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

ABSTRACT

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.