RESUMEN
The ultrastructural organization of the blood labyrinthine barrier (BLB) was investigated in the human vestibular endorgan, the utricular macula, using postmortem specimens from individuals with documented normal auditory and vestibular function and surgical specimens from patients with intractable Meniere's disease. Transmission electron microscopic analysis of capillaries located in the normal human utricular stroma showed vascular endothelial cells with few pinocytotic vesicles, covered by a smooth and uniform basement membrane surrounded by pericyte processes. Meniere's disease specimens revealed differential ultrastructural pathological changes in the cellular elements of the microvasculature. With moderate degeneration of the BLB, there were numerous vesicles within the vascular endothelial cells (VECs), with increased numbers at the abluminal face, pericyte process detachment and disruption of the perivascular basement membrane surrounding the VECs. With severe degeneration of the BLB, there was severe vacuolization or frank apparent necrosis of VECs and loss of subcellular organelles. A higher severity of BLB degenerative changes was associated with a higher degree of basement membrane thickening and edematous changes within the vestibular stroma. This study presents the first ultrastructural analysis of the capillaries constituting the BLB in the human vestibular macula utricle from normal and Meniere's disease.
Asunto(s)
Máculas Acústicas/anatomía & histología , Máculas Acústicas/patología , Capilares/anatomía & histología , Capilares/patología , Voluntarios Sanos , Enfermedad de Meniere/patología , Células Endoteliales/patología , Humanos , Microscopía Electrónica de TransmisiónRESUMEN
Cephalopods (octopus, squid and cuttlefish) are some of the most intriguing molluscs, and they represent economically important commercial marine species for fisheries. Previous studies have shown that cephalopods are sensitive to underwater particle motion, especially at low frequencies in the order of 10 Hz. The present paper deals with quantitative modeling of the statocyst system in three cephalopod species: Octopus vulgaris, Sepia officinalis and Loligo vulgaris. The octopus's macula/statolith organ was modeled as a 2nd-order dynamic oscillator using parameter values estimated from scanning electron micrograph images. The modeling results agree reasonably well with experimental data (acceleration threshold) in the three cephalopod species. Insights made from quantitative modeling and simulating the particle motion sensing mechanism of cephalopods elucidated their underwater particle motion detection capabilities. Sensitivity to emerging environmental issues, such as low frequency noise caused by near-shore wind farms and increasing levels of carbon dioxide in the ocean, and sensitivity to sounds produced by impending landslides were investigated in octopus using the model.
Asunto(s)
Cefalópodos/fisiología , Células Ciliadas Auditivas/fisiología , Audición/fisiología , Máculas Acústicas/anatomía & histología , Animales , Cefalópodos/ultraestructura , Ambiente , Células Ciliadas Auditivas/ultraestructura , Modelos Teóricos , Percepción de Movimiento , Umbral Sensorial/fisiologíaRESUMEN
PURPOSE: To identify and measure the mean size of the utricular macula using 3-T imaging. METHODS: One hundred one examinations using a 3-T magnetic resonance scanner and standard temporal bone protocol were performed over a 9-month period. Asymptomatic sides were then retrospectively evaluated using the axial T2-driven equilibrium sequence (0.3-mm slice thickness). We performed the following analyses: (1) reported frequency at which this structure could be identified and (2) calculated the mean size of the utricular macula. RESULTS: The utricular macula was identified in all 101 cases as an ellipsoid area of T2 hypointensity in the utricle. The average anteroposterior x transverse x craniocaudal dimensions were 1.7 x 1.5 x 1.0 mm. CONCLUSIONS: The utricular macula is consistently identified with 3-T imaging in asymptomatic patients.
Asunto(s)
Máculas Acústicas/anatomía & histología , Imagen por Resonancia Magnética/métodos , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Magnetismo , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Hueso Temporal/anatomía & histologíaRESUMEN
The vestibular system detects head movements such as angular rotation, translation, and head position relative to gravity. It acts to stabilize the eyes and posture through subcortical reflexes. Its signals are also integrated at the cortical level to participate in the elaboration of a body scheme, used for different functions such as spatial orientation and motor control. The vestibular nerve shows a resting discharge rate that is modulated up or down according to head motion or position. Central functioning depends on the detection of an asymmetry between signals coming from a pair of peripheral sensors, one on either side. In pathological cases, unilateral peripheral dysfunction is interpreted by the central system as an asymmetry resulting from a change in head position leading to nystagmus, postural disturbances, and vertigo. The dysfunction can be either a deficit, such as observed in vestibular neuronitis, or hyperactivity such as observed in neurovascular compression syndrome of the VIIIth nerve. Anatomically, the VIIIth nerve has a long Root Entry Zone (REZ) that extends over 10mm before entering the brainstem. The VIIIth nerve is also physiologically close to numerous vessels at the pontocerebellar angle and internal auditory meatus. Therefore, vestibular syndrome resulting from neurovascular compression syndrome of the VIIIth nerve may exist, but it is very difficult to prove using radiological imagery.
