Vascular and neuronal effects of general anesthesia on the brain: An fMRI study

Abstract Background and Purpose A number of functional magnetic resonance imaging (fMRI) studies rely on application of anesthetic agents during scanning that can modulate and complicate interpretation of the measured hemodynamic blood oxygenation level‐dependent (BOLD) response. The purpose of the present study was to investigate the effect of general anesthesia on two main components of BOLD signal including neuronal activity and vascular response. Methods Breath‐holding (BH) fMRI was conducted in wakefulness and under anesthesia states in 9 patients with drug‐resistant epilepsy who needed to get scanned under anesthesia during laser interstitial thermal therapy. BOLD and BOLD cerebrovascular reactivity (BOLD‐CVR) maps were compared using t ‐test between two states to assess the effect of anesthesia on neuronal activity and vascular factors ( p < .05). Results Overall, our findings revealed an increase in BOLD‐CVR and decrease in BOLD response under anesthesia in several brain regions. The results proposed that the modulatory mechanism of anesthetics on neuronal and vascular components of BOLD signal may work in different ways. Conclusion This experiment for the first human study showed that anesthesia may play an important role in dissociation between neuronal and vascular responses contributed to hemodynamic BOLD signal using BH fMRI imaging that may assist the implication of general anesthesia and interpretation of outcomes in clinical setting.