Summating Potential Amplitude Research Articles

Click SP/AP Area Ratio Vesrus Tone Burst SP Amplitude to Diagnose Ménière's Disease Using Electrocochleography.

To evaluate the sensitivity and the specificity of summating potential (SP)/action potential (AP) area under the curve (AUC) ratio by a transtympanic electrode and a click stimulus (TT-CS), SP/AP AUC ratio by an extratympanic electrode and a click stimulus (ET-CS) and SP amplitude value by a transtympanic electrode and tone burst stimulus (TT-TBS) in regard of Ménière's disease (MD) diagnosis. This is the first study that compares SP amplitude value performed by a TT-TBS and the SP/AP AUC ratio performed by a TT-CS. Retrospective comparative study. Ninety-five patients met the inclusion criteria for electrocochleography (ECochG) testing in a tertiary care center. The sensitivity and specificity of our different ECochG protocols were calculated in regardof the diagnosis of MD. The patients' mean age was 54 years old (female predominance). The sensitivity and the specificity of SP/AP area ratio by a TT-CS were 88.5% and 70.0%, respectively. On the other hand, the sensitivity and specificity for the SP amplitude value by a TT-TBS were 60.0% and 55.6%, respectively. SP/AP area ratio by TT-CS was statistically better than SP amplitude value by TT-TBS to detect MD disease (P = .016). However, no difference was identified between SP/AP area ratio by ET-CS and SP amplitude value by a TT-TBS (P = .573). SP/AP area ratio by click stimulation has higher sensitivity and specificity to detect MD compared to SP amplitude value by tone burst stimulation. ECochG would be extremely useful in the diagnosis of MD if we use the SP/AP area ratio (sensitivity: 88.5%); therefore, it changes the bad reputation of ECochG sensitivity using SP/AP amplitude ratio (sensitivity: 51.7%) for the diagnosis of MD.

Minimum Detectable Differences in Electrocochleography Measurements: Bayesian-Based Predictions.

Physiology of the cochlea and auditory nerve can be assessed with electrocochleography (ECochG), a technique that involves measuring auditory evoked potentials from an electrode placed near or within the cochlea. Research, clinical, and operating room applications of ECochG have in part centered on measuring the auditory nerve compound action potential (AP) amplitude, the summating potential (SP) amplitude, and the ratio of the two (SP/AP). Despite the common use of ECochG, the variability of repeated amplitude measurements for individuals and groups is not well understood. We analyzed ECochG measurements made with a tympanic membrane electrode in a group of younger normal-hearing participants to characterize the within-participant and group-level variability for the AP amplitude, SP amplitude, and SP/AP amplitude ratio. Results show that the measurements have substantial variability and that, especially with smaller sample sizes, significant reduction in variability can be obtained by averaging measurements across repeated electrode placements within subjects. Using a Bayesian-based model of the data, we generated simulated data to predict minimum detectable differences in AP and SP amplitudes for experiments with a given number of participants and repeated measurements. Our findings provide evidence-based recommendations for the design and sample size determination of future experiments using ECochG amplitude measurements, and the evaluation of previous publications in terms of sensitivity to detecting experimental effects on ECochG amplitude measurements. Accounting for the variability of ECochG measurements should result in more consistent results in the clinical and basic assessments of hearing and hearing loss, either hidden or overt.

The summating potential in human electrocochleography: Gaussian models and Fourier analysis.

In recent electrocochleographic studies, the amplitude of the summating potential (SP) was an important predictor of performance on word-recognition in difficult listening environments among normal-hearing listeners; paradoxically the SP was largest in those with the worst scores. SP has traditionally been extracted by visual inspection, a technique prone to subjectivity and error. Here, we assess the utility of a fitting algorithm [Kamerer, Neely, and Rasetshwane (2020). J Acoust Soc Am. 147, 25-31] using a summed-Gaussian model to objectify and improve SP identification. Results show that SPs extracted by visual inspection correlate better with word scores than those from the model fits. We also use fast Fourier transform to decompose these evoked responses into their spectral components to gain insight into the cellular generators of SP. We find a component at 310 Hz associated with word-identification tasks that correlates with SP amplitude. This component is absent in patients with genetic mutations affecting synaptic transmission and may reflect a contribution from excitatory post-synaptic potentials in auditory nerve fibers.

2-Hydroxypropyl-β-cyclodextrin Ototoxicity in Adult Rats: Rapid Onset and Massive Destruction of Both Inner and Outer Hair Cells Above a Critical Dose.

