UBC Theses and Dissertations
Efficiency of single versus multiple stimuli for 40-Hz auditory steady-state responses Fontaine, Charles Maurice
Auditory steady-state responses (ASSRs) were elicited in normal-hearing, awake adults to 500-, 1000-, 2000-, and 4000-Hz carrier frequencies amplitude-modulated in the 40-Hz range in three conditions: individually [monotic-single(MS)--one carrier], simultaneously in one ear [monotic-multiple(MM)--total four carriers], and simultaneously in both ears [dichotic-multiple(DM)--total eight carriers], at intensities of 30, 55, and 80 dBHL. In general, response amplitudes (collapsed across frequency and intensity) decreased with increasing number of simultaneous stimuli, and were 270, 155, and 107 nV for MS, MM and DM conditions, respectively. Amplitude decreases at 30 dBHL, however, were not significant. Relative efficiency (relative test efficiency of multiple versus single conditions) increased from single- to multiple-stimulus conditions, but there was no significant difference between MM and DM conditions. Mean relative efficiencies were 1.00, 1.38, and 1.39 for MS, MM and DM conditions, respectively. At 80 dBHL, there was no significant increase in relative efficiency with multiple stimuli. These results suggest that 40-Hz ASSRs to low and moderate intensities are most efficiently assessed using monotic-multiple stimuli, and that there may be little advantage to simultaneously stimulating both ears. High intensities might be more efficiently assessed using single stimuli.
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