Ge 3.0 t signa excite hdx system

Participants were seated in a dimly lit magnetically shielded room. MEG data were collected at a sample rate of 678.17 Hz and pass-band filtered between 1 and 200 Hz, using a whole-head 248-channel system, Magnes 3600 (4D Neuroimaging, San Diego, California), with the magnetometers arranged in a helmet shaped array. MEG signals were segmented into epochs of 1300 ms length, starting 500 ms before the target onset. Epochs were visually inspected and manually rejected when contaminated by eye blinks, movement artefacts or electrical noise. Statistical analyses included only datasets with at least 60% of trials. We did not record electrooculography (EOG). On average, 20% of the trials were rejected from these datasets (min 9% - max 40%). Before the experiment, participants’ head shape and the location of five head coils were recorded with a 3-D digitizer (Fastrak Polhemus). In a separate session, anatomical MRI images were acquired with a GE 3.0 T Signa Excite HDx system (General Electric, USA), using an 8-channel head coil and a sagittal-isotropic 3-D fast spoiled gradient-recalled sequence. During data processing, each participant’s structural MRI image, the digitized coils positions and head shape were co-registered using a surface-matching technique adapted from (Kozinska, Carducci, & Nowinski, 2001 (link)) to constrain source localization.