Rising-frequency chirp stimuli effectively enhance the amplitude and shorten the latency of 40-hz auditory steady-state response.

Objective: To evaluate the effects of changes in group delay from a click signal to a chirp signal on the 40-Hz Auditory Steady-State Response (ASSR) using magnetoencephalography (MEG).
Design: In this study, each participant was exposed to 10 chirp signals with gradually varying group delays from the CE chirp to the click at 60 dB nHL. The 40-Hz ASSR was measured using MEG and evaluated for amplitude and latency in the maximum signal channel at the click signal measured in each hemisphere.
Study Sample: Ten native Japanese speakers without histories of auditory diseases (8 males and 2 females, mean age 28.4 ± 5.70 years) participated in the study.
Results: The 40-Hz ASSR amplitude increased with the group delay of the chirp signal, was most efficient with the CE-chirp (longest group delay) and was significantly larger in the contralateral hemisphere for the CE-chirp than with the click signal. No significant differences were observed in ipsilateral hemispheres. The latency of the 40-Hz ASSR decreased as the group delay of the chirp signal increased.
Conclusions: This study demonstrated that chirp signals, particularly the CE chirp, are more efficient than click signals in eliciting a 40-Hz ASSR, especially in the contralateral hemisphere.