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1.
J Acoust Soc Am ; 149(2): 788, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33639814

RESUMO

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.


Assuntos
Percepção da Fala , Fala , Estimulação Acústica , Audição , Testes Auditivos , Humanos , Ruído
2.
J Physiol ; 598(13): 2703-2717, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32298483

RESUMO

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.


Assuntos
Traumatismos da Medula Espinal , Vibração , Eletromiografia , Reflexo H , Humanos , Contração Muscular , Músculo Esquelético , Espasmo
3.
Anat Rec (Hoboken) ; 303(3): 487-493, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-30632683

RESUMO

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.


Assuntos
Cóclea/patologia , Potenciais Evocados Auditivos do Tronco Encefálico/fisiologia , Transplante de Células-Tronco Mesenquimais/métodos , Células-Tronco Mesenquimais , Animais , Cóclea/fisiopatologia , Feminino , Inflamação/patologia , Inflamação/fisiopatologia , Masculino , Ratos , Ratos Sprague-Dawley
4.
Front Cell Neurosci ; 13: 492, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31824265

RESUMO

Cochlear implantation (CI) is now widely used to provide auditory rehabilitation to individuals having severe to profound sensorineural hearing loss (SNHL). However, CI can lead to electrode insertion trauma (EIT) that can cause damage to sensory cells in the inner ear resulting in loss of residual hearing. Even with soft surgical techniques where there is minimal macroscopic damage, we can still observe the generation of molecular events that may initiate programmed cell death via various mechanisms such as oxidative stress, the release of pro-inflammatory cytokines, and activation of the caspase pathway. In addition, individuals with CI may be exposed to noise trauma (NT) due to occupation and leisure activities that may affect their hearing ability. Recently, there has been an increased interest in the auditory community to determine the efficacy of drug-eluting electrodes for the protection of residual hearing. The objective of this study is to determine the effect of NT on implanted cochlea as well as the otoprotective efficacy of dexamethasone eluting electrode to implanted cochlea exposed to NT in a guinea pig model of CI. Animals were divided into five groups: EIT with dexamethasone eluting electrode exposed to NT; EIT exposed to NT; NT only; EIT only and naïve animals (control group). The hearing thresholds were determined by auditory brainstem recordings (ABRs). The cochlea was harvested and analyzed for transcript levels of inflammation, apoptosis and fibrosis genes. We observed that threshold shifts were significantly higher in EIT, NT or EIT + NT groups compared to naive animals at all the tested frequencies. The dexamethasone eluting electrode led to a significant decrease in hearing threshold shifts in implanted animals exposed to NT. Proapoptotic tumor necrosis factor-α [TNF-α, TNF-α receptor 1a (TNFαR1a)] and pro-fibrotic transforming growth factor ß1 (TGFß) genes were more than two-fold up-regulated following EIT and EIT + NT compared to the control group. The use of dexamethasone releasing electrode significantly decreased the transcript levels of pro-apoptotic and pro-fibrotic genes. The dexamethasone releasing electrode has shown promising results for hearing protection in implanted animals exposed to NT. The results of this study suggest that dexamethasone releasing electrode holds great potential in developing effective treatment modalities for NT in the implanted cochlea.

5.
Sensors (Basel) ; 19(17)2019 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-31480734

RESUMO

Visual evoked potentials (VEPs) are used in clinical applications in ophthalmology, neurology, and extensively in brain-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.

6.
J Acoust Soc Am ; 145(1): 540, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30710975

RESUMO

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.


Assuntos
Potenciais Evocados Auditivos , Modelos Neurológicos , Adulto , Encéfalo/fisiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Tempo de Reação
7.
Biomed Tech (Berl) ; 64(1): 81-91, 2019 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-29095692

RESUMO

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.


Assuntos
Eletromiografia/instrumentação , Músculo Esquelético/fisiologia , Doenças do Sistema Nervoso , Traumatismos da Medula Espinal/fisiopatologia , Conversão Análogo-Digital , Exercício Físico , Humanos , Monitorização Fisiológica , Movimento , Registros
8.
J Neurophysiol ; 120(4): 1765-1771, 2018 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-30067124

RESUMO

Intermuscular coherence allows the investigation of common input to muscle groups. Although beta-band (15-30 Hz) intermuscular coherence is well understood as originating from the cortex, the source of intermuscular coherence at lower frequencies is still unclear. We used a wearable device that recorded electromyographic (EMG) signals during a 24-h period in four lower limb muscles of seven spinal cord injury patients (American Spinal Cord Injury Association impairment scale: A, 6 subjects; B, 1 subject) while they went about their normal daily life activities. We detected natural spasms occurring during these long-lasting recordings and calculated intermuscular coherence between all six possible combinations of muscle pairs. There was significant intermuscular coherence at low frequencies, between 2 and 13 Hz. The most likely source for this was the spinal cord and its peripheral feedback loops, because the spinal lesions in these patients had interrupted connections to supraspinal structures. This is the first report to demonstrate that the spinal cord is capable of producing low-frequency intermuscular coherence with severely reduced or abolished descending drive. NEW & NOTEWORTHY This is the first report to demonstrate that intermuscular coherence between lower limb muscles at low frequencies can be produced by the spinal cord with severely reduced or abolished descending drive.


