Burst Stimuli Research Articles

Temporal patterns in electrical nerve stimulation: Burst gap code shapes tactile frequency perception.

We have previously described a novel temporal encoding mechanism in the somatosensory system, where mechanical pulses grouped into periodic bursts create a perceived tactile frequency based on the duration of the silent gap between bursts, rather than the mean rate or the periodicity. This coding strategy may offer new opportunities for transmitting information to the brain using various sensory neural prostheses and haptic interfaces. However, it was not known whether the same coding mechanisms apply when using electrical stimulation, which recruits a different spectrum of afferents. Here, we demonstrate that the predictions of the burst gap coding model for frequency perception apply to burst stimuli delivered with electrical pulses, re-emphasising the importance of the temporal structure of spike patterns in neural processing and perception of tactile stimuli. Reciprocally, the electrical stimulation data confirm that the results observed with mechanical stimulation do indeed depend on neural processing mechanisms in the central nervous system, and are not due to skin mechanical factors and resulting patterns of afferent activation.

The Genetics of Variation of the Wave 1 Amplitude of the Mouse Auditory Brainstem Response

This is the first genome-wide association study with the Hybrid Mouse Diversity Panel (HDMP) to define the genetic landscape of the variation in the suprathreshold wave 1 amplitude of the auditory brainstem response (ABR) both pre- and post-noise exposure. This measure is correlated with the density of the auditory neurons (AN) and/or the compliment of synaptic ribbons within the inner hair cells of the mouse cochlea. We analyzed suprathreshold ABR for 635 mice from 102 HMDP strains pre- and post-noise exposure (108dB 10kHz octave band noise exposure for 2h) using auditory brainstem response (ABR) wave 1 suprathreshold amplitudes as part of a large survey (Myint et al., Hear Res 332:113-120, 2016). Genome-wide significance levels for pre- and post-exposure wave 1 amplitude across the HMDP were performed using FaST-LMM. Synaptic ribbon counts (Ctbp2 and mGluR2) were analyzed for the extreme strains within the HMDP. ABR wave 1 amplitude varied across all strains of the HMDP with differences ranging between 2.42 and 3.82-fold pre-exposure and between 2.43 and 7.5-fold post-exposure with several tone burst stimuli (4kHz, 8kHz, 12kHz, 16kHz, 24kHz, and 32kHz). Immunolabeling of paired synaptic ribbons and glutamate receptors of strains with the highest and lowest wave 1 values pre- and post-exposure revealed significant differences in functional synaptic ribbon counts. Genome-wide association analysis identified genome-wide significant threshold associations on chromosome 3 (24kHz; JAX00105429; p < 1.12E-06) and chromosome 16 (16kHz; JAX00424604; p < 9.02E-07) prior to noise exposure and significant associations on chromosomes 2 (32kHz; JAX00497967; p < 3.68E-08) and 13 (8kHz; JAX00049416; 1.07E-06) after noise exposure. In order to prioritize candidate genes, we generated cis-eQTLs from microarray profiling of RNA isolated from whole cochleae in 64 of the tested strains.This is the first report of a genome-wide association analysis, controlled for population structure, to explore the genetic landscape of suprathreshold wave 1 amplitude measurements of the mouse ABR. We have defined two genomic regions associated with wave 1 amplitude variation prior to noise exposure and an additional two associated with variation after noise exposure.

Maximum Output and Low-Frequency Limitations of B71 and B81 Clinical Bone Vibrators: Implications for Vestibular Evoked Potentials.

