Association between Long Range Temporal Correlations in Functional MRI BOLD signal and the Excitatory / Inhibitory Metabolites Ratio

Motivation: Animal and computational studies have been used as a basis to assume a link between excitatory-inhibitory (E/I) ratio and Hurst exponent (H) in the human brain; however, it has yet to be sufficiently demonstrated in healthy human subjects. Goal(s): We seek to test the E/I-Hurst link in the visual cortex during rest and movie-watching. Approach: Multi-echo functional MRI, sLASER, and MEGAPRESS sequences are used in 17 healthy human adults (ages 21-53 years; 13 female, 4 male) with MRS voxel ROI in visual cortex. Results: E/I and Hurst are not significantly correlated in either the MRS voxel ROI or visual network. Impact: Hurst exponent (H) is assumed to correlated with excitatory-inhibitory (E/I) ratio without sufficient human evidence. Given the role of E/I imbalance in neuropsychiatric illness and the technical difficulty to measure it, understanding if H acts as its proxy is critical.