An evolutionary gap in primate default mode network organization

The default mode network (DMN) in humans is active during rest and self-directed thought. Comparing the DMN across humans and non-hominoid primates (macaques, marmosets, and mouse lemurs) reveals major differences in connectivity. In non-hominoid primates, the medial prefrontal cortex shows weak engagement with the posterior cingulate cortex, whereas strong correlated activity between these regions is a key human DMN feature. Instead, a fronto-temporal resting-state network involving the medial prefrontal cortex appears consistently across non-hominoid species. These shared features among non-hominoid primates, absent in humans, indicate a substantial gap in DMN organization and its associated cognitive functions.

Study at a glance

Abstract

SUMMARY The human default mode network (DMN) is engaged at rest and in cognitive states such as self-directed thoughts. Interconnected homologous cortical areas in primates constitute a network considered as the equivalent. Here, based on a cross-species comparison of the DMN between humans and non-hominoid primates (macaques, marmosets, and mouse lemurs), we report major dissimilarities in connectivity profiles. Most importantly, the medial prefrontal cortex (mPFC) of non-hominoid primates is poorly engaged with the posterior cingulate cortex (PCC), though strong correlated activity between the human PCC and the mPFC is a key feature of the human DMN. Instead, a fronto-temporal resting-state network involving the mPFC was detected consistently across non-hominoid primate species. These common functional features shared between non-hominoid primates but not with humans suggest a substantial gap in the organization of the primate’s DMN and its associated cognitive functions.