2-Hydroxypropyl-β-cyclodextrin (HPβCD), a cholesterol chelator, is being used to treat diseases associated with abnormal cholesterol metabolism such as Niemann-Pick C1 (NPC1). However, the high doses of HPβCD needed to slow disease progression may cause hearing loss. Previous studies in mice have suggested that HPβCD ototoxicity results from selective outer hair cell (OHC) damage. However, it is unclear if HPβCD causes the same type of damage or is more or less toxic to other species such as rats, which are widely used in toxicity research. To address these issues, rats were given a subcutaneous injection of HPβCD between 500 and 4000mg/kg. Distortion product otoacoustic emissions (DPOAE), the cochlear summating potential (SP), and compound action potential (CAP) were used to assess cochlear function followed by quantitative analysis of OHC and inner hair cell (IHC) loss. The 3000- and 4000-mg/kg doses abolished DPOAE and greatly reduced SP and CAP amplitudes. These functional deficits were associated with nearly complete loss of OHC as well as ~ 80% IHC loss over the basal two thirds of the cochlea. The 2000-mg/kg dose abolished DPOAE and significantly reduced SP and CAP amplitudes at the high frequencies. These deficits were linked to OHC and IHC losses in the high-frequency region of the cochlea. Little or no damage occurred with 500 or 1000mg/kg of HPβCD. The HPβCD-induced functional and structural deficits in rats occurred suddenly, involved damage to both IHC and OHC, and were more severe than those reported in mice.

The Effect of Test, Electrode, and Rate on Electrocochleography Measures.

Electrocochleography (ECochG) is the measurement of stimulus-related cochlear potentials and the compound action potential (AP). Its primary clinical application is with the assessment of inner ear disorders. There are few studies examining the variability of ECochG measures. The objective of the study was to examine the effect of test (i.e., initial versus retest), electrode (i.e., extratympanic versus tympanic), and stimulus rate (i.e., 7.7 versus 77.7/sec) on ECochG indices (i.e., summating potential [SP] amplitude, AP latency, AP amplitude, SP/AP amplitude ratio, and SP/AP area ratio). Correlational and three-factor repeated measures designs were employed. Eighteen normal-hearing young adults participated. ECochG responses were obtained with 90 dB nHL click stimuli for an initial test and retest at two stimulus rates with a commercially available extratympanic (TIPtrode™) and tympanic (Lilly TM-Wick) electrode. Separate repeated measures linear mixed-model analysis of variance examined the effect of test, electrode, and rate for all ECochG indices. Test-retest variability was also examined with correlation analyses; an examination of mean test-retest differences and their 95% confidence intervals (CI); and construction of Bland-Altman plots. The presence of SP and AP responses varied across experimental conditions. Electrode and rate were statistically significant predictors (p < 0.05) of SP and AP responses: SP and AP responses were more likely to be present with the tympanic electrode and at the slow rate. Statistically significant correlations (p < 0.05) were found between initial tests and retests with all ECochG indices with both electrodes with the exception of SP amplitude with the TIPtrode™ electrode. There were no significant main effects of test (initial versus retest) or interactions of test and electrode or rate for any of the ECochG indices (p > 0.05). The 95% CI of the mean test-retest differences contained 0 confirming that the effect of test was not statistically significant. There was a statistically significant main effect of electrode (p < 0.05) on three ECochG measures. The Lilly TM-Wick electrode produced larger SP amplitudes, AP amplitudes, and SP/AP area ratios than TIPtrode™ electrodes. A statistically significant main effect of rate (p < 0.05) was identified for all ECochG measures. The effect of rate on AP latency and amplitude was expected. Increasing the stimulus rate prolonged the AP latency and decreased AP amplitude. SP amplitude was larger for the faster rate. There was no difference between electrodes with regard to test-retest measures. However, considering the higher likelihood of ECochG SP and AP responses and larger SP amplitude, SP/AP amplitude ratio, and SP/AP area ratio indices, the tympanic electrode placement is recommended for clinical practice. The addition of a fast stimulus rate may be considered for enhanced SP amplitude, SP/AP amplitude ratio, and SP/AP area ratio albeit with the consideration of the loss of SP and AP responses in some individuals.

Are age-related changes in cortical motor representations linked with facilitation/inhibition in the primary motor cortex?

Are age-related changes in cortical motor representations linked with facilitation/inhibition in the primary motor cortex?

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

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.

