Nociceptive stimuli can induce a transient suppression of electroencephalographic oscillations in the alpha frequency band (ie, alpha event-related desynchronization, α-ERD). Here we investigated whether α-ERD could be functionally distinguished in 2 temporally and spatially segregated subcomponents as suggested by previous studies. In addition, we tested whether the degree of dependence of nociceptive-induced α-ERD magnitude on the prestimulus α-power would have been larger than the degree of dependence on the poststimulus α-power. Our findings confirmed the dissociation between a sensory-related α-ERD maximally distributed over contralateral central electrodes, and a task-related α-ERD (possibly affected by motor-related activity), maximally distributed at posterior parietal and occipital electrodes. The cortical sources of these activities were estimated to be located at the level of sensorimotor and bilateral occipital cortices, respectively. Importantly, the time course of the α-ERD revealed that functional segregation emerged only at late latencies (400 to 750 ms) whereas topographic similarity was observed at earlier latencies (250 to 350 ms). Furthermore, the nociceptive-induced α-ERD magnitude was significantly more dependent on prestimulus than poststimulus α-power. Altogether these findings provide direct evidence that the nociceptive-induced α-ERD reflects the summation of sensory-related and task-related cortical processes, and that prestimulus fluctuations can remarkably influence the non-phase-locked nociceptive α-ERD.
PERSPECTIVE: Present results extend the functional understanding of α-oscillation suppression during pain perception and demonstrate the influence of prestimulus variability on this cortical phenomenon. This work has the potential to guide pain clinicians in a more accurate interpretation on physiological and psychological modulations of α-oscillations.