Regions of Interest Definition

The first five volumes of each run were discarded prior to any analyses. The following pre-processing steps were applied to all functional localizer data: non-brain removal using FSL’s brain extraction tool, motion correction using FSL’s MCFLIRT linear realignment tool, spatial smoothing using a 5 mm FWHM Gaussian kernel, high-pass temporal filtering with a 100 s cutoff, and un-distorting of the EPI data to correct for magnetic field distortions by means of individual field maps. EPI data were registered to each participant’s T1-weighted anatomical scan using BBR, and normalized to a standard Montreal Neurological institute (MNI-152) template.

After preprocessing the functional localizer runs for each fMRI time-series for each participant, the data were submitted to a fixed effects general linear model using FSL’s fMRI expert analysis tool (FEAT), with one predictor that was convolved with a double-gamma model of the hemodynamic response function (HRF) for each block type (face, places, fixation). Regions of interest (ROIs) were identified individuating the peaks showing greater activity for faces than for places (uncorrected, p < 0.05) in regions that have previously been implicated in face processing (for a review, see Collins and Olson, 2014). Spheres of 9 mm radius were generated, centered on the voxel with the highest activation within each peak. This ROI size (average = 106 voxels after intersection with the brain mask) was selected because it provided the best coverage of face-selective activations in the ATLs across individuals, and because it was consistent with previous MVPA studies that have demonstrated sensitivity to facial identity in the ATLs (Kriegeskorte et al., 2007; Goesaert and Op de Beeck, 2013; Anzellotti et al., 2014). Our face-selective ROIs included bilateral FFA located in the mid fusiform gyrus, the OFA, located in the inferior occipital gyrus, and the anterior temporal face area, located on the ventral surface of the ATLs. In some participants, multiple face-selective regions were identified in the ventral ATLs. For these participants the vATL functional ROI was centered on the most inferior peak, on the inferior temporal or fusiform gyrus, along the anterior collateral sulcus, consistent with previous work (Tsao et al., 2008; Rajimehr et al., 2009; Nestor et al., 2011; O’Neil et al., 2014). To control for effects driven by the low-level perceptual features of our stimuli, we additionally generated a 9-mm spherical ROI in EVC around the voxel showing the greatest activation for all visual stimuli (faces + places) vs. fixation within V1/BA17 as defined by the Juelich Histological Atlas in FSL. None of the face-selective ROIs overlapped in any participant at this sphere size, however the EVC and OFA ROIs overlapped partially in two participants. All ROIs were aligned to the individual subject’s (non-normalized) functional space using the FMRIB’s Linear Image Registration Tool. Given the wealth of data suggesting that the face-processing network is strongly lateralized to the right hemisphere (Sergent et al., 1992; Kanwisher et al., 1997; Rossion et al., 2003; Snowden et al., 2004; Gainotti, 2007, 2013, 2015; Gainotti and Marra, 2011; Duchaine and Yovel, 2015), we chose to restrict our analysis to face-processing ROIs (vATL, FFA, and OFA) in the right hemisphere, and bilateral EVC.