Altered local coherence in the default mode network due to sevoflurane anesthesia

Abstract

Recently we introduced a robust measure, integrated local correlation (ILC), of local connectivity in the brain using fMRI data which reflects the temporal correlation of brain activity in every voxel neighborhood. The current work studies ILC in fMRI data obtained in the absence and presence of sevoflurane anesthesia (0%, 2%, and 1% end-tidal concentration, respectively) administered to healthy volunteers. ILC was determined specifically in regions of the default mode network (DMN) to address local changes in each state. In addition, a potential confound in analyses based on correlations due to signal-to-noise variations was addressed by wavelet denoising. This accommodated decreases in signal power commonly seen during anesthesia without artificially reducing derived correlations. Results showed that ILC was significantly reduced in the entire DMN during 2% sevoflurane yet recovered in the posterior and anterior cingulate cortices as well as inferior parietal cortex during 1% sevoflurane. By contrast, ILC remained attenuated prefrontally in the 1% condition, which indicates uncoupling of the frontal areas of DMN during light anesthesia. These results confirm widespread anesthetic-induced cortical suppression but also demonstrate that the local connectivity of the prefrontal cortex is rapidly reduced by sevoflurane. It remains to be seen whether these alterations arise locally as a direct consequence of anesthetic action on local neurons or are driven by distant changes in oscillations and activity elsewhere in the brain.

The Influence of Carbon Dioxide on Brain Activity and Metabolism in Conscious Humans

“…The CO 2 -induced reduction in sensorimotor connectivity is also in good agreement with a previous report by Biswal et al (1997). In our study, we have taken special precaution to minimize the influence of basal vascular state on BOLD signals, which were not accounted for in previous studies comparing fcMRI data across physiologic states (Biswal et al, 1997;Deshpande et al, 2010;Greicius et al, 2008;Horovitz et al, 2009). We have used visual-evoked fMRI signal as a reference with the assumption that the alterations in fMRI signal is solely due to a change in vascular state (Jones et al, 2005;Zappe et al, 2008a).…”

Propofol-Induced Frontal Cortex Disconnection: A Study of Resting-State Networks, Total Brain Connectivity, and Mean BOLD Signal Oscillation Frequencies

“…Disconnection of frontal DMN regions has also been observed in sevoflurane-induced sedation (Deshpande et al, 2010;Palanca et al, 2015), non-REM sleep (Horovitz et al, 2009;Samann et al, 2011), and MCS, VS/UWS and coma (Soddu et al, 2012;Vanhaudenhuyse et al, 2010). Interestingly, we found that a mesopontine area was also among the regions decreasing in the total brain connectivity map.…”

Functional Magnetic Resonance Imaging of the Domestic Dog: Research, Methodology, and Conceptual Issues

“…Seed-based and independent component analyses (ICA) were used and identified dissociation between the anterior and posterior regions of the DMN. Further, while this dissociation was seen for both awake and anesthetized dogs, the degree of dissociation was higher in anesthetized dogs in keeping with prior human results that anesthesia modulated the structure of resting state networks such as the DMN (Deshpande, Kerssens, Sebel, & Hu, 2010). In all, this investigation into resting state fMRI with dogs revealed comparative differences in the traits of the DMN between humans/monkeys and dogs, namely localized anterior and posterior subnetworks in dogs and a connected DMN in humans.…”