title: Is sedation-induced BOLD fMRI low-frequency fluctuation increase mediated by increased motion?
abstract: 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.
authors.affiliation: Academic Radiology, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, UK, jaroslav.hlinka@gmail.com.
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Hlinka
authors.forename: Charilaos
authors.initials: C
authors.lastname: Alexakis
authors.forename: Jonathan G
authors.initials: JG
authors.lastname: Hardman
authors.forename: Quazi
authors.initials: Q
authors.lastname: Siddiqui
authors.forename: Dorothee P
authors.initials: DP
authors.lastname: Auer
mesh_terms: 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
chemical_list: D006993:Hypnotics and Sedatives