Effect of Changes in Stimulus Frequency and Intensity on Habituation of the Human Vertex Potential

Interposed between periodic presentations of a 1000‐Hz tone were stimuli of different frequencies and intensities. The amplitude of the vertex (V) potential to the 1000‐Hz tone became larger as the frequency of the intervening stimuli departed progressively from 1000 Hz. It also became larger when the sensation level of the 1000‐Hz tone was raised progressively above that of the intervening stimuli. The notion that changes in stimulus frequency and increases in stimulus intensity activate new neural units was adopted to explain the data. It was asserted that habituation of the V potential is greatest when the same neural units are repeatedly activated and least when new neural units are brought into play.