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1.
Life Sci ; 259: 118144, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32755624

RESUMO

AIMS: Although the vestibular system has been widely investigated over the past 50 years, there is still an unsolved mystery. Some special vestibular afferent (SVA) neurons responding to both rotation and linear force were found through neurophysiological techniques, however, the sensory overlap mechanism of SVA neurons is still unclear, which may be closely related to vestibular-related diseases. MATERIALS AND METHODS: To address the above-mentioned problem, a cupula buoyancy theory was established in the present study, where SVA neurons were considered semicircular canal afferent (SCCA) neurons. Then labyrinth anatomy and neural response dynamics of vestibular afferent neurons in chinchilla were investigated through vestibular labyrinth reconstruction and single unit recording technique, respectively. KEY FINDINGS: We analyzed the deflections of cupulae under multiple conditions with the help of Amira Software and predicted the neural response law of SCCA neurons to linear force based on the cupula buoyancy theory. Data analysis confirmed that the basic response characteristic of SVA neurons had no significant difference to those of SCCA neurons, but were significantly different from those of otolith afferent neurons. Further, the actual responses of SVA neurons to linear force are completely consistent with our predictions. These results strongly suggest that SVA neurons actually are SCCA neurons, and the cupula buoyancy theory is the key to the sensory overlap mechanism of SCCA neurons. SIGNIFICANCE: Our study revealed the real identity of SVA neurons and provided a reasonable mechanism for sensory overlap of rotation and linear force, which improved our understanding about the vestibular system.


Assuntos
Neurônios Aferentes/fisiologia , Rotação , Sensação/fisiologia , Vestíbulo do Labirinto/lesões , Vestíbulo do Labirinto/fisiologia , Animais , Chinchila , Feminino , Movimentos da Cabeça , Modelos Anatômicos , Membrana dos Otólitos/fisiologia , Canais Semicirculares/fisiologia , Vestíbulo do Labirinto/anatomia & histologia
2.
Med Sci (Paris) ; 36(6-7): 581-591, 2020.
Artigo em Francês | MEDLINE | ID: mdl-32614308

RESUMO

Following partial or total loss of peripheral vestibular inputs, a phenomenon called central vestibular compensation takes place in the hours and days following the injury. This neuroplasticity process involves a mosaic of profound rearrangements within the brain stem vestibular nuclei. Among them, the setting of a new neuronal network is maybe the most original and unexpected, as it involves an adult reactive neurogenesis in a brain area not reported as neurogenic so far. Both the survival and functionality of this newly generated neuronal network will depend on its integration to pre-existing networks in the deafferented structure. Far from being aberrant, this new structural organization allows the use of inputs from other sensory modalities (vision and proprioception) to promote the restoration of the posture and equilibrium. We choose here to detail this model, which does not belong to the traditional niches of adult neurogenesis, but it is the best example so far of the reparative role of the adult neurogenesis. Not only it represents an original neuroplasticity mechanism, interesting for basic neuroscience, but it also opens new medical perspectives for the development of therapeutic approaches to alleviate vestibular disorders.


Assuntos
Encéfalo/citologia , Neurogênese/fisiologia , Neurônios/fisiologia , Postura/fisiologia , Doenças Vestibulares/reabilitação , Núcleos Vestibulares/lesões , Adulto , Células-Tronco Adultas/citologia , Células-Tronco Adultas/fisiologia , Animais , Encéfalo/fisiologia , Humanos , Células-Tronco Neurais/fisiologia , Plasticidade Neuronal/fisiologia , Doenças Vestibulares/fisiopatologia , Núcleos Vestibulares/patologia , Núcleos Vestibulares/fisiologia , Vestíbulo do Labirinto/lesões , Vestíbulo do Labirinto/patologia , Vestíbulo do Labirinto/fisiologia
3.
PLoS One ; 15(6): e0233843, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32497147

