The marmoset is a highly vocal platyrrhine monkey that shares key anatomical and functional features with humans, offering insights into the evolution of brain connectivity. Although similarities in vocalization features with humans have been reported, it remains unclear whether marmosets possess an arcuate fasciculus (af) homolog. This study delineates white matter tracts in marmosets, establishing homologies with those observed in other primates, including macaques, chimpanzees, and humans. The presence of an af homolog in marmosets is confirmed by tracer and ultra-high-resolution diffusion magnetic resonance imaging datasets. We compare cortical connectivity patterns across these species and find the af in marmosets terminates in the ventral frontal cortex, with greater similarity to humans than macaques. Furthermore, we link af connectivity with vocalization-related brain activation in both marmosets and humans. Collectively, our findings suggest that a dorsal pathway, which emerged early in marmoset evolution, has evolved convergently with humans, despite their distant phylogenetic kinship.
Protocols to reconstruct major white matter tracts in marmosets, in a consistent manner with other primate species [1,2], situable with XTRACT [1].
stepX.(1-n): codes for Figure X and attached Supplementary Figures.
[1] Warrington, S. et al. XTRACT - Standardised protocols for automated tractography in the human and macaque brain. Neuroimage 217, 116923, doi:10.1016/j.neuroimage.2020.116923 (2020).
[2] Bryant, K. L., Li, L., Eichert, N. & Mars, R. B. A comprehensive atlas of white matter tracts in the chimpanzee. PLoS Biol 18, e3000971, doi:10.1371/journal.pbio.3000971 (2020).