Modern Methods for Interrogating the Human Connectome

Abstract

Objectives: Connectionist theories of brain function took hold with the seminal contributions of Norman Geschwind a half century ago. Modern neuroimaging techniques have expanded the scientific interest in the study of brain connectivity to include the intact as well as disordered brain.

Methods: In this review, we describe the most common techniques used to measure functional and structural connectivity, including resting state functional MRI, diffusion MRI, and electroencephalography and magnetoencephalography coherence. We also review the most common analytical approaches used for examining brain interconnectivity associated with these various imaging methods.

Results: This review presents a critical analysis of the assumptions, as well as methodological limitations, of each imaging and analysis approach.

Conclusions: The overall goal of this review is to provide the reader with an introduction to evaluating the scientific methods underlying investigations that probe the human connectome.

Keywords: Complex network analysis; Diffusion MRI; EEG/MEG coherence; Human connectome; Independent components analysis; Resting state fMRI.

Figure 1

a) Bilateral finger tapping task activation student’s t-score, thresholded, and overlaid on BOLD-weighted EPI, the black box indicates the maximum activated region, b) mean timeseries of the black box region in (a) superposed on the task timing (high regions are periods of finger tapping), c) whole-brain false color map overlaid on high resolution anatomy (overlay indicates regions of high correlation to the region defined by the black box), and d) timeseries of spontaneous BOLD fluctuations in the boxed region.

Figure 2

Examples of within and among network connectivity information. The left panel shows brain regions parcellated from resting fMRI data using group ICA and the right panel shows the functional network connectivity matrix among these regions (cross-correlation).