Short-term habituation of auditory evoked potential and neuromagnetic field components in dependence of the interstimulus interval.

Repeated auditory stimulation results usually in a response decrement of event-related potential components. In the current study, we investigated the impact of the interstimulus interval (ISI) on the response decrement. Healthy subjects were stimulated with trains of five tones, with an ISI of 600, 1,200, or 1,800 ms within the trains. Auditory evoked potentials (AEP) were recorded from the vertex, as well as neuromagnetic auditory evoked fields (AEF) from the left temporal region. Stimulus repetition led to a response decrement for the studied AEP components (N100 and P200) and AEF components (N100m and P200m). However, for all used ISIs, there was no further response decrement after the 2nd stimulus. The ISI affected only the magnitude but not the kind of the response decrement. No evidence for a gradual response decrement was revealed at any used ISI. This finding indicates that the response decrement is probably due to the refractoriness of cell assemblies involved in the generation of AEP and AEF components, rather than the result of a genuine habituation process. The finding questions habituation as the mechanism behind short-term decrements of AEP/AEF components.