Automated shimming was performed using the in-built standard Siemens algorithms. Data were acquired from 1024 points, FOV (field of view) 300 mm, TR (repetition time)/TE (echo time) 500/2.3 msec, flip angle 40°, bandwidth 4000 Hz, six averages. In order to maintain signal-to-noise ratio (SNR) and to limit scan time, data were acquired using a 13 × 13 × 13 scan acquisition matrix and data were interpolated for analysis to a 16 × 16 × 16 matrix, giving a nominal voxel size of 6.6 cm3 in an acquisition time of 46 min 17 sec. The center of the acquisition grid was positioned at the center of the skull. Data were reconstructed using the Siemens spectroscopy software (Syngo VB13©,
Siemens, Erlangen, Germany), with a single voxel Inhibitors,research,lifescience,medical placed over each hippocampus according to anatomical borders, and summed for each individual. Postprocessing and spectral peak BIX 01294 in vivo fitting were performed using the AMARES Inhibitors,research,lifescience,medical (Vanhamme et al. 1997) algorithm within the jMRUI software package
(Naressi et al. 2001) (Version 2.2). Data were corrected for the effects of saturation using the flip angle and T1 values (2.39 sec for PCr and 0.79 sec for ATP). Results were confirmed by independent blinded data analysis. Although a range of stimulation tasks have been developed to be performed while in an magnetic Inhibitors,research,lifescience,medical resonance imaging (MRI) scanner, these tasks require the subject to be able to see a projection screen by using MR-compatible mirrors placed over the coils. The design and dimensions of the spectroscopy head coil precluded placement of these mirrors and hence it was not possible to perform these tasks during spectroscopy. To stimulate continued Inhibitors,research,lifescience,medical cognitive activity during the spectroscopy acquisition, the
delayed recall parts of the verbal recall tasks were performed during Inhibitors,research,lifescience,medical the scan. These tasks were performed at the beginning of the CSI acquisition in order to minimize noise in the acquisition from the muscle movements during speech. Statistical analysis for significance was performed using the two-tailed Student’s t-test for paired samples with significance taken at P < 0.05. The baseline PCr/ATP ratio prior to intervention was averaged for each subject and this averaged too value was used as their baseline PCr/ATP ratio for comparison with PCr/ATP ratios after both lipid infusion and NA. Results Eight subjects underwent studies with cognitive activity, but one subject was only able to complete the lipid infusion arm of the cognitive activity studies. Subject characteristics at baseline (Table 1) were the same for those undergoing cognitive testing and those undergoing only resting studies (four subjects). Table 1 Subject characteristics Blood tests For all subjects, baseline fasting insulin, glucose, FFA, and β-hydroxybutyrate were normal (Table 2). The lipid infusion elevated FFA levels from 0.3 ± 0.2 mmol/L at baseline to 1.3 ± 0.3 mmol/L after 3 h and 1.2 ± 0.4 mmol/L after 4 h. During the noninfusion arm, circulating FFA levels decreased.