RESUMO

The vestibular system is essential to produce adequate postural responses enabling voluntary movement. However, how the vestibular system influences corticospinal output during postural tasks is still unknown. Here, we examined the modulation exerted by the vestibular system on corticospinal output during standing. Healthy subjects (n = 25) maintained quiet standing, head facing forward with eyes closed. Galvanic vestibular stimulation (GVS) was applied bipolarly and binaurally at different delays prior to transcranial magnetic stimulation (TMS) which triggered motor evoked potentials (MEPs). With the cathode right/anode left configuration, MEPs in right Soleus (SOL) muscle were significantly suppressed when GVS was applied at ISI = 40 and 130ms before TMS. With the anode right/cathode left configuration, no significant changes were observed. Changes in the MEP amplitude were then compared to changes in the ongoing EMG when GVS was applied alone. Only the decrease in MEP amplitude at ISI = 40ms occurred without change in the ongoing EMG, suggesting that modulation occurred at a premotoneuronal level. We further investigated whether vestibular modulation could occur at the motor cortex level by assessing changes in the direct corticospinal pathways using the short-latency facilitation of the SOL Hoffmann reflex (H-reflex) by TMS. None of the observed modulation occurred at the level of motor cortex. Finally, using the long-latency facilitation of the SOL H-reflex, we were able to confirm that the suppression of MEP at ISI = 40ms occurred at a premotoneuronal level. The data indicate that vestibular signals modulate corticospinal output to SOL at both premotoneuronal and motoneuronal levels during standing.


Assuntos
Eletromiografia/métodos , Tratos Piramidais/fisiologia , Posição Ortostática , Vestíbulo do Labirinto/fisiologia , Adulto , Potencial Evocado Motor/fisiologia , Feminino , Lateralidade Funcional/fisiologia , Reflexo H/fisiologia , Voluntários Saudáveis , Humanos , Masculino , Córtex Motor/fisiologia , Neurônios Motores/fisiologia , Músculo Esquelético/fisiologia , Estimulação Transcraniana por Corrente Contínua , Estimulação Magnética Transcraniana , Adulto Jovem
4.
Phys Ther ; 100(8): 1333-1342, 2020 08 12.
Artigo em Inglês | MEDLINE | ID: mdl-32399552

RESUMO

OBJECTIVE: The modified Clinical Test of Sensory Interaction and Balance (mCTSIB) is used to clinically assess vestibular sensory integration (VSI), the process by which the central nervous system integrates vestibular afference to maintain balance. The rate and effects of impaired VSI (IVSI) on prosthetic mobility in people with lower limb amputation (LLA) is unknown. The objective of this study was to use the mCTSIB to classify VSI in active community ambulators with LLA and to examine the relationship between IVSI and prosthetic mobility, as measured by the Component Timed Up and Go (cTUG) test. METHODS: This was a cross-sectional study with a convenience sample of 130 community ambulators with unilateral LLA. Classification of VSI was determined based on a time-based pass/fail mCTSIB performance. Participants were classified as having normal sensory integration (NSI) if they could balance for 30 seconds in every mCTSIB condition. Participants who failed condition 4 exclusively were classified as IVSI. Prosthetic mobility, as measured by the cTUG, was compared between NSI and IVSI groups. RESULTS: Of the 130 participants, 29 (22%) were classified as IVSI and 95 (73%) were classified as having NSI. Prosthetic mobility significantly differed between IVSI and NSI groups, with IVSI participants performing all components of the cTUG significantly slower. Medium to large effect sizes were found between groups during cTUG. CONCLUSIONS: These results suggest that 1 in 5 community ambulators with LLA have IVSI, with associated limitations in balance confidence and prosthetic mobility. IMPACT: The ability to integrate vestibular information was found to have a strong relationship with prosthetic mobility in active community ambulators with LLA, especially with performing a 180-degree step turn. Physical therapists can use the mCTSIB to classify sensory integration during prosthetic rehabilitation and develop an appropriate balance intervention. LAY SUMMARY: Active adults with LLA can use information from their senses to maintain their standing balance. Adults with LLA who have difficulty balancing on foam with closed eyes were slower to get in and out of a chair, walk, and perform a 180-degree step turn.


Assuntos
Amputados , Membros Artificiais , Equilíbrio Postural/fisiologia , Vestíbulo do Labirinto/fisiologia , Caminhada/fisiologia , Adulto , Idoso , Amputados/classificação , Estudos Transversais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fatores de Tempo , Adulto Jovem
5.
PLoS One ; 15(5): e0233262, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32413079

