Abstract
Fast-rising sensory events evoke a series of functionally heterogeneous event-related potentials (ERPs), which reflect the activity of both modality-specific and supramodal cortical generators overlapping in time and space. When stimuli are delivered at long and variable intervals (10-15 seconds), supramodal components appear as a large negative-positive biphasic deflection maximal at the scalp vertex (vertex wave) and dominate over modality-specific components. Stimulus repetition at 1 Hz induces a strong habituation of these supramodal components, which largely reflect stimulus saliency and behavioural relevance. However, the effect of stimulus repetition on lateralized modality-specific components is less clear. To comprehensively characterize how the different ERP waves habituate over time, we recorded the ERPs elicited by 60 identical somatosensory stimuli (either non-nociceptive Aβ or nociceptive Aδ), delivered at 1 Hz to healthy human participants. We show that the well-described spatiotemporal sequence of ERP components elicited by the first stimulus of the series is largely preserved in the smaller-amplitude, habituated response elicited by the last stimuli of the series. We also modelled the single-trial amplitude of the vertex wave elicited by the 60 Aβ and Aδ stimuli, and observed that it decays monotonically, with a largest drop of response magnitude at the first stimulus repetition, followed by much smaller decreases in subsequent repetitions. Altogether, these observations indicate that the main ERP constituents are preserved even when contextual modulations reduce the behavioural-relevance of the eliciting stimuli.
Significance We comprehensively characterized the decay of event-related potentials (ERPs) elicited by identical fast-rising stimuli repeated at short and regular intervals (1Hz). Our observations indicate that, although response amplitude is reduced by stimulus repetition, the ERPs are obligatory contributed by both modality-specific lateralized components and supramodal vertex components. This indicates a fundamental and unavoidable property of the central nervous system: its sensitivity to respond to sudden changes in the environment with a transient synchronization of thalamocortical activity that manifests itself as widespread brain potentials detectable in the human EEG.