DPOAE group delays versus electrophysiological measures of cochlear delay in normal human ears

Abstract

Group delays of 2 f1-f2 distortion product otoacoustic emissions (DPOAEs) were determined using both f1- and f2-sweep paradigms in 24 normal-hearing subjects. These DPOAE group delays were studied in comparison with cochlear delays estimated from derived band VIIIth nerve compound action potentials (CAPs) and auditory brainstem responses (ABRs) in the same subjects. The center frequencies of the derived bands in the electrophysiological experiment were matched with the f2-frequencies in the DPOAE recording to ensure that DPOAEs and derived CAPs and ABRs were generated at the same places along the cochlear partition, thus allowing for a direct comparison. The degree to which DPOAE group delays are larger in the f2- than in the f1-sweep paradigm is consistent with a theoretical analysis of the so-called wave-fixed model. Both DPOAE group delays are highly correlated with CAP- and ABR-derived measures of cochlear delay. The principal result of this study is that "roundtrip" DPOAE group delay in the f1-sweep paradigm is exactly twice as large as the neural estimate of the "forward" cochlear delay. The interpretation of this notion in the context of cochlear wave propagation properties and DPOAE-generating mechanisms is discussed.

Perception of across-frequency asynchrony and the role of cochlear delays

“…The latency-frequency functions estimated using otoacoustic emissions or ABR responses become shallower with increasing stimulus level (Neely et al, 1988;Schoonhoven et al, 2001;Sisto and Moleti, 2007). In contrast, Ruggero and Temchin (2007) argued that stimulus level has very little effect on the BM latency-frequency function and the effect is to slightly increase across-frequency latencies at high levels.…”

“…The exact form of changes in BM latency-frequency function with level is unknown. Some studies have suggested that the latencyfrequency function becomes shallower, exhibiting more synchronous responses across frequency as the level increases (e.g., Neely et al, 1988;Schoonhoven et al, 2001;Sisto and Moleti, 2007), while others have predicted a small effect of level in the opposite direction, i.e., a slight increase in the slope of the latency-frequency function at high levels (Ruggero and Temchin, 2007).…”

“…The BM delays have been estimated from measurements of the compound action potential (CAP) (Elberling, 1974;Eggermont, 1979;Schoonhoven et al, 2001), derived-bands and tone-burst auditory brainstem responses (Eggermont and Don, 1980;Neely et al, 1988;Don et al, 1993;Donaldson and Ruth, 1993;Don et al, 1998;Harte et al, 2009), distortion-product, transient-evoked, and stimulus-frequency otoacoustic emissions (Neely et al, 1988;Bowman et al, 1997;Ramotowski and Kimberley, 1998;Schoonhoven et al, 2001;Shera et al, 2002;Sisto and Moleti, 2007;Harte et al, 2009), and by using latency-frequency responses obtained postmortem (Von Békésy, 1949) and then assuming a compensation term for the effects of death on the cochlear function (Ruggero and Temchin, 2007). The latency (s) of peak BM responses has often been described by a power law, s ¼ af -b , where f is the tone frequency a and b are constants whose values differ across studies.…”

Perception of Across-Frequency Asynchrony by Listeners with Cochlear Hearing Loss

“…First, based on the published reports, it is not entirely clear that broader filters are associated with substantial changes to the BM latency-frequency function. Cochlear latency-frequency functions estimated from derivedband ABRs and otoacoustic emissions for different levels of the evoking stimuli have been shown to become shallower with increasing level and thus with increasing filter bandwidths (Neely et al 1988;Schoonhoven et al 2001; Sisto and Moleti 2007).…”

“…Of those delays, the build-up times of cochlear-filter responses dominate the frequency-dependent component of the overall delay (Ruggero and Temchin 2007). In humans, the frequency-dependent cochlear delays have been estimated from noninvasive physiological measurements of latencies of the compound action potential (Elberling 1974;Eggermont 1979;Schoonhoven et al 2001), the auditory-brainstem response (ABR; Eggermont and Don 1980;Neely et al 1988;Donaldson and Ruth 1993;Harte et al 2009), and otoacoustic emissions (Neely et al 1988;Bowman et al 1997;Schoonhoven et al 2001;Shera and Guinan 2003;Sisto and Moleti 2007;Harte et al 2009). Generally, the estimated cochlear-response latency in humans has been shown to decrease with increasing CF at a rate similar to that derived from direct physiological measurements in animals.…”