RESUMO

Previous unimodal PET and fMRI studies in humans revealed a reproducible vestibular brain activation pattern, but with variations in its weighting and expansiveness. Hybrid studies minimizing methodological variations at baseline conditions are rare and still lacking for task-based designs. Thus, we applied for the first time hybrid 3T PET-MRI scanning (Siemens mMR) in healthy volunteers using galvanic vestibular stimulation (GVS) in healthy volunteers in order to directly compare H215O-PET and BOLD MRI responses. List mode PET acquisition started with the injection of 750 MBq H215O simultaneously to MRI EPI sequences. Group-level statistical parametric maps were generated for GVS vs. rest contrasts of PET, MR-onset (event-related), and MR-block. All contrasts showed a similar bilateral vestibular activation pattern with remarkable proximity of activation foci. Both BOLD contrasts gave more bilateral wide-spread activation clusters than PET; no area showed contradictory signal responses. PET still confirmed the right-hemispheric lateralization of the vestibular system, whereas BOLD-onset revealed only a tendency. The reciprocal inhibitory visual-vestibular interaction concept was confirmed by PET signal decreases in primary and secondary visual cortices, and BOLD-block decreases in secondary visual areas. In conclusion, MRI activation maps contained a mixture of CBF measured using H215O-PET and additional non-CBF effects, and the activation-deactivation pattern of the BOLD-block appears to be more similar to the H215O-PET than the BOLD-onset.


Assuntos
Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Imagem por Ressonância Magnética , Imagem Multimodal , Tomografia por Emissão de Pósitrons , Vestíbulo do Labirinto/fisiologia , Mapeamento Encefálico , Circulação Cerebrovascular , Estimulação Elétrica , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Oxigênio/sangue , Percepção/fisiologia
6.
Int J Sports Med ; 41(9): 616-627, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32365387

RESUMO

US Soccer eliminated soccer heading for youth players ages 10 years and younger and limited soccer heading for children ages 11-13 years. Limited empirical evidence associates soccer heading during early adolescence with medium-to-long-term behavioral deficits. The purpose of this study was to compare sensory reweighting for upright stance between college-aged soccer players who began soccer heading ages 10 years and younger (AFE ≤ 10) and those who began soccer heading after age 10 (AFE > 10). Thirty soccer players self-reported age of first exposure (AFE) to soccer heading. Sensory reweighting was compared between AFE ≤ 10 and AFE > 10. To evaluate sensory reweighting, we simultaneously perturbed upright stance with visual, vestibular, and proprioceptive stimulation. The visual stimulus was presented at two different amplitudes to measure the change in gain to vision, an intra-modal effect; and change in gain to galvanic vestibular stimulus (GVS) and vibration, both inter-modal effects. There were no differences in gain to vision (p=0.857, η2=0.001), GVS (p=0.971, η2=0.000), or vibration (p=0.974, η2=0.000) between groups. There were no differences in sensory reweighting for upright stance between AFE ≤ 10 and AFE > 10, suggesting that soccer heading during early adolescence is not associated with balance deficits in college-aged soccer players, notwithstanding potential deficits in other markers of neurological function.


Assuntos
Cabeça/fisiologia , Destreza Motora/fisiologia , Equilíbrio Postural/fisiologia , Futebol/fisiologia , Adolescente , Adulto , Fatores Etários , Percepção Auditiva/fisiologia , Fenômenos Biomecânicos , Concussão Encefálica/prevenção & controle , Criança , Humanos , Vestíbulo do Labirinto/fisiologia , Vibração , Percepção Visual/fisiologia , Adulto Jovem
7.
J Sports Sci ; 38(15): 1799-1805, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32412332

RESUMO

Clinically feasible metrics, that can inform the concussion recovery decision making process by evaluating a unique domain beyond current testing domains (e.g., balance, neurocognition, symptoms, vestibular/ocular function) are still in need. The purpose of this study was to compare perceptual-motor control in adolescent athletes ≤21 days of sport-related concussion and healthy controls and evaluate the association of perceptual-motor control to the outcomes of commonly-used sport-related concussion clinical assessments. Athletes (age: 12-18 years) with sport-related concussion (n = 48) and healthy controls (n = 24) completed the Perception-Action Coupling Task (PACT), whose outcomes are mean reaction, movement, initiation, response time, and accuracy. ImPACT outcomes are verbal/visual memory scores, motor processing speed, and reaction time. Vestibular-Ocular Motor Screen (VOMS) outcomes are symptoms from: smooth pursuit, horizontal/vertical saccades, near-point of convergence, horizontal/vestibular ocular-reflex, and visual motion sensitivity. CONCUSSED demonstrated ~5% deficit in overall perceptual-motor accuracy during PACT compared to CONTROLS (p = 0.03). PACT accuracy negatively correlated with smooth pursuits(r = -0.29), and horizontal (r = -0.35)/vertical (r = -0.30) saccades. The C5.0 decision tree determined PACT accuracy was the most relevant predictor of sport-related concussion when no visual motion sensitivity symptoms were reported and Visual Memory was >66. Perceptual-motor control tests may complement current sport-related concussion assessments when neurocognition and vestibular/ocular motor system are not grossly impaired.


