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1.
Cereb Cortex ; 15(5): 552-62, 2005 May.
Artigo em Inglês | MEDLINE | ID: mdl-15319310

RESUMO

The study investigates early postnatal development of local field potentials (LFPs) in the primary auditory cortex of hearing and congenitally deaf cats. In hearing cats, LFPs elicited by electrical intracochlear stimulation demonstrated developmental changes in mid-latency range, including reductions in peak and onset latencies of individual waves and a maturation of their shape and latencies during the first 2 months of life. In long latency range (>80 ms), the P(1)/N(1) response appeared after the fourth week of life and further increased in amplitude and decreased in latency, reaching mature shapes between the fourth and sixth months after birth (p.n.). Cortical activated areas became increasingly smaller during the first 3 months of life, reaching mature values at the fourth month p.n. The layer-specific pattern of synaptic activity matured 4 months p.n. In congenitally deaf cats, the developmental pattern was different. The lowest cortical LFP thresholds were significantly smaller than in hearing controls, demonstrating a "hypersensitivity" to sensory inputs. The development of N(b) waves was delayed and altered and the long latency responses became smaller than in controls at the second and third months. The activated areas remained smaller than in controls until the third month, then they increased rapidly and exceeded the activated areas of age-matched controls. From the fourth month on, the activated areas decreased again and smaller synaptic currents were found in deaf cats than in controls. The presented data demonstrate that functional development of the auditory cortex critically depends on auditory experience.


Assuntos
Envelhecimento , Córtex Auditivo/fisiopatologia , Cóclea/fisiopatologia , Potenciais Evocados Auditivos , Perda Auditiva Neurossensorial/congênito , Perda Auditiva Neurossensorial/fisiopatologia , Plasticidade Neuronal , Estimulação Acústica/métodos , Animais , Gatos , Cóclea/inervação , Estimulação Elétrica/métodos
2.
Exp Brain Res ; 153(4): 605-13, 2003 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-12961053

RESUMO

To investigate possible cross-modal reorganization of the primary auditory cortex (field A1) in congenitally deaf cats, after years of auditory deprivation, multiunit activity and local field potentials were recorded in lightly anesthetized animals and compared with responses obtained in hearing cats. Local field potentials were also used for current source-density analyses. For visual stimulation, phase-reversal gratings of three to five different spatial frequencies and three to five different orientations were presented at the point of central vision. Peripheral visual field was tested using hand-held stimuli (light bar-shaped stimulus of different orientations, moved in different directions and flashed) typically used for neurophysiological characterization of visual fields. From 200 multiunit recordings, no response to visual stimuli could be found in A1 of any of the investigated animals. Using the current source-density analysis of local field potentials, no local generators of field potentials could be found within A1, despite of the presence of small local field potentials. No multiunit responses to somatosensory stimulation (whiskers, face, pinna, head, neck, all paws, back, tail) could be obtained. In conclusion, there were no indications for a cross-modal reorganization (visual, somatosensory) of area A1 in congenitally deaf cats.


Assuntos
Córtex Auditivo/crescimento & desenvolvimento , Córtex Auditivo/fisiopatologia , Surdez/fisiopatologia , Vias Neurais/crescimento & desenvolvimento , Plasticidade Neuronal/fisiologia , Recuperação de Função Fisiológica/fisiologia , Animais , Córtex Auditivo/anormalidades , Percepção Auditiva/fisiologia , Gatos , Surdez/complicações , Potenciais Somatossensoriais Evocados/fisiologia , Potenciais Evocados Visuais/fisiologia , Vias Neurais/anormalidades , Estimulação Luminosa , Estimulação Física , Córtex Somatossensorial/anormalidades , Córtex Somatossensorial/crescimento & desenvolvimento , Tato/fisiologia , Córtex Visual/anormalidades , Córtex Visual/crescimento & desenvolvimento , Córtex Visual/fisiologia , Percepção Visual/fisiologia
3.
Cereb Cortex ; 12(8): 797-807, 2002 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-12122028