Bone-conducted vestibular evoked myogenic potentials (VEMPs) are tuned to have their maximum amplitude in response to tone bursts at or below 250 Hz. The low-frequency limitations of clinical bone vibrators have not been established for transient, tone burst stimuli at frequencies that are optimal for eliciting VEMPs. Tone bursts with frequencies of 250 to 2000 Hz were delivered to B71 and B81 bone vibrators and their output was examined using an artificial mastoid. The lower-frequency limit of the transducers was evaluated by examining the spectral output of the bone vibrators. Maximum output levels were evaluated by measuring input-output functions across a range of stimulus levels. Both the B71 and B81 could produce transient tone bursts with frequency as low as 400 Hz. However, tone bursts with frequencies of 250 and 315 Hz resulted in output with peak spectral energy at approximately 400 Hz. From 500 to 2000 Hz, maximum output levels within the linear range were between 120 and 128 dB peak force level. The newer B81 bone vibrator had a maximum output approximately 5 dB higher than the B71 at several frequencies. These findings demonstrate that both transducers can reach levels appropriate to elicit bone-conducted VEMPs, but the low-frequency limitations of these clinical bone vibrators limit tone burst frequency to approximately 400 Hz when attempting to stimulate the otolith organs via tone bursts.

Human medial olivocochlear reflex: Contralateral activation effect on low and high frequency cochlear response

The role of the medial olivocochlear (MOC) reflex has been investigated by assessing changes of cochlear responses (CR) in humans. The CR consists of pre-neural and neural potentials originating from the inner ear, and at high signal levels is dominated by cochlear microphonic (CM). The CM originates from the outer hair cells, where the MOC fibers synapse, and there is little research about using it to investigate the MOC reflex in humans. The current study aimed to investigate the effect of contralateral activation of the MOC reflex on the CR in humans. The CR was recorded in female adults (n = 16) to 500 and 2000 Hz tone burst stimuli presented at 80 dB nHL with and without contralateral broadband noise (CBBN) at 40 dB SPL. Two different methods were utilized to quantify and analyze the CR data: peak amplitude and power spectrum. Results revealed enhancement of the CR amplitude with activation of the MOC reflex. Furthermore, on average, enhancement in the CR amplitude was observed to 500 Hz, but not 2000 Hz stimulus. The CR power spectrum findings revealed similar findings to the peak amplitude. These findings indicate the MOC effect is measurable when using a low frequency stimulus, but not high frequency. Moreover, the CR could be used as a potential tool to study the MOC reflex in humans.

Normative Data for Cortical Evoked Response Audiometry of a Heterogeneous Indian Population and Its Comparison with Behavioral Audiometry.

Objective:The objective of the study is to establish normative values of cortical evoked response audiometry (CERA) in a heterogeneous Indian population and correlate CERA threshold with pure tone audiometric (PTA) threshold values.Materials and Methods:A prospective study was carried out on 31 volunteers (n = 62) who had no otological or neurological complaints. Two study groups were formed; Group 1 with individuals from 20 to 40 years (mean age of 29.1 years) and Group 2 with individuals from 41 to 60 years (mean age of 46.2 years). The latencies and amplitudes of the waves of P1, N1, and P2 at threshold and 70 dBnHL were measured.Results:Twenty-nine participants (94% of the ears) had CERA threshold within 20 dB of true behavioral threshold with only 6% having a difference of >20 dB with their PTA thresholds. There was a significant difference (P < 0.05) at 70 dB in amplitudes for waves P1, N1, and P2 at 2 kHz and additionally at 1 kHz for N1 between the two groups.Conclusion:Normative values for CERA in a heterogeneous Indian population at 70 dB nHL using tone burst stimulus was found to have an average latency of 46.5, 90.1, and 155.5 ms for P1, N1, and P2, respectively. The average amplitude of P1 at 70 dB nHL was 4.3 μV, N1, was 6.5 μV and P2 was 3.2 μV. Hearing threshold obtained with CERA gave a good indication of the actual behavioral hearing threshold of the normal controls, and the age of an individual had a significant effect on the values obtained during CERA testing with N1 being significantly larger at 1 kHz and 2 kHz in older adults when compared to young adults.

