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Background: Vestibular schwannomas (VS) are benign intracranial tumors caused by loss of function of the merlin tumor suppressor. We tested three hypotheses related to radiation, hearing loss (HL), and VS cell survival: (1) radiation causes HL by injuring auditory hair cells (AHC), (2) fractionation reduces radiation-induced HL, and (3) single fraction and equivalent appropriately dosed multi-fractions are equally effective at controlling VS growth. We investigated the effects of single fraction and hypofractionated radiation on hearing thresholds in rats, cell death pathways in rat cochleae, and viability of human merlin-deficient Schwann cells (MD-SC). Methods: Adult rats received cochlear irradiation with single fraction (0 to 18 Gray [Gy]) or hypofractionated radiation. Auditory brainstem response (ABR) testing was performed for 24 weeks. AHC viabilities were determined using immunohistochemistry. Neonatal rat cochleae were harvested after irradiation, and gene- and cell-based assays were conducted. MD-SCs were irradiated, and viability assays and immunofluorescence for DNA damage and cell cycle markers were performed. Results: Radiation caused dose-dependent and progressive HL in rats and AHC losses by promoting expression of apoptosis-associated genes and proteins. When compared to 12 Gy single fraction, hypofractionation caused smaller ABR threshold and pure tone average shifts and was more effective at reducing MD-SC viability. Conclusions: Investigations into the mechanisms of radiation ototoxicity and VS radiobiology will help determine optimal radiation regimens and identify potential therapies to mitigate radiation-induced HL and improve VS tumor control.

This paper introduces and evaluates a speech signal manipulation scheme that generates transient speech induced binaural beats (SBBs). These SBBs can only be perceived when different signals are presented dichotically (to both ears). Event-related potentials were recorded in 22 normal-hearing subjects. Dichotic stimulus presentation reliably evoked auditory late responses (ALRs) in all subjects using such manipulated signals. As control measurements, diotic stimulation modalities were presented to confirm that the ALRs were not evoked by the speech signal itself or that the signal manipulation scheme created audible artifacts. Since diotic measurements evoked no ALRs, responses from dichotic stimulation are a pure correlate of binaural interaction. While there are several auditory stimuli (mostly modulated sinusoids or noise) that share this characteristic, none of them are based on running speech. Because SBBs can be added to any arbitrary speech signal, they could easily be combined with psychoacoustic tests, for example speech reception thresholds, adding an objective measure of binaural interaction.

Key points Cutaneous reflexes were tested to examine the neuronal mechanisms contributing to muscle spasms in humans with chronic spinal cord injury (SCI). Specifically, we tested the effect of Achilles and tibialis anterior tendon vibration on the early and late components of the cutaneous reflex and reciprocal Ia inhibition in the soleus and tibialis anterior muscles in humans with chronic SCI. We found that tendon vibration reduced the amplitude of later but not earlier cutaneous reflex in the antagonist but not in the agonist muscle relative to the location of the vibration. In addition, reciprocal Ia inhibition between antagonist ankle muscles increased with tendon vibration and participants with a larger suppression of the later component of the cutaneous reflex had stronger reciprocal Ia inhibition from the antagonistic muscle. Our study is the first to provide evidence that tendon vibration attenuates late cutaneous spasm-like reflex activity, likely via reciprocal inhibitory mechanisms, and may represent a method, when properly targeted, for controlling spasms in humans with SCI. Abstract The neuronal mechanisms contributing to the generation of involuntary muscle contractions (spasms) in humans with spinal cord injury (SCI) remain poorly understood. To address this question, we examined the effect of Achilles and tibialis anterior tendon vibration at 20, 40, 80 and 120 Hz on the amplitude of the long-polysynaptic (LPR, from reflex onset to 500 ms) and long-lasting (LLR, from 500 ms to reflex offset) cutaneous reflex evoked by medial plantar nerve stimulation in the soleus and tibialis anterior, and reciprocal Ia inhibition between these muscles, in 25 individuals with chronic SCI. We found that Achilles tendon vibration at 40 and 80 Hz, but not other frequencies, reduced the amplitude of the LLR in the tibialis anterior, but not the soleus muscle, without affecting the amplitude of the LPR. Vibratory effects were stronger at 80 than 40 Hz. Similar results were found in the soleus muscle when the tibialis anterior tendon was vibrated. Notably, tendon vibration at 80 Hz increased reciprocal Ia inhibition between antagonistic ankle muscles and vibratory-induced increases in reciprocal Ia inhibition were correlated with decreases in the LLR, suggesting that participants with a larger suppression of later cutaneous reflex activity had stronger reciprocal Ia inhibition from the antagonistic muscle. Our study is the first to provide evidence that tendon vibration suppresses late spasm-like activity in antagonist but not agonist muscles, likely via reciprocal inhibitory mechanisms, in humans with chronic SCI. We argue that targeted vibration of antagonistic tendons might help to control spasms after SCI.

Mesenchymal stem cell (MSC) therapy is an emerging treatment modality for various human diseases. Although induced pluripotent stem cells have been explored for the restoration of hearing, the potential of MSCs as a therapeutic strategy for various cochlear insults is not precisely known. MSCs possess anti-inflammatory, anti-apoptotic and neuroprotective properties, making them an attractive target for the treatment of inner ear disorders such as hair cell damage in response to inflammation. Most of the previous studies have used immunosuppression or the complex surgical techniques to deliver stem cells into the cochlea. However, no information is available regarding the biocompatibility and safety of MSCs in the inner ear in immunocompetent cochlea. The aim of the present study was to determine the effect of non-surgical administration of rodent bone marrow derived MSCs (BM-MSCs) through transtympanic delivery on the cochlear function and to assess any adverse effects on the auditory system employing a rat model without immunosuppression. We observed that the transtympanic administration of BM-MSCs has no significant effect on the hearing thresholds as determined by auditory brainstem response and distortion product otoacoustic emissions. Histopathological examination revealed no recruitment of inflammatory leukocytes and edema in the cochlea of BM-MSCs administrated rats. The results of this study suggest that transtympanic administration of BM-MSCs is safe and can be explored in providing otoprotection against cochlear insults. Anat Rec, 303:487-493, 2020. © 2019 American Association for Anatomy.