RESUMO

The congenitally deaf cat suffers from a degeneration of the inner ear. The organ of Corti bears no hair cells, yet the auditory afferents are preserved. Since these animals have no auditory experience, they were used as a model for congenital deafness. Kittens were equipped with a cochlear implant at different ages and electro-stimulated over a period of 2.0-5.5 months using a monopolar single-channel compressed analogue stimulation strategy (VIENNA-type signal processor). Following a period of auditory experience, we investigated cortical field potentials in response to electrical biphasic pulses applied by means of the cochlear implant. In comparison to naive unstimulated deaf cats and normal hearing cats, the chronically stimulated animals showed larger cortical regions producing middle-latency responses at or above 300 microV amplitude at the contralateral as well as the ipsilateral auditory cortex. The cortex ipsilateral to the chronically stimulated ear did not show any signs of reduced responsiveness when stimulating the 'untrained' ear through a second cochlear implant inserted in the final experiment. With comparable duration of auditory training, the activated cortical area was substantially smaller if implantation had been performed at an older age of 5-6 months. The data emphasize that young sensory systems in cats have a higher capacity for plasticity than older ones and that there is a sensitive period for the cat's auditory system.


Assuntos
Córtex Auditivo/fisiologia , Percepção Auditiva/fisiologia , Surdez/fisiopatologia , Plasticidade Neuronal/fisiologia , Privação Sensorial/fisiologia , Fatores Etários , Animais , Córtex Auditivo/crescimento & desenvolvimento , Gatos , Implantes Cocleares , Nervo Coclear/crescimento & desenvolvimento , Nervo Coclear/fisiologia , Período Crítico Psicológico , Surdez/congênito , Surdez/terapia , Tempo de Reação/fisiologia
4.
Audiol Neurootol ; 6(4): 203-6, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11694728

RESUMO

Congenitally deaf cats were used as a model for human inborn deafness and auditory deprivation. The deaf cats were supplied with a cochlear implant, chronically exposed to an acoustic environment and conditioned to acoustic stimuli. In case of early implantation the cats learned to make use of the newly gained auditory channel behaviourally. Neurophysiological and fMRI data showed that the central auditory system was recruited, if implantation took place within a sensitive period of <6 months.


Assuntos
Córtex Auditivo/fisiologia , Implante Coclear , Surdez/congênito , Surdez/cirurgia , Plasticidade Neuronal/fisiologia , Animais , Tronco Encefálico/fisiologia , Gatos , Estimulação Elétrica , Neurônios/fisiologia , Período Pós-Operatório , Reflexo/fisiologia
5.
Arch Biochem Biophys ; 392(2): 208-18, 2001 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-11488594

RESUMO

The CD40 ligand molecule is unique, consisting of a receptor-binding domain anchored by an isoleucine zipper moiety. Exact determination of the multimeric state and its tendency to form molten globules has not been elucidated. Corroborating evidence of a trimerized molecule in aqueous solution was obtained from size-exclusion chromatography, laser light scattering, and analytical ultracentrifugation. A reversible acid-denatured molten globule state was observed from circular dichroism and fluorescence spectroscopy data. The molten globule state was characterized by a loss of tertiary structure with associated retention of secondary structure near pH 3. Once returned to pH 7, the acid-denatured state refolded over the course of 7 days resulting in approximately 90% recovery of the native structure. The molten globule state was characterized by a broadening of structural features in the second-derivative spectra of Fourier transform infrared spectroscopy. A component band at 1650 cm(-1) was shown to be alpha-helix and originate from amide carbonyl vibrations of the isoleucine zipper. Differential scanning calorimetry measurements characterized the pH-sensitive molten globule state at pH 3.3 as one lacking a well-defined unfolding transition with an accompanying baseline shift at 58 degrees C (a consequence of increased heat capacity). The tendency to form molten globules during acid denaturation stress permits an opportunity to study the process of partial protein unfolding with implications concerning stability. Although reversible molten globules can be formed, it is important to recognize the unusual nature since the molten globule state is formed exclusively within the beta-sheet receptor-binding region.


Assuntos
Ligante de CD40/química , Animais , Células CHO , Varredura Diferencial de Calorimetria , Cromatografia , Dicroísmo Circular , Cricetinae , Dimerização , Análise de Fourier , Concentração de Íons de Hidrogênio , Luz , Modelos Moleculares , Conformação Proteica , Dobramento de Proteína , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Espalhamento de Radiação , Espectrometria de Fluorescência , Temperatura , Ultracentrifugação
6.
Chem Commun (Camb) ; (22): 2390-1, 2001 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-12240090

RESUMO

The reversible formation of a coordinative bond between a polymer-bound Lewis-acidic metal complex and a flavin imide moiety allows complete extraction of riboflavin from aqueous solution at physiological pH and its quantitative release at pH 5.