Vestibular evoked myogenic potentials (VEMP) captured in the forearm flexor muscles: a study of its feasibility and reference ranges

OBJECTIVE:To determine the central tendency measures and variability of vestibular evoked myogenic potential (VEMP) with regard to the latency and wave amplitude when potentials are captured from the flexor muscles of the forearm.METHODS:Ten adult volunteers with normal hearing underwent examination of their forearm flexor muscles (right and left sides; 20 samples in total) for VEMP acquisition. To this end, 200 tone burst stimuli at a 500 Hz frequency and 95 dBnHL intensity were promediated.RESULTS:No statistical differences were observed in VEMP responses acquired from the right and left forearm flexor muscles concerning P34 and N44 latencies (p=0.32 and 0.90, respectively). The mean latency obtained for the P34 wave component was 34.9 ms (±2.6), with a lower limit equal to 29.3 and an upper limit equal to 40.4 ms. The average latency of the N44 wave component was 43.6 ms (±2.1), with a lower limit of 39.1 ms and an upper limit of 48.1 ms. The results were consistent and had low variability, and showed an average asymmetry index of 15.4 (±10.7). These findings indicate that potentials may be investigated in different age groups and in specific clinical populations, such as pathologies that may alter the neuronal transmission of the inferior vestibular pathway, especially when a longer portion is observed.CONCLUSIONS:VEMP recording from forearm flexors is both feasible and stable, with latency reference ranges between 29.3 and 40.4 ms for P34, and 39.1 and 48.1 ms for N44.

Chemogenetic Activation of Excitatory Neurons Alters Hippocampal Neurotransmission in a Dose-Dependent Manner.

Designer receptors exclusively activated by designer drugs (DREADD)-based chemogenetic tools are extensively used to manipulate neuronal activity in a cell type-specific manner. Whole-cell patch-clamp recordings indicate membrane depolarization, coupled with increased neuronal firing rate, following administration of the DREADD ligand, clozapine-N-oxide (CNO) to activate the Gq-coupled DREADD, hM3Dq. Although hM3Dq has been used to enhance neuronal firing in order to manipulate diverse behaviors, often within 30 min to 1 h after CNO administration, the physiological effects on excitatory neurotransmission remain poorly understood. We investigated the influence of CNO-mediated hM3Dq DREADD activation on distinct aspects of hippocampal excitatory neurotransmission at the Schaffer collateral-CA1 synapse in hippocampal slices derived from mice expressing hM3Dq in Ca2+/calmodulin-dependent protein kinase α (CamKIIα)-positive excitatory neurons. Our results indicate a clear dose-dependent effect on field EPSP (fEPSP) slope, with no change noted at the lower dose of CNO (1 μM) and a significant, long-term decline in fEPSP slope observed at higher doses (5–20 μM). Further, we noted a robust θ burst stimulus (TBS) induced long-term potentiation (LTP) in the presence of the lower CNO (1 μM) dose, which was significantly attenuated at the higher CNO (20 μM) dose. Whole-cell patch-clamp recording revealed both complex dose-dependent regulation of excitability, and spontaneous and evoked activity of CA1 pyramidal neurons in response to hM3Dq activation across CNO concentrations. Our data indicate that CNO-mediated activation of the hM3Dq DREADD results in dose-dependent regulation of excitatory hippocampal neurotransmission and highlight the importance of careful interpretation of behavioral experiments involving chemogenetic manipulation.

Hearing impairment and associated morphological changes in pituitary adenylate cyclase activating polypeptide (PACAP)-deficient mice

Pituitary adenylate cyclase activating polypeptide (PACAP) is a regulatory and cytoprotective neuropeptide, its deficiency implies accelerated aging in mice. It is present in the auditory system having antiapoptotic effects. Expression of Ca2+-binding proteins and its PAC1 receptor differs in the inner ear of PACAP-deficient (KO) and wild-type (WT) mice. Our aim was to elucidate the functional role of PACAP in the auditory system. Auditory brainstem response (ABR) tests found higher hearing thresholds in KO mice at click and low frequency burst stimuli. Hearing impairment at higher frequencies showed as reduced ABR wave amplitudes and latencies in KO animals. Increase in neuronal activity, demonstrated by c-Fos immunolabeling, was lower in KO mice after noise exposure in the ventral and dorsal cochlear nuclei. Noise induced neuronal activation was similar in further relay nuclei of the auditory pathway of WT and KO mice. Based on the similar inflammatory and angiogenic protein profile data from cochlear duct lysates, neither inflammation nor disturbed angiogenesis, as potential pathological components in sensorineural hearing losses, seem to be involved in the pathomechanism of the presented functional and morphological changes in PACAP KO mice. The hearing impairment is probably concomitant with the markedly accelerated aging processes in these animals.

