Propofol anesthesia reduces Lempel-Ziv complexity of spontaneous brain activity in rats.
Consciousness is thought to scale with brain complexity, and it may be diminished in anesthesia. Lempel-Ziv complexity (LZC) of field potentials has been shown to be a promising measure of the level of consciousness in anesthetized human subjects, neurological patients, and across the sleep-wake states in rats. Whether this relationship holds for intrinsic networks obtained by functional brain imaging has not been tested. To fill this gap of knowledge, we estimated LZC from large-scale dynamic analysis of functional magnetic resonance images (fMRI) in conscious sedated and unconscious anesthetized rats. Blood oxygen dependent (BOLD) signals were obtained from 30-min whole-brain resting-state scans while the anesthetic propofol was infused intravenously at constant infusion rates of 20mg/kg/h (conscious sedated) and 40mg/kg/h (unconscious). Dynamic brain networks were defined at voxel level by sliding window analysis of regional homogeneity (ReHo) of the BOLD signal. From scans performed at low to high propofol dose, the LZC was significantly reduced by 110%. The results suggest that the difference in LZC between conscious sedated and anesthetized unconscious subjects is conserved in rats and this effect is detectable in large-scale brain network obtained from fMRI.
Department of Anesthesiology and Center for Consciousness Science, University of Michigan, Ann Arbor, MI, United States. Electronic address: ahudetz@med.umich.edu.
Anthony G
AG
Hudetz
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States.
Xiping
X
Liu
Department of Psychiatry, University of Wisconsin-Madison, Madison, WI, United States.
Siveshigan
S
Pillay
Department of Neurology, University of Wisconsin-Madison, Madison, WI, United States.
Melanie
M
Boly
Department of Psychiatry, University of Wisconsin-Madison, Madison, WI, United States.
Giulio
G
Tononi
D018686:Anesthetics, Intravenous / Q000008:administration & dosage*; D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000502:physiology*; D001931:Brain Mapping; D003243:Consciousness / Q000187:drug effects* / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D015742:Propofol / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley
D018686:Anesthetics, Intravenous; D015742:Propofol