Assuntos
Compostos Aza , Riboflavina/isolamento & purificação , Compostos Aza/química , Sítios de Ligação , Concentração de Íons de Hidrogênio , Polímeros/química , Riboflavina/química , Compostos de Zinco/química
7.
Audiol Neurootol ; 6(6): 346-62, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11847463

RESUMO

Behavioral data indicate the existence of sensitive periods in the development of audition and language. Neurophysiological data demonstrate deficits in the cerebral cortex of auditory-deprived animals, mainly in reduced cochleotopy and deficits in corticocortical and corticothalamic loops. In addition to current spread in the cochlea, reduced cochleotopy leads to channel interactions after cochlear implantation. Deficits in corticocortical and corticothalamic loops interfere with normal processing of auditory activity in cortical areas. Thus, the deprived auditory cortex cannot mature normally in congenital deafness. This maturation can be achieved using auditory experience through cochlear implants. However, implantation is necessary within the sensitive period of the auditory system. The functional role of long-term potentiation and long-term depression, inhibition, cholinergic modulation and neurotrophins in auditory development and sensitive periods are discussed.


Assuntos
Córtex Auditivo/fisiologia , Surdez/congênito , Plasticidade Neuronal/fisiologia , Fatores Etários , Animais , Gatos , Implante Coclear , Surdez/cirurgia , Humanos
8.
Bratisl Lek Listy ; 101(2): 112-4, 2000.
Artigo em Eslovaco | MEDLINE | ID: mdl-11039219

RESUMO

The present paper introduces a registration method for the electrical field produced by a cochlear implant in the scala tympani in vitro. It was possible to determine the electrical potentials with high spatial resolution using an additional recording electrode. The results indicate that the efficacy of the stimulation by the more apical electrodes is higher than by the more basal ones. The reason is the decreasing cross-sectional area of the scala tympani, which represents a decreasing shunt between the stimulation electrodes.


Assuntos
Cóclea/fisiologia , Implante Coclear , Animais , Gatos , Estimulação Elétrica , Potenciais Evocados , Rampa do Tímpano/fisiologia
9.
Cereb Cortex ; 10(7): 714-26, 2000 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-10906318

RESUMO

The present study investigates the functional deficits of naive auditory cortices in adult congenitally deaf cats. For this purpose, their auditory system was stimulated electrically using cochlear implants. Synaptic currents in cortical layers were revealed using current source density analyses. They were compared with synaptic currents found in electrically stimulated hearing cats. The naive auditory cortex showed significant deficits in synaptic activity in infragranular cortical layers. Furthermore, there was also a deficit of synaptic activities at longer latencies (>30 ms). The 'cortical column' was not activated in the well-defined sequence found in normal hearing cats. These results demonstrate functional deficits as a consequence of congenital auditory deprivation. Similar deficits are likely in congenitally deaf children.


Assuntos
Córtex Auditivo/fisiologia , Surdez/genética , Sinapses/fisiologia , Animais , Córtex Auditivo/ultraestrutura , Gatos , Estimulação Elétrica , Tempo de Reação
10.
Bratisl Lek Listy ; 101(3): 170-2, 2000.
Artigo em Eslovaco | MEDLINE | ID: mdl-10870263

RESUMO

The influence of the electrode configuration on the efficacy of the electrical stimulation were investigated in the auditory nerve. For this purpose normal hearing cats were deafened by intrascalar application of neomycin and stimulated by a NUCLEUS-22 implant. Stimulation was performed in monopolar, bipolar and tripolar mode with all electrodes of the implant. The smallest thresholds were determined for monopolar stimulation, followed by tripolar and bipolar stimulation. The most focused stimulation was achieved by tripolar stimulation, followed by bipolar and monopolar stimulation. Tripolar stimulation is therefore suitable for beam forming in electrical stimulation of the auditory nerve.


Assuntos
Implante Coclear , Nervo Coclear/fisiologia , Animais , Gatos , Implantes Cocleares , Surdez/fisiopatologia , Estimulação Elétrica , Eletrodos Implantados
11.
Artigo em Inglês | MEDLINE | ID: mdl-10545807

RESUMO

Various devices have been developed to overcome the widespread phenomenon of different degrees of hearing deficits between mild and profound hearing loss. Basically, we differentiate between acoustic stimulation (hearing aids), restricted to cases with a partially functioning cochlear receptor, and electrical stimulation (cochlear implants), stimulating the auditory nerve directly in cases with profound or total hearing loss. For the first time, animal data have been collected that indicate the possibility of nearly interference-free use of both stimulation types simultaneously. In addition, we have gathered the first clinical patient experience, which confirms the encouraging results. Future implications for patients with severe high-frequency hearing loss are discussed.