Nanotechnology is a novel tool for handling of matter at the microscopic level, within the atomic, molecular, and supramolecular domains. While neuroscience and neuroengineering operate at the cellular level, their association with the nanotechnology is bringing synergic unexpected strides. In the last decade, an unprecedented increase in the successful application of nanotechnology methods to basic neuroscience and to clinical practice occurred. Novel nanotechnologies are expected to bring important insights into brain mechanisms and medical care to patients. The chapter details attempt from different disciplines to improve brain performance in both healthy people and patients who suffer from neurological disabilities. Applications of nanotechnology (with the advent of nanoparticles, nanowires, carbon nanotubes, devices, sensors, interfaces) are employed to augment, invasive/noninvasive record, stimulate, repair, cure, or regenerate the brain functions (sensory, motor/locomotor, cognitive/memory/learning, reward/emotion) and brain circuitry (in cortex, subcortex/basal ganglia/thalamus, brainstem, spinal cord).

Major depression disorder is often accompanied by the dysfunction of the lateral habenula nucleus (LHb). The onset of subclinical depression is often a precursor to the onset of major depression disorder (MDD), and the brain function patterns of patients with subclinical depression are similar to those of patients with major depression. Therefore, it seems that the functional connection pattern of LHb and its surrounding regions can be used to predict subclinical depression. This chapter reviews a subclinical depression prediction model that detects abnormal functional connections through machine learning. By means of resting-state functional magnetic resonance imaging (fMRI), the functional connections of the brain regions were calculated, and the functional brain network was modeled. Functional connections with significant differences were entered into the machine learning model as classifier features. Anomalous functional connections, which have a greater impact on classification results, are evaluated for accuracy, receiver operating characteristic curve (ROC), and area under curve (AUC). Based on the analysis of the functional connection network of the whole brain, we found five brain regions having the greatest difference between the subclinical depression (SD) group and the healthy control (HC) group: anterior cingulate cortex, thalamus, superior parietal lobule, superior frontal gyrus, and posterior superior temporal sulcus. Among the thalamus-related functional connections, the right posterior parietal thalamus, where LHb located, has the most abnormal functional connections, the number of which is 18, and in the left LHb, there are only 3 abnormal functional connections. At a significant level p < 0.01, the network node degree of ten subregions of the thalamus in the SD group showed a significant difference from the corresponding node degree in the HC group. Therefore, we believe that functional connection analysis based on the thalamus and habenula nucleus can provide a high accuracy biomarker for the prediction of subclinical depression.

Visual Evoked Potential (VEP)-based Brain–Computer Interfaces (BCIs) are common due to their advantages. Particularly Steady-State VEP (SSVEP) and code-modulated VEP (c-VEP) BCIs are dominating the field. While SSVEP BCIs are more practical and easy to be implemented with common displays, c-VEP BCIs require synchronization but provide more targets with sufficiently long encoding codes. However, a novel paradigm as known as ‘Quasi-Steady State VEP (QSS-VEP)’ incorporates the advantages of both c-VEP and SSVEP paradigms. With specially designed low jittered stimulation sequences and the well-established Continuous Loop Averaging Deconvolution (CLAD) method, it enables simultaneous acquisition of both QSS-VEP and transient VEPs at higher stimulation rates. In this study, pattern reversal stimulation at 10, 32, 50, and 70 reversal per second (rps) stimuli are presented to a dual display stimulator. The optimal stimulation rate and the feasibility of QSS-VEP paradigm in a simple BCI system are investigated. Moreover, a comparison of the QSS-VEP-based template matching and SSVEP-based template matching is given for one low (10rps) and one medium stimulation rate (32rps). It has been shown that the QSS-VEP method increases the SNR and therefore single sweep QSS-VEPs provide significantly higher performance in template matching-based classification in a BCI system. Recently, transient VEP retrieval from linear regression and random code estimation from the EEG using these transient VEPs as unitary signals has gained attention due to high performance in BCI applications. The CLAD method-based transient VEP extraction is an easier, yet efficient way compared to linear regression-based methods. Thus, EEG codes can be recognized with sufficiently high accuracy using the QSS-VEP and CLAD-based BCI paradigm in addition to extraction of clinically relevant transient VEP at high rates.

Background: Electrogram (EGM) morphology recurrence (EMR) mapping of persistent atrial fibrillation (PeAF) quantifies consistency of activation at each site and is expected to be high and rapid near drivers of PeAF. Objective: To compare EMR in the left (LA) and right atrium (RA) in patients undergoing first- vs second-time PeAF catheter ablation (CA). Methods: Multisite bipolar EGM mapping of the LA (265±153 sites) and RA (224±148 sites) prior to CA for PeAF was performed in 40 patients (29 males, age 63±9 yrs, CHA2DS2-VASc 2.4±1.5, LVEF 48±12%) undergoing first (Group 1, n=31) or second-time (Group 2, n=9) CA. After cross-correlation of each automatically detected EGM with every other EGM in the recording, the most recurrent EGM morphology was identified and its frequency (Rec%) and cycle length of recurrence (CL R ) were computed (figure). The minimum CL R sites were identified. Results: In group 1, shortest CL R was in the LA in 26 patients (84%) and RA in 5 patients (16%). In the LA, there were 1 (n=23), 2 (n=2), or 3 (n=1) areas of shortest CL R , most commonly in the pulmonary veins (PV; n=19). In the RA, there was only 1 area of shortest CL R . Minimum CL R was 174.1±25.4 ms (LA-179.6±37.4 vs RA-207.9±34.5, p=0.0004), with Rec% 95±10%. In group 2, shortest CL R was in the LA in 5 patients and RA in 5 patients (56%)– one had both LA and RA. In the LA/RA, there were 1 (n=3/4) or 2 (n=2/1) areas of shortest CL R . The most common LA site was non-PV (6/7, 85.7%). The minimum CL R was 182.1±26.2ms (LA-190.8±36.2 vs RA-196.0±30.5, p=0.6), with Rec% 96±5%. Conclusion: In 61% of patients undergoing initial CA for PeAF, EMR identified LA drivers in the PVs which may explain why PV isolation has been reported to have 50-60% success rates in PeAF. In patients undergoing a 2 nd ablation for PeAF, EMR identified predominantly nonPV drivers with even distribution of shortest CL R between RA and LA and diminished CL R gradient between the LA and RA. EMR may be a useful mapping tool to characterize potential drivers of PeAF.

