The effect of stimulus envelope shape on the auditory steady-state response

Auditory steady-state responses (ASSRs) are auditory evoked potentials that reflect phase-locked neuralactivity to periodic stimuli. ASSRs are often evoked by tones with a modulated envelope, with sinusoidalenvelopes being most common. However, it is unclear if and how the shape of the envelope affects ASSRresponses. In this study, we used various trapezoidal modulated tones to evoke ASSRs (modulationfrequency¼40 Hz) and studied the effect of four envelope parameters: attack time, hold time, decaytime and off time. ASSR measurements in 20 normal hearing subjects showed that envelope shapesignificantly influenced responses: increased off time and/or increased decay time led to responses witha larger signal-to-noise-ratio (SNR). Response phase delay was significantly influenced by attack timeand to a lesser degree by off time. We also simulated neural population responses that approximateASSRs with a model of the auditory periphery (Bruce et al. 2018). The modulation depth of the simulatedresponses, i.e. the difference between maximum and minimumfiring rate, correlated highly with theresponse SNRs found in the ASSR measurements. Longer decay time and off time enhanced the modu-lation depth both by decreasing the minimumfiring rate and by increasing the maximumfiring rate. Inconclusion, custom envelopes with long decay and off time provide larger response SNRs and the benefitover the commonly used sinusoidal envelope was in the range of several dB.

Jaar van publicatie:2019