Assuntos
Estimulação Acústica/métodos , Perda Auditiva Neurossensorial/reabilitação , Animais , Limiar Auditivo/fisiologia , Gatos , Implantes Cocleares , Nervo Coclear/fisiologia , Modelos Animais de Doenças , Estimulação Elétrica/métodos , Cobaias , Auxiliares de Audição , Perda Auditiva Neurossensorial/diagnóstico , Humanos , Pessoa de Meia-Idade , Cuidados Pós-Operatórios , Cuidados Pré-Operatórios , Ajuste de Prótese , Distribuição Aleatória , Índice de Gravidade de Doença , Percepção da Fala/fisiologia
12.
Science ; 285(5434): 1729-33, 1999 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-10481008

RESUMO

In congenitally deaf cats, the central auditory system is deprived of acoustic input because of degeneration of the organ of Corti before the onset of hearing. Primary auditory afferents survive and can be stimulated electrically. By means of an intracochlear implant and an accompanying sound processor, congenitally deaf kittens were exposed to sounds and conditioned to respond to tones. After months of exposure to meaningful stimuli, the cortical activity in chronically implanted cats produced field potentials of higher amplitudes, expanded in area, developed long latency responses indicative of intracortical information processing, and showed more synaptic efficacy than in naïve, unstimulated deaf cats. The activity established by auditory experience resembles activity in hearing animals.


Assuntos
Córtex Auditivo/fisiologia , Vias Auditivas/fisiologia , Cóclea/fisiologia , Implantes Cocleares , Surdez/fisiopatologia , Estimulação Acústica , Animais , Gatos , Condicionamento Psicológico , Surdez/congênito , Surdez/terapia , Estimulação Elétrica , Potenciais Evocados Auditivos , Audição , Sinapses/fisiologia , Fatores de Tempo
13.
Neuroreport ; 10(4): 781-7, 1999 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-10208548

RESUMO

Cortical activity can be substantially changed by the type of anaesthetic used, and by its dose level. For easy monitoring of depth of anaesthesia we describe the changes in electroencephalogram and electrocardiogram accompanying changes in depth of anaesthesia in the cat. Anaesthesia was induced by the volatile anaesthetic isoflurane. The high-frequency components (around 30 Hz) in the electroencephalogram disappear in deep anaesthesia. The electrocardiogram also shows substantial changes in contamination due to muscle fasciculations with anaesthesia level. Fasciculations appear as noise in the electrocardiogram. The amplitude of the electrical muscle activity contaminating the ECG can be easily used for the maintainance of a constant level of anaesthesia during a neurophysiological experiment.


Assuntos
Anestesia , Eletrocardiografia/efeitos dos fármacos , Eletroencefalografia/efeitos dos fármacos , Neurofisiologia/métodos , Animais , Gatos , Eletrofisiologia , Relaxamento Muscular/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/fisiologia , Fármacos Neuromusculares não Despolarizantes/farmacologia , Pancurônio/farmacologia , Nervo Vestibulococlear/efeitos dos fármacos , Nervo Vestibulococlear/fisiologia
14.
Hear Res ; 129(1-2): 1-6, 1999 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-10190746

RESUMO

According to Davis' (1965) model of the inner ear, a potential difference between the endocochlear potential and the hair cell resting potential drives the transduction current across the apical hair cell membrane. It is assumed that the endocochlear potential (EP) consists of two components. The first is a diffusion potential, which depends on the ionic composition of endolymph and perilymph and on the permeability of the perilymph-endolymph barrier. The second is an electrogenic component which is determined by active ion transport across the perilymph-endolymph barrier. In birds, the EP is between +8 and +20 mV. Little is known about the underlying mechanisms responsible for the measured EP in birds. The present paper studies whether ionic compositions of endo- and perilymph might explain the EP in birds. Concentrations of Na+, K+, Ca2+ and Cl- in pigeon scala vestibuli, scala tympani and scala media were determined with ion-selective microelectrodes. Na+, K+, Ca2+ and Cl- were 150.0, 4.2, 1.4 and 117.0 mM in perilymph (scala tympani and scala vestibuli). In scala media, the concentrations of K+, Ca2+ and Cl- were 140.6, 0.23 and 142.1 mM.