Background: While pulmonary vein isolation (PVI) for treatment of persistent atrial fibrillation (PeAF) is successful in approximately 50%, acute termination of PeAF is rarely observed. Prolongation of cycle length (CL) by 10% is often utilized as an indicator of successful catheter ablation (CA). Objective: To evaluate coronary sinus (CS) cycle length (CL) before and after CA for PeAF. Methods: CA for PeAF was performed in 31 patients (24males, age 63±9 yrs, CHA2DS2-VASc 2.3±1.7, LVEF 49±10%) with PVI, with 4 (13%) also having posterior wall isolation. A multielectrode catheter was placed in the CS and maintained throughout the procedure. CS electrograms were recorded for 10 seconds prior to CA and after completion of CA. No patient reverted to sinus rhythm during CA. CS CL was determined using customized software for activation detection and verified visually, excluding ventricular activation and low quality signals (n=3). The shortest CL among the recording electrodes was used for analysis. Results: CS CL pre- and post-CA were 182.4±23.0 and 191.6± 29.9 ms (p= 0.04) with change from baseline of 5.4±12.7%. The figure shows the histogram for change in CS CL from baseline. Only 7/28 (25%) of patients had CS CL prolongation >10%. Of ten patients who were free of AF off anti-arrhythmic drugs at 1 year, CS CL increased 4.0±6.1%; 2/10 had CS CL prolongation >10%. Of 6 patients with recurrent AF, CS CL increased 13.8±20.7%; 4/6 had CS CL prolongation >10%. Conclusion: Our data demonstrate that CS CL prolongation >10% is not a useful marker of outcomes in patients undergoing catheter ablation for PeAF. This highlights the need to identify other indicators of acute ablation success.

Visual evoked potentials (VEPs) are used in clinical applications in ophthalmology, neurology, and extensively in brain&ndash, computer interface (BCI) research. Many BCI implementations utilize steady-state VEP (SSVEP) and/or code modulated VEP (c-VEP) as inputs, in tandem with sophisticated methods to improve information transfer rates (ITR). There is a gap in knowledge regarding the adaptation dynamics and physiological generation mechanisms of the VEP response, and the relation of these factors with BCI performance. A simple, dual pattern display setup was used to evoke VEPs and to test signatures elicited by non-isochronic, non-singular, low jitter stimuli at the rates of 10, 32, 50, and 70 reversals per second (rps). Non-isochronic, low-jitter stimulation elicits quasi-steady-state VEPs (QSS-VEPs) that are utilized for the simultaneous generation of transient VEP and QSS-VEP. QSS-VEP is a special case of c-VEPs, and it is assumed that it shares similar generators of the SSVEPs. Eight subjects were recorded, and the performance of the overall system was analyzed using receiver operating characteristic (ROC) curves, accuracy plots, and ITRs. In summary, QSS-VEPs performed better than transient VEPs (TR-VEP). It was found that in general, 32 rps stimulation had the highest ROC area, accuracy, and ITRs. Moreover, QSS-VEPs were found to lead to higher accuracy by template matching compared to SSVEPs at 32 rps. To investigate the reasons behind this, adaptation dynamics of transient VEPs and QSS-VEPs at all four rates were analyzed and speculated.

Visual Evoked Potentials (VEPs) are used in clinical applications in ophthalmology, neurology and extensively in brain computer interface (BCI) research. BCI literature covers steady state VEP (SSVEP) and code modulated VEP (c-VEP) BCIs along with sophisticated methods to improve information transfer rates (ITR). There is a gap of knowledge regarding the VEP adaptation dynamics, physiological generation mechanisms and relation with BCI performance. A simple dual display VEP switch was developed to test signatures elicited by non-isochronic, non-singular, low jitter stimuli at the rates of 10, 32, 50 and 70 reversals per second (rps). Non-isochronic, low-jitter stimulation elicits Quasi-Steady-State VEPs (QSS-VEPs) that are utilized for simultaneous generation of transient VEP and QSS-VEP. QSS-VEP is a special case of c-VEPs and it is assumed that it shares the similar generators of the SSVEPs. Eight subjects were recorded and the performance of the overall system was analyzed by means of Receiver Operating Characteristic (ROC) curves, accuracy plots and ITRs. In summary QSS-VEPs performed better than transient VEPs. It was found that in general 32rps stimulation had the highest ROC area, accuracy and ITRs in general. To investigate the reasons behind this, adaptation dynamics of transient VEPs and QSS-VEPs at all four rates were analyzed and speculated. Moreover, QSS-VEPs were found to lead to higher accuracy by the template matching compared to SSVEPs at 10rps and 32rps.

Gaze detection by Steady State Visually Evoked Potentials (SSVEPs) has been a very popular topic for neural rehabilitation and especially Brain Computer Interface (BCI) research. Visual Evoked Potentials (VEPs) provide reliable robust electrophysiological signals for communication and control applications. In this research Quasi-Steady-State VEPs (QSS-VEPs) and their correspondence in this kind of dual target gaze detection application has been demonstrated. Methods for a dual target BCI switch has been developed. Since QSS-VEPs enable acquisition of both SSVEP and transient VEP (TR-VEP) signals at the same time, exploitation of them in a two target BCI application was reasonable. Stimulations of low and high rate pattern-reversal VEPs were utilized in gaze detection. QSS-VEPs and transient VEPs were compared. Receiver Operating Characteristics (ROC) curves were calculated in order to assess performance. We have found that it is possible to achieve high accuracy or ROC area values with QSS-VEPs. The best performance was obtained at 50 reversal per second (rps) stimulation rate. At this rate deconvolved transient signals, which normally has low performance compared to QSS-VEPs, resulted in comparable Information Transfer Rates (ITR) with QSS-VEPs.

This work relates to recent advances in the field of auditory event-related potentials (ERP), specifically deconvolution-based ERP acquisition and single-trial processing. An efficient stimulus sequence optimization method for ERP deconvolution is proposed, achieving consistent noise attenuation within a broad designated frequency range. Furthermore, a stimulus presentation paradigm for the fast, interleaved acquisition of auditory brainstem, middle-latency and late responses featuring alternating periods of high-rate deconvolution sequences, and subsequent low-rate stimulation is investigated in 20 normal hearing subjects. Deconvolved sequence responses containing early and middle-latency ERP components are fused with subsequent late responses using a time-frequency resolved weighted averaging method based on cross-trial regularity, yielding a uniform signal-to-noise ratio of the full-range auditory ERP across investigated timescales. Obtained average ERP waveforms exhibit morphologies consistent with both literature values and reference recordings acquired in 15 normal hearing subjects using a prior art approach to full-range auditory ERP acquisition, with all prominent waves being visible in the grand average waveforms. Results suggest the proposed interleaved stimulus presentation and associated ERP processing methodology to be suitable for the fast, reliable extraction of full-range auditory processing correlates in future ERP studies.

