Continuous- and Discrete-Time Stimulus Sequences for High Stimulus Rate Paradigm in Evoked Potential Studies

Abstract

To obtain reliable transient auditory evoked potentials (AEPs) from EEGs recorded using high stimulus rate (HSR) paradigm, it is critical to design the stimulus sequences of appropriate frequency properties. Traditionally, the individual stimulus events in a stimulus sequence occur only at discrete time points dependent on the sampling frequency of the recording system and the duration of stimulus sequence. This dependency likely causes the implementation of suboptimal stimulus sequences, sacrificing the reliability of resulting AEPs. In this paper, we explicate the use of continuous-time stimulus sequence for HSR paradigm, which is independent of the discrete electroencephalogram (EEG) recording system. We employ simulation studies to examine the applicability of the continuous-time stimulus sequences and the impacts of sampling frequency on AEPs in traditional studies using discrete-time design. Results from these studies show that the continuous-time sequences can offer better frequency properties and improve the reliability of recovered AEPs. Furthermore, we find that the errors in the recovered AEPs depend critically on the sampling frequencies of experimental systems, and their relationship can be fitted using a reciprocal function. As such, our study contributes to the literature by demonstrating the applicability and advantages of continuous-time stimulus sequences for HSR paradigm and by revealing the relationship between the reliability of AEPs and sampling frequencies of the experimental systems when discrete-time stimulus sequences are used in traditional manner for the HSR paradigm.

Improved Transient Response Estimations in Predicting 40 Hz Auditory Steady-State Response Using Deconvolution Methods

“…However, the solution can be mathematically unstable without appropriate control of the frequency property of the CLAD stimulus sequence. Various measures (e.g., Wang et al, 2006 , 2013a ) have been proposed to deal with this issue since the first introduction of the CLAD method (Delgado and Ozdamar, 2004 ). The most important aspect of the CLAD sequence design is the sequence of ISI-jitters and its optimization to avoid unusual amplification of contamination noise in EEG (Ozdamar et al, 2007 ; Peng et al, 2017 ).…”

“…The CLAD method is based on the linear convolution model between the transient response to individual stimuli in ASSR and the ASSR stimulus sequence (Delgado and Ozdamar, 2004 ; Bohorquez et al, 2007 ; Ozdamar et al, 2007 ; Wang et al, 2013a ). In the classical ASSR paradigm, the isochronic stimulus sequence is used and transient responses to individual stimuli cannot be obtained mathematically from overlapped steady state responses due to the singular nature of inverse problems when the same inter-stimulus intervals (ISIs) are used in the whole sequence.…”

Auditory brainstem and middle latency responses recorded at fast rates with randomized stimulation

“…The QSD, CLAD, and LS methods present different approaches to deconvolve overlapping auditory responses evoked by low-jittered stimuli. These methods have been efficiently used in several clinical and research applications (e.g., Bohorquez et al, 2009;Gutschalk et al, 2009;Presacco et al, 2010;Wang et al, 2013;Bardy et al, 2014b).…”

Least-squares (LS) deconvolution of a series of overlapping cortical auditory evoked potentials: a simulation and experimental study

“…Multiple parameters can affect the deconvolution process, such as the amount of jitter in the stimulus sequence, the sampling rate, the length of the deconvolved response, and the amount of overlap of the response. All these parameters influence the effectiveness of the deconvolution, specifically in noisy environments as already demonstrated (Bardy et al 2014a, Wang et al 2013a.…”