Assuntos
Traumatismos em Atletas/diagnóstico , Concussão Encefálica/diagnóstico , Testes Neuropsicológicos , Adolescente , Traumatismos em Atletas/fisiopatologia , Concussão Encefálica/fisiopatologia , Criança , Cognição/fisiologia , Estudos Transversais , Árvores de Decisões , Humanos , Memória/fisiologia , Destreza Motora/fisiologia , Músculos Oculomotores/fisiologia , Percepção/fisiologia , Tempo de Reação , Vestíbulo do Labirinto/fisiologia
8.
Invest Ophthalmol Vis Sci ; 61(5): 4, 2020 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-32392313

RESUMO

Purpose: Acceleration plays a great impact on the vestibular system, but is attributed little influence over vision. This study aims to explore how visual and vestibular acceleration affect roll-plane oculomotor responses, including their addiative effect. Methods: Seated in a mechanical sled, 13 healthy volunteers (7 men, 6 women; mean age 25 years) were exposed to a series of visual (VIS) optokinetic, vestibular (VES) whole-body, and combined (VIS + VES) rotations. This was carried out at two acceleration intensities. Subjects wore a video-based eye tracker, enabling analysis of torsional and skewing eye movement responses, which were used to evaluate the individual response to each trial. The tracker also contained accelerometers allowing head tracking. Results: Both ocular torsion and vertical skewing were sensitive to acceleration intensities for VES and VIS + VES. For VIS only, skewing exhibited such a response. An increased acceleration yielded a decreased torsion-skewing ratio for VIS, explained by the change in skewing, but remained unchanged for VES and VIS + VES. Torsion exhibited particularly reliable summative effect, yielding a relative contribution of 32% VIS and 75% VES during low acceleration, and 19% and 85%, respectively, during high acceleration. Conclusions: The change in the skewing response to different intensities indicates that the visual system is more sensitive to visual accelerations than previously described. Eye movements showed reliable summative effects, indicating a robust visual-vestibular integration that indicates their integrative priorities for each acceleration, with the visual system being more involved during low accelerations. Such objective quantifications could hold clinical utility when assessing sensory mismatch in vertiginous patients.


Assuntos
Aceleração , Movimentos Oculares/fisiologia , Reflexo Vestíbulo-Ocular/fisiologia , Adulto , Feminino , Voluntários Saudáveis , Humanos , Masculino , Percepção de Movimento/fisiologia , Estimulação Luminosa , Rotação , Vestíbulo do Labirinto/fisiologia
9.
Am J Otolaryngol ; 41(4): 102468, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32248954

RESUMO

PURPOSE: Evaluation of specific computerized posturographic parameters in patients with Menière's disease (MD) following the intratympanic injection of gadolinium, a contrast agent, used in radiological diagnosing. MATERIALS AND METHODS: We have observed 12 adult patients with unilateral Menière's Disease subjected to inner ear magnetic resonance imaging (MRI) examination after intratympanic gadolinium injection (ITG). The diagnoses have been performed according to the guidelines of the American Academy of otolaryngology. Before and after 24 h the ITG, all patients were subjected to the clinical evaluation and computerized posturography (CP), in 4 conditions depending on open/closed eyes and with/without foam cushion under feet. RESULTS: After ITG, in the affected ear the MRI confirmed the endolymphatic hydrops revealing a thin or even disappeared perilymphatic space. The statokinesigram showed improvement of stability only with closed eyes on a foam cushion. The CP performed 24 h after the contrast intratympanic injection showed a significant reduction of Path Length and Confidence Ellipse Area, due to an improvement of vestibular function on static balance. This improvement could be directly dependent to intratympanic pressure modification mediated by volume of contrast liquid, by "columella effect". CONCLUSIONS: This study demonstrates the absence of vestibular damage in patients undergoing intratympanic gadolinium infiltration and confirms the relationship between intratympanic pressure and vestibular stability modifications providing positive evidences for an applicative use of CP as a functional assessment to better address diagnosis and follow-up in MD patients treated with intratympanic injections.


