Significance of Non-phase Locked Oscillatory Brain Activity in Response to Noxious Stimuli.
BACKGROUND
Although current pain-evoked electroencephalographic (EEG) studies provide valuable information regarding human brain regions involved in pain, they have mostly considered neuronal responses which oscillate in phase following a painful event. In many instances, cortical neurons respond by generating bursts of activity that are slightly out of phase from trial-to-trial. These types of activity bursts are known as induced brain responses. The significance of induced brain responses to pain is still unknown.


METHODS
In this study, 23 healthy subjects were given both non-painful and painful transcutaneous electrical stimulations in separate testing blocks (stimulation strength was kept constant within blocks). Subjective intensity was rated using a numerical rating scale, while cerebral activity tied to each stimulation was measured using EEG recordings. Induced brain responses were identified using a time frequency wavelet transform applied to average-removed single trials.


RESULTS
Results showed a pain-specific burst of induced theta activity occurring between 180 and 500 ms post-shock onset. Source current density estimations located this activity within the dorsolateral prefrontal cortex (DLPFC, bilaterally), however, only right DLPFC activity predicted a decrease in subjective pain as testing progressed.


CONCLUSIONS
This finding suggests that non-phase locked neuronal responses in the right DLPFC contribute to the endogenous attenuation of pain through time.


CONCLUSIONS
This article presents neuroimaging findings demonstrating that, in response to pain, non-phase locked bursts of theta activity located in the right dorsolateral prefrontal cortex are associated with a progressive decrease in subjective pain intensity, which has potentially important implications regarding how humans endogenously control their experiences of pain.
1School of Rehabilitation,Université de Sherbrooke,Sherbrooke, QC,Canada,J1H 5N4.
Raphaël
R
Dufort Rouleau
1School of Rehabilitation,Université de Sherbrooke,Sherbrooke, QC,Canada,J1H 5N4.
Lydia
L
Lagrandeur
1School of Rehabilitation,Université de Sherbrooke,Sherbrooke, QC,Canada,J1H 5N4.
Kathya
K
Daigle
4Department of Psychology,Faculty of Arts and Science,Université de Sherbrooke,Sherbrooke, QC,Canada,J1K 2R1.
Dominique
D
Lorrain
1School of Rehabilitation,Université de Sherbrooke,Sherbrooke, QC,Canada,J1H 5N4.
Guillaume
G
Léonard
2Department of Diagnostic Radiology,Université de Sherbrooke,Sherbrooke, QC,Canada,J1H 5N4.
Kevin
K
Whittingstall
1School of Rehabilitation,Université de Sherbrooke,Sherbrooke, QC,Canada,J1H 5N4.
Philippe
P
Goffaux
D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D004558:Electric Stimulation / Q000379:methods; D004569:Electroencephalography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D059906:Neuroimaging; D009474:Neurons / Q000378:metabolism; D010146:Pain / Q000175:diagnosis / Q000503:physiopathology; D055815:Young Adult
Dorsolateral prefrontal cortex; EEG; Induced brain activity; PAIN; Theta