Determining hierarchical functional networks from auditory stimuli fMRI

• Type of Material: Article
• Authors: Rajan S. Patel, Emory University; Frederick Bowman, Emory University; James Rilling, Emory University
• Language: English
• Date: 2006-05-01
• Publisher: Wiley
• Publication Version: Final Published Version
• Copyright Statement: © 2006 Wiley-Liss, Inc.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1002/hbm.20245
• Title of Journal or Parent Work: Human Brain Mapping
• Volume: 27
• Issue: 5
• Start Page: 462
• End Page: 470
• Grant/Funding Information: None declared
• Keywords: Image Processing, Computer-Assisted; Frontal Lobe; Language Tests; Algorithms; Temporal Lobe; Brain Mapping; Bayes Theorem; Gyrus Cinguli; Acoustic Stimulation; Speech Perception; Functional Laterality; Verbal Behavior; Neural Pathways; Cerebral Cortex; Humans; Magnetic Resonance Imaging; Nerve Net; Language
• Research Categories: Biology, Neuroscience; Health Sciences, Public Health; Health Sciences, Radiology; Biology, Biostatistics

Abstract

We determined connectivity of the human brain using functional magnetic resonance imaging (fMRI) while subjects experienced auditory stimuli in a 2-by-2 factorial design. The two factors in this study were "speaker" (same or different speaker) and "sentence" (same or different sentences). Connectivity studies allow us to ask how spatially remote brain regions are neurophysiologically related given these stimuli. In the context of this study, we examined how the "speaker" effect and "sentence" effect influenced these relationships. We applied a Bayesian connectivity method that determines hierarchical functional networks of functionally connected brain regions. Hierarchy in these functional networks is determined by conditional probabilities of elevated activity. For example, a brain region that becomes active a superset of the time of another region is considered ascendant to that brain region in the hierarchical network. For each factor level, we found a baseline functional network connecting the primary auditory cortex (Brodmann's Area [BA] 41) with the BA 42 and BA 22 of the superior temporal gyrus (STG). We also found a baseline functional network that includes Wernicke's Area (BA 22 posterior), STG, and BA 44 for each factor level. However, we additionally observed a strong ascendant connection from BA 41 to the posterior cingulate (BA 30) and Broca's Area and a stronger connection from Wernicke's Area to STG and the posterior cingulate while passively listening to different sentences rather than the same sentence repeatedly. Finally, our results revealed no significant "speaker" effect or interaction between "speaker" and "sentence."