Neural origin of spontaneous hemodynamic fluctuations in rats under burst-suppression anesthesia condition.
Spontaneous hemodynamic signals fluctuate coherently within many resting-brain functional networks not only in awake humans and lightly anesthetized primates but also in animals under deep anesthesia characterized by burst-suppression electroencephalogram (EEG) activity and unconsciousness. To understand the neural origin of spontaneous hemodynamic fluctuations under such a deep anesthesia state, epidural EEG and cerebral blood flow (CBF) were simultaneously recorded from the bilateral somatosensory cortical regions of rats with isoflurane-induced burst-suppression EEG activity. Strong neurovascular coupling was observed between spontaneous EEG "bursts" and CBF "bumps," both of which were also highly synchronized across the 2 hemispheres. Functional magnetic resonance imaging (fMRI) was used to image spontaneous blood oxygen level-dependent (BOLD) signals under the same anesthesia conditions and showed similar BOLD "bumps" and dependence on anesthesia depth as the CBF signals. The spatiotemporal BOLD correlations indicate a strong but less-specific coherent network covering a wide range of cortical regions. The overall findings reveal that the spontaneous CBF/BOLD fluctuations under unconscious burst-suppression anesthesia conditions originate mainly from underlying neural activity. They provide insights into the neurophysiological basis for the use of BOLD- and CBF-based fMRI signals for noninvasively imaging spontaneous and synchronous brain activity under various brain states.
Liu
Xiao
X
Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN 55455, USA.
Zhu
Xiao-Hong
XH
Zhang
Yi
Y
Chen
Wei
W
D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001931:Brain Mapping; D058256:Brain Waves / Q000187:drug effects*; D002560:Cerebrovascular Circulation / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004569:Electroencephalography / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007530:Isoflurane / Q000494:pharmacology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects; D017711:Nonlinear Dynamics; D010100:Oxygen / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley; D013003:Somatosensory Cortex / Q000098:blood supply / Q000187:drug effects / Q000502:physiology; D013223:Statistics as Topic
D018685:Anesthetics, Inhalation; D007530:Isoflurane; D010100:Oxygen