Assuntos
Espasmo/fisiopatologia , Traumatismos da Medula Espinal/fisiopatologia , Adulto , Ritmo beta , Potencial Evocado Motor , Retroalimentação Fisiológica , Feminino , Humanos , Perna (Membro)/fisiopatologia , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/inervação , Músculo Esquelético/fisiopatologia
9.
Rev. colomb. cardiol ; 25(4): 243-248, jul.-ago. 2018. tab, graf
Artigo em Espanhol | LILACS, COLNAL | ID: biblio-985466

RESUMO

Resumen El dolor torácico es uno de los principales motivos de consulta al sistema de urgencias, y este es secundario a condiciones como el síndrome coronario agudo entre otras. Para su diagnóstico se requiere no sólo el resultado de la troponina, sino una evaluación clínica completa en la que se tengan en cuenta factores de riesgo cardiovascular, características del dolor y hallazgos electrocardiográficos. La interpretación inadecuada de las troponinas ultrasensibles lleva a que se someta al paciente a riesgos innecesarios a causa de estudios como el cateterismo cardiaco. Se llevó a cabo un estudio de corte trasversal en un hospital de Bogotá, en el que la causa principal de consulta en el servicio de urgencias fue el dolor torácico, y la primera causa de hospitalización en Cardiología el síndrome coronario agudo. Se recolectaron datos de 411 pacientes a quienes se les realizó arteriografía coronaria, la mayoría hombres con factores de riesgo como hipertensión arterial, tabaquismo y un evento coronario previo. Dentro de los estudios paraclínicos, la fracción de eyección promedio estuvo cercana al 50% y sólo en 201 pacientes se encontraron lesiones epicárdicas significativas.De la muestra analizada, el 13% tenía creatinina mayor de 1,5 mg/dl como causa alterna de elevación del biomarcador y 28% tenía disfunción ventricular izquierda de algún grado. La mayoría de los pacientes en quienes no se documentaron lesiones angiográficamente significativas en el cateterismo cardiaco, la troponina no cumplía criterios de positividad con base en el aumento del 20% respecto al valor inicial si este era positivo o de 50% en caso de que el primer valor fuese negativo. Adicionalmente, del grupo de pacientes con enfermedad coronaria angiográficamente significativa fue más frecuente la combinación de tres o más factores de riesgo cardiovascular en presencia de biomarcador positivo.


Abstract Chest pain is one of the main reasons for consulting the Emergency Department, and it is secondary to conditions, such as acute coronary syndrome. For its diagnosis, it not only requires a Troponin result, but also a full clinical evaluation, in which factors like cardiovascular risk have to be taken into account, as well as characteristics of the pain and the findings on the electrocardiogram. The poor interpretation of the ultrasensitive Troponins leads to the patient being subjected to unnecessary risks due to studies such as cardiac catheterisation. A cross-sectional study was conducted in a hospital in Bogota, in which chest pain was the main reason for consulting the Emergency Department, and acute coronary syndrome the first cause of admission to Cardiology. The study included a total of 411 patients on whom a coronary angiography was performed. The majority were males with risk factors such as arterial hypertension, smokers, and with a previous coronary event. Among the para-clinical studies, the mean ejection fraction was around 50%, and significant epicardial lesions were found in only 201 patients.Of the sample analysed, 13% had a creatinine greater than 1.5 mg/dl as an alternative cause of the elevation of the biomarker, and 28% had some degree of left ventricular function. the majority of patients that did not have significant angiographic lesions in the cardiac catheterisation documented, the Troponin did not meet the criteria for being positive, based on an increase of 20% as regards the initial value if this was positive or 50% in the case where the first value was negative. Furthermore, of the patient group with significant angiographic coronary disease, the combination of three or more cardiovascular risk factors was the most frequent in the presence of a positive biomarker.


Assuntos
Humanos , Masculino , Feminino , Síndrome Coronariana Aguda , Infarto do Miocárdio com Supradesnível do Segmento ST , Angina Pectoris , Angiografia Coronária , Troponina T , Infarto do Miocárdio
10.
Int J Audiol ; 57(6): 399-406, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29378459

RESUMO

OBJECTIVE: 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. DESIGN: 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. STUDY SAMPLE: Fourteen right ears of young normal hearing subjects were tested. RESULTS: 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. CONCLUSIONS: 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.


Assuntos
Estimulação Acústica/métodos , Limiar Auditivo/fisiologia , Potenciais Evocados Auditivos/fisiologia , Ruído , Adulto , Tronco Encefálico/fisiologia , Potenciais Evocados Auditivos do Tronco Encefálico/fisiologia , Feminino , Voluntários Saudáveis , Humanos , Masculino , Tempo de Reação , Fatores de Tempo , Adulto Jovem
11.
Transl Vis Sci Technol ; 6(3): 5, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-28553559

RESUMO

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.

