Average evoked potentials and amplitude modulation.
Average auditory evoked potentials (AEPs) to amplitude modulated (AM) linear voltage ramps within a limited intensity range were investigated in a group of 4 subjects. Increasing linear voltage ramps evoked the familiar vertex potential; the average AEP to decreasing ramps was difficult to measure because of its small amplitude. The amplitude of the average AEP to increasing ramps depended on the tone that preceded it. The average amplitude was largest when the tone preceding the onset of the ramp was constant and decreased in amplitude when the slope of the preceding tone deviated from zero either in the positive or negative direction with the positive slope having the more marked attenuating effect. The standard deviation (S.D.) of the distributions of reaction times to stimulus onset correlated negatively with the average AEP amplitude. The attenuation of the averaged AEP appeared to be related to the uncertainty of the subjects as to when the various types of stimuli occurred. The above findings on AM ramp stimuli closely parrellel our previously reported findings on frequency modulated ramp stimuli.
D000161:Acoustic Stimulation; D000328:Adult; D005072:Evoked Potentials, Auditory; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011930:Reaction Time