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Abstract:
Abstract: The use of chemical spectroscopy in the imaging of
cognitive processes is appealing because it allows a direct
measurement of the neural substrates of energy metabolism. However,
the reliability of using spectroscopy for functional imaging
requires further study. This study compared fMRI [EPI-BOLD;
TR=3,TE=40, Flip Angle=90] and single voxel FMRS [PRESS; TR 00 ms;
TE=30 ms; FID pts 48; Spectral Width 00 Hz] data obtained from
identical volumes during an auditory monitoring task. Six
participants listened to a broad range of 500 ms tones and
monitored for identical, adjacent tones with scanner noise serving
as a control condition. Results from fMRI were used to specify the
region of interest for the PRESS sequences. fMRI analysis was
limited to the PRESS volume. Within this volume, 23.3% of the
voxels showed significant activation at p < .001. For the
PRESS analysis, fourier transformed normalized spectra obtained
during auditory monitoring were subtracted from spectra obtained
during rest. Between subject t-tests were used at specific spectral
points of interest to quantify statistically consistent changes.
Our findings reveal a reliable increase in glutamate in auditory
cortex across participants during tone monitoring. These results
strongly suggest that spectral measures of glutamate may serve as a
reliable and specific maker of neural excitation in sensory
cortex.
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