Human Summating Potential Using Continuous Loop Averaging Deconvolution: Response Amplitudes Vary with Tone Burst Repetition Rate and Duration

Abstract

Electrocochleography (ECochG) to high repetition rate tone bursts may have advantages over ECochG to clicks with standard slow rates. Tone burst stimuli presented at a high repetition rate may enhance summating potential (SP) measurements by reducing neural contributions resulting from neural adaptation to high stimulus repetition rates. To allow for the analysis of the complex ECochG responses to high rates, we deconvolved responses using the Continuous Loop Averaging Deconvolution (CLAD) technique. We examined the effect of high stimulus repetition rate and stimulus duration on SP amplitude measurements made with extratympanic ECochG to tone bursts in 20 adult females with normal hearing. We used 500 and 2,000 Hz tone bursts of various stimulus durations (12, 6, 3 ms) and repetition rates (five rates ranging from 7.1 to 234.38/s). A within-subject repeated measures (rate x duration) analysis of variance was conducted. We found that, for both 500 and 2,000 Hz stimuli, the mean deconvolved SP amplitudes were larger at faster repetition rates (58.59 and 97.66/s) compared to slower repetition rates (7.1 and 19.53/s), and larger at shorter stimulus duration compared longer stimulus duration. Our concluding hypothesis is that large SP amplitude to short duration stimuli may originate primarily from neural excitation, and large SP amplitudes to long duration, fast repetition rate stimuli may originate from hair cell responses. While the hair cell or neural origins of the SP to various stimulus parameters remains to be validated, our results nevertheless provide normative data as a step toward applying the CLAD technique to understanding diseased ears.

Keywords: auditory nerve; cochlea; continuous loop averaging deconvolution; high stimulus rate; phase locking; tone burst.

Figure 1

Standard click ECochG responses from one of the participants (P9). Two traces (top) were recorded and averaged (bottom) depicting a typical ECochG response. The SP and AP are labeled on the averaged tracing, though standard ECochG data was not formally assessed during this study.

Figure 2

CLAD deconvolved, 500 Hz tone burst ECochG measurements from one participant (P9) across stimulus duration (12 ms—top; 6 ms—middle; 3 ms—bottom). Responses to increasing repetition rate are displayed from top to bottom in each panel. SP amplitude was measured as the baseline at 1 ms to the SP waveform midpoint (SP). The SP waveform midpoint (SP) was measured from onset (O).

Figure 3

CLAD deconvolved, 2,000 Hz tone burst ECochG measurements from one participant (P9) across stimulus duration (12 ms—top; 6 ms—middle; 3 ms—bottom). Responses to increasing repetition rate are displayed from top to bottom in each panel. SP amplitude was measured as the baseline at 1 ms to the SP waveform midpoint (SP). The SP waveform midpoint (SP) was measured from onset (O).

Figure 4

(A) SP amplitudes to 500 and 2,000 Hz varied with stimulus repetition rate (7.1, 19.53, and 58.59/s). SP amplitude to both 500 and 200 Hz were larger for 58.59/s compared to rates 7.1 and 19.53/s. (B) SP amplitudes to 500 and 2,000 Hz varied significantly with stimulus duration (12, 6, and 3 ms). SP amplitudes to 500 Hz were significantly larger for 3 ms stimulus duration than for 12 ms durations and 6 ms durations. Likewise, SP amplitudes to 2,000 Hz were significantly larger for the 3 ms stimulus duration than for 12 and 6 ms durations.

Figure 5

Mean SP amplitude values for the 12 ms duration, 6 ms duration, and 3 ms duration as a function of repetition rate for the 500 Hz condition.

Figure 6

Mean SP amplitude values for the 12 ms duration, 6 ms duration, and 3 ms duration as a function of repetition rate for the 2,000 Hz condition.

Figure 7

Spectral filtering of a CLAD deconvolved tone burst ECochG waveform (top) for the 500 Hz, 12 ms, 58.59/s condition. Displayed in descending order, four spectral band pass filters were applied: 0–250, 0–300, 0–350, and 0–450 Hz. SP indicates the pre-defined midpoint of the 12 ms duration.