A Methodology for Detecting Field Potentials from the External Ear Canal: NEER and EVestG

An algorithm called the neural event extraction routine (NEER) and a method called Electrovestibulography (EVestG) for extracting field potentials (FPs) from artefact rich and noisy ear canal recordings is presented. Averaged FP waveforms can be used to aid detection of acoustic and or vestibular pathologies. FPs were recorded in the external ear canal proximal to the ear drum. These FPs were extracted using an algorithm called NEER. NEER utilises a modified complex Morlet wavelet analysis of phase change across multiple scales and a template matching (matched filter) methodology to detect FPs buried in noise and biological and environmental artefacts. Initial simulation with simulated FPs shows NEER detects FPs down to −30 dB SNR (power) but only 13–23% of those at SNR’s <−6 dB. This was deemed applicable to longer duration recordings wherein averaging could be applied as many FPs are present. NEER was applied to detect both spontaneous and whole body tilt evoked FPs. By subtracting the averaged tilt FP response from the averaged spontaneous FP response it is believed this difference is more representative of the vestibular response. Significant difference (p < 0.05) between up and down whole body (supine and sitting) movements was achieved. Pathologic and physiologic evidence in support of a vestibular and acoustic origin is also presented

A comparison of burst and amplitude modulated electrical stimulation of the cochlear

This is a publisher’s version of an article published in Journal of Clinical Engineering 1992. This version is reproduced with permission of Lippincott Wilkins & Williams.On average, the maximum firing rates of cells in the inferior colliculus, when stimulated with either bursts or ramps (amplitude modulated bursts) of biphasic pulsatile electrical stimuli, increased as the pulse rate was increased from 125 to 4000 pulses per second (pps). The fact that this firing rate has increased, on average, up to 4000 pps is evidence that a mechanism for high pulse rate discriminability exists. This firing rate increase was not on a 1:1 basis with the stimulus, but rather a time-averaged firing rate determination. Ramp stimuli generate a wider dynamic range of firing rates than those of burst stimuli, suggesting the potential for a higher rate of information transfer for cochlear implant patients. The finding of temporal information in transient “onset” responses (a response seen only in the first 10 ms post-stimulus onset) of ramp-evoked responses-more than burst-evoked responses-support high pulse rate discriminability and the use of ramp stimuli for encoding high pulse rate information to implant patients

Development of an ultra low noise, miniature signal conditioning device for vestibular evoked response recordings

BACKGROUND: Inner ear evoked potentials are small amplitude (<1 μV(pk)) signals that require a low noise signal acquisition protocol for successful extraction; an existing such technique is Electrocochleography (ECOG). A novel variant of ECOG called Electrovestibulography (EVestG) is currently investigated by our group, which captures vestibular responses to a whole body tilt. The objective is to design and implement a bio-signal amplifier optimized for ECOG and EVestG, which will be superior in noise performance compared to low noise, general purpose devices available commercially. METHOD: A high gain configuration is required (>85 dB) for such small signal recordings; thus, background power line interference (PLI) can have adverse effects. Active electrode shielding and driven-right-leg circuitry optimized for EVestG/ECOG recordings were investigated for PLI suppression. A parallel pre-amplifier design approach was investigated to realize low voltage, and current noise figures for the bio-signal amplifier. RESULTS: In comparison to the currently used device, PLI is significantly suppressed by the designed prototype (by >20 dB in specific test scenarios), and the prototype amplifier generated noise was measured to be 4.8 [Formula: see text] @ 1 kHz (0.45 μV(RMS) with bandwidth 10 Hz-10 kHz), which is lower than the currently used device generated noise of 7.8 [Formula: see text] @ 1 kHz (0.76 μV(RMS)). A low noise (<1 [Formula: see text] ) radio frequency interference filter was realized to minimize noise contribution from the pre-amplifier, while maintaining the required bandwidth in high impedance measurements. Validation of the prototype device was conducted for actual ECOG recordings on humans that showed an increase (p < 0.05) of ~5 dB in Signal-to-Noise ratio (SNR), and for EVestG recordings using a synthetic ear model that showed a ~4% improvement (p < 0.01) over the currently used amplifier. CONCLUSION: This paper presents the design and evaluation of an ultra-low noise and miniaturized bio-signal amplifier tailored for EVestG and ECOG. The increase in SNR for the implemented amplifier will reduce variability associated with bio-features extracted from such recordings; hence sensitivity and specificity measures associated with disease classification are expected to increase. Furthermore, immunity to PLI has enabled EVestG and ECOG recordings to be carried out in a non-shielded clinical environment