Electrophysiological evidence for detrimental impact of a reappraisal emotion regulation strategy on subsequent cognitive control in schizophrenia.

In healthy individuals, there is evidence that effective implementation of an emotion regulation strategy has beneficial effects on temporally proximal cognitive control task performance. This effect occurs because both of these processes rely heavily on the prefrontal cortex. Individuals with schizophrenia (SZ) have impairments in both emotion regulation and cognitive control that are driven by structural and functional abnormalities of the prefrontal cortex; however, it is unknown whether emotion regulation attempts fail to benefit subsequently performed cognitive control tasks in people with SZ. The present study examined whether attempts to increase or decrease negative emotion via reappraisal have differential effects on subsequent cognitive control in a sample of outpatients diagnosed with SZ (n = 30) and demographically matched healthy controls (CN; n = 29). Participants completed a combined emotion regulation and cognitive control task in which numerical Stroop trials were presented immediately after unpleasant or neutral images that were either increased via reappraisal, decreased via reappraisal, or passively viewed. The electroencephalogram was recorded while participants performed the reappraisal-Stroop task and event related potentials (ERPs) were used to index emotion regulation effectiveness (late positive potential: LPP) and cognitive control (sustained potential: SP). Both CN and SZ evidenced higher LPP amplitude for unpleasant than neutral stimuli consistent with robust neural response to unpleasant stimuli. Although CN demonstrated neurophysiological evidence of effective use of reappraisal to increase and decrease negative emotion, SZ only showed an effective ability to increase negative emotion via reappraisal. CN displayed enhanced cognitive control following increase trials and impaired cognitive control following decrease trials, as indicated by modulation of SP amplitude. In SZ, increase instructions impaired cognitive control and decrease instructions had no effect on cognitive control. Findings suggest that emotion regulation abnormalities may play an underrecognized role in general cognitive control deficits that occur in SZ. (PsycINFO Database Record

Cycling on a Bike Desk Positively Influences Cognitive Performance.

PurposeCycling desks as a means to reduce sedentary time in the office has gained interest as excessive sitting has been associated with several health risks. However, the question rises if people will still be as efficient in performing their desk-based office work when combining this with stationary cycling. Therefore, the effect of cycling at 30% Wmax on typing, cognitive performance and brain activity was investigated.MethodsAfter two familiarisation sessions, 23 participants performed a test battery [typing test, Rey auditory verbal learning test (RAVLT), Stroop test and Rosvold continuous performance test (RCPT)] with electroencephalography recording while cycling and sitting on a conventional chair.ResultsTyping performance, performance on the RAVLT and accuracy on the Stroop test and the RCPT did not differ between conditions. Reaction times on the Stroop test and the RCPT were shorter while cycling relative to sitting (p < 0.05). N200, P300, N450 and conflict SP latency and amplitude on the Stroop test and N200 and P300 on the RCPT did not differ between conditions.ConclusionsThis study showed that typing performance and short-term memory are not deteriorated when people cycle at 30% Wmax. Furthermore, cycling had a positive effect on response speed across tasks requiring variable amounts of attention and inhibition.

Apical hair cell degeneration causes the increase in the amplitude of summating potential

Conclusion: This study indicates that the lesion of hair cells in the apical turn of the cochlea can cause the change in the summating potential (SP)/Compound potential (CAP) ratio.Objectives: Electrocochleography is a valuable clinic test for diagnosis of cochlear pathologies and the ratio of SP to CAP has been used to identify Meniere’s disease. However, it remains controversial whether the increase of the SP/CAP ratio represents exclusively the endolymphatic hydrops.Method: This study measured the SP and CAP in mice that displayed outer hair cell (OHC) degeneration in the apical section of the cochlea as their age increased.Results: As compared with the mice aged 8–10 months, the 24-month old mice displayed a significant increase in the amplitude of SP at 12–16 kHz. This result suggests that the degeneration of OHCs in the apical turn leads to the increase of the + SP at the middle frequencies. In contrast, the aging mice did not have a significant change in the CAP amplitude at super-threshold levels.

