Abstract

Background: PET-fMRI have taught a great deal about brain dynamics asso- ciated with anesthetic unconsciousness(GA). However, this has not yet trans- lated into EEG clinical applications.These work follows 2 objectives: (a) determine a correspondence between EEG source analysis and changes described by imaging techniques during GA; (b) search for a scalp EEG correlate that mirrors common electrical/imaging changes. methods: 9 volunteers were studied (Cl Tr regNCT01962285).Propofol TCI was administered in a stepwise manner of 0.5mg/mL increases every 7 min- utes until loss of response to command (LOC), followed by two 0.5μg/mL steps up; emergence phase consisted of a 0.5μg/mL stepwise decrease until 0mg/mL. Propofol were sample at each step.EEG signals were obtained at 128 Hz acquisition rate using a 38 Ag/AgCl surface electrode cap . Recordings were analyzed of f-line using custom scripts in Igor Pro (WaveMetrics Inc) and eLORETA (electrical source analysis)(2); all epochs for analysis were band- pass filtered (0.01-30 Hz) and artifact-free. Twenty epochs of 1sec duration were used for eLORETA analysis and one 60sec epoch was used to calculate Power Spectral Density (PSD) and Coefficient of Variation (CV)(2). Results: Analysis were obtained for 19 common low impedance electrodes;all categories were compared to Basal condition. An evident β and (at higher Cp) α band “activation” in the precuneus, cuneus and posterior cingulate cortices is observed even before LOC; at the highest propofol Cp there is evident wide- spread δ waves. The process of step-wise reduction of propofol from Deep to return of command) did not follow the reverse order of induction. Both PSD and CV analysis of the 7 to 16 Hz band were able to dif ferentiate preLOC from postLOC conditions, more evidently in posterior midline electrodes (Oz better than Pz or Cz). Conclusions: (a) EEG source analysis confirms the involvement of precuneus, cuneus and posterior cingulate cortices (b) Two dif ferent signal analysis techniques allow to dif ferentiate preLOC from postLOC conditions when using the occipital midline electrode (Oz). References: 1. Philos Trans A Math Phys En