Influence of repetition rate and pause upon the cortical potential evoked by various acoustic stimulation in man (author's transl)

Abstract

In agreement with earlier experiments an increase of amplitude of the medium components (80-250 ms: Non-Pon) with decreasing repetition rate or increasing interval between the stimuli (sinusoidal tones, white noise, craftsman noise) is observed. There is no influence of the variable intervals upon the off-effect, if sinusoidal tones and white noise are used. A small increase of the amplitude difference Noff-Poff results if bursts of craftsman noise are used for stimulation. The amplitude of a peak in the range 300-400 ms which can be regarded approximatively as the peak of the long lasting dc-component, related to the positive peak (Pon) around 200 ms shows also an increasing tendency if the interval between stimuli is enlarged. Pon itself is augmented if related to the preceding section before stimulus on-set. Therefore the increase of the slow component expresses only an increase of the positive component Pon or is based upon a dc-shift which is added to the preceding section as well as to the range of the dc-component beginning around 300 ms after stimulus on-set. Using only sinusoidal tones a reduction takes place of the amplitude of the potential evoked by a tone of constant duration if the silent pauses are smaller than 2500 ms. If the pause preceding a tone of constant duration is reduced down to 300 ms the decrease of the amplitude is around 50-60%. The amplitude of the off-effect however is not affected. Only if related on the positive component Pon the slow component shows a small decrease. If related on the preceding section there is no change caused by different pauses preceding a tone of constant duration. Both, the latency of on- and off-components is also not influenced by the variable pause. Only the peak of the slow component shows a shift in the way that there is a maximum if the duration of the pause corresponds to half of the interval. In this case there is also a clear maximum of the amplitude of the potential evoked by the tone of variable duration. The results throw some light upon the different origin of the components of the evoked response and the overlapping of dc-shifts.