Functional diffusion‐weighted magnetic resonance spectroscopy of the human primary visual cortex at 7 T

Purpose: Microstructural and metabolic changes directly related to neuronal activation have been investigated using functional diffusion‐weighted spectroscopy. Methods: The volume of interest was positioned in the primary visual cortex. A time series of alternating diffusion‐ and non‐diffusion‐weighted 1 H spectra was acquired at 7 T employing stimulated echo acquisition mode sequence and a long diffusion time (Δ = 245 ms). Time‐resolved series of metabolite apparent diffusion coefficient values were derived. Results: Significant increases in apparent diffusion coefficient of 3.3 ± 1.4% ( p = 0.05) and 3.9 ± 0.9% ( p = 0.002) for total n‐acetyl aspartate and total creatine, respectively, and 8.1 ± 2.5% ( p = 0.03) for total choline were observed in response to visual stimulation. Conclusion: The increase in apparent diffusion coefficient for these metabolites is a potential indication for microstructural changes in neurons during neural activation and/or for an increase in the energy‐dependent cytoplasmic streaming associated with enhanced metabolism during visual stimulation. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.