Multivariate analysis of single-sweep evoked brain potentials for pharmaco-electroencephalography.
OBJECTIVE
Current findings on altered evoked potentials (EPs) caused by morphine are based on common alterations for a group of subjects after drug administration. However, this ignores the analysis of individual responses, which may explain the clinical differences in efficacy. Therefore, we explored the individual responses to morphine in terms of the altered single-sweep characteristics in a placebo-controlled crossover study. To account for multifactorial mechanisms, several characteristics were assessed simultaneously by multivariate pattern analysis (MVPA).


METHODS
EPs were recorded from 62 channels and obtained before and after morphine and placebo administration during repeated electrical stimulations of the oesophagus in 12 healthy males. Additionally, the pain detection threshold was recorded to reflect the subjective analgesic effect in each subject. The characteristics of the sweeps were extracted by a multivariate matching pursuit algorithm with Gabor atoms implemented with a variable amplitude and constant phase across the sweeps. The single-sweep amplitudes were used as input to an MVPA algorithm to discriminate individual responses. The accuracy of the MVPA for each individual subject was used for correlation analysis of the analgesic effect.


RESULTS
The mean classification accuracy when discriminating pre- and posttreatment morphine responses was 72% (p = 0.01). The individual classification accuracy was positively correlated to the analgesic effect of morphine (p = 0.03). Furthermore, the 2 posttreatment responses were classified and validated by the classification of the 2 pretreatment responses (p = 0.001).


CONCLUSIONS
The alterations in the single-sweep EPs after morphine reflect the analgesic effect. The MVPA approach is a novel methodology for monitoring the individual efficacy of analgesics.
Department of Gastroenterology and Hepatology, Mech-Sense, Aalborg University Hospital, Aalborg, Denmark.
Carina
C
Graversen
Anne Estrup
AE
Olesen
Camilla
C
Staahl
Asbjørn Mohr
AM
Drewes
Dario
D
Farina
D000328:Adult; D000701:Analgesics, Opioid / Q000008:administration & dosage*; D002540:Cerebral Cortex / Q000187:drug effects* / Q000502:physiology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004558:Electric Stimulation; D004569:Electroencephalography / Q000379:methods*; D004947:Esophagus / Q000502:physiology; D005071:Evoked Potentials / Q000187:drug effects*; D006801:Humans; D007206:Individuality; D008297:Male; D008875:Middle Aged; D009020:Morphine / Q000008:administration & dosage*; D015999:Multivariate Analysis; D017288:Pain Threshold / Q000187:drug effects; D012815:Signal Processing, Computer-Assisted
D000701:Analgesics, Opioid; D009020:Morphine