A Method for First-Order Earthquake Depth Estimation Using Superarrays

Source depth estimation is a key process in earthquake location, hazard assessment, and nuclear monitoring. For instance, hypocentral depth is an important parameter affecting the spatial attenuation of ground motions resulting from an earthquake and an important indicator of natural versus man‐made events. Resolving transition zone phase complexity is important in sparsely monitored areas, for improved location and magnitude estimation of a seismic event at regional‐to‐teleseismic distances. In response to this need, we demonstrate a new approach to first‐order depth estimation. Depth phases are notoriously difficult to identify, specifically for shallower events. The usual way of determining the depth of focus of an earthquake is to measure the difference Δ t P − pP between the arrival time of the direct P wave and the arrival time of the surface reflection pP . Once Δ t P − pP is calculated, the depth of the focus can then be estimated closely, assuming that the velocity structure between the surface and the event focus is satisfactorily known. Although this method sounds simple, one major challenge remains: depth‐phase identification. For this reason, many monitoring agencies pick few depth phases from earthquakes shallower than 70 km. For example, depth‐phase observations were reported for only about 5% of the analyst‐reviewed events listed in the revised event bulletins of the Prototype International Data Centre during the Group of Scientific Experts Technical Test No 3 (GSETT‐3) experiment (Murphy and Barker, 2006). Routine depth‐phase identification is complicated by issues including (1) focal mechanism (affecting the relative P and pP or sP amplitude), (2) differential attenuation effects, (3) variations of surface topography and of subsurface structure at the depth‐phase bounce points, (4) earthquake epicentral distance (e.g., complex coda of P phases bottoming at the transition zone of the upper and lower mantle makes pP identification difficult), (5) rupture duration for large earthquakes ( M …

The protective effect of Borago Officinalis extract on amyloid β (25-35)-induced long term potentiation disruption in the dentate gyrus of male rats.

Alzheimer's disease (AD) begins with impairment in synaptic functions before developing into later neurodegeneration and neural loss. In the present study we have examined the protective effects of Borago Officinalis (borage) extract on amyloid β (Aβ)--Induced long term potentiation (LTP) disruption in hippocampal dentate gyrus (DG). Wistar male rats received intrahippocampal (IHP) injection of the Aβ (25-35) and borage extract throughout gestation (100 mg/kg). LTP in perforant path- DG synapses was assessed using electrophysiology method and field excitatory post- synaptic potential (fEPSP) slope and population spike (PS) amplitude were measured by 400 Hz tetanization. Finally, the total thiol content of hippocampus was measured using colorimetric reaction based on the Ellman's method. The results showed that Aβ (25-35) significantly decreased fEPSP slope and SP amplitude comparing with the control and sham group, whereas borage extract administration increased these parameters compared to the Aβ group. Aβ induced a remarkable decrease in total thiol content of hippocampus and borage prevented the decrease of the hippocampal total sulfhydryl (SH) groups. This data suggest that Aβ (25-35) can effectively inhibit LTP in the granular cells of the DG in hippocampus, and borage supplementation reverse the synaptic plasticity in DG following Aβ treatment and that borage consumption may lead to an improvement of AD-induced cognitive dysfunction.

Electrocochleography in individuals with Meniere′s disease

Background: Electrocochleography (ECochG) is a useful tool helping in the diagnosis of Meniere's disease (MD). Extra-tympanic ECochG is a non-invasive technique to record the amplitude of summating potential (SP) alone or the amplitude ratio of SP and action potential (AP). Objectives: The present study was aimed to measure the SP and AP amplitudes alone and the ratio (SP/AP) in individuals with normal hearing and in those with MD. Materials and Methods: A total of 63 ears from 34 individuals with normal hearing and those with MD were selected for the study. Individuals with MD had hearing impairment in the range of mild to moderate sensorineural hearing loss. Extra-tympanic non-invasive ECochG recording was done for all the participants. Results: The results of the study revealed that in individuals with normal hearing, 75.75% of the individual ear had SP responses noticeable, whereas in individuals with MD, only 46.66% had SP waveforms present. Further, the mean latency and amplitude of SP were found to be 0.93 msec and 0.29 μV, respectively, in Meniere's ear, whereas in normal ears, they were 0.64 msec and 0.11 μV, respectively. In addition to that, a significant difference in SP/AP amplitude ratio between individuals with normal hearing and those with MD was also reported. Conclusion: Therefore, from the present study one can conclude that the SP values increase both in terms of latency and amplitude in pathological condition. Also, it can be concluded that SP/AP amplitude ratio can help in differentiating individuals with MD from individuals with normal hearing.

