Mapping putative hubs in human, chimpanzee and rhesus macaque connectomes via diffusion tractography

Abstract

Mapping anatomical brain networks with graph-theoretic analysis of diffusion tractography has recently gained popularity, because of its presumed value in understanding brain function. However, this approach has seldom been used to compare brain connectomes across species, which may provide insights into brain evolution. Here, we employed a data-driven approach to compare interregional brain connections across three primate species: 1) the intensively studied rhesus macaque, 2) our closest living primate relative, the chimpanzee, and 3) humans. Specifically, we first used random parcellations and surface-based probabilistic diffusion tractography to derive the brain networks of the three species under various network densities and resolutions. We then compared the characteristics of the networks using graph-theoretic measures. In rhesus macaques, our tractography-defined hubs showed reasonable overlap with hubs previously identified using anterograde and retrograde tracer data. Across all three species, hubs were largely symmetric in the two hemispheres and were consistently identified in medial parietal, insular, retrosplenial cingulate and ventrolateral prefrontal cortices, suggesting a conserved structural architecture within these regions. However, species differences were observed in the inferior parietal cortex, polar and medial prefrontal cortices. The potential significance of these interspecies differences is discussed.

Evolutionary and Developmental Changes in the Lateral Frontoparietal Network: A Little Goes a Long Way for Higher-Level Cognition

“…As can be seen in Figure 9A, frontoparietal regions were found to have a larger number of functional connections to other regions, thus demonstrating greater possibility for integration of information within these regions (Miranda-Dominguez et al, 2014). Additional support for this claim comes from several studies comparing functional (Mars et al, 2011; Neubert et al, 2014) and structural (Li et al, 2013) networks between humans and macaques. In one study, researchers used DTI to estimate structural frontoparietal connections, and then used structural connections to constrain possible functional connections among regions using resting-state fMRI (Mars et al, 2011).…”

“…Differences between humans and macaques were found when investigating functional and structural connections of RLPFC and inferior parietal regions using diffusion-weighted MRI (Li et al, 2013; Miranda-Dominguez et al, 2014). As can be seen in Figure 9A, frontoparietal regions were found to have a larger number of functional connections to other regions, thus demonstrating greater possibility for integration of information within these regions (Miranda-Dominguez et al, 2014).…”

Using Diffusion Tractography to Predict Cortical Connection Strength and Distance: A Quantitative Comparison with Tracers in the Monkey

“…Here, we focus on using tractography to estimate the presence and weight ("strength") of long-distance connections between GM regions. This involves analysis of "parcellated connectomes"; that is, estimating connectivity between brain subdivisions (parcels) in humans or nonhuman primates (NHPs) (Sporns et al, 2005;Harriger et al, 2012;Li et al, 2013;van den Heuvel et al, 2015).…”

Optimization of large-scale mouse brain connectome via joint evaluation of DTI and neuron tracing data

“…As a magnetic resonance imaging (MRI) technique, DTI is able to infer axonal fiber orientations of living brains in 3D space by measuring restricted water diffusion in tissue. Based on the DTI tractography, many macro-scale fiber pathways of mammalian brains such as human (Assaf and Pasternak, 2008; Bassett and Bullmore, 2009; Mori et al, 2008), macaque (Chen et al, 2013; Li et al, 2013; Rilling et al, 2008), or mouse (Calamante et al, 2012; Moldrich et al, 2010; Zhang et al, 2002) were reconstructed and analyzed. Later, it has been pointed out that in order to fully understand how the brain works, a comprehensive map of brain inter-regional wiring diagram on a large scale, namely connectome, is required (Bullmore and Sporns, 2009; Sporns et al, 2005; Van Essen, 2013).…”