Page 149 - Demo

Interoception and Facial Emotion Perception1475of the preprocessed corrugator data (1%) and 149 trials of the preprocessed zygomaticus data (3%) were excluded from further processing. Data of each trial was baseline-corrected by subtraction, z-scored by participant and muscle region and averaged within the response window of each trial. Electrocardiography. We recorded the participants%u2019 electrocardiograms to provide (delayed) auditory feedback about heartbeats in the heartbeat discrimination task (see Procedure section). Three disposable 35mm AG/AgCl electrodes were attached to the participants%u2019 upper bodies. The negative electrode (Vin-) was placed under the right collarbone, the positive electrode (Vin+) on the left bottom rib, and the ground electrode below the right ribs. The data was recorded with a sampling rate of 1000Hz using a BIOPAC MP150 system (see Supplemental Materials for details on data recording and preprocessing). As irregularities in the ECG recordings might have resulted in imprecise heartbeat feedback, we visually inspected the recorded data and excluded trials with irregularities from calculating objective interoception measures. Cardiac interoceptive accuracy and interoceptive trait prediction error. We calculated cardiac interoceptive accuracy by dividing the number of trials that were correctly responded to in the heartbeat discrimination task by the total number of trials (excluding trials with irregularities). To rule out that differences in baseline heart rate could explain individual differences in cardiac interoceptive accuracy, we calculated a correlation (Spearman%u2019s rank) between the two measures, which was not significant (p = 0.69). The interoceptive trait prediction error was calculated according to Garfinkel et al. (2016): Both cardiac interoceptive accuracy scores and interoceptive sensibility scores were centered and scaled. Then, the difference between the two values was calculated for each participant as a measure of their individual interoception trait prediction error, with positive scores reflecting an overestimation and negative scores reflecting an underestimation of interoceptive abilities. Information about the distribution of both interoception measure scores can be found in Table 3. Interoceptive attention. We used the Interoceptive Attention Scale (IATS; Gabriele et al., 2022) to assess self-reported interoceptive attention regarding a variety of body sensations (e.g., heartbeat, hunger, need to urinate,..). Interoceptive attention for each of the 21 IATS-items are rated on a 5-point Likert scale (1 = disagree