Excitation and electroporation by MHz bursts of nanosecond stimuli

Intense nanosecond pulsed electric field (nsPEF) is a novel modality for cell activation and nanoelectroporation. Applications of nsPEF in research and therapy are hindered by a high electric field requirement, typically from 1 to over 50 kV/cm to elicit any bioeffects. We show how this requirement can be overcome by engaging temporal summation when pulses are compressed into high-rate bursts (up to several MHz). This approach was tested for excitation of ventricular cardiomyocytes and peripheral nerve fibers; for membrane electroporation of cardiomyocytes, CHO, and HEK cells; and for killing EL-4 cells. MHz compression of nsPEF bursts (100–1000 pulses) enables excitation at only 0.01–0.15 kV/cm and electroporation already at 0.4–0.6 kV/cm. Clear separation of excitation and electroporation thresholds allows for multiple excitation cycles without membrane disruption. The efficiency of nsPEF bursts increases with the duty cycle (by increasing either pulse duration or repetition rate) and with increasing the total time “on” (by increasing either pulse duration or number). For some endpoints, the efficiency of nsPEF bursts matches a single “long” pulse whose amplitude and duration equal the time-average amplitude and duration of the bursts. For other endpoints this rule is not valid, presumably because of nsPEF-specific bioeffects and/or possible modification of targets already during the burst. MHz compression of nsPEF bursts is a universal and efficient way to lower excitation thresholds and facilitate electroporation.

Cortical auditory evoked potential in assessment of neonates: a study about minimum level of responses in term and preterm newborns

IntroductionThe study of the threshold level of cortical auditory response in adults has been investigated in previous studies. Due to maturational issues, little is known about these responses in neonates. Technological advances with automatic analysis devices now allow investigation in specific populations. Thus, new studies are needed to establish the feasibility of using this auditory potential to identify the lowest levels of responses in children. ObjectiveVerify and compare latency and amplitude in 80dBnNA and the minimum level of cortical auditory response in term and preterm neonates. MethodsA cross-sectional, comparative study involving 59 neonates, 35 full-term births and 24 preterm births, with positive results in the Neonatal Hearing Screening. The Hearlab system was used to investigate the P1i auditory potential with tone burst stimulus at frequencies of 500, 1000, 2000 and 4000Hz. The minimum response level search ranged from 80 to 0dBNA and was detected automatically. The results were compared between groups, evaluating the latency and amplitude in 80dBNA and the minimum level of cortical auditory response. ResultsThe mean values obtained for the minimum level of cortical auditory response in term group were 26±8.81; 26.14±6.97; 29±7.65 and 29.43±7.04dBNA and for preterm neonates of 31.96±10.41; 34.13±11.34; 33.64±11.03 and 37.73±11.92dBNA, for the frequencies of 500, 1000, 2000 and 4000Hz, respectively. There was a difference between groups for the latency of P1i at 4000Hz and the minimum response levels at 500, 1000 and 4000Hz, with higher values for preterm infants. ConclusionIt was possible to obtain latency and amplitude values at 80dBnNA and the minimum level of cortical response in term and preterm newborns, with different results between groups, with higher values in those born preterm.

Mismatch Negativity in Children with Cochlear Implant.