To evaluate the accuracy with which the innovative QASSR method predicts behavioral thresholds in adult patients with sensorineural hearing loss.Subjects were tested at four carrier frequencies (500, 1000, 2000, and 4000 Hz).The resulting QASSR recordings were analyzed for thresholds and magnitude/phase characteristics. Tone-burst ABR was recovered from QASSR signal using CLAD method and analyzed in the time domain. The electrophysiological estimates were compared to hearing thresholds determined behaviorally.Sixteen ears of nine volunteer subjects recruited from a clinical population.All mean threshold estimates differed less than 3 dB for QASSR and less than 5 dB for ABR at 1000, 2000 and 4000Hz (carrier or pure-tone test frequencies). The largest differences were observed for both at 500 Hz (5.63 and 11.56 dB respectively).The audiometric configurations of QASSR and ABR estimates followed those of the respective behaviorally determined configurations across ears tested.QASSR method merges two dissimilar stimulation techniques, transient and steady-state, to create a hybrid stimulation-and-analysis paradigm that seems to improve the overall performance of the electrophysiological threshold estimation. The unique feature of the QASSR technique is the additional information afforded by the transient ABR, recovered from the same recording. The QASSR thus holds promise to be a very useful tool for practical clinical applications.

Approximately 3,762 m of coiled tubing (CT) became stuck downhole in a live, offshore high-pressure well. The CT parted after fatigue limitations were exceeded. This paper discusses a snubbing operation that was conducted to fish the parted CT. To ensure flawless execution the following was employed: Successful job design, operational planning, and execution. A complex engineered solution to improve the fishing operation and clean up debris. Introduction of well control applications (hot tapping) to help minimize risk of pressure becoming trapped in the CT. Multiple successful trials. A unique job design was introduced and executed according to plan. Careful engineering, study, and yard trials supported the actual operation. The crew's technical expertise helped improve safety and enhanced efficiency. Significant underbalance skill and fishing proficiency helped make the fishing operation successful. The operator and service company improved their understanding and operational competence by fully communicating with all parties involved. The operator was able to remove parted CT and perform plug and abandonment (P&A) operations in this live, high-pressure offshore well with no incidents or spills. The successful engineering and testing during this campaign are discussed.

An onshore operator in Thailand faced the challenges of placing bridge plug and perforations with 2-m accuracy in a horizontal multi-stage interval prior to a fracturing operation and efficiently cleaning out the sand from the wellbore after fracturing. The solution selected to solve these two challenges was a fiber-optic-enabled coiled tubing (CT) string to support real-time plug set / perforation accuracy and sand cleanout, the first of this kind of operation in the Asia-Pacific region. A fiber-optic cable was carefully pre-installed for slack management inside the CT string before the CT was stabbed into the well. The fiber cable provided real-time telemetry from a casing collar locator (CCL) downhole tool to a digital data interrogator on the surface to gain more accuracy in the horizontal section. Once precisely positioned, the CT was pressurized to activate the hydraulic setting tools for plug set and activating the firing head for perforation guns fired at the exact target depth. Using CT deployment, the operator also avoided the gun moving upward and becoming stuck in the well, which is a risk with a wireline and tractor application. The fiber-optics application also enhanced wellbore cleanout efficiency after fracturing with the advantage of real-time downhole circulating pressure. The application goals were achieved as planned for this project, proving that CT can be used in this horizontal well section in conjunction with fiber optics. The fiber-optic real-time digital data from the downhole tool provided more accurate depth measurements for placing plug set and perforations, as well as monitoring bottomhole pressure to control smooth sand cleanout in the wellbore. This application also helped minimize the risk of operational failures due to the perforation gun moving upward after firing and the risk of the downhole tool becoming stuck (because CT can have larger pulling capacity than electric line operations). This new application also proved to be cost effective because CT fiber-optics applications can perform both perforation and sand cleanout operations, eliminating the requirement for electric line and tractor on location, saving both time and costs. The advantages and benefits of using the CT fiber-optic digital application for placing bridge plug, perforations, and sand cleanout in horizontal well completions have shown significant improvement in terms of operational efficiency, cost savings delivered to meet the well operator's budget, and safety supporting multistage fracturing zones.

The effects of rate on auditory-evoked potentials (AEP) to short noise gaps (12 ms) recorded at high sampling rates using wide-band filters were investigated.Auditory brainstem (ABR), middle latency (MLR), late latency (LLR) and steady-state (ASSR) responses were simultaneously recorded in adult subjects at four gap rates (0.5, 1, 5 and 40 Hz). Major components (V, Na, Pa, Nb, Pb, N1 and P2) were identified at each rate and analysed for latency/amplitude characteristics. Gap responses at 40 Hz were recovered from Quasi-ASSRs (QASSR) using the CLAD deconvolution method.Fourteen right ears of young normal hearing subjects were tested.All major components were present in all subjects at 1 Hz. P1 (P50) appeared as a low-pass filtered component of Pa and Pb waves. At higher rates, N1 and P2 disappeared completely while major ABR-MLR components were identified. Peak latencies were mostly determined by noise onsets slightly delayed by offset responses.Major AEP components can be recorded to short gaps at 1 Hz using high sampling rates and wide-band filters. At higher rates, only ABR and MLRs can be recorded. Such simultaneous recordings may provide a complete assessment of temporal resolution and processing at different levels of auditory pathways.

We determined if the overlap of transient (tr) pattern electroretinograms (PERG(tr)) can explain the generation of the steady-state (SS) pattern electroretinogram (PERG(SS)), and investigated the relationship between the two types of responses.Slightly jittered pattern reversals were used to generate quasi SS (QSS) PERG(SS) responses from eight normal subjects, recorded using lower eyelid skin electrodes, at rates between 6.9 and 26.5 reversals per second (rps). Jittered quasi PERG(SS) were deconvolved using the frequency domain continuous loop averaging deconvolution method. Additionally, conventional PERG(tr) at 2.2 rps and PERG(SS) at each of the QSS stimulation rates were obtained from all subjects. Two synthetic PERG(SS) responses were constructed at each stimulation rate, one using the PERG(tr) obtained at that rate, and the other using the conventional 2.2 rps PERG(tr). Synthetic responses then were compared to the recorded PERG(SS) using amplitude, latency, and spectral measurements.Findings indicate that the PERG(SS) obtained at SS rates can be predicted using the superposition of deconvolved tr PERGs at each particular rate. Although conventional PERG(tr) can explain PERG(SS) obtained at rates below 15.4 rps (≥ 97% correlation), for higher reversal rates only deconvolved responses obtained at that rate can produce the recorded SS responses (96% vs. 65% correlation at 26.5 rps).The study shows that PERG(SS) results from the overlapping of tr PERG(tr) waveforms generated at that reversal rate. The first two peaks (N(SS) and P(SS)) of the PERG(SS) reflect N35 and P50 waves of the tr PERG(tr). The N95 amplitude is reduced at conventional (16 rps) SS rates, but contributes to the overall PERG(SS) amplitude.