Assuntos
Columbidae/metabolismo , Endolinfa/metabolismo , Perilinfa/metabolismo , Animais , Cálcio/metabolismo , Cloretos/metabolismo , Feminino , Células Ciliadas Auditivas/metabolismo , Masculino , Mamíferos/metabolismo , Potenciais da Membrana , Potássio/metabolismo , Sódio/metabolismo
15.
J Biol Chem ; 274(1): 418-23, 1999 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-9867859

RESUMO

Recent progress in the understanding of immune function indicates that the interaction of CD40L with its receptor, CD40, plays a pivotal role in both humoral immunity and cell-mediated defense against pathogens. Functional studies of this interaction on both dendritic cells and malignant cells have demonstrated that CD40L also plays an important role in immune surveillance and anti-tumor immunity. CD40L exists in nature predominantly as a membrane-anchored molecule. To develop CD40L as a potential therapeutic, it is important to optimize soluble forms of this molecule that could be used in a clinical setting. Several reports have shown that soluble forms of CD40L, like CD40 antibodies, are biologically active. In the present report we demonstrate that the incorporation of an isoleucine zipper trimerization motif significantly enhances the biological activity of soluble CD40L.


Assuntos
Isoleucina/química , Zíper de Leucina , Glicoproteínas de Membrana/metabolismo , Animais , Biopolímeros , Antígenos CD40/metabolismo , Ligante de CD40 , Células CHO , Varredura Diferencial de Calorimetria , Cricetinae , Eletroforese em Gel de Poliacrilamida , Glicoproteínas de Membrana/química , Glicoproteínas de Membrana/isolamento & purificação , Conformação Proteica , Termodinâmica
16.
Hear Res ; 121(1-2): 11-28, 1998 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-9682804

RESUMO

This paper investigates the spatial resolution of electrical intracochlear stimulation in order to enable further refinement of cochlear implants. For this purpose electrical potential distributions around a conventional human intracochlear electrode (NUCLEUS-22) were measured in a tank, in cat cadaver cochleae and in living cat cochleae. Potential gradients were calculated where of importance. The values were compared to spatial tuning curves from cat primary auditory afferents in electrical mono-, bi-, and various tripolar stimulation modes. Finally, a lumped element model was developed to elucidate the single fiber data. Tank potential measurements show the principal features of the different stimulation modes but are not sufficient to explain all the features of experimental data from single fibers. Intracochlear potential measurements indicate an increase in spatial resolution in an apical direction. The single fiber data also confirm that a tripolar stimulus configuration provides significantly better spatial resolution than any other stimulation mode presently in use.


Assuntos
Implantes Cocleares , Fibras Nervosas/fisiologia , Neurônios Aferentes/fisiologia , Nervo Vestibulococlear/fisiologia , Animais , Gatos , Potenciais Microfônicos da Cóclea/fisiologia , Estimulação Elétrica , Humanos , Técnicas In Vitro , Modelos Biológicos
17.
Hear Res ; 120(1-2): 109-20, 1998 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-9667435

RESUMO

The extent of hair cell regeneration following acoustic overstimulation severe enough to destroy tall hair cells, was determined in adult pigeons. BrdU (5-bromo-2'-deoxyuridine) was used as a proliferation marker. Recovery of hearing thresholds in each individual animal was measured over a period of up to 16 weeks after trauma. In ears with loss of both short and tall hair cells, little or no functional recovery occurred. In ears with less damage, where significant functional recovery did occur, there were always a few rows of surviving hair cells left at the neural edge of the basilar papilla. In the region of hair cell loss, numerous BrdU labeled cells were found. However, only a small minority of these cells were regenerated hair cells, the majority being monolayer cells. Irrespective of the extent of the region of hair cell loss, regenerated hair cells were observed predominantly in a narrow strip at the transition from the abneural area of total hair cell loss and the neural area of hair cell survival. With increasing damage this strip moved progressively towards the neural edge of the papilla. No regeneration of hair cells was observed in the abneural region of total hair cell loss, even up to 16 weeks after trauma. The results indicate that there is a gradient in the destructive effect of loud sound across the width of the basilar papilla, from most detrimental at the abneural edge to least detrimental at the neural edge. Both tall and short hair cells can regenerate after sound trauma. Whether they do regenerate or not depends on the degree of damage to the area of the papilla where they normally reside. Regeneration of new hair cells occurs only in a narrow longitudinal band, which moves from abneural into the neural direction with increasing damage. In the area neural to this band, hair cells survive the overstimulation. In the area abneural to this band, sound damage is so severe, that no regeneration of hair cells occurs. As a consequence morphological and functional deficits persist.