The excitability of units in the central nucleus of the inferior colliculus to monaural electrical stimulation

This is an item from the Proceedings of the Australian Physiological and Pharmacological Society (1992), 23(2), published by Australian Physiological and Pharmacological Society. This version is reproduced with the permission of publisher.Single unit responses to electric stimuli can be markedly different to those obtained with comparable acoustic stimuli. For the development of future cochlear implant coding strategies a detailed understanding of the effects of electrical stimulation is required. This study investigated the comparative number of single units exhibiting excitatory responses in the central nucleus of the inferior colliculus to monaural electric versus acoustic stimuli

Gray and White Matter Voxel-Based Morphometry of Alzheimer’s Disease With and Without Significant Cerebrovascular Pathologies

Alzheimer’s disease (AD) is the most common type of dementia, and AD individuals often present significant cerebrovascular disease (CVD) symptomology. AD with significant levels of CVD is frequently labeled mixed dementia (or sometimes AD-CVD), and the differentiation of these two neuropathologies (AD, AD-CVD) from each other is challenging, especially at early stages. In this study, we compared the gray matter (GM) and white matter (WM) volumes in AD (n = 83) and AD-CVD (n = 37) individuals compared with those of cognitively healthy controls (n = 85) using voxel-based morphometry (VBM) of their MRI scans. The control individuals, matched for age and sex with our two dementia groups, were taken from the ADNI. The VBM analysis showed widespread patterns of significantly lower GM and WM volume in both dementia groups compared to the control group ( P  < .05, family-wise error corrected). While comparing with AD-CVD, the AD group mainly demonstrated a trend of lower volumes in the GM of the left putamen and right hippocampus and WM of the right thalamus (uncorrected P  < .005 with cluster threshold, K  = 10). The AD-CVD group relative to AD tended to present lower GM and WM volumes, mainly in the cerebellar lobules and right brainstem regions, respectively (uncorrected P  < .005 with cluster threshold, K  = 10). Although finding a discriminatory feature in structural MRI data between AD and AD-CVD neuropathologies is challenging, these results provide preliminary evidence that demands further investigation in a larger sample size

Geroscience: Linking Aging to Chronic Disease

Mammalian aging can be delayed with genetic, dietary, and pharmacologic approaches. Given that the elderly population is dramatically increasing and that aging is the greatest risk factor for a majority of chronic diseases driving both morbidity and mortality, it is critical to expand geroscience research directed at extending human healthspan

Longitudinal Functional Study of Murine Aging: A Resource for Future Study Designs

ABSTRACT Aging is characterized by systemic declines in tissue and organ functions. Interventions that slow these declines represent promising therapeutics to protect against age‐related disease and improve the quality of life. In this study, several interventions associated with lifespan extension in invertebrates or improvement of age‐related disease were tested in mouse models to determine if they were effective in slowing tissue aging in a broad spectrum of functional assays. Benzoxazole, which extends the lifespan of Caenorhabditis elegans, slowed age‐related femoral bone loss in mice. Rates of change were established for clinically significant parameters in untreated mice, including kyphosis, blood glucose, body composition, activity, metabolic measures, and detailed parameters of skeletal aging in bone. These findings have implications for the study of preclinical physiological aging and therapies targeting aging. Finally, an online application was created that includes the calculated rates of change and that enables power and variance to be calculated for many clinically important metrics of aging with an emphasis on bone. This resource will help in future study designs employing novel interventions in aging mice. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research