Introduction The mismatch negativity (MMN) is a negative long-latency auditory potential elicited by any discriminable change in a repetitive aspect of auditory stimulation. This evoked potential can provide cortical information about the sound processing, including in children who use cochlear implants. Objective To identify MMN characteristics regarding latency, amplitude, and wave area in cochlear implanted children and to identify associations among language development, speech perception and family involvement. Methods This is a descriptive, observational, cross-sectional study, which compared two groups: study group—children with cochlear implant, and control group—hearing children. The children were submitted to MMN evaluation with non-verbal tone burst stimulus, differing in frequency in sound field at 70 dBHL, with SmartEP equipment (Intelligent Hearing Systems, Miami, FL, USA). Speech perception and language development questionnaires were also applied, and the family participation in the rehabilitation process was classified. Results The occurrence of MMN was 73.3% for the control group and 53.3% for the study group. Values of latency, amplitude and area of MMN of children using cochlear implants were similar to those of hearing children, and did not differ between groups. The occurrence of MMN was not correlated to the variables of hearing, language and family categories. Conclusion Children with cochlear implants showed similar MMN responses to those of the children in the control group, with mean latency, amplitude and area of 208.9 ms (±12.8), -2.37 μV (±0.38) and 86.5 μVms (±23.4), respectively. There was no correlation between the presence of MMN and children's performance in the auditory and language development tests or family involvement during rehabilitation.

Deep Brain Stimulation of the Subthalamic Nucleus Induces Impulsive Responses to Bursts of Sensory Evidence.

Decisions are made through the integration of external and internal inputs until a threshold is reached, triggering a response. The subthalamic nucleus (STN) has been implicated in adjusting the decision bound to prevent impulsivity during difficult decisions. We combine model-based and model-free approaches to test the theory that the STN raises the decision bound, a process impaired by deep brain stimulation (DBS). Eight male and female human subjects receiving treatment for Parkinson's disease with bilateral DBS of the STN performed an auditory two-alternative forced choice task. By ending trials unpredictably, we collected reaction time (RT) trials in which subjects reached their decision bound and non-RT trials in which subjects were forced to make a decision with less evidence. A decreased decision bound would cause worse performance on RT trials, and we found this to be the case on left-sided RT trials. Drift diffusion modeling showed a negative drift rate. This implies that in the absence of new evidence, the amount of evidence accumulated tends to drift toward zero. If evidence is accumulated at a constant rate this results in the evidence accumulated reaching an asymptote, the distance of which from the bound was decreased by DBS (p = 0.0079, random shuffle test), preventing subjects from controlling impulsivity. Subjects were more impulsive to bursts of stimuli associated with conflict (p < 0.001, cluster mass test). In addition, DBS lowered the decision bound specifically after error trials, decreasing the probability of switching to a non-RT trial after an error compared to correct response (28% vs. 38%, p = 0.005, Fisher exact test). The STN appears to function in decision-making by modulating the decision bound and drift rate to allow the suppression of impulsive responses.

Sodium salicylate alters temporal integration measured through increasing stimulus presentation rates

Objective: High doses of sodium salicylate (SS) are known to induce tinnitus, general hyperexcitability in the central auditory system, and to cause mild hearing loss. We used the auditory brainstem response (ABR) to assess the effects of SS on auditory sensitivity and temporal processing in the auditory nerve and brainstem. ABRs were evoked using tone burst stimuli varying in frequency and intensity with presentation rates from 11/s to 81/s.Design: ABRs were recorded and analysed prior to and after SS treatment in each animal, and peak 1 and peak 4 amplitudes and latencies were determined along with minimal response threshold.Study Sample: Nine young adult CBA/CaJ mice were used in a longitudinal within-subject design.Results: No measurable effects of presentation rate were found on ABR threshold prior to SS; however, following SS administration increasing stimulus rates lowered ABR thresholds by as much as 10 dB and compressed the peak amplitude by intensity level functions.Conclusions: These results suggest that SS alters temporal integration and compressive nonlinearity, and that varying the stimulus rate of the ABR may prove to be a useful diagnostic tool in the study of hearing disorders that involve hyperexcitability.

The Effects of Riluzole on Cisplatin-induced Ototoxicity.

