Characteristics of the Deconvolved Transient AEP from 80 Hz Steady-State Responses to Amplitude Modulation...

This study aimed to validate the existence and investigate the characteristics of the transient responses from conventional auditory steady-state responses (ASSRs) using deconvolution methods capable of dealing with amplitude modulated (AM) stimulation. Conventional ASSRs to seven stimulus rates were recorded from 17 participants. A deconvolution method was selected and modified to accommodate the AM stimulation. The calculated responses were examined in terms of temporal features with respect to different combinations of stimulus rates. Stable transient responses consisting of early stage brainstem responses and middle latency responses were reconstructed consistently for all rate combinations, which indicates that the superposition hypothesis is applicable to the generation of approximately 80 Hz ASSRs evoked by AM tones (AM-ASSRs). The new transient responses are characterized by three pairs of peak-troughs named as n₀p₀, n₁p₁, and n₂p₂ within 40 ms. Compared with conventional ABR-MLRs, the n₀p₀ indicates the first neural activity where p₀ might represent the main ABR components; the n₁ is the counterpart of N10; the p₂ is corresponding to the robust Pa at about 30 ms; the p₁ and n₂ are absent of real counterparts. The peak-peak amplitudes show a slight decrease with increasing stimulation rate from 75 to 95 Hz whereas the peak latencies change differently, which is consistent with the known rate-effect on AEPs. This is direct evidence for a transient response derived from AM-ASSRs for the first time. The characteristic components offer insight into the constitution of AM-ASSRs and may be promising in clinical applications and fundamental studies.