Frequency Tuning Curves Derived from Auditory Steady State Evoked Potentials: A Proof-of-Concept Study

Abstract

Objectives: Assess the feasibility of drawing tuning curves from the masking function of steady state potentials. Develop a noninvasive tool for research applications on cochlear frequency selectivity in sedated animais. Obtain pilot human data validating auditory steady state evoked potential-derived (ASSEP) tuning curves against psychophysical data.,.Design: ASSEP tuning curves were drawn in 10 Beagle puppies and six human adults using amplitude-modulated probes. Two probe frequencies (1 and 2 kHz) were used in dogs and only one (2 kHz) in humans. The modulation rates of the two probes were set to 81 and 88 Hz, respectively. Psychophysical tuning curves were obtained in 12 normal human subjects using the same maskers and either a pure-tone or an amplitude-modulated probe to verity if the latter had a specific effect on tuning curve parameters. Six of these 12 subjects participated in the electrophysiologic measurements. For each tuning curve, the intensity of the narrowband masker required just to mask the fixed probe was plotted for different masker center frequencies. Masker center frequencies extended to about half an octave above and an octave below the probe frequencies in 1DO-Hzsteps. Tuning curve width (010dB values), high-and low-frequency slopes (in dB/octave) and the masker frequency yielding the lowest masking threshold (maximal masker frequency) were computed. Canine 010 dB values obtained were compared with those published for several species with other techniques. For humans, ASSEP and psychophysical tuning curves were directly compared in the same subjects and with published data.Results: ln dogs, the ASSEP method yielded reproducible tUlîing curves with qualitative and quantitative parameters similar to other physiologic measures of tuning obtained in various animais. 010 dB values were greater at 2 than at1 kHz, reflecting the well-known correlation between sharpness of tuning and central frequency. ln humans, ASSEP 010 dB values were slightly smaller than the psychophysical ones, but were greater by a factor of 2 than those obtained with previously published electrophysiologic procedures. ln both species, detuning-a shift of the tip of the curve away from the probe frequency-was frequently observed as upward shifts with a maximal value of 200 Hz. Human psychophysical tuning curves also showed a certain amount of upward detuning. The intraindividual comparison of the two types of probes performed on human sUbjects with the psychophysical method did not indicate a specific effect of the amplitude-modulated probe on the curve parameters. Neither did the intraindividual comparisons indicate that an amplitude-modulated probe per se promoted detuning. Detuning has been observed with several other techniques and is usually attributed to nonlinear interactions between masker and probe in simultaneous masking.Conclusions: The results demonstrate the feasibility of measuring realistic ASSEP tuning curves in sedated dogs and in sleeping human

Stimulus-Frequency Otoacoustic Emission Suppression Tuning in Humans: Comparison to Behavioral Tuning

“…The fact that we found a close relationship between mean PTCs and mean SFOAE STCs suggest that the former are to a large extent shaped by cochlear mechanics (e.g., Pickles 1979;Evans 2001). This view is also supported by a good agreement between our estimates of sharpness of tuning and those obtained with evoked potential tuning curves (Eggermont 1977;Harrison et al 1981;Harrison 1984;Markessis et al 2009). …”

Time-efficient measures of auditory frequency selectivity

“…It remains unclear how sweep direction or general differences between measurement paradigms would lead to disagreements only at 4000 Hz but not at the remaining signal frequencies. Similarly, our data are in good agreement with Q 10 s of PTCs recorded with either traditional or fast methods at corresponding masker bandwidths for 1000 and 2000 Hz, but at 4000 Hz our subjects appear to have narrower curves (Kluk & Moore, 2004; Malicka et al, 2009; Markessis et al, 2009). Thus, it is most plausible that the observed differences at 4000 Hz reflect individual differences in frequency selectivity.…”

“…The difference in tuning was caused by greater susceptibility of GN-PTC method to training effects, because the run 2 curves had widths comparable to GN-AM-PTC (Table 2). Accordingly, amplitude modulating the probe does not affect the PTC width (Markessis et al, 2009), but it makes the task easier when combined with a gated-noise masker. This conclusion is also supported by the substantially lower rejection rate of PTCs in the GN-AM-PTCs condition as compared to GN-PTCs.…”

“…Beats can provide a salient detection cue that leads to a narrowing of the PTC tip (Kluk & Moore, 2004, 2005). To the best of our knowledge, there is only one study that evaluated the effects of signal amplitude modulation on the PTC features measured using the three-alternative forced-choice method (Markessis et al, 2009). That study did not reveal significant differences between the PTCs measured with an unmodulated pure-tone signal and with a signal modulated at either a rate of 81 Hz or 88 Hz, for 1000 and 2000 Hz signal frequencies respectively.…”

Using the Auditory Steady State Response to Record Response Amplitude Curves. A Possible Fast Objective Method for Diagnosing Dead Regions

“…Markessis et al (2009) estimated ETC-tip frequencies in normally hearing subjects by recording ASSR thresholds in the presence of masking noise. They found that the tips of the ASSR ETCs were often shifted to frequencies higher than the signal, which they referred to as detuning.…”