The production and characterization of an active recombinant N-acetylgalactosamine-6-sulfate sulfatase (GALNS) in Escherichia coli BL21(DE3) has been previously reported. In this study, the effect of the signal peptide (SP), inducer concentration, process scale, and operational mode (batch and semi-continuous) on GALNS production were evaluated. When native SP was presented, higher enzyme activity levels were observed in both soluble and inclusion bodies fractions, and its removal had a significant impact on enzyme activation. At shake scale, the optimal IPTG concentrations were 0.5 and 1.5 mM for the strains with and without SP, respectively, whereas at bench scale, the highest enzyme activities were observed with 1.5 mM IPTG for both strains. Noteworthy, enzyme activity in the culture media was only detected when SP was presented and the culture was carried out under semi-continuous mode. We showed for the first time that the mechanism that in prokaryotes recognizes the SP to mediate sulfatase activation can also recognize a eukaryotic SP, favoring the activation of the enzyme, and could also favor the secretion of the recombinant protein. These results offer significant information for scaling-up the production of human sulfatases in E. coli.

Various portable monitors have been used to quantify physical activity but most rely on detecting limb movement with a sensor rather than measuring muscle activity. Our first goal was to design and validate a portable system for recording surface electromyographic activity (EMG) from eight muscles over 24 h. The modular system includes: (1) preamplifiers that filter and amplify signals; (2) a preprocessor unit for further filtering and amplification, signal offset and power supply modification; (3) a data-logger for analog-to-digital conversion; a flash memory card for data storage and (4) a rechargeable battery. The equipment samples EMG at 1000 Hz, has a resolution of 2.6 μV and records signals up to 10 mV. The built-in analog filters create a bandwidth appropriate for surface EMG. Our second aim was to test the system biologically by recording EMG from able-bodied and spinal cord injured participants. Modifications were made to electrodes for remote preamplifier placement, and to the battery connection after pilot testing. Thereafter, 31 consecutive 24-h EMG recordings were successful. Both the engineering and biological validation of this system establishes it as a valuable tool for measuring physical activity from different muscles in real-world environments whether individuals have an intact or damaged nervous system.

Heart rate variability analysis is a promising method for measuring pain in premature infants. The Lomb algorithm was adapted and compared with fast Fourier transform (FFT) for the purposes of PSD estimation. Both FFT and the Lomb algorithm had similar low frequency (LF) estimation error rates. However, the Lomb algorithm had a significant smaller error rate than FFT when estimating high frequency (HF). In addition, the ECG signals of two premature infants in the newborn intensive care unit were analyzed while undergoing a routine heel stick, a common painful procedure. The Lomb algorithm performed as expected marking a decrease in both LF and HF power in the presence of pain.

OBJECTIVES Both 80 Hz auditory steady state responses (ASSRs) and tone burst auditory brainstem responses (ABRs) have been shown to provide reasonable estimates of the behavioral thresholds. Although ASSRs provide statistically objective estimates that can be easily automated by computers, they present no information for the neurophysiological interpretation of the results. ABRs, on the other hand, do not provide easily automated information and usually need expert interpretation of the recorded waveforms. A recently developed continuous loop averaging deconvolution algorithm offers an alternative solution by acquiring slightly jittered 80 Hz quasi auditory steady state responses (QASSRs), thus enabling the acquisition of both recordings simultaneously. The purpose of this study is to investigate a specially developed 80 Hz QASSR paradigm for simultaneous acquisition for both responses for threshold detection purposes. DESIGN Sixteen ears from eight adults with normal hearing were tested. Amplitude modulated QASSRs were obtained using slightly jittered temporal sequences of tone bursts presented at a mean rate of 78.125 Hz. Four carrier frequencies (500, 1000, 2000, and 4000 Hz) at several stimulus intensity levels were monaurally presented and QASSRs to 128 sweeps blocks were recorded. The ABRs were extracted using the CLAD algorithm. Wave V was visually identified and analyzed in the time domain as in everyday clinical practice. In addition, statistically objective ƒMP computation method was used to automatically detect ABR threshold as well. The QASSRs were analyzed in the frequency domain and magnitudes, phase delays, and thresholds were obtained. Phasor (polar plot) diagrams were constructed. QASSR and ABR hearing thresholds were obtained and compared with behavioral thresholds. RESULTS Study reveals that the QASSR method provides accurate objective estimation of the audiometric thresholds from extracted ASSRs and latency/amplitude information from extracted ABRs. The largest mean threshold difference for QASSR was within 5 dB for all carrier frequencies including 500 Hz. For auditory threshold estimation in adults with normal hearing, the Hotelling's T-Square test in four dimensions in the frequency domain was more accurate than the ƒMP or visual ABR threshold detection in the time domain. CONCLUSIONS Simultaneously recorded ASSR and ABR from QASSRs provide accurate and effective method for frequency-specific hearing threshold estimation with neurophysiological information in adults with normal hearing. Further research is required for hearing-impaired adults, newborns, and infants.

Clonus can disrupt daily activities after spinal cord injury. Here an algorithm was developed to automatically detect contractions during clonus in 24-hour electromyographic (EMG) records. Filters were created by non-linearly scaling a Mother (Morlet) wavelet to envelope the EMG using different frequency bands. The envelope for the intermediate band followed the EMG best (74.8–193.9 Hz). Threshold and time constraints were used to reduce the envelope peaks to one per contraction. Energy in the EMG was measured 50 ms either side of each envelope (contraction) peak. Energy values at 5 % and 95 % maximal defined EMG start and end time, respectively. The algorithm was as good as a person at identifying contractions during clonus (p = 0.946, n=31 spasms, 7 subjects with cervical spinal cord injury), and marking start and end times to determine clonus frequency (intra class correlation coefficient, α: 0.949), contraction intensity using root mean square EMG (α: 0.997) and EMG duration (α: 0.852). On average the algorithm was 574 times faster than manual analysis performed independently by two people (p≤ 0.001). This algorithm is an important tool for characterization of clonus in long-term EMG records.