Asunto(s)
Nervio Vestibular/anatomía & histología , Nervio Vestibular/fisiología , Máculas Acústicas/anatomía & histología , Máculas Acústicas/fisiología , Animales , Oído Interno/anatomía & histología , Oído Interno/fisiología , Humanos , Canales Semicirculares/anatomía & histología , Canales Semicirculares/fisiología , Nervio Vestibular/citología , Vestíbulo del Laberinto/inervación , Vestíbulo del Laberinto/fisiología , Enfermedades del Nervio Vestibulococlear/patología , Enfermedades del Nervio Vestibulococlear/fisiopatologíaRESUMEN
The macula lagena located at the apical end of the cochlea in birds is characterized by the presence of numerous otoliths with unclear sensory functions. These otoliths are reported to be similar to those in the vestibular system but their detailed features in morphology are unknown. In the present study, we examined the number, size and shape of otoliths from the macula lagena in Chinese domestic chickens (Gallus Ling Nan) with a scanning electron microscope for morphometry. For chickens aged 10-15 post-hatch days, the otoliths in each macula lagena were counted to be 16,055 +/- 4038 (mean +/- S.D., n = 4). The average length and width were 12.98 +/- 3.70 microm and 5.10 +/- 1.48 microm (n = 526 otoliths), respectively. The ratio of length to width for the otolith was 2.58 +/- 0.39 (n = 526 otoliths) and remained relatively constant despite their variations in physical size. Almost all the otoliths were in regular shape and appeared like isolated cylinders with smooth facets at each end, but a few of them (0.025% of 64,221 otoliths screened) were found to be in odd shapes, such as T-shape and cross-shape. The results suggest that otoliths in the macula lagena and those in the vestibular system of bird's inner ear have similar physical properties and may play a similar role in sensing gravitational and acceleration signals.
Asunto(s)
Máculas Acústicas/anatomía & histología , Membrana Otolítica/anatomía & histología , Máculas Acústicas/ultraestructura , Animales , Pollos , Microscopía Electrónica de Rastreo , Membrana Otolítica/ultraestructura , Vestíbulo del Laberinto/anatomía & histologíaRESUMEN
This study describes the morphometric changes taking place in the utricular macula of mice with ages in geometric progression from 1 to 512 days after birth. By using design-based stereological methods, the total volume and surface area of the sensory epithelium as well the total number of the hair cells and supporting cells were estimated. Finally, the numerical density, volume density, and mean volume of the individual cell types were determined. The major changes were found in the number of the individual cell types during the first couple of weeks, and a mature composition of cell types was not attained until 16 days after birth. There was no change in the total number of cells and no decline in the number of hair cells within the time period studied.
Asunto(s)
Máculas Acústicas/anatomía & histología , Máculas Acústicas/crecimiento & desarrollo , Morfogénesis , Factores de Edad , Animales , Animales Recién Nacidos , Epitelio/anatomía & histología , Epitelio/crecimiento & desarrollo , Femenino , Ratones , EmbarazoRESUMEN
The surface morphology of 20 human maculae sacculi is presented. Individual data on the total area, shape and the relative area of the pars superior are given. The mean area of 14 adult maculae was (mean +/- SD) 2.35 +/- 0.31 mm2. The ratio between the length and width of the macula was 2.54 +/- 0.28. The pars superior was significantly larger than the pars inferior. The percentage of pars superior was 56.4 +/- 4.7. As regards the shape of the macula, there was a large interindividual variability. The findings are discussed, taking into consideration comparative anatomy as well as spatial orientation.
Asunto(s)
Máculas Acústicas/anatomía & histología , Máculas Acústicas/embriología , Anciano , Anciano de 80 o más Años , Técnicas de Cultivo , Femenino , Humanos , Recién Nacido , Masculino , Persona de Mediana Edad , FotograbarRESUMEN
In a letter to Robert Hooke, written on 5 February, 1675, Isaac Newton wrote "If I have seen further than certain other men it is by standing upon the shoulders of giants." In his context, Newton was referring to the work of Galileo and Kepler, who preceded him. However, every field has its own giants, those men and women who went before us and, often with few tools at their disposal, uncovered the facts that enabled later researchers to advance knowledge in a particular area. This review traces the history of the evolution of views from early giants in the field of vestibular research to modern concepts of vestibular organ organization and function. Emphasis will be placed on the mammalian maculae as peripheral processors of linear accelerations acting on the head. This review shows that early, correct findings were sometimes unfortunately disregarded, impeding later investigations into the structure and function of the vestibular organs. The central themes are that the macular organs are highly complex, dynamic, adaptive, distributed parallel processors of information, and that historical references can help us to understand our own place in advancing knowledge about their complicated structure and functions.
