Recording of auditory brainstem response at high stimulation rates using randomized stimulation and averaging

Abstract

The recording of auditory brainstem response (ABR) at high stimulation rates is of great interest in audiology. It allows a more accurate diagnosis of certain pathologies at an early stage and the study of different mechanisms of adaptation. This paper proposes a methodology, which we will refer to as randomized stimulation and averaging (RSA) that allows the recording of ABR at high stimulation rates using jittered stimuli. The proposed method has been compared with quasi-periodic sequence deconvolution (QSD) and conventional (CONV) stimulation methodologies. Experimental results show that RSA provides a quality in ABR recordings similar to that of QSD and CONV. Compared with CONV, RSA presents the advantage of being able to record ABR at rates higher than 100 Hz. Compared with QSD, the formulation of RSA is simpler and allows more flexibility on the design of the pseudorandom sequence. The feasibility of the RSA methodology is validated by an analysis of the morphology, amplitudes, and latencies of the most important waves in ABR recorded at high stimulation rates from eight normal hearing subjects.

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

“…The digital blanking process considers as null values any EEG samples in which stimulus artifact occurs. Using RSA notation (Valderrama et al, 2012), let y(n), s(n) (n ¼ 1,…, N), J, and N be, respectively, the digitized EEG, the synchronization signal (indicating with the value of 1 the start of each stimulus, and 0 otherwise), the length of the averaging window, and the total number of EEG samples. Considering a stimulation sequence with K stimuli, the index of the samples in which each stimulus starts can be represented by m(k) (k ¼ 1,…, K).…”

“…Since RSA does not perform deconvolution, this method must deal with interference derived from the contamination produced by overlapping adjacent responses. Interference associated with overlapping responses can be reduced with averaging in RSA provided that the amount of jitter is large enough to enable positive and negative components of such interference to be canceled with averaging (Valderrama et al, 2012). In addition to this, the digital blanking process in RSA entails nonuniform averaging of auditory responses along the averaging window, and small amounts of jitter could lead to significant differences in terms of quality between different segments of the response.…”

“…The jitter of a stimulation sequence measures the dispersion of the ISI compared with a periodical presentation of stimuli, with constant ISI. The most relevant methods used to obtain AEPs at high rates are maximum length sequences (MLS) (Eysholdt and Schreiner, 1982), ADJAR (Woldorff, 1993), quasiperiodic sequence deconvolution (QSD) (Jewett et al, 2004), continuous loop averaging deconvolution (CLAD) (Ozdamar et al, 2003a;Ozdamar et al, 2003b;Delgado and Ozdamar, 2004;Ozdamar and Bohorquez, 2006), least-squares (LS) deconvolution (Bardy et al, 2014a), and randomized stimulation and averaging (RSA) (Valderrama et al, 2012).…”

“…The RSA method is fully described in Valderrama et al (2012). In comparison with other methods based on deconvolution, RSA (a) allows a precise control of the jitter of the stimulation sequence, (b) presents generation of stimulation sequences that is not subject to any particular constraint in the frequency domain, and (c) allows auditory responses to be processed separately.…”

“…The total number of iterations can be set either as a predefined value, or automatically, in which case the method stops iterating when the differences between AEP estimates in successive iterations are negligible. As in RSA, the generation of stimulation sequences in I-RSA is based on randomized stimulation, where the ISI of the stimuli varies randomly according to a predefined probability distribution (Valderrama et al, 2012).…”