Assuntos
Células Ciliadas Auditivas/fisiopatologia , Perda Auditiva Provocada por Ruído/fisiopatologia , Regeneração Nervosa/fisiologia , Nervo Vestibulococlear/fisiopatologia , Estimulação Acústica , Animais , Membrana Basilar/fisiopatologia , Bromodesoxiuridina , Divisão Celular , Sobrevivência Celular , Columbidae , Replicação do DNA/fisiologia
18.
IEEE Trans Biomed Eng ; 45(6): 773-82, 1998 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-9609942

RESUMO

A signal processor-based (DSP32C) stimulation system for cochlear implants has been developed. This system allows up to 14 stimulation channels (place principle) and conserves the time structure of the acoustic signal (periodicity principle). Any combination of these features is possible; in compressed analogue mode, pulsatile mode, or combinations of both. The system also takes electrical crosstalk into account caused by the electrical properties of the inner ear and compensates for it. Lateral inhibition strategies improve spatial resolution. Finally, the system offers an interface for the generation of quick continuous interleaved sampling strategies (CIS); up to 11,000 pulses/s per channel.


Assuntos
Implantes Cocleares , Fonética , Processamento de Sinais Assistido por Computador , Software , Apresentação de Dados , Desenho de Equipamento , Humanos , Interface Usuário-Computador
19.
J Neurosci Methods ; 79(1): 79-85, 1998 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-9531463

RESUMO

Functional electrical stimulation in alert experimental animals is often hampered, as free mobility of the animals is limited by the leads. On the other hand, portable devices carrying the power supply are not always accepted by the animal. For wireless transmission of power and stimulus code a system designed for implantation is described below. The power for the implant is supplied inductively by a rotating magnetic field. The stimulation signal is radio-transmitted by FM in the 140 MHz range and processed by the implant. Finally, a current source is driven for electrical stimulation. The present design is intended to be used for electrical cochlear stimulation. However, the circuit can also be used for other types of functional electrical stimulation.


Assuntos
Implantes Cocleares , Estimulação Elétrica/instrumentação , Estimulação Elétrica/métodos , Animais , Fontes de Energia Elétrica , Campos Eletromagnéticos , Eletrônica/instrumentação , Desenho de Equipamento/instrumentação , Humanos , Ondas de Rádio
20.
Hear Res ; 115(1-2): 101-12, 1998 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-9472739

RESUMO

Cochlear implantation in congenitally deaf children leads to electrical stimulation of an entirely naive central auditory system. In this case, processes of central auditory maturation are induced by the electric stimuli. For the study of these processes the deaf white cat (DWC) appears to be an appropriate model. However, a knowledge of the basic data of these animals is necessary before such a model may be used. This paper presents these data and is one of a series of publications concerning congenital deafness in children and cochlear implantation. In our strain 72% of the animals are totally deaf as judged by the absence of any brain stem evoked potentials at click intensities up to 120 dB SPL peak equivalent. Primarily, there is a degeneration of the entire organ of Corti during the first postnatal weeks. An absence of acoustically evoked brain stem responses in the early postnatal weeks shows that DWCs probably never have any hearing experience. Months after the degeneration of the organ of Corti, the spiral ganglion starts to degenerate from the midportion of the cochlea. However, even in adult cats (2 years), a sufficient number of functionally intact auditory afferents remain, which are suitable for electrical cochlear stimulation.


Assuntos
Doenças do Gato/congênito , Surdez/congênito , Surdez/veterinária , Estimulação Acústica , Animais , Limiar Auditivo/fisiologia , Doenças do Gato/fisiopatologia , Doenças do Gato/cirurgia , Gatos , Implante Coclear , Surdez/cirurgia , Modelos Animais de Doenças , Estimulação Elétrica , Potenciais Evocados Auditivos do Tronco Encefálico/fisiologia , Degeneração Neural , Fibras Nervosas/fisiologia , Neurônios Aferentes/fisiologia , Órgão Espiral/fisiopatologia , Gânglio Espiral da Cóclea/fisiopatologia
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