The influences of contralateral recording on auditory steady-state response (ASSR) thresholds in normal hearing adults

The Auditory steady-state response (ASSR) is a scalp-recorded auditory evoked potential that is captured by far-field electrodes. It is elicited by periodic, transient or modulated acoustic stimuli. The possible effects of shifting the response recording channel on 40Hz ASSR thresholds and their recording times were evaluated and compared in this study. Thirty subjects with normal hearing (thresholds of 500 to 4000 Hz ≤ 15 dB HL), with ages ranged from 18 to 30 years, gave written informed consent were enrolled in this study. Right-handed subjects were selected. New chirp stimuli using a two-channel EP recording system, the Eclipse, were presented only to the right ear via insert earphones. Thresholds for central frequencies (0.5, 1, 2 and 4 KHz) and their total recording time in the ipsilateral- (recording from the right-EEG channel) and contralateral-array (recording from the left-EEG channel) relative to the stimulus ear were evaluated at 40Hz repetition rate. The mean contralateral ASSR thresholds to 40 Hz rate were about 2.25 dB HL better than the ipsilateral mean (that only significant at 2000 Hz central frequency; P.value=0.03). Also, the mean contralateral ASSR recording time was about 5.31 minutes better than the ipsilateral mean (Pvalue=0.0005). In awaking adults with normal hearing, the contralateral 40Hz ASSR is slightly more accurate in threshold estimation and shorter in recording time than the ipsilateral one. This method is promising despite these differences may clinically be significant.