Brainsight tms mri co registration system

TMS target sites were identified on an individual participant basis using the Brainsight TMS-MRI co-registration system (Rogue Research). In each participant, the results of the statistical contrast of Scenes > Faces were overlaid onto a high-resolution anatomical scan. The rOPA target site was defined as the peak voxel of scene selectivity within the rOPA, with the rOFA target site representing the peak voxel of face selectivity within the rOFA. We chose OFA as the active control site since OPA and OFA both contain retinotopic representations of the contralateral lower visual field but differ in their category selectivity (scene-selective vs. face-selective). Prior TMS studies of OPA have also used OFA as an active control site (e.g., Dilks et al., 2013 (link)).

A MagStim Super Rapid stimulator (The MagStim Company, Whitland, UK) was used to deliver stimulation with a figure of eight coil (70 mm). Resting motor threshold (RMT) was defined as a minimal intensity of stimulation inducing twitches in the contralateral first dorsal interosseous muscle of the right hand in at least 5 of 10 stimulations at rest. The average RMT intensity was 60.7% ± 7.2 in the experiment.
The target site [MNI: Montreal Neurological Institute, −57 −15 −35] was selected from previous fMRI and TMS studies (Jung and Lambon Ralph, 2016 (link); Visser et al., 2012 (link)). The coordinate was located on the ventrolateral ATL (Fig. 1C) and transformed to each participant's native space. Statistical Parametric Mapping software (SPM8, Wellcome Trust Centre for Neuroimaging, London, UK) was used to normalize participants’ MRI scan against the MNI template and to convert the target coordinate to the untransformed individual native space coordinate using the inverse of each resulting transformation. These native space coordinates guided the frameless stereotaxy, via a Brainsight TMS-MRI co-registration system (Rogue Research, Montreal, Canada).

cTBS (600 pulses at 50 Hz for 40 s) was delivered over the stimulation sites using a Magstim SuperRapid 2 with a figure-of-eight coil (70 mm standard coil, MagStim Company, Whitland, UK) according to Huang et al. (Huang et al., 2005 (link)). cTBS was applied during the ATL and Oz at 80% of the resting motor threshold (RMT). The mean of stimulation intensity was 49.1% ranging from 36% to 61%.
All subjects were scanned to obtain a high-resolution T1-weighted anatomical image (in-plane resolution of 1 mm and a slice thickness of 1.8 mm with an acquisition matrix 256 × 256 voxels) using a 3T Philips MR Achieva scanner prior to the experiment.
The target ATL site was based on a previous distortion-corrected fMRI study (Visser et al., 2012 (link)) [MNI: −57, −15, −34]. The ATL coordinate was transformed into each subject's native space by normalizing each subject's MRI scan against the MNI template using Statistical Parametric Mapping software (SPM8, Wellcome Trust Centre for Neuroimaging, London, UK). Then, the inverse of each resulting transformation was used to convert the target MNI coordinate to the untransformed individual naïve space coordinate. These ATL coordinates were used to guide the frameless stereotaxy, Brainsight TMS-MRI co-registration system (Rogue Research, Montreal, Canada). The control site was the occipital pole (Oz) localised by international 10–20 system.