ABSTRACT
EPs can be extracted from the background EEG if subjects are exposed to repeated brief sensory stimuli. For standard neurological applications, auditory, somatosensory, and visual stimuli are the most important. e corresponding specic EPs are called AEPs (auditory evoked potentials), SEPs (somatosensory evoked potentials), and VEPs (visual evoked potentials), respectively. e most common methods of stimulation are (1) presenting auditory clicks via earphones (AEP), (2) presenting brief electrical pulses to peripheral sensory nerves such as the median or the tibial nerve, and (3) presenting inverting checkerboard patterns on a computer screen (VEP). Further modalities, involving olfactory or thermal stimuli, for example, will not be discussed here. Dierent subtypes of AEP and SEP can be observed with dierent latencies aer stimulus onset. In this chapter, we focus on the earliest responses known as the brainstem AEP (BAEP, brainstem auditory evoked potential) and the early SEP. ere are later AEP and SEP components, but these reect higher processing stages and have gained less importance in everyday neurological examination. e required frequency of repeated stimulus presentation strongly varies with modality and ranges from about 1 Hz for VEPs to 2−3 Hz for SEPs, up to 10−20 Hz for BAEPs.
