Josh Grooms

BME MS Defense Presentation

Monday February 9, 2015 at 1:00 – 3:00 PM

Emory University, Health Sciences Research Building – Rollins Auditorium (First Floor)

Advisor: Shella Keilholz, PhD

Committee Members:

Shella Keilholz, PhD

Xiaoping Hu, PhD

Charles Epstein, MD

Title: Examining the Relationship between BOLD fMRI and Infraslow EEG in the Resting Human Brain

Abstract:

Functional magnetic resonance imaging (fMRI) is currently at the forefront of research on cognition and the brain’s large-scale organization. Patterns found in the hemodynamic signals that it records have been strongly linked to various behaviors and cognitive pathologies. These signals are widely assumed to reflect local neuronal activity, but our understanding of the exact relationship between them remains incomplete. To address this, researchers use multimodal approaches that pair fMRI signals with known measures of neuronal activity, such as electroencephalography (EEG). It has long been thought that the infraslow (< 0.1 Hz) fMRI signals, which have become so important to the study of brain function, might have a direct electrophysiological counterpart. If so, the impact could be substantial; EEG could be positioned as a low-cost alternative to fMRI when fMRI is impractical. Additionally, with its wide availability and high temporal resolution, EEG could become much more influential in the studying of functional brain networks. Previous studies have produced indirect support for the fMRI-EEG relationship, but until recently the hypothesized link between their infraslow signals had not been tested in humans. The objective of this study was to investigate and characterize this link by examining infraslow fMRI and EEG signals that were simultaneously recorded in resting human adults. We present evidence strongly favoring the link by demonstrating significant stationary and dynamic correlations between the two signal types. Moreover, functional brain networks appear to be a fundamental unit of this coupling. We conclude that infraslow electrophysiology is likely playing an important role in the dynamic configuration of the resting state brain networks that are well-known in fMRI research. Our results provide new insights into the neuronal underpinnings of hemodynamic activity and a foundational point on which the use of infraslow EEG in functional connectivity studies can be based.