Assuntos
Meios de Contraste/administração & dosagem , Orelha Interna/diagnóstico por imagem , Gadolínio/administração & dosagem , Doença de Meniere/diagnóstico por imagem , Doença de Meniere/fisiopatologia , Equilíbrio Postural , Pressão , Vestíbulo do Labirinto/fisiologia , Adulto , Idoso , Hidropisia Endolinfática/diagnóstico por imagem , Feminino , Humanos , Injeção Intratimpânica , Imagem por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Membrana Timpânica
10.
PLoS One ; 15(4): e0231334, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32275736

RESUMO

Subthreshold stochastic vestibular stimulation (SVS) is thought to enhance vestibular sensitivity and improve balance. However, it is unclear how SVS affects standing and walking when balance is challenged, particularly when the eyes are open. It is also unclear how different methods to determine stimulation intensity influence the effects. We aimed to determine (1) whether SVS affects stability when balance is challenged during eyes-open standing and overground walking tasks, and (2) how the effects differ based on whether optimal stimulation amplitude is derived from sinusoidal or cutaneous threshold techniques. Thirteen healthy adults performed balance-unchallenged and balance-challenged standing and walking tasks with SVS (0-30 Hz zero-mean, white noise electrical stimulus) or sham stimulation. For the balance-challenged condition, participants had inflatable rubber hemispheres attached to the bottom of their shoes to reduce the control provided by moving the center of pressure under their base of support. In different blocks of trials, we set SVS intensity to either 50% of participants' sinusoidal (motion) threshold or 80% of participants' cutaneous threshold. SVS reduced medial-lateral trunk velocity root mean square in the balance-challenged (p < 0.05) but not in the balance-unchallenged condition during standing. Regardless of condition, SVS decreased step-width variability and marginally increased gait speed when walking with the eyes open (p < 0.05). SVS intensity had minimal effect on the standing and walking measures. Taken together, our results provide insight into the effectiveness of SVS at improving balance-challenged, eyes-open standing and walking performance in healthy adults.


Assuntos
Marcha , Equilíbrio Postural , Vestíbulo do Labirinto/fisiologia , Adulto , Feminino , Humanos , Masculino , Modelos Neurológicos , Postura , Limiar Sensorial , Processos Estocásticos , Potenciais Evocados Miogênicos Vestibulares
11.
J Neurosci ; 40(15): 3035-3051, 2020 04 08.
Artigo em Inglês | MEDLINE | ID: mdl-32127493

RESUMO

Navigation often requires movement in three-dimensional (3D) space. Recent studies have postulated two different models for how head direction (HD) cells encode 3D space: the rotational plane hypothesis and the dual-axis model. To distinguish these models, we recorded HD cells in female rats while they traveled different routes along both horizontal and vertical surfaces from an elevated platform to the top of a cuboidal apparatus. We compared HD cell preferred firing directions (PFDs) in different planes and addressed the issue of whether HD cell firing is commutative-does the order of the animal's route affect the final outcome of the cell's PFD? Rats locomoted a direct or indirect route from the floor to the cube top via one, two, or three vertical walls. Whereas the rotational plane hypothesis accounted for PFD shifts when the animal traversed horizontal corners, the cell's PFD was better explained by the dual-axis model when the animal traversed vertical corners. Responses also followed the dual-axis model (1) under dark conditions, (2) for passive movement of the rat, (3) following apparatus rotation, (4) for movement around inside vertical corners, and (5) across a 45° outside vertical corner. The order in which the animal traversed the different planes did not affect the outcome of the cell's PFD, indicating that responses were commutative. HD cell peak firing rates were generally equivalent along each surface. These findings indicate that the animal's orientation with respect to gravity plays an important role in determining a cell's PFD, and that vestibular and proprioceptive cues drive these computations.SIGNIFICANCE STATEMENT Navigating in a three-dimensional (3D) world is a complex task that requires one to maintain a proper sense of orientation relative to both local and global cues. Rodent head direction (HD) cells have been suggested to subserve this sense of orientation, but most HD cell studies have focused on navigation in 2D environments. We investigated the responses of HD cells as rats moved between multiple vertically and horizontally oriented planar surfaces, demonstrating that HD cells align their directional representations to both local (current plane of locomotion) and global (gravity) cues across several experimental conditions, including darkness and passive movement. These findings offer critical insights into the processing of 3D space in the mammalian brain.


