Brain states govern the spatio-temporal dynamics of resting state functional connectivity

Abstract

Previously, using simultaneous task-free fMRI and optic-fiber-based neuronal calcium recordings in the anesthetized rat, we identified BOLD responses directly related to slow calcium waves, revealing a cortex-wide and spatially organized BOLD correlate (Schwalm et al. 2017). Here, with these bimodal recordings, we reveal two distinct brain states: persistent state, in which compartmentalized network activity was observed, including defined subsets such as the default mode network; and slow wave state, dominated by a cortex-wide component, suggesting a strong functional coupling of brain activity. In slow wave state we find a correlation between slow wave events and the strength of functional connectivity. These findings suggest that indeed down-up transitions of neuronal excitability drive cortex-wide functional connectivity. This study provides strong evidence that previously reported changes in functional connectivity are highly dependent on the brain's current state and directly linked with cortical excitability and slow waves generation.

Mind blanking is a distinct mental state linked to a recurrent brain profile of globally positive connectivity during ongoing mentation

“…On the other hand, an all-to-all positive inter-areal connectivity has the lowest occurrence probability and high similarity to the connectivity matrices preceding MB reports. This global inter-region positive connectivity has been previously reported to occur with high prevalence in NREM slow-wave sleep 28,29 . In this sleep stage, the brain's slow wave activity reflects minimal neuronal firing.…”

Isoflurane-Induced Burst Suppression Is a Thalamus-Modulated, Focal-Onset Rhythm With Persistent Local Asynchrony and Variable Propagation Patterns in Rats

“…The brain rhythm presented in this study, by adopting the definition proposed by Steriades et al, can also be labeled as "slow oscillation, " with the neurons cycling between on and off states at a frequency less than 1 Hz (Steriade et al, 1993). Indeed, rodent studies that employed isoflurane to model slow oscillation have revealed similar spatiotemporal properties of cortical dynamics (Sanchez-Vives, 2020), including focal onset followed by cortex-wide propagation waves (Stroh et al, 2013;Aedo-Jury et al, 2020). However, in clinical anesthesiology, "slow oscillation" has been specifically reserved to label an EEG pattern that is qualitatively different from the rhythm presented in this study (Purdon et al, 2015).…”

The (Un)Conscious Mouse as a Model for Human Brain Functions: Key Principles of Anesthesia and Their Impact on Translational Neuroimaging

“…On the other hand, burst suppression and slow waves that propagate unabated across the cortical surface (see ''Crossing the Borders: GABAergic Slow Waves and Burst Suppression'' section) promote FC that can span extensive cortical networks in humans and rats, occasionally reaching into the basal ganglia and thalamic structures (Liu et al, 2011(Liu et al, , 2013bGolkowski et al, 2017;Schwalm et al, 2017;Aedo-Jury et al, 2019). Isoflurane concentrations as low as 1.3% in ventilated rats were found sufficient to induce highly synchronized large-scale FC patterns in fronto-cortical and striatal regions, and to suppress most thalamo-cortical and intra-subcortical connections (Figure 8C; Paasonen et al, 2018).…”

“…Although blurred in temporal resolution, this technique permits the assessment of dynamic whole-brain signatures based on FC. Combining Ca 2+ imaging or electrophysiology with fMRI (Thompson et al, 2013;Keilholz, 2014;Schmid et al, 2016;Schwalm et al, 2017;Lurie et al, 2018;Schlegel et al, 2018;Matsui et al, 2018;Aedo-Jury et al, 2019;van Alst et al, 2019), these signatures can be linked to the cortical states, and hence be employed to determine the nature and level of sedation (see ''Brain States Under Anesthesia'' and ''Limitations in Maintaining Stable Brain States'' sections).…”

“…Such flanking approaches of FC have previously been shown to reveal valuable information on anesthetic effects on murine fMRI tasks (Nasrallah et al, 2014b;Schroeter et al, 2017;Shim et al, 2018). More advanced FC applications have been used to track spatial and temporal aspects of intermediate brain state transitions as a function of anesthesia in mice (Grandjean et al, 2017a;Gutierrez-Barragan et al, 2018) and rats (Schwalm et al, 2017;Aedo-Jury et al, 2019). Finally, the relations of FC and its structural scaffold have been already used to formulate restingstate dynamics as cortical signatures of anesthesia in monkeys (Barttfeld et al, 2015;Uhrig et al, 2018) and humans (Roberts et al, 2019).…”