We evaluated the effects of dexamethasone base (DXMb) containing electrode arrays in a guinea pig model of cochlear implantation to determine if eluted DXMb could protect the cochlea against electrode insertion trauma (EIT)-induced: 1) loss of hair cells; 2) disruption of neural elements; 3) increases in hearing thresholds; 4) increased electrical impedance and 5) fibrosis. A guinea pig model of EIT-induced hearing and hair cell losses was used to test silicone electrode arrays that contained either 10%, 1%, 0.1%, or 0% levels of micronized DXMb. These four types of electrode arrays were implanted into the scala tympani via basal turn cochleostomies and left in place for 3 months. Hearing thresholds were determined by ABR and CAP recordings in response to a series of defined pure tone stimuli (i.e. 16-0.5 kHz). Changes in impedance were measured between the implant electrode and a reference electrode. Hair cell counts and neural element integrity were determined by confocal microscopy analyses of stained organ of Corti whole mounts obtained from 90 day post-implantation animals. Fibrosis was measured in Masson trichrome stained cross-sections through the organ of Corti. The results showed that either 10% or 1.0% DXMb eluting electrode arrays protected; hearing thresholds, hair cells, and neural elements against EIT-induced losses and damage. Electrode arrays with 0.1% DXMb only partial protected against EIT-induced hearing loss and damage to the cochlea. Protection of hearing thresholds and organ of Corti sensory elements by electrode-eluted DXMb was still apparent at 3 months post-EIT. All three concentrations of DXMb in the electrode arrays prevented EIT-induced increases in impedance. EIT-initiated fibrosis was significantly reduced within the implanted cochlea of the two DXMb concentrations tested. In conclusion, DXMb eluting electrodes protected the cochlea against long term increases in hearing thresholds, loss of hair cells, damage to neural elements and increases in impedance and fibrosis that result from EIT-initiated damage. The protection achieved by DXMb-eluting electrodes was dose dependent. Establishing a significant level of trauma induced elevation in hearing thresholds was important for the determination of the otoprotective effects of array-eluted DXMb.

Background The auditory middle-latency response (transient) and the 40-Hz auditory steady state response (ASSR) are modulated by anesthetics. However, the quantitative relation between these evoked responses is difficult to obtain because of technical limitations of the recording methods used to obtain transients at high stimulation rates. This study uses continuous-loop averaging deconvolution to fill this technical gap and to study the relation between the transient and ASSR waveform during general anesthesia. Methods The authors recorded 5- and 40-Hz transients and 40-Hz ASSRs in 13 subjects during general anesthesia. The 5- and 40-Hz transients were used to predict the 40-Hz ASSR by linearly superimposing the transient waveforms. The predicted and recorded ASSRs were analyzed and compared using phasor and Hotelling T(2) analyses. Results Grand-averaged recordings revealed differences in the early middle-latency peaks between 5- and 40-Hz transients, e.g., the peak P(x) was present only in 5-Hz transient. Only the predicted 40-Hz ASSR derived from the 40-Hz transient matched the actual ASSR. Phasor analysis showed that the early peaks contribute significantly to the steady state waveform, and this explains why 5-Hz transient does not predict the 40-Hz ASSR. Oscillations in both the 5- and 40-Hz transients were observed during anesthesia. Discussion The 40-Hz ASSR represents a composite waveform and arises when transient waveforms elicited with a 40-Hz stimulation rate are overlapped and superimposed. During general anesthesia, the morphology of the transient is dependent on the rate of stimulus presentation. The composite nature of the ASSR may explain nonmonotonic anesthetic dose-response relations observed by others.

Objective In this study, the superposition theory of the 40-Hz auditory steady-state response (ASSR) generation is investigated using auditory brainstem response (ABR) and middle latency responses (MLRs) obtained with 40Hz jittered sequences with the continuous loop averaging deconvolution (CLAD) algorithm. Methods Click sequences at around 40Hz with high (maximum length sequence), medium and low jitters were presented to normal hearing awake adult subjects monaurally. Overlapping MLR responses were deconvolved using the frequency domain CLAD method. In addition, conventional auditory MLRs at 4.88Hz and ASSRs at 39.1Hz were obtained in all subjects. Synthetic ASSRs were constructed using different rate and jitter MLRs as base recordings. Contributions of the primary components were investigated by wave elimination using phasors. Results Findings indicate that the generation of the 40-Hz ASSRs can be explained successfully by the superposition of the ABR and MLR waves generated at that stimulation rate. N a –P a and N b –P b components of the MLR contribute about equally (45% each), while the wave V of the ABR contributes a lesser amount (10%). Conclusions Forty-Hertz ASSRs are composite responses generated by the superposition of the major waves of the ABR and the MLR. Dramatic amplitude increase of the ASSR at 40Hz is primarily due to the superposition of the resonating P b component to the P a wave. Significance Several unexplained properties of the 40-Hz ASSR can be explained by the stimulus and brain state dependent characteristics of the slow ABR, the P a and the P b components of the MLR.

OBJECTIVE: The current international standard (IEC 60601-1-8) stipulates that medical device audible alarms should be priority-encoded and validated for efficacy. Evidence suggests that the melodic alarms described in the standard are not functioning as originally intended. We present a multi-disciplinary, human factors paradigm for audible alarm development whereby urgency information is encoded via modulation of the physical characteristics of sounds. We also test the feasibility of this approach using information measures. METHODS: We designed series of experimental sounds that varied along controlled physical and acoustical dimensions. Subjects rated these sound series for perceived urgency. Based on these ratings, selected sounds from each series were assigned a priority category from 'low' to 'high' - we call these resulting sets of sounds 'urgency-codecs'. The method of categorical judgments (based on information theory) was used to compare each urgency-codec for ability to convey urgency information. RESULTS: Subjects were consistent in their ratings of the three series of experimental sounds for perceived urgency. The urgency data pertaining to one of the series (harmonic interval) was successfully fit to a psychophysical empirical law. The urgency-codec derived from another sound series (melodic interval) was found to have the highest signal (correct interpretation of urgency level by subjects) transmission rate. CONCLUSIONS: The proposed paradigm is feasible, and it offers an evidence-based strategy for alarm sound design and testing. This approach would be performed before implementation of new alarm sounds in clinical settings, and should result in development of alarm sounds that satisfy the requirements of priority-encoding and validation. Language: en

Behavioral detection of gaps in noise (GIN) is commonly used to evaluate auditory temporal resolution. Late latency responses (LLRs) to such stimuli are studied as electrophysiological measures of temporal resolution. The current study was conducted to investigate the characteristics of auditory brainstem and middle latency responses (ABRs/MLRs) elicited by GIN. Additionally, Quasi Auditory Steady State Responses (QASSRs) were quantified to obtain an Objective Gap Detection Threshold (OGDT). Six young, normal hearing subjects were monaurally stimulated using silent gaps (durations 0ms–12ms) embedded in a white-noise signal. QASSRs were deconvolved using the CLAD (Continuous Loop Averaging Deconvolution) algorithm to obtain an estimate of the transient responses to individual gaps. Derived ABRs/MLRs were consistently characterized by three positive waves and three negative waves that diminished with decreasing gap duration. Early auditory evoked responses (ABR/MLR) to GINs were reliably recorded and computed OGDTs yielded results that are consistent with behavioral tests. This methodology may be applied to objectively diagnose patients with auditory disorders related with temporal resolution deficiencies.