Assuntos
Movimentos da Cabeça/fisiologia , Locomoção/fisiologia , Percepção Espacial/fisiologia , Animais , Comunicação Celular , Escuridão , Eletrodos Implantados , Fenômenos Eletrofisiológicos , Feminino , Gravitação , Individualidade , Neurônios/fisiologia , Orientação , Propriocepção/fisiologia , Desempenho Psicomotor/fisiologia , Ratos , Ratos Long-Evans , Rotação , Vestíbulo do Labirinto/fisiologia
12.
Artigo em Chinês | MEDLINE | ID: mdl-32086900

RESUMO

Objective:To establish a new method for detecting vestibular function by testing cervical vestibular-evoked myogenic potential induced by galvanic vestibular stimulation in normal population. Method:Twenty normal ears were tested for cervical vestibular evoked myogenic potential induced by galvanic vestibular stimulation. SPSS 18.0 software was used to analyze the obtained data. Result:In all healthy subjects mastoid-forehead galvanic vestibular stimulation produced a positive-negative biphasic EMG responses on SCM ipsilateral to the cathodal electrode. The latency of p13 was(11.52±3.05) ms. The latency of n23 was(15.31±3.38) ms. The amplitude of p13-n23 was(40.55±27.93) µV. The interval of p13-n23 was(3.53±1.38) ms. The interaural asymmetry ratio(AR, %) of p13, n23 latency, the amplitude and interval were respectively(6.96±6.79)%, (6.47±5.93)%, (28.08±26.42)% and (16.61±11.11)%. There was no significant difference in all parameters between the right and left ears of all subjects. Conclusion:The value of cervical vestibular-evoked myogenic potential induced by galvanic vestibular stimulation in normal subjects can be established to explore methods for diagnosis, treatment and researching mechanism of auditory neuropathy and vestibular neuropathy.


Assuntos
Estimulação Acústica , Potenciais Evocados Miogênicos Vestibulares , Vestíbulo do Labirinto/fisiologia , Eletromiografia , Humanos , Pescoço
13.
Proc Natl Acad Sci U S A ; 117(6): 3232-3238, 2020 02 11.
Artigo em Inglês | MEDLINE | ID: mdl-31988119

RESUMO

Theories of cerebellar functions posit that the cerebellum implements internal models for online correction of motor actions and sensory estimation. As an example of such computations, an internal model resolves a sensory ambiguity where the peripheral otolith organs in the inner ear sense both head tilts and translations. Here we exploit the response dynamics of two functionally coupled Purkinje cell types in the vestibular part of the caudal vermis (lobules IX and X) to understand their role in this computation. We find that one population encodes tilt velocity, whereas the other, translation-selective, population encodes linear acceleration. We predict that an intermediate neuronal type should temporally integrate the output of tilt-selective cells into a tilt position signal.


Assuntos
Potenciais de Ação/fisiologia , Vermis Cerebelar , Movimento/fisiologia , Células de Purkinje/fisiologia , Animais , Vermis Cerebelar/citologia , Vermis Cerebelar/fisiologia , Macaca , Masculino , Postura/fisiologia , Rotação , Vestíbulo do Labirinto/fisiologia
14.
Artigo em Inglês | MEDLINE | ID: mdl-31940234

RESUMO

The vestibular system contributes to regulating sympathetic nerve activity and blood pressure. Initial studies in decerebrate animals showed that neurons in the rostral ventrolateral medulla (RVLM) respond to small-amplitude (<10°) rotations of the body, as in other brain areas that process vestibular signals, although such movements do not affect blood distribution in the body. However, a subsequent experiment in conscious animals showed that few RVLM neurons respond to small-amplitude movements. This study tested the hypothesis that RVLM neurons in conscious animals respond to signals from the vestibular otolith organs elicited by large-amplitude static tilts. The activity of approximately one-third of RVLM neurons whose firing rate was related to the cardiac cycle, and thus likely received baroreceptor inputs, was modulated by vestibular inputs elicited by 40° head-up tilts in conscious cats, but not during 10° sinusoidal rotations in the pitch plane that affected the activity of neurons in brain regions providing inputs to the RVLM. These data suggest the existence of brain circuitry that suppresses vestibular influences on the activity of RVLM neurons and the sympathetic nervous system unless these inputs are physiologically warranted. We also determined that RVLM neurons failed to respond to a light cue signaling the movement, suggesting that feedforward cardiovascular responses do not occur before passive movements that require cardiovascular adjustments.


Assuntos
Estado de Consciência/fisiologia , Bulbo/fisiologia , Neurônios/fisiologia , Vestíbulo do Labirinto/fisiologia , Potenciais de Ação/fisiologia , Animais , Gatos , Pressorreceptores/fisiologia , Sistema Nervoso Simpático/fisiologia
15.
Audiol Neurootol ; 25(1-2): 35-41, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31927546

RESUMO

BACKGROUND: The peripheral vestibular end organ is considered to consist of semi-circular canals (SCC) for detection of angular accelerations and the otoliths for detection of linear accelerations. However, otoliths being phylogenetically the oldest part of the vestibular sensory organs are involved in detection of all motions. SUMMARY: This study elaborates on this property of the otolith organ, as this concept can be of importance for the currently designed vestibular implant devices. Key Message: The analysis of the evolution of the inner ear and examination of clinical examples shows the robustness of the otolith system and inhibition capacity of the SCC. The otolith system must be considered superior to the SCC system as illustrated by evolution, clinical evidence, and physical principles.


