fMRI data acquisition and analysis fMRI data acquisition Functional images were acquired on a 3T BRUKER MedSpec 30/100 system (Bruker Corporation, Billerica, MA), equipped with a standard birdcage head coil. Functional images were collected with a single shot gradient echo-planar imaging (EPI) sequence with the following parameters: echo time TE = 25 msec, flip angle 90°, repetition time TR = 2000 msec, acquisition bandwidth 100 kHz. Twenty-six axial slices were taken in an interleaved fashion (pixel matrix = 64 × 64 and in-plane resolution = 3 × 3 mm, resulting in a field of view of 19.2 cm, a slice thickness of 4 mm, and an
interslice gap Inhibitors,research,lifescience,medical of 1mm), oriented parallel to the bicommissural plane (AC-PC). The total number of functional scans collected per participant was 780 for the experimental conditions
and 233 for the FEF-L. Additionally, Inhibitors,research,lifescience,medical three-dimensional (3D) high-resolution whole brain images were acquired from each subject (MP-RAGE sequence, 160 slices, 1 mm thickness) in a separate session on a 3T Siemens MAGNETOM TIM Trio (Siemens AG, Munich and Berlin, Germany), used to align the functional data slices onto a 3D stereotactic coordinate reference system. fMRI data preprocessing All fMRI data analyses were carried out using the SPM8 software package (Wellcome Department of Imaging Neuroscience, London, U.K.) with Matlab 7 (Mathworks, Natick, MA). After EPI volumes were Inhibitors,research,lifescience,medical corrected for motion, distortion, and slice timing, they were realigned, unwarped, normalized to Inhibitors,research,lifescience,medical the Montreal Neurological Institute (MNI) template (3 × 3 × 3 mm resolution), and spatially smoothed (8 mm). fMRI data first-level analysis Each motion period (time between end of still period and beginning of target identification period, see above) was modeled as a boxcar
this research spanning the length of 6000 msec, convolved with the standard selleck catalog hemodynamic response function, representing activation Inhibitors,research,lifescience,medical during MOT and LUM, respectively. Accordingly, a design matrix was fitted with regressors for MOT and LUM. Trials that showed erroneous behavioral performance were modeled just as regular MOT and LUM trials, yet labeled as JUNK. JUNK and BASELINE (modeled as a boxcar spanning the duration of 4000 msec ITIs) entered the analysis as additional regressors. For first-level analysis, contrast images were computed combining the parameter estimates of the Anacetrapib corresponding experimental conditions (MOT, LUM). For the FEF-L, a design matrix was fitted with regressors for FIX and SACC, each modeled as a boxcar with a duration of 15 s and convolved with the standard hemodynamic response function. Computing contrast images combining the parameter estimates of FIX and SACC, effects of the two regressors were compared to each other resulting in FEF-L activation. This was done on the group level due to the circumstance that individual subjects showed large variations in activation strength.