232 For all behavioral analyses the threshold for significance was set at p < 0.05 and partial eta-squared (ηp 2) was computed as a measure of effect size, with ηp 2 of 0.01 considered small, 0.06 considered medium, and 0.14 considered a large effect size 52,53. To conduct analysis of variance (ANOVA) and correlations, potential outliers and the assumptions of normality and homogeneity were checked. Pharmacological manipulation To test the first hypothesis, that DCS would lead to larger nocebo responses than a placebo, we examined whether nocebo hyperalgesia differed between the DCS and Control groups. A 2x2 mixed model ANOVA was performed, with group as the between-subjects factor and trial type as within-subjects factor (first extinction nocebo trial, first extinction control trial). We also examined the reduction of nocebo magnitudes after extinction. To compare extinction between the pharmacological groups, a 2x2 mixed model ANOVA was performed with group as the between-subjects factor and time of measurement (pre to post) as within-subjects factor with two levels (nocebo-control trial difference before extinction, nocebo-control trial difference after extinction). fMRI analyses In preprocessing the data anatomical scans were skull stripped with the Brain Extraction Toolbox (BET; 54. Subsequent preprocessing was conducted in SPM12 (Wellcome Department of Cognitive Neurology, London; www.fil.ion.ucl.ac.uk/spm) running on MATLAB 2021A (MathWorks, Natick MA, USA; https://www.mathworks.com/products/matlab.htm. Functional scans
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