Mapping anatomical connectivity between visual cortex and the pulvinar in human neonates

Abstract

The primate pulvinar contains extensive, reciprocal connections with visual cortex. Through this connectivity the pulvinar is thought to regulate communication within and between cortical visual areas and facilitate the processing of low- and high-level visual information (Saalmann & Kastner 2011). Here, we explored the development of these connections in humans. We analyzed diffusion imaging data collected in neonates (37-42w gestation) as part of the developing human connectome project (Bastiani et al. 2019). To identify cortical regions for tracking, we aligned an adult retinotopic atlas (Wang et al. 2015) to each neonate’s native brain. Probabilistic tractography (FSL) was performed between individual retinotopic maps and the pulvinar in accordance with prior analyses in adults (Arcaro et al. 2015). Briefly, an initial tractography analysis was performed to identify the most probable thalamic radiations interconnecting cortical areas and the pulvinar. A second analysis restricted to tracking through these radiations identified voxels in the pulvinar with the largest connectivity values with each cortical map. Data were normalized and aligned to a 40-week neonate template for group-level analyses. For occipital cortical maps, the largest connectivity values were within the ventral lateral pulvinar. Medial to this tracking was a region of the ventral pulvinar that was most strongly connected with motion-sensitive maps TO1&2. For posterior parietal maps the largest connectivity values were within the dorsal pulvinar. Tracking from parietal maps extended to the superior colliculus. Overall, pulvino-cortical tracking in neonates followed the known white matter pathways in adults and the spatial organization of connections within the pulvinar was in good correspondence with the organization previously found in adults (Arcaro et al. 2015). These results indicate that the pulvino-cortical pathways that support visual processing in adults are established in utero. We propose that these connections play an important role in shaping postnatal development across visual cortex.