Frontoparietal connectivity as a product of convergent evolution in rodents and primates: functional connectivity topologies in grey squirrels, rats, and marmosets

Abstract

Robust frontoparietal connectivity is a defining feature of primate cortical organization. Whether mammals outside the primate order, such as rodents, possess similar frontoparietal functional connectivity organization is a controversial topic. Previous work has primarily focused on comparing mice and rats to primates. However, as these rodents are nocturnal and terrestrial, they rely much less on visual input than primates. Here, we investigated the functional cortical organization of grey squirrels which are diurnal and arboreal, thereby better resembling primate ecology. We used ultra-high field resting-state fMRI data to compute and compare the functional connectivity patterns of frontal regions in grey squirrels (Sciurus carolinensis), rats (Rattus norvegicus), and marmosets (Callithrix jacchus). We utilized a fingerprinting analysis to compare interareal patterns of functional connectivity from seeds across frontal cortex in all three species. The results show that grey squirrels, but not rats, possess a frontoparietal connectivity organization that resembles the connectivity pattern of marmoset lateral prefrontal cortical areas. Since grey squirrels and marmosets have acquired an arboreal way of life but show no common arboreal ancestor, the expansion of the visual system and the formation of a frontoparietal connectivity architecture might reflect convergent evolution driven by similar ecological niches in primates and tree squirrels.

A comparative analysis of the antiviral response in two bat species reveals conserved and divergent innate immune pathways

“…When comparing human versus mouse transcriptional response, we observe a similar correlation to that observed between the two bat species (r=0.441 between human and mouse versus r=0.427 between the two bats). This seemingly low correlation between the two bat species is in agreement with the fact that these two bat species belong to the two major bat suborders, Yangochiroptera and Yinpterochiroptera, whose last common ancestor is predicted to have existed ~60 million years ago 40,73 (while primates and rodents split approximately 90 million years ago 74,75 ). This finding is consistent with the notion that different bat species, while having a largely conserved genetic program upregulated in response to viral infection, may still differ in the level of upregulation of specific genes and that there may be high diversity across bat species in their response to viruses.…”