Generalization of the primary tone phase variation method: An exclusive way of isolating the frequency-following response components

Abstract

The primary tone phase variation (PTPV) technique combines selective sub-averaging with systematic variation of the phases of multitone stimuli. Each response component having a known phase relationship with the stimulus components phases can be isolated in the time domain. The method was generalized to the frequency-following response (FFR) evoked by a two-tone (f 1 and f 2) stimulus comprising both linear and non-linear, as well as transient components. The generalized PTPV technique isolated each spectral component present in the FFR, including those sharing the same frequency, allowing comparison of their latencies. After isolation of the envelope component f 2f 1 from its harmonic distortion 2f 2-2f 1 and from the transient auditory brainstem response, a computerized analysis of instantaneous amplitudes and phases was applied in order to objectively determine the onset and offset latencies of the response components. The successive activation of two generators separated by 3.7 ms could be detected in all (N ¼ 12) awake adult normal subjects, but in none (N ¼ 10) of the sleeping/sedated children with normal hearing thresholds. The method offers an unprecedented way of disentangling the various FFR subcomponents. These results open the way for renewed investigations of the FFR components in both human and animal research as well as for clinical applications. V

Subcortical neural generators of the envelope-following response in sleeping children: A transfer function analysis

“…As eight different SCs were expected to be potentially present in the two-tone evoked FFR response ( Lucchetti et al, 2018 ), implementation of the gPTPV method required that each of the five EFR stimuli be composed of a subset of eight different sub-stimuli s k (t) differing only by their primary phases φ 1 and φ 2 . Values for φ 1 and φ 2 for the k = { 1 , ..., 8 } sub-stimuli are found on Table 2 Table 2 Two-tone stimulus primary phase values φ 1 and φ 2 for the set of 8 stimuli indexed by k.…”

“…Furthermore, it has been suggested that there may be cortical sources contributing to the FFR at frequencies below 200 Hz ( Coffey et al, 2019;Tichko and Skoe, 2017 ). Moreover, along the auditory neuraxis, more centrally located generators are more affected by sleep and sedation ( Aoyagi et al, 1993;Lucchetti et al, 2018 ). Results are therefore likely to differ according to the combination of stimulus spectra, recording montages and sleep-wake state.…”

“…Cross-correlation between stimulus and response ( Galbraith, 1994 ) is another technique that has been applied for latency measurements, but as discussed in King et al (2016) is limited to low-frequency stimuli and would not work for the multiple SCs evoked by complex stimuli. In the current study, we revisited the question of the subcortical EFR generator(s) recorded in sleeping or sedated children from simultaneous horizontal (earlobe to earlobe) and vertical (Vertex to seventh cervical vertebra spinous process) recordings by taking advantage of the recently described generalized Primary Tone Phase Variation (gPTPV) method ( Lucchetti et al, 2018 ). The gPTPV method is able to isolate a given target SC in the temporal domain so that it can be subjected to several precise measurements including onset latency, duration and phase shift measurements.…”

“…The gPTPV method is able to isolate a given target SC in the temporal domain so that it can be subjected to several precise measurements including onset latency, duration and phase shift measurements. By combining the two latter measurements, multiple sequential generators can be disclosed ( Lucchetti et al, 2018 ). The gPTPV method is superior to the standard technique of adding responses evoked by stimuli of opposite polarities to get rid of the TFS ( Aiken and Purcell, 2013 ) because contrary to the latter method, it also separates the EFR from its harmonic distortion components and from the ABR transient ones.…”

Spectrally specific temporal analyses of spike-train responses to complex sounds: A unifying framework

“…The energy at 2F 0 in S(f ) may reflect one or more of the following sources: (1) rectifier distortion to carrier energy at F 0 , (2) beating between (carrier) harmonics that are separated by 2F 0 , and (3) effects of transduction nonlinearities on the beating between (carrier) harmonics that are separated by F 0 . In these special cases, additional stimulus phase variations can be used to separate out these components (Billings and Zhang, 1994;Lucchetti et al, 2018).…”