Abstracts

To examine the cortical response in a cognitive task in regions with altered NAA. Disrupted levels of the ratio of Cr/NAA are associated with the epileptic condition yet it is not clear what impact these disrupted levels might have on function. This work co-registers CSI data with functional MR maps based on the blood oxygenation level dependent (BOLD) contrast mechanism to investigate the relationship between changes in the ratio of Cr/NAA and the BOLD signal., Subjects: N=16 intractable epilepsy patients were examined. All patients gave informed consent and the protocols were approved by the two institution[apos]s IRBs.
Tasks: fMRI data was acquired using language mapping with sentence comprehension tasks involving reading, listening to speech, and a word generation task. Together these tasks activated numerous cortical regions associated with attention, working memory, primary visual and auditory, premotor and motor cortex, and the classic language regions.
fMRI was run on a 1.5T Siemens Sonata, gradient echo EPI with alpha = 80, TE=45msec, TR=1500sec, FOV=22cm, 18 slices, 6mm, 64 x 64 matrix. Activation maps were thresholded at p[lt]0.05 (corrected). Chemical Shift Imaging was performed at 4Tesla using a Varian INOVA console and quad head coil, a LASER sequence (10mm thick, 80x100mm FOV selection), with 24x24 matrix and 192x192mm FOV. T1 maps were used to correct for partial volume effects based on gray/white/csf segmentation. The Cr/NAA ratio was calculated as a function of gray matter content and statistical decrements in Cr/NAA with p[lt]0.05 highlighted on anatomic images. Data were co-registered using the Yale BioimageSuite software package, http://www.bioimagesuite.org/., fMRI responses are detectable in regions demonstrating decreased Cr/NAA ratio and this is consistent across a number of brain regions. The figure below shows BOLD activation (top row) in a language task in the insula and a significant change in the Cr/NAA (bottom row) in this same region. In other subjects regions that show decreased Cr/NAA but normal BOLD response include temporal and sensory/motor cortical regions., Areas of altered Cr/NAA show functional MRI BOLD responses to cognitive tasks. Furtherwork is needed to examine the limits of this preserved functional ability.[figure1], (Supported by NIH NS038467-07, EB00473.)