fMRI experiments

MRI data were acquired on a Siemens Verio 3T magnet at the Scientific Imaging and Brain Research Center at Carnegie Mellon University, using a 32-channel phased array head coil. Four controls with no prior MRI experience completed a practice session in a mock scanner, acclimating to the experimental conditions and minimizing head motion. All patients had been scanned previously at the UPMC Children's Hospital of Pittsburgh. Participants practiced the experimental tasks outside the scanner.

The visual presentations were generated using MATLAB (MathWorks) and Psychtoolbox (http://www.psychtoolbox.org). Images were back-projected onto a screen in the bore of the scanner (visual angle = 16°). A trigger pulse from the scanner synchronized the onset of the stimulus presentation to the beginning of the image acquisition. During the category localizer tasks, a central fixation dot remained on the screen to orient participants' fixation. Participants were instructed to maintain fixation and eye movement data were collected using an ASL eye tracker (Applied Science Laboratories). Analysis of eye positions confirmed that all patients maintained fixation within the 1.5° of visual angle from the center of the screen during the task [excluding blinks, gaze deviation from the center: 1.02°±.31° (horizontally), 1.24°±.36° (vertically)].

Participants completed three runs of an fMRI category localizer task (Nestor et al., 2016; except patient N.N. and his control who completed 2 runs). The functional runs adopted a block design with stimuli from five categories (Fig. 4A): faces, houses, objects, scrambled objects, and words. Each run consisted of three repeats of each category (8 TRs, 16 images) in pseudorandom order with a fixation baseline (4 TRs) between all conditions. Thus, each run contained 15 categories and 16 fixation baselines and lasted 6 min 8 s (184 TRs). Participants indicated detection of an immediately repeating image (one-back task) via an MR compatible button glove using the right index finger. This response instruction was designed to engage participants maximally while keeping the task relatively easy for the children (overall accuracy: 95.2 ± 3.6%, no patient/control group difference: F_(1,18) = 1.21, p = 0.286, one-way ANOVA).

Category-selectivity and EVC activation in the patients. A, Stimuli used in the fMRI category localizer experiment. B, A visualization of category-selective and EVC ROIs in each of the six VOTC patients. Pink arrows point to the site of the resection. Each colored sphere indicates one identifiable category-selective or EVC ROI (see color legend on the bottom left). The z values at the bottom left corner on each axial slice denotes the position of that slice in the z- (inferior–superior) axis in native space. All ROIs were defined in native space. C, Statistical maps of category-selective activation (p < 0.005) in each patient obtained from two representative contrasts: face–house, and word–face contrast.

A high-resolution (1 mm³ isotropic voxels, 176 slices, acquisition matrix = 256 × 256, TR = 2300 ms, TE = 1.97 ms, inversion time = 900 ms, flip angle = 9°, acceleration/GRAPPA = 2, scan time = 5 min 21 s) T1-weighted whole-brain image was acquired for each participant using a magnetization prepared rapid gradient echo imaging sequence for localization, coregistration, and surface reconstruction purposes.

In six patients and matched controls, fMRI data were collected with a BOLD contrast-sensitive echoplanar imaging sequence (TR = 2000 ms, TE = 30 ms, voxel size = 2.5 mm³, interslice time = 79 ms, flip angle = 79°, acceleration/GRAPPA = 2, 27 slices). In the other four patients and matched controls, fMRI data with whole-brain coverage (69 slices) were collected with a multiband acceleration factor of 3 and voxel size = 2 mm³ (all else equal to standard protocol). For all participants, slice prescriptions were AC–PC aligned.