Slow evoked cortical potentials from ten young normal-hearing subjects have been recorded as responses to linear frequency ramps of a continuous pure tone. Frequency changes from 10 to 500 Hz were studied; the rate of frequency change was varied from 0.02 to 50 kHz/s while the duration of the change was varied from 10 to 500 ms. The rate of frequency change was shown to have the greatest bearing on the responses except for frequency ramp durations below 50 ms and frequency changes below 50 Hz. The base frequencies (250-4000 Hz) and sound levels (20-80 dB HL) exerted an influence on the evoked responses that was qualitatively similar to their influence on behavioral thresholds. The direction of the frequency sweep had no significant influence on the evoked responses. A functional model is proposed in which the time derivate of the signal frequency is integrated with an adaptable integration time that is controlled by the rate of the frequency change.

No abstract

No abstract

The auditory sensitivity for detecting linear frequency sweeps of a continuous pure tone has been studied in ten young subjects with cochlear hearing loss. The mean thresholds were elevated by a factor of 2.8 as compared with a normal group over the whole range of ramp durations studied (10-500 msec). The results show that this elevation is most likely caused mainly by the cochlear lesion per se, other possible factors having only a minor effect. No clear correlations could be found between thresholds for frequency change and results of other pure tone audiometric tests. Such tests thus cannot predict a subject's frequency discrimination. Acfa Ololaryngol83

No abstract