Masked datasets from an fMRI experiment on the impact of semantic priming on the perception of ambivalent (male versus female) faces

Twenty-four female native Dutch speakers participated in the fMRI experiment and gained monetary compensation for their participation. Only female participants were recruited for the study, in order to avoid gender-related confounding factors. The study was approved by the local ethics committee (CMO Arnhem-Nijmegen, Radboud University Medical Center, ethical approval for studies on healthy human subjects at the Donders Centre for Cognitive Neuroimaging, no ECG 2012-0910-058) and conducted in accordance with their guidelines. All participants signed informed consent forms before the experiment. The data from seven subjects were excluded from the analysis: 3 subjects failed to finish the task and 4 subjects exhibited head motion that exceeded the maximum acceptance rate of 2 [mm]. The remaining 17 subjects (females, age 18-29 years) reported no neurological diseases, and had normal or corrected-to-normal vision. 

A set of realistic 3D faces was morphed across gender (from extremely female to extremely male) using FaceGen Modeller 3.5 (Singular Inversions, www.facegen.com). The morphing procedure started from 40 distinct faces. For each face, we gradually modulated gender features in 5 steps with the same amount of feature transformation in each step. The face stimuli were presented frontally and cropped around the oval of the face. We controlled for luminance using SHINE toolbox for MATLAB. The perceptual boundary within gender continuum of faces was established in a separate behavioral experiment.

Each trial started with priming: presentation of a gender-related word 'man' or 'vrouw' for 0.2 [s]. Then, after the fixation cross 0.25 [s]), a face was presented (0.5 [s]), followed by an inter-trial period of a randomized length of 5-7 [s]. Participants were asked to perform a matching task: respond 'yes' if a word and subsequent picture corresponded in gender, and 'no' otherwise. The experiment was carried out in Dutch. The buttons were counterbalanced across subjects. The experiment was divided into 6 blocks in order to avoid fatigue. Each block consisted of 50 trials. The order of stimuli was randomized across blocks and participants. We used Presentation software (version 17.1, www.neurobs.com) in order to screen the stimuli during the experiment.

Functional images were acquired using 3T Skyra MRI system (Siemens Magnetom), T2* weighted echo-planar images (gradient-echo, repetition-time TR = 1760 [ms], echo-time TE = 32 [ms],  0.7 [ms] echo spacing, 1626 hz/Px bandwidth, generalized auto-calibrating partially parallel acquisition (GRAPPA), acceleration factor 3, 32 channel brain receiver coil). In total, 78 axial slices were acquired (2.0 [mm] thickness, 2.0*2.0 [mm] in plane resolution,  212 [mm] field of view (FOV) whole brain, anterior-to-posterior phase-encoding direction).

The data reprocessing was performed using SPM12 (Welcome Trust Center for Neuroimaging, University College London, UK). Functional scans were realigned to the first scan of the first run with further realignment to the mean scan. We performed slice-time correction on realigned images to account for differences in image acquisition between slices. Motion-related components were removed from the data using a data-driven ICA-AROMA. Denoised functional scans were spatially normalized to the Montreal Neurological Institute (MNI) space without changing the voxel size. Normalized data were smoothed spatially with a Gaussian kernel of 6 [mm] full-width at half-maximum.

We extracted region-of-interest (ROI) mask using Anatomical Automatic Labeling atlas (AAL). According to our a priori hypothesis, we preselected the bilateral SPL (4288 voxels) and the bilateral IPL (3792 voxels).