Introduction Riluzole (2-amino-6-trifluoromethoxy benzothiazole) is known as a neuroprotective, antioxidant, antiapoptotic agent. It may have beneficial effects on neuronal cell death due to cisplatin-induced ototoxicity. Objective To evaluate the effect of riluzole on cisplatin-induced ototoxicity in guinea pigs. Methods Twenty-four guinea pigs, studied in three groups, underwent auditory brainstem response evaluation using click and 8 kHz tone burst stimuli. Subsequently, 5 mg/kg of cisplatin were administered to all animals for 3 days intraperitoneally (i.p.) to induce ototoxicity. Half an hour prior to cisplatin, groups 1, 2 and 3 received 2 ml of saline i.p., 6 mg/kg of riluzole hydrochloride i.p., and 8 mg/kg of riluzole hydrochloride i.p., respectively, for 3 days. The auditory brainstem responses were repeated 24 hours after the last drug administration. The cochleae were analyzed by transmission electron microscopy (TEM). Results After drug administiration, for 8,000 Hz stimulus, group 1 had significantly higher threshold shifts when compared with groups 2 ( p < 0.05) and 3 ( p < 0.05), and there was no significant difference in threshold shifts between groups 2 and 3 ( p > 0.05). Transmission electron microscopy findings demonstrated the protective effect of riluzole on the hair cells and the stria vascularis, especially in the group treated with 8 mg/kg of riluzole hydrochloride. Conclusion We can say that riluzole may have a protective effect on cisplatin- induced ototoxicity. However, additional studies are needed to confirm these results and the mechanisms of action of riluzole.

Toward Optimizing cVEMP: 2,000-Hz Tone Bursts Improve the Detection of Superior Canal Dehiscence

Background: The cervical vestibular evoked myogenic potential (cVEMP) test measures saccular and inferior vestibular nerve function. The cVEMP can be elicited with different frequency stimuli and interpreted using a variety of metrics. Patients with superior semicircular canal dehiscence (SCD) syndrome generally have lower cVEMP thresholds and larger amplitudes, although there is overlap with healthy subjects. The aim of this study was to evaluate which metric and frequency best differentiate healthy ears from SCD ears using cVEMP. Methods: Twenty-one patients with SCD and 23 age-matched controls were prospectively included and underwent cVEMP testing at 500, 750, 1,000 and 2,000 Hz. Sound level functions were obtained at all frequencies to acquire threshold and to calculate normalized peak-to-peak amplitude (VEMPn) and VEMP inhibition depth (VEMPid). Third window indicator (TWI) metrics were calculated by subtracting the 250-Hz air-bone gap from the ipsilateral cVEMP threshold at each frequency. Ears of SCD patients were divided into three groups based on CT imaging: dehiscent, thin or unaffected. The ears of healthy age-matched control subjects constituted a fourth group. Results: Comparing metrics at all frequencies revealed that 2,000-Hz stimuli were most effective in differentiating SCD from normal ears. ROC analysis indicated that for both 2,000-Hz cVEMP threshold and for 2,000-Hz TWI, 100% specificity could be achieved with a sensitivity of 92.0%. With 2,000-Hz VEMPn and VEMPid at the highest sound level, 100% specificity could be achieved with a sensitivity of 96.0%. Conclusion: The best diagnostic accuracy of cVEMP in SCD patients can be achieved with 2,000-Hz tone burst stimuli, regardless of which metric is used.

Air-Conducted Vestibular Evoked Myogenic Potential Testing in Children, Adolescents, and Young Adults: Thresholds, Frequency Tuning, and Effects of Sound Exposure.