Assuntos
Membrana dos Otólitos/fisiologia , Reflexo Vestíbulo-Ocular/fisiologia , Vestíbulo do Labirinto/fisiologia , Humanos , Sáculo e Utrículo/fisiologia , Canais Semicirculares/fisiologia
16.
PLoS One ; 14(12): e0226216, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31826016

RESUMO

In humans, to reduce deviations from a perfect upright position, information from various sensory cues is combined and continuously weighted based on its reliability. Combining noisy sensory information to produce a coherent and accurate estimate of body sway is a central problem in human balance control. In this study, we first compared the ability of the sensorimotor control mechanisms to deal with altered ankle proprioception or vestibular information (i.e., the single sensory condition). Then, we evaluated whether successive stimulation of difference sensory systems (e.g., Achilles tendon vibration followed by electrical vestibular stimulation, or vice versa) produced a greater alteration of balance control (i.e., the mix sensory condition). Electrical vestibular stimulation (head turned ~90°) and Achilles tendon vibration induced backward body sways. We calculated the root mean square value of the scalar distance between the center of pressure and the center of gravity as well as the time needed to regain balance (i.e., stabilization time). Furthermore, the peak ground reaction force along the anteroposterior axis, immediately following stimulation offset, was determined to compare the balance destabilization across the different conditions. In single conditions, during vestibular or Achilles tendon vibration, no difference in balance control was observed. When sensory information returned to normal, balance control was worse following Achilles tendon vibration. Compared to that of the single sensory condition, successive stimulation of different sensory systems (i.e., mix conditions) increased stabilization time. Overall, the present results reveal that single and successive sensory stimulation challenges the sensorimotor control mechanisms differently.


Assuntos
Tendão do Calcâneo/fisiologia , Equilíbrio Postural , Vestíbulo do Labirinto/fisiologia , Adulto , Tornozelo/fisiologia , Estimulação Elétrica , Feminino , Humanos , Masculino , Propriocepção , Vibração , Adulto Jovem
17.
PLoS One ; 14(11): e0224619, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31697727

RESUMO

Noisy galvanic vestibular stimulation (nGVS) has been shown to enhance postural stability during stimulation, and the enhancing effect has been observed to persist for several hours post-stimulation. However, these effects were observed without proper control (sham condition) and the possibility of experimental bias has not been ruled out. The lasting effect of nGVS on postural stability therefore remains in doubt. We investigated the lasting effect of nGVS on postural stability using a control (sham) condition to confirm or infirm the possibility of experimental bias. 28 participants received either nGVS or a sham stimulation. Static postural control was examined before stimulation, immediately after 30 minutes of nGVS and one-hour post-stimulation. Results showed a significant improvement of sway velocity (p<0.05) and path length (p<0.05) was observed following nGVS, as previously shown. A similar improvement of sway velocity (p<0.05) and path length (p<0.05) was observed in sham group and no significant difference was found between nGVS group and sham group (p>0.05), suggesting that the observed postural improvement in nGVS could be due to a learning effect. This finding suggests the presence of experimental bias in the nGVS effect on postural stability, and highlights the need to use a sham condition in the exploration of the nGVS effect so as to disentangle the direct effect of the electrical stimulation from a learning effect. Furthermore, numerous parameters and populations need to be tested in order to confirm or infirm the presence of a real long-lasting effect of nGVS on postural stability.


Assuntos
Equilíbrio Postural/fisiologia , Vestíbulo do Labirinto/fisiologia , Estimulação Elétrica , Humanos , Adulto Jovem
18.
Hum Mov Sci ; 68: 102525, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31731210

