Experiences in Computer Audiometry (ECoG and ERA)

By the ear-drum arrangement of electrode action potentials of the 8th nerve may be recorded down to the threshold intensities of click stimuli. A decrease in the amplitude of these potentials was observed with ipsilateral presentation of a masking noise. Contralateral conditioning sound stimulation caused either an increase or a decrease of click-evoked action potentials. The increase was observed with intensities of conditioning stimuli exceeding 50-60 dB SL, whereas the decrease was stated at higher stimulation levels. The former effect was ascribed to the activity of the olivo-cochlear fibres and the latter effect to reflex contraction of the middle ear muscles

Scalp-derived slow auditory evoked responses were studied in different conditions of sound stimulation. The peak latencies of these responses were longer, and the peak amplitude was lower for tone bursts as compared to effects of intensity-modulated tonal stimuli. With equal intensities of tonal increments, the peak latencies of derived responses were shorter and the amplitude was greater at higher steady-tone levels. In most cases, there was a close correspondence of the objective and subjective thresholds for both tone bursts and intensity-modulated stimuli. On the grounds of data obtained, the problems related to cross-examination and control test procedures during computer audiometry are discussed