Andrei Manzhurtsev1,2,3, Petr Menschchikov4,5, Alexei Yakovlev6,4,7, Maxim Ublinskiy6,4, Olga Bozhko6, Dmitrii Kupriyanov5, Tolib Akhadov6, Sergei Varfolomeev4,8, Natalia Semenova6,4,8,7. 1. Clinical and Research Institute of Emergency Pediatric Surgery and Trauma, Bol´shaya Polyanka St. 22, 119180, Moscow, Russian Federation. andrey.man.93@gmail.com. 2. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Kosygina St. 4, 119334, Moscow, Russian Federation. andrey.man.93@gmail.com. 3. Moscow State University, Leninskie Gory st., 1, 119991, Moscow, Russian Federation. andrey.man.93@gmail.com. 4. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Kosygina St. 4, 119334, Moscow, Russian Federation. 5. LLC Philips Healthcare, 13, Sergeya Makeeva St., 123022, Moscow, Russian Federation. 6. Clinical and Research Institute of Emergency Pediatric Surgery and Trauma, Bol´shaya Polyanka St. 22, 119180, Moscow, Russian Federation. 7. Semenov Institute of Chemical Physics, Russian Academy of Sciences, Kosygina St. 4, 119334, Moscow, Russian Federation. 8. Moscow State University, Leninskie Gory st., 1, 119991, Moscow, Russian Federation.
Abstract
OBJECTIVE: To measure N-acetyl aspartyl glutamate (NAAG) and N-acetyl aspartate (NAA) concentrations in visual cortex activated by a continuous stimulation in a 3 T field. METHODS: NAAG and NAA spectra were obtained with MEGA-PRESS pulse sequence (TE/TR = 140/2000 ms; δONNAAG/δOFFNAAG = 4.61/4.15 ppm; δONNAA/δOFFNAA = 4.84/4.38 ppm) in 14 healthy volunteers at rest and upon stimulation by a radial checkerboard flickering at a frequency of 8 Hz. Spectra of all subjects were frequency and phase aligned and then averaged. Additionally, to obtain the time-dependency data, spectra were divided into time sections of 64 s each. The intensities of NAA, NAAG and lactate + macromolecular (Lac + MM) signals were defined by integration of the real part of spectra. The heights of the central resonance of NAAG and NAA signals were measured. RESULTS: The NAAG and NAA concentrations, measured with 2.5% and 0.5% error, respectively, were unaffected by visual activation. A significant increase in the Lac + MM signal by ~ 12% is clearly observed. No stimulation-induced time dependency was found for NAAG or NAA, while the increase in Lac + MM was gradual. The concentration values in visual cortex are in good agreement with the 7 T MRS measurements: [NAAG] = 1.55 mM, [NAA] = 11.95 mM. CONCLUSION: The MEGA-PRESS pulse sequence together with the spectral preprocessing techniques allowed to demonstrate that the concentrations of NAAG and NAA in the visual cortex remain constant during continuous visual stimulation within the margin of error. An increase in the lactate signal intensity signifies the activation of the anaerobic glycolysis in activated visual cortex.
OBJECTIVE: To measure N-acetyl aspartyl glutamate (NAAG) and N-acetyl aspartate (NAA) concentrations in visual cortex activated by a continuous stimulation in a 3 T field. METHODS:NAAG and NAA spectra were obtained with MEGA-PRESS pulse sequence (TE/TR = 140/2000 ms; δONNAAG/δOFFNAAG = 4.61/4.15 ppm; δONNAA/δOFFNAA = 4.84/4.38 ppm) in 14 healthy volunteers at rest and upon stimulation by a radial checkerboard flickering at a frequency of 8 Hz. Spectra of all subjects were frequency and phase aligned and then averaged. Additionally, to obtain the time-dependency data, spectra were divided into time sections of 64 s each. The intensities of NAA, NAAG and lactate + macromolecular (Lac + MM) signals were defined by integration of the real part of spectra. The heights of the central resonance of NAAG and NAA signals were measured. RESULTS: The NAAG and NAA concentrations, measured with 2.5% and 0.5% error, respectively, were unaffected by visual activation. A significant increase in the Lac + MM signal by ~ 12% is clearly observed. No stimulation-induced time dependency was found for NAAG or NAA, while the increase in Lac + MM was gradual. The concentration values in visual cortex are in good agreement with the 7 T MRS measurements: [NAAG] = 1.55 mM, [NAA] = 11.95 mM. CONCLUSION: The MEGA-PRESS pulse sequence together with the spectral preprocessing techniques allowed to demonstrate that the concentrations of NAAG and NAA in the visual cortex remain constant during continuous visual stimulation within the margin of error. An increase in the lactate signal intensity signifies the activation of the anaerobic glycolysis in activated visual cortex.
Authors: Joseph H Neale; Rafal T Olszewski; Laura M Gehl; Barbara Wroblewska; Tomasz Bzdega Journal: Trends Pharmacol Sci Date: 2005-09 Impact factor: 14.819