress, and the area under the curve related to subjective stress increase (subjective-AUCi) was calculated similarly to cortisol. The difference score between consecutive measurements on the VAS characterized the acute subjective stress response and subjective stress recovery, respectively.

All imaging was performed on Philips 3 Tesla MRI scanners (Philips Medical Systems). Whole-brain 3-dimensional T1-weighted (3D-T1) structural images were acquired using an identical sequence for both studies; repetition time (TR)/echo time (TE) = 10/4.6 ms, voxel size = 0.75 × 0.75 × 0.8 mm, flip angle = 8°. Resting-state functional magnetic resonance imaging (fMRI) was performed using 2-dimensional echo planar imaging-sensitivity encoding (EPI-SENSE) sequences: study 1 (TR/TE = 2000/35 ms, voxel size = 2.7 × 2.7 × 3.4 mm, flip angle = 72.5°, gap = 0.43 mm, Nvolumes = 202, scan time = 7 min) and study 2 (TR/TE = 1600/23 ms, voxel size = 4 mm isotropic, flip angle = 70°, gap = 0.40 mm, Nvolumes = 300, scan time = 8:13 min).

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