Structural magnetic resonance imaging (MRI) was performed in all participants for use during TMS neuronavigation. Participants received T1-weighted anatomical magnetic resonance imaging scan on a 3T scanner (GE Healthcare, Ltd., UK) using a 3D spoiled gradient echo sequence (Buss et al., 2020 (link)). T1-weighted anatomical MRIs were analyzed with Freesurfer 6.0 or 7.1 (documented and freely)1 to obtain cortical gray matter thickness (GMT) measurements. One AD participant’s scan was excluded due to a Freesurfer segmentation error.
GMT measurements in all participants (n = 15 CU and n = 25 AD) was extracted for the left hemisphere mean cortical thickness (average left hemisphere GMT; LH Cortical Thickness) and left precentral thickness (from Desikan-Killiany atlas; Left Precentral Thickness) to serve as covariates in the subsequent nested regression analysis. In order to control for any differences in cortical atrophy, scalp-to-cortex distance (SCD) was measured using Brainsight™ (Rogue Research Inc., Canada) to calculate the in-plane distance between the motor cortex stimulation target and the participant’s scalp along the purported TMS trajectory on each individual’s T1-weighted MRI scan (Brem et al., 2020 (link)).
GMT measurements in all participants (n = 15 CU and n = 25 AD) was extracted for the left hemisphere mean cortical thickness (average left hemisphere GMT; LH Cortical Thickness) and left precentral thickness (from Desikan-Killiany atlas; Left Precentral Thickness) to serve as covariates in the subsequent nested regression analysis. In order to control for any differences in cortical atrophy, scalp-to-cortex distance (SCD) was measured using Brainsight™ (Rogue Research Inc., Canada) to calculate the in-plane distance between the motor cortex stimulation target and the participant’s scalp along the purported TMS trajectory on each individual’s T1-weighted MRI scan (Brem et al., 2020 (link)).
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