1H MRS at 7T Demonstrates a Strong Correlation Between Stimulus-Induced γ-Frequency in the Visual Cortex & the Glutamine/GABA Ratio.

Mary Charlotte Stephenson¹, Matthew J. Brookes¹, Darren Price¹, Antonio Napolitano², Susan T. Francis¹, Peter G. Morris¹

The peak frequency of stimulus-induced visual γ-oscillations, measured using magnetoencephalograpy, has been shown to be predicted by the resting concentration of γ-amino butyric acid (GABA). However, cortical network models show that the oscillatory frequency depends on the balance between excitatory and inhibitory neurotransmitters. In this study we utilize the increased spectral resolution and signal available at 7T to quantify glutamate, glutamine and GABA. Our results indicate a stronger correlation between γ-frequency and glutamate/GABA than for GABA alone. The strongest correlation was found for glutamine/GABA where the glutamine concentration is thought to be closely related to the glutamate neurotransmitter pool size