The augmenting/reducing phenomenon in the auditory evoked potential

Auditory evoked potentials (AEPs) were recorded to 4 intensities of tones (70, 80, 90, 100 dB) in 22 normal subjects. Augmenting (generally increasing amplitude with increasing stimulus intensity) and reducing (a levelling off or decrease in amplitude with increasing stimulus intensity) were found to occur at both central (Cz, C3, C4) and temporal (T3, T4) placements, regardless of which peak or peak-through measure was examined. There were generally low levels of agreement between central amplitude/intensity response patterns and those at temporal placements. An individual was seldom classified the same way (i.e. augmenter or reducer) when the augmenting or reducing was assessed using different AEP measures. These results suggest that in the AEP the suitability of the conventional definition and the validity of certain interpretations of augmenting/reducing are questionable.