A comparison of three methods of using transtympanic electrocochleography for the diagnosis of Meniere's disease: Click summating potential measurements, tone burst summating potential amplitude measurements, and biasing of the summating potential using a low frequency tone

Conclusion: Stimulus biasing modulated the amplitude of the tone burst evoked summating potential (SP) in ears affected by Meniere's disease less than in normal ears. A reduced SP bias ratio added diagnostic accuracy for the diagnosis of Meniere's disease. Objectives: To evaluate the effect of stimulus biasing on the human tone burst SP, and to determine if stimulus biasing could contribute to the electrocochleography as a means of confirming the diagnosis of Meniere's disease. Patients and methods: Patients referred for transtympanic electrocochleography (TT ECochG) were assessed prospectively on clinical grounds according to the AAO-HNS criteria and a scale devised by one of the authors. A Meniere's group of ears and a non-Meniere's group of ears was determined. The ears opposite a Meniere's ear were not included in the analysis. The ratio of the click SP amplitude and the action potential (AP) amplitude (SP/AP ratio), the tone burst SP amplitude at 500 Hz,1 kHz, 2kHz and 8 kHz, and the effect of stimulus biasing on the tone burst SP were measured. Results: A unipolar stimulus biasing ratio established for the modulation of the 1 kHz tone burst SP separated the Meniere's ears from the non-Meniere's ears with a sensitivity of 85% at a specificity of 80.6% and the difference between groups reached statistical significance (p=0.016). The 1 kHz SP amplitude measurements and the stimulus biasing measurements were superior to the click SP/AP ratio for identifying the Meniere's group. A combination of 1 kHz SP amplitude measurements and SP bias ratio separated the Meniere's ears from the non-Meniere's ears with an accuracy of 85%.

Improved sensitivity of electrocochleography in the diagnosis of Meniere's disease

ECochG has long been shown to complement the diagnosis of MD, primarily through measurement of the SP/AP amplitude ratio. While reported in the literature to be highly specific to this disorder, ECochG's sensitivity in the general MD population remains relatively low (ranging from 20–65%). The current study assessed the sensitivity and specificity of the ECochG protocol we employ for suspected MD patients, which includes measuring both the amplitudes and areas of the SP and AP to clicks (to derive the SP/AP amplitude and area ratios), and the SP amplitudes to 1000 and 2000 Hz tone bursts. A retrospective chart review was conducted to compare ECochG results from 178 suspected MD patients with their eventual diagnoses. Measurements of highest sensitivity and specificity (determined using a logistic regression analysis) included: SP amplitude, SP area, SP/AP area ratio, and total SP-AP area. Sensitivity and specificity values associated with these measures were 92% and 84%, respectively. The sensitivity value is considerably higher than previously reported, and is attributable to the inclusion of area measurements in our protocol.SumarioLa ECochG ha demostrado ser complementaria en el diagnóstico de la enfermedad de Meniere (MD) principalmente medi-ante la medición de la amplitud del ratio SP/AP. Mientras que se ha reportado en la literatura la alta especificidad de la ECochG, su sensibilidad en la población general con MD permanece relativamente baja (en un rango del 20 al 65%). Este estudio evalúa la sensibilidad y la especificidad del protocolo de ECochG que empleamos en pacientes con sospecha de MD, el cual incluye la medición tanto de la amplitud y las áreas de SP y AP con clics (para derivar los ratios de área y amplitud SP/AP), y las amplitudes de SP con burst tonales de 1000 y 2000Hz. Se construyó una tabla retrospectiva para comparar los resultados de ECochG de 178 pacientes con sospecha de MD, con sus diagnósticos eventuales. Las mediciones de la más alta sensibilidad y especificidad (determinadas mediante un análisis de regresión logística) incluyeron: amplitud SP, área SP, ratio de área SP/AP y área total SP-AP. La sensibilidad y la especificidad asociadas con estas mediciones fueron 92% y 84% respectivamente. El valor de sensibilidad es considerable-mente mayor que el previamente reportado y se atribuye a la inclusión de la medición del área en nuestro protocolo.

Gust occurrence in simulated non-stationary winds

An investigation is presented of peak gust intensity in non-stationary winds of different durations, in which the non-turbulent component of the event is fully controlled. A typical downburst was simulated repeatedly using a technique that utilizes a parametric analytical model of the downburst's non-turbulent winds, and an amplitude-modulated Gaussian stochastic process for the turbulent component. The peak gust strength of each event was expressed as a peak factor in relation to the largest non-turbulent speed. The properties of the simulated downburst peak factors are compared with those of stationary events of varied duration. A parametric study in which the non-turbulent component of the wind was simulated using a sine wave, which can be related to a downburst through the use of a “storm period” (SP) parameter, was conducted. A range of SP and turbulence amplitude modulation factors were used, and the properties of the peak factors are discussed.