12.
Int J Audiol ; 55(12): 748-757, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27686167

RESUMO

OBJECTIVES: To evaluate the accuracy with which the innovative QASSR method predicts behavioral thresholds in adult patients with sensorineural hearing loss. DESIGN: 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. STUDY SAMPLE: Sixteen ears of nine volunteer subjects recruited from a clinical population. RESULTS: 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. CONCLUSIONS: 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.


Assuntos
Audiometria de Resposta Evocada/métodos , Audiometria de Tons Puros/métodos , Limiar Auditivo/fisiologia , Potenciais Evocados Auditivos do Tronco Encefálico/fisiologia , Perda Auditiva Neurossensorial/fisiopatologia , Estimulação Acústica/métodos , Adulto , Idoso , Feminino , Perda Auditiva Neurossensorial/psicologia , Humanos , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes
13.
Hear Res ; 337: 12-24, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-26892906

RESUMO

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.


Assuntos
Implante Coclear/efeitos adversos , Implante Coclear/métodos , Dexametasona/farmacologia , Eletrodos/efeitos adversos , Células Ciliadas Auditivas/patologia , Neurônios/patologia , Animais , Cóclea/fisiologia , Cóclea/cirurgia , Relação Dose-Resposta a Droga , Feminino , Fibrose/patologia , Cobaias , Audição , Masculino , Rampa do Tímpano/fisiologia , Silicones/química , Estresse Mecânico
14.
Annu Int Conf IEEE Eng Med Biol Soc ; 2016: 944-947, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28268480

RESUMO

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.


Assuntos
Algoritmos , Frequência Cardíaca/fisiologia , Dor/fisiopatologia , Eletrocardiografia , Análise de Fourier , Humanos , Recém-Nascido , Recém-Nascido Prematuro , Unidades de Terapia Intensiva Neonatal
15.
Hum Mov Sci ; 40: 134-53, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25553560

RESUMO

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<.0001). P produced higher Intensity than WS for all muscles during HS (p<.0001), and VM and RF during CS (p<.001). The CON phase produced higher Intensity than ECC for the vasti muscles during CS (p<.0003), and VM and RF during HS (p<.0001). Intensity increased across repetitions plateauing earlier for the vasti than RF during CS. Regardless of the machine, Intensity levels peaked between the 25-53 Hz and 46-82 Hz (2nd and 3rd wavelets) bands. The results indicate that when the objective is increasing power through isoinertial training, P machines at HS appear to be the most effective alternative.


Assuntos
Eletromiografia/métodos , Músculo Quadríceps/fisiologia , Treinamento de Força , Adulto , Feminino , Análise de Fourier , Humanos , Masculino , Movimento , Contração Muscular , Fadiga Muscular/fisiologia , Análise de Ondaletas , Adulto Jovem
16.
Invest Ophthalmol Vis Sci ; 55(12): 8560-70, 2014 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-25477321

RESUMO

PURPOSE: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.


Assuntos
Eletrorretinografia/métodos , Células Ganglionares da Retina/fisiologia , Feminino , Humanos , Masculino , Tempo de Reação/fisiologia , Adulto Jovem
17.
Clin Neurophysiol ; 125(10): 2079-89, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24618216

RESUMO

OBJECTIVE: Due to overlapping, temporal information is mostly lost in high rate steady-state pattern electroretinograms (PERGSS). This study develops a deconvolution method and a display/recording system to "unwrap" PERGSS and obtain a transient, "per stimulus" response (PERGtr) 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.


Assuntos
Eletrodiagnóstico/métodos , Retina/fisiologia , Adulto , Eletrodiagnóstico/instrumentação , Eletrorretinografia/instrumentação , Eletrorretinografia/métodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Processamento de Sinais Assistido por Computador , Adulto Jovem
18.
Invest Ophthalmol Vis Sci ; 55(4): 2469-75, 2014 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-24667861

RESUMO

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.


Assuntos
Eletrodos , Eletrorretinografia/instrumentação , Glaucoma/fisiopatologia , Doenças do Nervo Óptico/fisiopatologia , Nervo Óptico/fisiopatologia , Células Ganglionares da Retina/fisiologia , Animais , Modelos Animais de Doenças , Glaucoma/diagnóstico , Camundongos , Camundongos Endogâmicos C57BL , Doenças do Nervo Óptico/diagnóstico , Estimulação Luminosa
19.
Food Sci Technol Int ; 20(5): 365-72, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23744119

RESUMO

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.


Assuntos
Aspergillus oryzae/metabolismo , Dessecação/métodos , Manipulação de Alimentos/métodos , Oligossacarídeos/biossíntese , Soluções , Sacarose , Reatores Biológicos , Frutas , Resíduos Industriais , Osmose , Prebióticos , Reciclagem , Rosaceae , Solanum
20.
Artigo em Inglês | MEDLINE | ID: mdl-25571013

RESUMO

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.


Assuntos
Percepção Auditiva , Estimulação Acústica/métodos , Adulto , Potenciais Evocados Auditivos , Humanos , Ilusões , Masculino , Adulto Jovem
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