Is sedation-induced BOLD fMRI low-frequency fluctuation increase mediated by increased motion?
OBJECTIVE
Increases in low-frequency fluctuations (LFF, 0.01-0.1 Hz) of BOLD fMRI signal were observed during sedation and sleep. We tested the hypothesis that sedation-induced LFF increases may be mediated by increased head motion likely associated with these brain states.


METHODS
Twenty healthy volunteers were scanned in resting-state baseline and (15 thereof) in midazolam sedation condition. After standard preprocessing, LFF power was computed from average time series from 14 ROIs representing 5 functional networks (visual, motor, auditory, default mode, dorsal attentional). We assessed the effects of sedation on LFF and indirect effects of head motion (mean relative displacement) using mediation analysis.


RESULTS
Sedation increased LFF power with the indirect effect of motion on sedation-induced LFF significant for all networks. Global mean corrected data showed similar but weaker results: significant total effect for auditory, motor and visual; significant mediation for auditory and motor networks. Motion was strongly correlated with LFF even at baseline. Reported results were significant at p < 0.05.


CONCLUSIONS
The study confirms that conscious sedation induces LFF increase, but demonstrates that this effect is mediated by increased head motion. Hence, caution in design and interpretation is recommended for studies comparing subjects or conditions differently predisposing to head motion.
Hlinka
Jaroslav
J
Academic Radiology, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, UK, jaroslav.hlinka@gmail.com.
Alexakis
Charilaos
C
Hardman
Jonathan G
JG
Siddiqui
Quazi
Q
Auer
Dorothee P
DP
D001303:Auditory Cortex / Q000502:physiology; D006257:Head / Q000502:physiology; D006801:Humans; D006993:Hypnotics and Sedatives; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009038:Motion; D020671:Posterior Horn Cells / Q000502:physiology; D017397:Prefrontal Cortex / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D012016:Reference Values; D012890:Sleep / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology
D006993:Hypnotics and Sedatives