Pediatric vestibular evaluations incorporate cervical and ocular vestibular evoked myogenic potential (c- and oVEMP, respectively) testing; however, in children, c- and oVEMP thresholds have been minimally investigated and frequency tuning is unknown. Children are also at risk for unsafe sound exposure secondary to VEMP. While it is unknown if VEMP threshold testing leads to cochlear changes, it is possible that this risk increases due to the increased number of trials needed to obtain a threshold. Obtaining VEMP thresholds at various frequencies in children provides further information for pediatric normative VEMP data. Assessing for cochlear changes after VEMP threshold testing would provide information on the safety of threshold VEMP testing in children. The objectives of this study were to (1) characterize c- and oVEMP thresholds in children, adolescents, and young adults with normal hearing using 500 and 750 Hz tone burst (TB) stimuli, (2) compare frequency tuning of 500 and 750 Hz TB, and (3) assess whether cochlear changes exist after VEMP threshold testing. It is hypothesized that children, adolescents, and young adults would not show age-related changes to the vestibular system. Therefore, reliable VEMP thresholds would be seen below maximum acoustical stimulation levels (e.g., <125 dB SPL) and frequency tuning will be similar for 500 and 750 Hz TB stimuli. Ten children (age 4-9), 10 adolescents (age 10-19), and 10 young adults (age 20-29) with normal hearing and tympanometry participated. All subjects received c- and oVEMP testing at maximum stimulation and threshold. To address frequency tuning, but not exceed recommended sound exposure allowance, subjects received a 500 Hz TB stimulus in one ear and a 750 Hz TB stimulus in the other ear. Subjects completed tympanometry pre-VEMP, and audiometric threshold testing, distortion product otoacoustic emission testing, and subjective questionnaire pre- and post-VEMP to study the effect of VEMP exposure on cochlear function for each stimulus frequency. (1) cVEMP thresholds were determined for both stimulus frequencies for children (500 Hz = 106 dB SPL; 750 Hz = 106 dB SPL), adolescents (500 Hz = 107.5 dB SPL; 750 Hz = 109.5 dB SPL), and young adults (500 Hz = 111.5 dB SPL; 750 Hz = 112 dB SPL). oVEMP thresholds were also obtained in response to both stimulus frequencies for children (500 Hz = 111.1 dB SPL; 750 Hz = 112.2 dB SPL), adolescents (500 Hz = 112.5 dB SPL; 750 Hz = 114.5 dB SPL), and young adults (500 Hz = 116 dB SPL; 750 Hz = 117 dB SPL). Similar thresholds were found between groups except for children who had significantly lower thresholds compared with adults for cVEMP (500 Hz: p = 0.002; 750 Hz: p = 0.004) and oVEMP (500 Hz: p = 0.01; 750 Hz: p = 0.02). In addition, equivalent ear-canal volume and VEMP thresholds were linearly correlated. (2) There was no significant effect of stimulus frequency on VEMP response rates, latencies, peak to peak amplitudes, or thresholds, suggesting similar frequency tuning for 500 and 750 Hz. (3) There were no significant effects of VEMP threshold testing on cochlear function for either stimulus frequency. Children, adolescents, and young adults show VEMP thresholds below high stimulation levels and had similar frequency tuning between 500 and 750 Hz. Use of 750 Hz could be regarded as the safer stimuli due to its shorter duration and thus reduced sound exposure. Children with smaller ear-canal volume had present responses at maximum stimulation and lower thresholds, suggesting that VEMP testing could be initiated at lower acoustic levels to minimize sound exposure and optimize testing.

Random Neuronal Networks show homeostatic regulation of global activity while showing persistent changes in specific connectivity paths to theta burst stimuli

Learning in neuronal networks based on Hebbian principle has been shown to lead to destabilizing effects. Mechanisms have been identified that maintain homeostasis in such networks. However, the way in which these two opposing forces operate to support learning while maintaining stability is an active area of research. In this study, using neuronal networks grown on multi electrode arrays, we show that theta burst stimuli lead to persistent changes in functional connectivity along specific paths while the network maintains a global homeostasis. Simultaneous observations of spontaneous activity and stimulus evoked responses over several hours with theta burst training stimuli shows that global activity of the network quantified from spontaneous activity, which is disturbed due to theta burst stimuli is restored by homeostatic mechanisms while stimulus evoked changes in specific connectivity paths retain a memory trace of the training.

Evaluation of saccular and inferior vestibular nerve function in children with auditory neuropathy spectrum disorder.

