The marmoset default-mode network identified by deactivations in task-based fMRI studies

SUMMARY Understanding the default-mode network (DMN) in the common marmoset (Callithrix jacchus) has been challenging due to inconsistencies with human and marmoset DMNs. By analyzing task-negative activation in fMRI studies, we identified medial prefrontal cortical areas, rostral auditory areas, entorhinal cortex, posterior cingulate cortex area 31, hippocampus, hypothalamus, and basomedial amygdala as marmoset DMN components. Notable, medial and posterior parietal areas that were previously hypothesized to be part of the DMN were activated during visual task blocks. Seed analysis using resting-state fMRI showed strong connectivity between task-negative areas, and tracer data supported a structural network aligning with this functional DMN. These findings challenge previous definition of the marmoset DMN and reconcile many inconsistencies with the DMNs observed in humans, macaque monkeys, and even rodents. Overall, these results highlight the marmoset as a powerful model for DMN research, with potential implications for studying neuropsychiatric disorders where DMN activity and connectivity are altered.