In this study a general formula for the signal to noise ratio (SNR) of the maximum length sequence (MLS) deconvolution averaging is developed using the frequency domain framework of the generalized continuous loop averaging deconvolution procedure [Ozdamar and Bohórquez, J. Acoust. Soc. Am. 119, 429-438 (2006)]. This formulation takes advantage of the well known equivalency of energies in the time and frequency domains (Parseval's theorem) to show that in MLS deconvolution, SNR increases with the square root of half of the number of stimuli in the sweep. This increase is less than that of conventional averaging which is the square root of the number of sweeps averaged. Unlike arbitrary stimulus sequences that can attenuate or amplify phase unlocked noise depending on the frequency characteristics, the MLS deconvolution attenuates noise in all frequencies consistently. Furthermore, MLS and its zero-padded variations present optimal attenuation of noise at all frequencies yet they present a highly jittered stimulus sequence. In real recordings of evoked potentials, the time advantage gained by noise attenuation could be lost by the signal amplitude attenuation due to neural adaptation at high stimulus rates.

In this study, a frequency domain formulation of continuous loop averaging deconvolution (CLAD) of overlapping evoked potentials is developed and applied for the extraction of transient responses from recordings obtained at high stimulation rates. This formulation allows for a faster execution of CLAD by using fast Fourier transform algorithms. The frequency characteristics of the deconvolution filter depends exclusively on the stimulus sequence and determines whether the noncoherent noise is amplified or attenuated in different frequencies. A formula for calculating the signal-to-noise ratio (SNR) achieved by the deconvolution process is developed. The newly developed theory and the methodology is applied to the extraction of the auditory brainstem and middle latency responses using various sequences. The effects of the sequence used and the number of sweeps averaged in ongoing acquisition on SNR are examined by using single sweep recordings. The results verify the deconvolution theory and the methodology and show its limitations. Depending on the frequency characteristics of the sequence, the deconvolution process can amplify or attenuate the EEG noise. Proper selection of the stimulus sequence can increase the SNR enhancement obtained with conventional averaging.

Purpose To compare a new method for steady-state pattern electroretinogram (PERGx) with a validated method (PERGLA) in normal controls and in patients with optic neuropathy. Methods PERGx and PERGLA were recorded in a mixed population (n = 33, 66 eyes) of younger controls (C1; n = 10, age 38 ± 8.3 years), older controls (C2; n = 11, 57.9 ± 8.09 years), patients with early manifest glaucoma (G; n = 7, 65.7 ±11.6 years), and patients with nonarteritic ischemic optic neuropathy (N; n = 5, mean age 59.4 ± 8.6 years). The PERGx stimulus was a black-white horizontal grating generated on a 14 × 14 cm LED display (1.6 cycles/deg, 15.63 reversals/s, 98% contrast, 800 cd/m2 mean luminance, 25° field). PERGx signal and noise were averaged over 1024 epochs (∼2 minutes) and Fourier analyzed to retrieve amplitude and phase. Partial averages (16 successive samples of 64 epochs each) were also analyzed to quantify progressive changes over recording time (adaptation). Results PERGLA and PERGx amplitudes and latencies were correlated (Amplitude R2 = 0.59, Latency R2 = 0.39, both P < 0.0001) and were similarly altered in disease. Compared to PERGLA, however, PERGx had shorter (16 ms) latency, higher (1.39×) amplitude, lower (0.37×) noise, and higher (4.2×) signal-to-noise ratio. PERGx displayed marked amplitude adaptation in C1 and C2 groups and no significant adaptation in G and N groups. Conclusions The PERGx high signal-to-noise ratio may allow meaningful recording in advanced stages of optic nerve disorders. In addition, it quantifies response adaptation, which may be selectively altered in glaucoma and optic neuropathy. Translational Relevance A new PERG method with increased dynamic range allows recording of retinal ganglion cell function in advanced stages of optic nerve disorders. It also quantifies the response decline during the test, an autoregulatory adaptation to metabolic challenge that decreases with age and presence of disease.

Dexamethasone is a synthetic corticosteroid that is routinely administered via intratympanic injections for the treatment of sudden idiopathic sensorineural hearing loss (Plontke et al., 2009) with...

Binaural beat (BB) illusions are experienced as continuous central pulsations when two sounds with slightly different frequencies are delivered to each ear. It has been shown that steady-state auditory evoked potentials (AEPs) to BBs can be captured and investigated. The authors recently developed a new method of evoking transient AEPs to binaural beats using frequency modulated stimuli. This methodology was able to create single BBs in predetermined intervals with varying carrier frequencies. This study examines the effects of the BB duration and the frequency modulating component of the stimulus on the binaural beats and their evoked potentials. Normal hearing subjects were tested with a set of four durations (25, 50, 100, and 200 ms) with two stimulation configurations, binaural dichotic (binaural beats) and diotic (frequency modulation). The results obtained from the study showed that out of the given durations, the 100 ms beat, was capable of evoking the largest amplitude responses. The frequency modulation effect showed a decrease in peak amplitudes with increasing beat duration until their complete disappearance at 200 ms. Even though, at 200 ms, the frequency modulation effects were not present, the binaural beats were still perceived and captured as evoked potentials.

