Functional Connectivity in Nonhuman Primate Brain Using Blood Oxygenation Level- Dependent Functional Magnetic Resonance Imaging and Electrophysiology

Abstract

The identification of patterns of highly correlated low frequency Magnetic Resonance Imaging (MRI) signals in resting states provides a powerful approach to assess brain functional organization. However, functional MRI (fMRI) studies rely on detecting hemodynamic changes as revealed by blood oxygenation level-dependent (BOLD) signals to infer underlying neuronal activity. Precise interpretations of fMRI studies require a deep understanding of the relationships between BOLD signal changes and their corresponding electrophysiological signatures [e.g., local field potentials (LFPs)]. This thesis evaluates whether brain inter-regional correlations in resting state fMRI signals reliably measure functional connectivity, and investigates the dynamic nature of functional connectivity in both fMRI and frequency-specific LFPs. The spatial local correlation profiles and dynamic changes in functional connectivity between LFPs and submillimeter resolution BOLD at 9.4T are compared within primary somatosensory (S1) cortex in squirrel monkeys. This thesis reports high spatial correspondence at a columnar level between BOLD and LFPs, and suggests that resting state fMRI dynamic connectivity is reflective more of low frequency LFP coherence than high frequency LFP coherence in S1 cortex.