PT - JOURNAL ARTICLE AU - Ben J. Harrison AU - Christopher G. Davey AU - Hannah S. Savage AU - Alec J. Jamieson AU - Christine A. Leonards AU - Bradford A. Moffat AU - Rebecca K. Glarin AU - Trevor Steward TI - Dynamic Subcortical Modulators of Human Default Mode Network Function AID - 10.1101/2021.10.27.466172 DP - 2021 Jan 01 TA - bioRxiv PG - 2021.10.27.466172 4099 - http://biorxiv.org/content/early/2021/11/24/2021.10.27.466172.short 4100 - http://biorxiv.org/content/early/2021/11/24/2021.10.27.466172.full AB - The brain’s ‘default mode network’ (DMN) enables flexible switching between internally and externally focused cognition. Precisely how this modulation occurs is not well understood, although may involve key subcortical mechanisms, including hypothesized influences from the basal forebrain (BF) and mediodorsal thalamus (MD). Here, we used ultra-high field (7T) functional magnetic resonance imaging to examine the involvement of the BF and MD across states of task-induced DMN activity modulation. Specifically, we mapped DMN activity suppression (‘deactivation’) when participants transitioned between rest and externally focused task performance, as well as DMN activity engagement (‘activation’) when task performance was internally (i.e., self) focused. Consistent with recent rodent studies, the BF showed overall activity suppression with DMN cortical regions when comparing the rest to external task conditions. Further analyses, including dynamic causal modelling, confirmed that the BF drove changes in DMN cortical activity during these rest-to-task transitions. The MD, by comparison, was specifically engaged during internally focused cognition and demonstrated a broad excitatory influence on DMN cortical activation. These results provide the first direct evidence in humans of distinct basal forebrain and thalamic circuit influences on the control of DMN function and suggest novel mechanistic avenues for ongoing translational research.Competing Interest StatementThe authors have declared no competing interest.