PURPOSE We recorded pattern electroretinograms (PERGs) simultaneously from each eye in mice using binocular stimulation and a common noncorneal electrode. METHODS The PERG was derived simultaneously from each eye in 71 ketamine/xylazine anesthetized mice (C57BL/6J, 4 months old) from subcutaneous needles (active, snout; reference, back of the head; ground, root of the tail) in response to contrast-reversal of gratings (0.05 cycles/deg, >95% contrast) generated on two custom-made light-emitting diode (LED) tablets alternating at slight different frequencies (OD, 0.984 Hz; OS, 0.992 Hz). Independent PERG signals from each eye were retrieved using one channel continuous acquisition and phase-locking average (OD, 369 epochs of 492 ms; OS, 372 epochs of 496 ms). The PERG was the average of three consecutive repetitions. RESULTS Binocular snout PERGs had high amplitude (mean, 25.3 μV, SD 6.6) and no measurable interocular cross-talk. Responses were reliable (test-retest variability within-session, 14%, SD 7; between sessions, 25%, SD 9; interocular asymmetry within-session, 9%, SD 7; between sessions, 13%, SD 5). Retinal ganglion cells (RGCs) were the main source of the binocular snout PERG, as optic nerve crush in three mice abolished the signal. CONCLUSIONS The PERG, a sensitive measure of RGC function, is used increasingly in mouse models of glaucoma and optic nerve disease. Compared to current methods, the binocular snout PERG represents a substantial improvement in terms of simplicity and speed. It also overcomes limitations of corneal electrodes that interfere with invasive procedures of the eye and facilitates experiments based on comparison between the responses of the two eyes.

High-speed resistance training is used to increase power; however, momentum can reduce the effectiveness of high-speed (HS) training when using weight-stack (WS) machines. This study used a non-linear scaled wavelet analysis to assess differences between pneumatic (P) and WS during seven HS or controlled speed (CS) repetitions. Vastus medialis (VM) and lateralis (VL), and rectus femoris (RF) EMG data were collected during leg extension exercises performed by five regular weight-trainers (mean age ± SD, 23.2 ± 2.9 years). Data were analyzed using continuous wavelet analysis to assess temporal Intensity distribution across eight frequency bands. Significant differences occurred due to speed for all muscles (p

Objective Due to overlapping, temporal information is mostly lost in high rate steady-state pattern electroretinograms (PERG SS ). This study develops a deconvolution method and a display/recording system to "unwrap" PERG SS and obtain a transient, "per stimulus" response (PERG tr ) regardless of reversal rate. Methods Processing and instrumentation, including high temporal resolution display and acquisition were developed for deconvolving PERGs acquired at high rates by slight jittering of reversal onsets at a given mean rate. Results The system was successfully tested at eight rates from 2.2 to 78.1rps. At medium rates (17.4–41.2rps) recordings with conventional morphology (N35–P50–N95) but earlier peaks and higher amplitudes were extracted up to 40rps. At higher rates, smaller triphasic responses were obtained, exhibiting similar peak latencies, but reversed polarity. Oscillating potentials (OPs) were also recorded at all rates after deconvolution. Conclusions Transient PERGs and OPs can be extracted from quasi steady-state PERG recordings obtained at high rates with a deconvolution algorithm using high temporal resolution display and acquisition systems. Significance The methodology to extract transient and oscillatory responses from steady-state PERGs could be useful in understanding high rate responses and diagnosis of various retinal diseases by revealing temporal information on waveform components which cannot be normally observed.

In the food industry, osmotic dehydration can be an important stage to obtain partially dry foodstuffs. However, the remaining spent osmotic solution at the end of the process could become a waste with an important environmental impact due to the large amount of organic compounds that it might contain. Since one of the most important osmotic agents used in osmotic dehydration is sucrose, this spent osmotic solution could be used to be biotransformed to produce fructooligosaccharides by a fructosyltransferase. This study evaluated the production of fructooligosaccharides using the fructosyltransferase produced by Aspergillus oryzae N74, and the spent osmotic solution that resulted in the osmotic dehydration of Andes berry ( Rubus glaucus) and tamarillo ( Cyphomandra betacea). Assays were conducted at small and bioreactor scales, using spent osmotic solution with or without re-concentration. At small scale no significant difference ( p > 0.05) was observed in the fructooligosaccharides production yield, ranging from 31.18% to 34.98% for spent osmotic solution from tamarillo osmotic dehydration, and from 33.16% to 37.52% for spent osmotic solution from Andes berry osmotic dehydration, using either the SOS with or without re-concentration. At bioreactor scale the highest fructooligosaccharides yield of 58.51 ± 1.73% was obtained with spent osmotic solution that resulted from tamarillo osmotic dehydration. With the spent osmotic solution from Andes berry osmotic dehydration the yield was 49.17 ± 2.82%. These results showed the feasibility of producing fructooligosaccharides from spent osmotic solution that is considered a waste in food industry.

This work presents the implementation of a small, light and wireless electroencephalogram (EEG) and intracranial EEG (iEEG) acquisition system called "Wireless Neuro Boards" (WIRNEBOs), intended for electrophysiological recordings in small animal models. The system consists of two devices: a battery powered transmitter, in charge of the acquisition and transmission tasks, whose dimensions and weight are 58 mm by 38 mm by 10 mm and 25 g respectively, and a receiver which is connected to a host computer to store and process the acquired signals. The main characteristics of the WIRNEBOs include the use of 24 bits, 8 channels medical Analog Front End (AFE). The system was tested with a sample rate of 500 samples per second (SPS) and has power autonomy up to 8 hours and presents an electric noise of less than 1μV. The wireless radiofrequency (RF) link did not present any corruption or data loss in a range up to 5 meters. Modular design is novel; allowing the implementation of new versions with higher number of channels and improvements in sample rate, autonomy, range of the communications, among others.

Auditory binaural beat (BB) illusions are elicited when two sinusoidal sounds with slightly differing frequencies are presented separately to each ear. Neural processing of BBs can be explored using auditory evoked potentials (AEP). In this study BB AEP topography is investigated using eight bipolar channels with 9 electrodes (Fz, Cz, Pz, Oz, A1, A2, T3, T4 and Neck) and a ground placed on the forehead. Young adults with normal hearing were recorded with the BB paradigm using 400 Hz, 50 ms beats with a repetition rate of 1 Hz. The Electroencephalogram (EEG) was acquired at 5Ksps and - references, Neck and Avg ((A2+A1)/2), were generated offline. Results demonstrated that while the Avg reference montage showed higher peak amplitudes for all electrodes, the A1 and A2 earlobe electrodes exhibited significant activity for the first BB peak (100 ms) when referenced to the Neck. Additionally, the Neck reference revealed several differences between scalp regions: a maximum amplitude at Cz for the second peak (180 ms), a polarity reversal for early peaks and substantial suppression of late peaks at T3 and T4. These results suggest lateral generators for the first BB peak and deep central/rostral generators for the late BB peaks.