Constructing a cochlear transducer function from the summating potential using a low-frequency bias tone

A new method is developed to construct a cochlear transducer function using modulation of the summating potential (SP), a dc component of the electrical response of the cochlea to a sinusoid. It is mathematically shown that the magnitude of the SP is determined by the even-order terms of the power series representing a nonlinear function. The relationship between the SP magnitudes and the second derivative of the transducer function was determined by using a low-frequency bias tone to position a high-frequency probe tone at different places along the cochlear transducer function. Two probe tones (6 kHz and 12 kHz) ranging from 70 to 90 dB SPL and a 25-Hz bias tone at 130 dB SPL were simultaneously presented. Electric responses from the cochlea were recorded by an electrode placed at the round window to obtain the SP magnitudes. The experimental results from eight animals demonstrated that the SP magnitudes as a function of bias levels are essentially proportional to the second derivative of a sigmoidal Boltzmann function. This suggests that the low-frequency modulated SP amplitude can be used to construct a cochlear transducer function.

Amplitude effects on electrocochleography outcomes.

Electrocochleography measures in humans were examined to determine factors affecting results. Retrospective study. Analysis was performed on data from 479 patients seen from 1998 to 2002 who underwent electrocochleography with a tympanic membrane electrode. Measures from click evoked electrocochleography (the summating potential to action potential ratio [SP/AP]) were compared with tone evoked electrocochleography (the SP amplitude). Findings indicate a strong correlation between click and tone measures if the AP from click measures was over 1 microV (P <.001), but no significant correlation between these measures if the AP was under 1 microV. Results were also analyzed with respect to patient hearing sensitivity and final diagnosis. Tympanic membrane electrocochleography is more efficacious when the AP from click stimulation is over 1 microV.

Rate influences on tone burst summating potential amplitude in electrocochleography: clinical a and experimental b data

Electrocochleographic recordings of action and summating potentials are widely used in the electrophysiological assessment of endolymphatic hydrops (ELH). Increased amplitudes of the summating potential (SP) in response to tone burst stimuli are indicative of positive ELH. This study reports the effect of repetition rate of tone burst stimulation on the SP amplitude. Using transtympanic electrocochleography (ECochG), the SP in response to 1 kHz tone bursts was recorded in both a Ménière and a non-Ménière population. Absolute values of the SP were systematically higher in the Ménière group. Moreover, in the Ménière and non-Ménière groups, the response amplitudes of the SP at a repetition rate of 8.4 tone bursts/s were only 66 and 32%, respectively, of the maximal response amplitude which was obtained at the rate of 37.4 tone bursts/s. Additionally, in normal guinea pigs chronically implanted with a round window electrode, the SP was recorded to 0.5–16 kHz tone burst stimulations presented at 100 dB SPL with the same different repetition rates. Similar enhancement of the SP amplitude was observed from 8.4 to 37.4 stimuli/s, whatever the frequency. This effect is interpreted as an increased asymmetry of vibration of the cochlear partition, whose mechanical operating point would not return to the normal resting position at high repetition rates, since it is permanently shifted in ELH.

Use of electrocochleography in the diagnosis of Meniere's disease.

The diagnosis of Meniere's disease has always been a source of confusion. There is no single test that is definitive for the diagnosis. Recent advances have enabled clinicians to noninvasively test the function of the inner ear and its associated neural pathways. The electrocochleogram (ECOG) has been advocated as a reliable test that is diagnostic for Meniere's disease. This study was undertaken to assess the value of ECOG in establishing the diagnosis of Meniere's disease. Patients who were suspected of having Meniere's disease were prospectively entered into a study of the diagnostic value of ECOG. Each patient had a complete evaluation including a detailed history, physical examination, laboratory studies, and audiometric tests. University otolaryngology clinic. A group of 199 patients who presented to a neurotology clinic and were suspected to have symptoms consistent with Meniere's disease. ECOG testing. Audiometric thresholds, action potential magnitude (AP), summating potential amplitude (SP), AP latency, and clinical evaluations were assessed. The ECOG was found to correlate with historical and audiometric criteria that are used to diagnose the disease. The percentage of abnormal ECOG did not correlate with stage of disease or duration of time that symptoms were present. The ECOG has limited value in the diagnosis of Meniere's disease. It appears to correlate with the length of time patients experience symptoms and their audiometric findings. It was not correlated with the number of symptoms that the patient experienced at the time that the study was conducted.