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.

Relations between speech‐reception, psychophysical temporal processing, and subcortical electrophysiological measures of auditory function in humans

“…The interpretation of these results, however, is unclear because the effect has been found to depend mainly on changes of the SP, which has traditionally been thought to originate from inner hair cell receptor potentials rather than from neural elements ( Durrant, Wang, Ding, Salvi, 1998 , Eggermont, 2017 ). 2 Some recent studies, however, suggest that the SP may include neural components ( Kennedy, Kaf, Ferraro, Delgado, Lichtenhan, 2017 , Pappa, Hutson, Scott, Wilson, Fox, Masood, Giardina, Pulver, Grana, Askew, Fitzpatrick, 2019 ). The interpretation of the association between the AP/SP ratio and speech-reception thresholds thus hinges on the interpretation of the SP, which has not yet been fully elucidated.…”

Cochlear Microphonic and Summating Potential Responses from Click-Evoked Auditory Brain Stem Responses in High-Risk and Normal Infants

“…These recording techniques are supported by recent studies of the SP in human adults. Kennedy et al (2017) studied stimulus rate in amplitude of the human SP, and reported that faster repetition rates (58 to 97/s) showed higher amplitude SP compared to slower rates (7–19/s), using a filter setting similar to the present study (3–3000 Hz). The rate in the present study was intermediate, at 37/s, due to concerns about reducing Wave I and V amplitude at faster rates in newborns.…”

Relative changes in the cochlear summating potentials to paired-clicks predict speech-in-noise perception and subjective hearing acuity

“…We speculate that, in addition to EPSPs, the reduction of synaptic adaptation due to synaptic loss may also contribute to larger SP ratios to very short ICIs in cochlear synaptopathy. In contrast, SP amplitudes to short stimuli were reported to be slightly reducing, because of adaptation, in normal-hearing humans as stimulus repetition rate increased 21 . Proper adaptation is important in maintaining normal hearing function because it is a fundamental principle of sensory processing that enables sensory information to be represented adequately 32 and remain robust to noise 33 .…”

“…Wave I), it may be more sensitive to synaptopathic pathology. In normal-hearing human listeners, SP amplitudes to short duration stimuli are found to be reducing as stimulus repetition rate increased 21 . In contrast, as excitatory post-synaptic potentials (EPSPs) from cochlear nerve terminals under the inner hair cells may contribute to SP 8 , the loss of a negative EPSP could enhance SP in cochlear synaptopathy.…”

“…21 . Proper adaptation is important in maintaining normal hearing function because it is a fundamental principle of sensory processing that enables sensory information to be represented adequately32 and remain robust to noise33 .High-risk subjects in who had putative cochlear synaptopathy were shown to have poorer speech discrimination scores when the task was performed under conditions of degradation (e.g., noise, time-compression, reverberation).…”