Distraction affects frontal alpha rhythms related to expectancy of pain: An EEG study

previous electroencephalographic (EEG) evidence has shown event-related desynchronization (ERD) of alpha rhythms before predictable painful stimuli, as a possible neural concomitant of attentional preparatory processes (babiloni, c., brancucci, a., babiloni, f., capotosto, p., carducci,f, cincotti, f., arendt-nielsen, l., chen, a.c., rossini, P.M., 2003. anticipatory cortical responses during the expectancy of a predictable painful stimulation. a high-resolution electroencephalography study. eur. j. neurosci. 18 (6) 1692-700). this study tested the hypothesis that alpha ERD before predictable painful stimuli is reduced as an effect of distraction. a visual warning stimulus preceded a laser painful stimulation, which was strictly followed by visual imperative stimuli. In the pain (control) condition, no task was required after the imperative stimuli. In the pain + movement condition, subjects had to perform a movement of the right index finger. In the pain + cognition condition, they had to mentally perform an arithmetical task. EEG data were recorded in 10 subjects from 30 electrodes. artifact-free recordings were spatially enhanced by surface Laplacian transformation. alpha ERD was computed at three alpha sub-bands according to subjects' individual alpha frequency peak (i.e., about 6-8 Hz, 8-10 Hz, 10-12 Hz). compared to the control condition, the subjects reported a significantly lower stimulus intensity perception and unpleasantness in the pain + movement and pain + cognition conditions. In addition, there was a cancellation of the alpha 3 ERD (i.e., about 10-12 Hz) in pain + cognition condition and even a generation of a statistically significant alpha 3 ERS in pain + movement condition. these effects were maximum over fronto-central midline. these results suggest that distraction during the expectancy of pain is related to a reduced neural desynchronization of fronto-central midline alpha rhythms (i.e., reduced cortical activation) towards an overt hyper-synchronization (cortical idling).