The aim of the current work was to evaluate the function of the saccule and inferior vestibular nerve in children with auditory neuropathy spectrum disorder (ANSD) by recording the cervical-evoked myogenic potentials (C-VEMP) on those children and to compare C-VEMP results in ANSD children of pre-lingual onset to those in ANSD children of post-lingual onset. The study included 38 ANSD children of pre-lingual onset, 16 ANSD children of post-lingual onset, and 20 control children. All participant children were subjected to C-VEMP testing using 500Hz tone burst stimuli. The vast majority of ANSD children of pre-lingual onset (35 out of 38; 92.1%) had bilateral intact C-VEMP response with C-VEMP parameters (amplitude, asymmetric ratio, latency, and inter-aural latency difference) that were not statistically different than those in the control children. Only three children had bilateral absent C-VEMP response. On the other hand, the majority of ANSD children of post-lingual onset (11 out of 16; 68.75%) had bilateral absent C-VEMP response. The remaining five children had bilateral intact C-VEMP response with C-VEMP parameters that were not statistically different than those in the control children. The pathology of ANSD spares the saccule and inferior vestibular nerve in the vast majority of ANSD children of pre-lingual onset, while it involves them in the majority of ANSD of post-lingual onset reflecting different site(s) of lesion between the two ANSD categories. Such results have important clinical implications as regards to the management of ANSD in children.

Intra-Cochlear Electrocochleography During Cochear Implant Electrode Insertion Is Predictive of Final Scalar Location.

Electrocochleography (ECochG) patterns observed during cochlear implant (CI) electrode insertion may provide information about scalar location of the electrode array. Conventional CI surgery is performed without actively monitoring auditory function and potential damage to intracochlear structures. The central hypothesis of this study was that ECochG obtained directly through the CI may be used to estimate intracochlear electrode position and, ultimately, residual hearing preservation. Intracochlear ECochG was performed on 32 patients across 3 different implant centers. During electrode insertion, a 50-ms tone burst stimulus (500 Hz) was delivered at 110 dB SPL. The ECochG response was monitored from the apical-most electrode. The amplitude and phase changes of the first harmonic were imported into an algorithm in an attempt to predict the intracochlear electrode location (scala tympani [ST], translocation from ST to scala vestibuli [SV], or interaction with basilar membrane). Anatomic electrode position was verified using postoperative computed tomography (CT) with image processing. CT analysis confirmed 25 electrodes with ST position and 7 electrode arrays translocating from ST into SV. The ECochG algorithm correctly estimated electrode position in 26 (82%) of 32 subjects while 6 (18%) electrodes were wrongly identified as translocated (sensitivity = 100%, specificity = 77%, positive predictive value = 54%, and a negative predictive value = 100%). Greater hearing loss was observed postoperatively in participants with translocated electrode arrays (36 ± 15 dB) when compared with isolated ST insertions (28 ± 20 dB HL). This result, however, was not significant (p = 0.789). Intracochlear ECochG may provide information about CI electrode location and hearing preservation.

Measurements of bone conduction auditory brainstem response with the new audiometric bone conduction transducer Radioear B81

Objective: To compare recordings of bone conduction (BC) stimulated auditory brainstem response (ABR) obtained using the newer BC transducer Radioear B81 and the conventional BC transducer Radioear B71. Balanced electromagnetic separation transducer (BEST) design found in the B81 may influence the ABR magnitudes and latencies, as well as electrical artefacts.Design: ABRs to tone burst stimuli of 500 Hz, 2000 Hz, 4000 Hz, click stimulation, and broad-band chirp stimulation at 20 and 50 dB nHL were recorded. For each device, stimulus and intensity level, the ABR Jewett wave V amplitude and latency were obtained. The device-related electrical stimulus artefacts on the ABR recordings were also analysed by calculating the Hilbert envelope of the peri-stimulus recording segments.Study sample: Twenty-three healthy adults with normal hearing were included in the study.Results: The ABRs obtained by the B81 were similar to that of the B71 in terms of ABR wave V amplitude and latency. However, the B81 produced smaller electrical artefacts than B71 and this difference was statistically significant. Conclusions: The BC transducer Radioear B81 provides ABRs comparable to Radioear B71 while causing smaller artefacts.