Relationships of Ongoing Activity, Stimulus Response Variability, and Behavioral Performance in the Human Brain

The question of interaction between ongoing neuronal activity and evoked responses has been addressedfor different species, sensory systems and measurement modalities. Among other findings, there is con-verging evidence for an interaction of occipital alpha-rhythm amplitudewith the visual evoked potential.Here, we test the hypothesis that the modulatory role of an ongoing rhythmmight not be confined to thevisual system and the occipital alpha rhythm, but instead may be generalized to other sensory systems.Using an online EEG analysis approach, we investigated the influence of the Rolandic alpha-rhythm onthe somatosensory evoked potential (SEP). We triggered vibrotactile stimulation during periods of highRolandic alpha-rhythm amplitude. Analysis revealed significant effects of pre-stimulus Rolandic alphaamplitude on the amplitude of the N140 and P260 components of the SEP, known to be linked to cogni-tive processing, but not on early sensory components. The N140–P260 complex shows a different focusin topography than the early sensory components and the pre-stimulus Rolandic alpha rhythm. Theseresults indicate an involvement of Rolandic alpha-rhythm in higher cognitive processing. Inmore generalterms – and in the context of similar studies in the visual system – our findings suggest that modulationof late EP components by ongoing rhythms might be a characteristic and possibly universal feature ofsensory systems.© 2009 Elsevier B.V. All rights reserved.