Auditory steady-state responses to 40-Hz click trains: Relationship to middle latency, gamma band and beta band responses studied with deconvolution

Objective: The nature of the auditory steady-state responses (ASSR) evoked with 40-Hz click trains and their relationship to auditory brainstem and middle latency responses (ABR/MLR), gamma band responses (GBR) and beta band responses (BBR) were investigated using superposition theory. Transient responses obtained by continuous loop averaging deconvolution (CLAD) and last click responses (LCR) were used to synthesize ASSRs and GBRs. Methods: ASSRs were obtained with trains of low jittered 40 Hz clicks presented monaurally and deconvolved using a modified CLAD. Resulting transient responses and modified LCRs were used to predict the ASSRs and the GBR. Results: The ABR/MLR obtained with deconvolution predicted accurately the steady portion of the ASSR but failed to predict its onset portion. The modified LCR failed to fully predict both portions. The GBRs were predicted by narrow band filtering of the ASSRs. Significant BBR activity was found both in the ASSRs and deconvolved ABR/MLRs. Conclusions: Simulations using deconvolved ABR/MLRs obtained at 40 Hz predict fully the steady state but not the onset portion of the ASSRs, thus confirming the superposition theory. Significance: Click rate adaptation plays a significant role in ASSR generation with click trains and should be considered in evaluating convolved response generation theories. (C) 2010 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.