Neurochemical and BOLD responses during neuronal activation measured in the human visual cortex at 7 Tesla

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Authors	BEDNAŘÍK Petr TKAC Ivan GIOVE Federico DINUZZO Mauro DEELCHAND Dinesh K. EMIR Uzay E. EBERLY Lynn E. MANGIA Silvia
Year of publication	2015
Type	Article in Periodical
Magazine / Source	JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
MU Faculty or unit	Central European Institute of Technology
Citation
Web	http://www.nature.com/jcbfm/journal/v35/n4/full/jcbfm2014233a.html
Doi	http://dx.doi.org/10.1038/jcbfm.2014.233
Field	Neurology, neurosurgery, neurosciences
Keywords	Functional Spectroscopy; GABA quantification; Neurochemistry; Visual Stimulation
Description	Several laboratories have consistently reported small concentration changes in lactate, glutamate, aspartate, and glucose in the human cortex during prolonged stimuli. However, whether such changes correlate with blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) signals have not been determined. The present study aimed at characterizing the relationship between metabolite concentrations and BOLD-fMRI signals during a block-designed paradigm of visual stimulation. Functional magnetic resonance spectroscopy (fMRS) and fMRI data were acquired from 12 volunteers. A short echo-time semiLASER localization sequence optimized for 7 Tesla was used to achieve full signal-intensity MRS data. The group analysis confirmed that during stimulation lactate and glutamate increased by 0.26 +/- 0.06 mu mol/g (similar to 30%) and 0.28 +/- 0.03 mu mol/g (similar to 3%), respectively, while aspartate and glucose decreased by 0.20 +/- 0.04 mu mol/g (similar to 5%) and 0.19 +/- 0.03 mu mol/g (similar to 16%), respectively. The single-subject analysis revealed that BOLD-fMRI signals were positively correlated with glutamate and lactate concentration changes. The results show a linear relationship between metabolic and BOLD responses in the presence of strong excitatory sensory inputs, and support the notion that increased functional energy demands are sustained by oxidative metabolism. In addition, BOLD signals were inversely correlated with baseline.-aminobutyric acid concentration. Finally, we discussed the critical importance of taking into account linewidth effects on metabolite quantification in fMRS paradigms.
Related projects:	CEITEC - Central European Institute of Technology