RESUMO

Prior work demonstrates that humans spontaneously synchronize their head and trunk kinematics to a broad range of driving frequencies of perceived mediolateral motion prescribed using optical flow. Using a closed-loop visuomotor error augmentation task in an immersive virtual environment, we sought to understand whether unifying visual with vestibular and somatosensory feedback is a control goal during human walking, at least in the context of head and trunk stabilization. We hypothesized that humans would minimize visual errors during walking - i.e., those between the visual perception of movement and actual movement of the trunk. We found that subjects did not minimize errors between the visual perception of movement and actual movement of the head and trunk. Rather, subjects increased mediolateral trunk range of motion in response to error-augmented optical flow with positive feedback gains. Our results are more consistent with our alternative hypothesis - that visual feedback can override other sensory modalities and independently compel adjustments in head and trunk position. Also, aftereffects following exposure to error-augmented optical flow included longer, narrower steps and reduced mediolateral postural sway, particularly in response to larger amplitude positive feedback gains. Our results allude to a recalibration of head and trunk stabilization toward more tightly regulated postural control following exposure to error-augmented visual feedback. Lasting reductions in mediolateral postural sway may have implications for using error-augmented optical flow to enhance the integrity of walking balance control through training, for example in older adults.


Assuntos
Equilíbrio Postural/fisiologia , Percepção Visual/fisiologia , Caminhada/fisiologia , Adaptação Fisiológica/fisiologia , Adulto , Fenômenos Biomecânicos , Teste de Esforço/métodos , Retroalimentação Sensorial/fisiologia , Feminino , Movimentos da Cabeça/fisiologia , Humanos , Masculino , Desempenho Psicomotor/fisiologia , Tronco/fisiologia , Vestíbulo do Labirinto/fisiologia , Adulto Jovem
19.
Braz J Otorhinolaryngol ; 85(6): 788-798, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31606334

RESUMO

INTRODUCTION: People with vestibular loss present a deficit in the vestibular system, which is primarily responsible for promoting postural control, gaze stabilization, and spatial orientation while the head moves. There is no effective treatment for a bilateral loss of vestibular function. Recently, a vestibular implant was developed for people with bilateral loss of vestibular function to improve this function and, consequently, the quality of life of these patients. OBJECTIVE: To identify in the scientific literature evidence that vestibular implants in people with vestibular deficit improves vestibular function. METHODS: One hundred and forty six articles were found from five databases and 323 articles from the gray literature mentioning the relationship between vestibular implant and vestibular function in humans. The PICOS strategy (Population, Intervention, Comparison and Outcome) was used to define the eligibility criteria. The studies that met the inclusion criteria for this second step were included in a qualitative synthesis, and each type of study was analyzed according to the bias risk assessment of the Joanna Briggs Institute through the critical assessment checklist Joanna Briggs institute for quasi-experimental studies and the Joanna Briggs institute critical assessment checklist for case reports. RESULTS: Of the 21 articles included in reading the full text, 10 studies were selected for the qualitative analysis in the present systematic review. All ten articles analyzed through the critical assessment checklist Joanna Briggs institute showed a low risk of bias. The total number of samples in the evaluated articles was 18 patients with vestibular implants. CONCLUSIONS: Taken together, these findings support the feasibility of vestibular implant for restoration of the vestibulo-ocular reflex in a broad frequency range and illustrate new challenges for the development of this technology.


Assuntos
Implante Coclear , Doenças Vestibulares/cirurgia , Vestíbulo do Labirinto/fisiologia , Adulto , Distribuição por Idade , Idoso , Potenciais Evocados , Feminino , Humanos , Masculino , Doença de Meniere/fisiopatologia , Pessoa de Meia-Idade , Qualidade de Vida , Distribuição por Sexo , Doenças Vestibulares/fisiopatologia , Testes de Função Vestibular
20.
Elife ; 82019 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-31591962

RESUMO

Mature locomotion requires that animal nervous systems coordinate distinct groups of muscles. The pressures that guide the development of coordination are not well understood. To understand how and why coordination might emerge, we measured the kinematics of spontaneous vertical locomotion across early development in zebrafish (Danio rerio) . We found that zebrafish used their pectoral fins and bodies synergistically during upwards swims. As larvae developed, they changed the way they coordinated fin and body movements, allowing them to climb with increasingly stable postures. This fin-body synergy was absent in vestibular mutants, suggesting sensed imbalance promotes coordinated movements. Similarly, synergies were systematically altered following cerebellar lesions, identifying a neural substrate regulating fin-body coordination. Together these findings link the vestibular sense to the maturation of coordinated locomotion. Developing zebrafish improve postural stability by changing fin-body coordination. We therefore propose that the development of coordinated locomotion is regulated by vestibular sensation.


Assuntos
Locomoção , Desempenho Psicomotor , Vestíbulo do Labirinto/fisiologia , Nadadeiras de Animais/fisiologia , Animais , Embrião não Mamífero , Músculo Esquelético/fisiologia , Peixe-Zebra
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