10/ Very grateful to @lingzhongfan.bsky.social LQ Cheng, DY Li, YH Lu, WD Hopkins, CC Sherwood, @tingsterx.bsky.social CR Liu, George Paxinos, TZ Jiang, CY Chu for making this possible!

9/ Our findings suggest the presence of an earlier-emerged dorsal pathway in marmosets that convergently evolved aspects of its connectivity with humans, despite their distant phylogenetic kindship.

8/ In summary, we identified an arcuate fasciculus homolog in marmoset brains that corresponds with those in other primates and found that marmosets exhibited a more similar connection pattern of the af with humans in the vPFC.

7/ Transforming this activation into the marmoset cortex, we also observed overlap in their af connectivity patterns, which was further supported by fMRI and electrophysiological experiments on marmoset vocalizations.

6/ Given the shared features of vocalization between marmosets and humans, we explored the involvement of af in vocal communication. This was supported by the overlap between human “speech” functional activation and af connectivity.

5/ We then examined the cortical connections of the af. Utilizing a large datasets from humans, chimpanzees, macaques, and marmosets, we found that the connection between the af and ventral PFC (A45c) was stronger in marmosets than in macaques.

4/ Following a “1 seed, 2 target” approach, we reconstructed the af and three branches of slf, demonstrating the disambiguation of these tracts in marmosets.

3/ To address the controversy around the existence of the af homologue in marmosets, we collected retrograde and anterograde tracer data, along with ultra-high-resolution dMRI data. Our tracing results revealed clear connections between A45 and AuCM/Tpt via a dorsal pathway.

2/ The marmoset is a highly vocal monkey sharing vocalization features with humans, suggesting a potential neuroanatomical precursor of language. But do marmosets have an arcuate fasciculus (af)?