Orbitofrontal cortex activity related to emotional processing changes across the menstrual cycle

Protopopescu et al. 10.1073/pnas.0502818102.

Supporting Information

Files in this Data Supplement:

Supporting Text
Supporting Figure 4
Supporting Figure 5

Supporting Figure 4

Fig. 4. (a) Z-Shim functional MRI. Conventional echo-planar images (EPIs) with induced susceptibility artifact are shown (arrows) (Upper). Note how EPI signal is recaptured with single-shot z-shim EPI method (Lower). (b) Functional results (finger-tapping experiment) overlaid on structural images in scans with induced susceptibility artifact (arrows) (Upper). Note how functional signal is recaptured (Lower).

Supporting Figure 5

Fig. 5. Glass brain rendering of a statistical parametric mapping (SPM) F-map (using 11 normal subjects from the current study in the negative go condition). Note adequate coverage of the orbitofrontal cortex regions discussed.

Supporting Text

Nonuniform sampling across the brain is an important limitation of functional MRI (fMRI). Structural variations cause perturbations in the magnetic field that result in signal loss, spatial-distortion in the image, and areas where the signal-to-noise is so low that little information can be provided. MR signals attenuate significantly in the brain regions near bone-tissue or air-tissue interfaces (e.g., the ventral-frontal, parahippocampal/amygdala, and the inferior lateral temporal areas) due to distorted magnetic fields in these regions. Our laboratory has developed and validated a peer reviewed "double-encoding" technique to reduce such susceptibility artifacts and to facilitate fMRI studies in these brain regions. In the new technique, a set of echo-planar images (EPIs) are obtained by combining images encoded with 16 different refocusing gradients, and then two optimized refocusing gradient amplitudes are chosen for each slice to obtain optimal signal recovery in specific brain regions of interest. This technique effectively recovers signals in the ventral-frontal and meso-temporal regions, while still allowing for reasonable temporal sampling (Fig. 4). This technique has allowed us to examine blood oxygen level-dependent activity in the orbitofrontal cortex region in the current study (Fig. 5).