The posterior associative white matter network between the human temporal and parietal brain lobes

DANIEL BULLOCK; FRANCO PESTILLI; HIROMASA TAKEMURA; CESAR F. CAIAFA

San Diego

Conferencia; Society for Neuroscience 2016; 2016

SfN

Two major cortical pathways of visual information have been hypothesized in the primate brain; the ventral and dorsal streams (Goodale & Millner 1992). New evidence for direct white matter pathways within the posterior human cortex, communicating information between these streams, has renewed interest in this hypothesis. Recent findings suggest that there are at least three vertical fiber tracts connecting the dorsal and ventral streams. These tracts proceed all the way from the occipital lobe, in the case of the vertical occipital fasciculus (Yeatman et al 2014; Takemura et al 2015), to the parietal lobe, as is the case for the parietal arcuate (Catani et al 2005; Weiner et al 2016). In the present work, we compare the statistical strength of evidence (Pestilli et al 2014) for the major tracts connecting the dorsal and ventral stream in the posterior human cortex.We used diffusion-weighted magnetic resonance imaging data from two publicly available data sets (Human Connectome Project; Rokem et al 2015). A total of 26 hemispheres were analyzed. We used ensemble tracking methods (Takemura et al 2016) to build whole-brain connectomes using multiple probabilistic tracking methods (600,000 fascicles) per brain. White matter tract identification was performed using published methods (Yeatman et al 2016; Takemura et al 2015). In addition, we developed an automated tract segmentation method using a combination of cortical parcellation (Destrieux et al 2010), fascicle projection, and density measures.We report a new tract-segmentation method and measure the statistical evidence for multiple white matter tracts connecting the two visual information processing streams, such as the arcuate fasciculus, the parietal arcuate, and vertical occipital fasciculus. Our results reproduce previous findings from both in-vivo and postmortem studies (Lawes et al 2008; de Champfleur 2013, Takemura et al 2015, Weiner et al 2016). Our findings extend beyond previous results, suggesting a more complex network of ventro-dorsal communication than previously established.Historically, neuroanatomical observations have focused on a number of associative white matter tracts running predominantly rostro-caudally, for example, the superior and inferior longitudinal fasciculi (Catani et al 2012). The dorsal and ventral streams, running posterior to anterior, have typically been described as parallel and structurally segregated. Our results provide quantitative evidence that an extensive network of communication pathways exist between these two functional streams. We provide a detailed description of the major structural organization of such a network.