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. 2020 Oct 2;11:507199. doi: 10.3389/fpsyg.2020.507199

FIGURE 1.

FIGURE 1

fMRI paradigm. Subjects viewed either gray-scale faces with neutral, sad or fearful faces in the activation condition and houses in the control condition in a blocked design. Face stimuli were selected from the Karolinska Directed Emotional Faces (KDEF) dataset (http://www.emotionlab.se/resources/kdef; permission for publication of KDEF stimuli was kindly provided by the Karolinska Institutet, Department of Neuroscience, Section of Psychology, Stockholm, Sweden; Lundqvist et al., 1998). House stimuli were selected from the internet. To ensure equalized size of face and house images, stimuli were resized to 500 × 400 pixel using ImageMagick for Linux. For purpose of color and luminance matching, stimuli were transferred into gray-scale images and adjusted for mean luminance using the SHINE toolbox for MATLAB (Willenbockel et al., 2010). The paradigm consisted of two sessions, including 16 blocks each (4 blocks with neutral, sad and fearful faces, respectively; 4 house blocks). The sessions were divided by a short break of 20 s. Each block included 11 stimuli that were presented for 900 ms with an inter-stimulus interval of 425 ms. Blocks lasted ∼14 s each and were separated with blank periods (duration: 5.6 s) in which only a centered fixation cross was shown. The order of blocks remained the same across all subjects, whereas the order of images in each block was pseudo-randomized. To ensure attention, subjects were asked to indicate via button press with the right index finger when a stimulus was shown twice consecutively. Within one block, either two or three stimulus-pairs arose, which sum up to 40 target events in the whole fMRI paradigm. The total duration of the fMRI paradigm was ∼11 min. The fMRI paradigm used in the present study was a slightly modified version of the standard paradigm used in our group (e.g., Frässle et al., 2016b) to adapt for the assessment of children. First, to minimize the total scanning time, the number of blocks was reduced from 44 to 32. Second, the stimulus presentation time was tripled to 900 ms. Third, the number of stimuli per block was reduced from 20 to 11. Fourth, the number of different face identities was reduced from 30 to 20 (10 female and 10 male identities). The number of different houses was also reduced from 30 to 20, to match it with the number of face stimuli.