Event-Related Potentials (ERPs) – An Up-to-Date Technique in Cognitive Neurosciences

Non-invasively recorded ERPs provide a superb temporal resolution that goes far beyond other up-to-date techniques such as fMRI, PET or TMS. Beyond that, in the auditory modality, the ERP technique offers the unique opportunity to differentiate between attentive behavioral processing and preattentive stimulus detection such as during intraoperative sedation. The current report summarizes a series of cognitive studies that, on the one hand, emphasize time-dependent cognitive functioning in the auditory domain and on the other hand, provide an insight into cognitive functioning where other techniques fail due to logistical reasons [i.e., in cochlear implant (CI) users or during anesthesia]. A first line of evidence comes from studies in awake healthy subjects. It was shown that even a 300µs interaural stimulus delay causes a preattentive cortical ERP that indicates automatic discriminative auditory processing. Moreover, there was evidence for a fast preattentive auditory discrimination within the first stimuli of a complex auditory sequence. In contrast, electrophysiological indicators of attentive stimulus selection processes were delayed by several seconds, thus indicating a dynamic function for attention-dependent auditory processing, whereas preattentive discrimination resembles a preset-like function. Several studies were conducted during anesthesia. It became clear that cortical preattentive auditory discrimination still operates during sevofluran sedation. Beyond that, meaningful auditory novel events (i.e., dog barks) led to a cortical ERP that has formerly been linked to an attentive orienting reaction in awake subjects. Thus, we obtained evidence for a more detailed intraoperative auditory perception than was previously assumed. There is a strong need for objective evaluation in post-implant rehabilitation for CI users, but magnetic interference contraindicates fMRI or TMS. ERPs indicated that CI users preattentively monitor even weak stimulus changes that fail to activate attentively guided selection responses. However, preliminary results indicate that CI users differ from normal controls by means of amplified occipital scalp activation in an auditory discrimination task, thus pointing to a recruitment of the visual cortex for distinctive processing in the auditory modality.