Abstract
Mechanisms of anesthetic drug-induced sedation and unconsciousness are still incompletely understood. Functional neuroimaging modalities provide a window to study brain function changes during anesthesia allowing us to explore the sequence of neuro-physiological changes associated with anesthesia. Cerebral perfusion change under an assumption of intact neurovascular coupling is an indicator of change in large-scale neural activity. In this experiment, we have investigated resting state cerebral blood flow (CBF) changes in the human brain during mild sedation, with propofol. Arterial spin labeling (ASL) provides a non-invasive, reliable, and robust means of measuring cerebral blood flow (CBF) and can therefore be used to investigate central drug effects. Mild propofol sedation-related CBF changes were studied at rest (n = 15), in a 3 T MR scanner using a PICORE-QUIPSS II ASL technique. CBF was reduced in bilateral paracingulate cortex, premotor cortex, Broca’s areas, right superior frontal gyrus and also the thalamus. This cerebral perfusion study demonstrates that propofol induces suppression of key cortical (frontal lobe) and subcortical (thalamus) regions during mild sedation.
Highlights
Mechanisms of anesthetic drug-induced sedation and unconsciousness are still incompletely understood
To test our regional hypotheses concerning areas commonly reported in studies of arousal, we calculated the paired t-test with a small volume family-wise error (FWE) correction (p < 0.05), within thalamus, brainstem, and a set of regions included in the default mode network (DMN) (Buckner et al, 2008)
We have used arterial spin labeling (ASL)-Functional magnetic resonance imaging (fMRI) to demonstrate that mild propofol sedation is associated with a reduction in cerebral blood flow (CBF) in some of the key cortical and subcortical areas involved in modulating consciousness while the blood flow in the brainstem and the DMN remains broadly unaffected
Summary
Mechanisms of anesthetic drug-induced sedation and unconsciousness are still incompletely understood. Techniques including Positron Emission Tomography and Blood Oxygen Level Dependent (BOLD) contrast-based Functional magnetic resonance imaging (fMRI) have been utilized to explore the neural correlates of anesthetic-related changes in consciousness and arousal. Recent improvements in arterial spin labeling (ASL) methodology, a measurement of tissue blood flow, render it practical to quantify pharmacological effects in the human brain. It is completely non-invasive, being based on an endogenous tracer (magnetically labeled arterial blood) and, since the perfusion signal is encoded in the difference between control and tagged images, it is minimally affected by baseline drift, making it suitable for long-term studies or those with low frequency changes. ASL-based techniques are, especially suited for physiological and pharmacological studies of brain activity
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