Abstract
Models of cognitive function typically focus on the cerebral cortex and hence overlook functional links to subcortical structures. This view does not consider the role of the highly-conserved ascending arousal system’s role and the computational capacities it provides the brain. We test the hypothesis that the ascending arousal system modulates cortical neural gain to alter the low-dimensional energy landscape of cortical dynamics. Here we use spontaneous functional magnetic resonance imaging data to study phasic bursts in both locus coeruleus and basal forebrain, demonstrating precise time-locked relationships between brainstem activity, low-dimensional energy landscapes, network topology, and spatiotemporal travelling waves. We extend our analysis to a cohort of experienced meditators and demonstrate locus coeruleus-mediated network dynamics were associated with internal shifts in conscious awareness. Together, these results present a view of brain organization that highlights the ascending arousal system’s role in shaping both the dynamics of the cerebral cortex and conscious awareness.
Highlights
Models of cognitive function typically focus on the cerebral cortex and overlook functional links to subcortical structures
We extend our analysis to a cohort of experienced meditators and demonstrate changes in the cortical dynamical signatures following LC-mediated network dynamics were associated with internal shifts in conscious awareness
Using the residuals from these regressions from the LC signal, τLC and the BMN signal, τBNM, we focused on the difference between these signals and identified time points associated with phasic bursts of LC activity that led to sustained adrenergic influence over evolving brain-state dynamics
Summary
Models of cognitive function typically focus on the cerebral cortex and overlook functional links to subcortical structures. Neural activity rapidly reconfigures the functional large-scale network architecture of the brain to facilitate coordination between otherwise segregated cortical regions How this flexibility is implemented in the brain without altering structural connectivity remains an open question in systems neuroscience. The two systems have been linked with distinct and complimentary computational principles: the noradrenergic LC is presumed to modulate interactions between neurons (multiplicative gain; Fig. 1a, red)[13], whereas the cholinergic BNM is presumed to facilitate divisive normalization (response gain; Fig. 1a, green)[14] Based on these anatomical and computational features, we have hypothesized that the interaction between these two neuromodulatory systems is crucial for mediating the dynamic, flexible balance between integration and segregation in the brain[15]
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