Asunto(s)
Máculas Acústicas/anatomía & histología , Máculas Acústicas/fisiología , Modelos Neurológicos , Vestíbulo del Laberinto/anatomía & histología , Vestíbulo del Laberinto/fisiología , Células Ciliadas Auditivas/diagnóstico por imagen , Historia del Siglo XIX , Historia del Siglo XX , Humanos , Otolaringología/historia , UltrasonografíaRESUMEN
The 3-dimensional shape of the human utricular macula and its orientation in the skull are quantitated in this report, which is one of a series. The semicircular canals and utricular macula were reconstructed in 3 dimensions on a computer from 3 human temporal bones. The 238 to 279 triangles in the entire area of the utricular macula were made by drawing lines between 2 adjacent points every 200-microm width of the utricular macula in each section. We calculated the angles between each triangle and each estimated standard axis in the skull. This study provides standard data regarding the 3-dimensional morphological aspects of the utricular macula for further investigation of the function of the utriculus. We determined that the 3-dimensional shape of the utricular macula was not a plane, but was a curved surface like that of an ellipsoid. We believe this shape is necessary for the utricular macula to detect wide-range linear acceleration.
Asunto(s)
Máculas Acústicas/anatomía & histología , Diseño Asistido por Computadora , Oído Interno/anatomía & histología , Imagenología Tridimensional , Humanos , Modelos Anatómicos , Técnicas Estereotáxicas , Hueso Temporal/anatomía & histologíaRESUMEN
The 3-dimensional shape of the human saccular macula and its orientation in the skull were quantitated in this study. The semicircular canals and saccular maculae were reconstructed 3-dimensionally on a computer from 3 human temporal bones. The 380 to 522 triangles in the entire area of the saccular macula were made by drawing lines between 2 adjacent points every 100-pm width of the saccular macula in each section. The angles between each triangle and each estimated standard axis in the skull obtained were calculated. This information will provide standard data regarding the 3-dimensional morphological aspects of the saccular macula for further investigations of the function of the sacculus. It was determined that the 3-dimensional shape of the saccular macula was not a plane, but was a curved surface like that of an ellipsoid. It is thought that this shape is necessary in order for the saccular macula to detect wide-range linear acceleration.
Asunto(s)
Máculas Acústicas/anatomía & histología , Imagenología Tridimensional/métodos , Humanos , Procesamiento de Imagen Asistido por Computador , Modelos Biológicos , Técnicas EstereotáxicasRESUMEN
Mammalian vestibular maculae are anatomically organized for complex parallel processing of linear acceleration information. Anatomical findings in rat maculae are provided in order to underscore this complexity, which is little understood functionally. This report emphasizes that a synthetic approach is critical to understanding how maculae function and the kind of information they conduct to the brain.
Asunto(s)
Máculas Acústicas/anatomía & histología , Vestíbulo del Laberinto/anatomía & histología , Máculas Acústicas/ultraestructura , Animales , Células Ciliadas Auditivas/ultraestructura , Microscopía Electrónica , Ratas , Sinapsis/ultraestructura , Vestíbulo del Laberinto/ultraestructuraRESUMEN
The structure of the vestibular organs of the teleost fish (bluegill), newts (Japanese fire-belly newt), frogs (black-spotted pond frog), snapping turtles and birds (chicks) was morphologically compared, with particular attention to the lagena macula, and the differences between animal species with relation to evolution were considered. Teleost fish had no striola on the lagena macula. The striola of newts were short and restricted to the central area of the macula, but those of frogs, snapping turtles and chicks extended from the anterior to posterior edges of the macula. This indicates that the frog is more highly evolved than the newt. The length of the kinocilium of sensory hairs was equal to that of the longest stereocilium in teleost fish and newts, but the kinocilia of frogs, snapping turtles and chicks were longer than the longest stereocilium. This indicates that the function of the lagena of teleost fish and newts is for hearing whilst in the other animals they are for posture. The diameter of the sensory hair bundles is small in teleost fish and frogs, but large in newts and snapping turtles. This indicates that the sensitivity of the sensory cells of the lagena towards outer force is low in teleost fish and frogs, high in newts and snapping turtles and intermediate in birds. The lagena of snapping turtles protrudes from the basilar papilla into the vestibule but the lagena of chicks lies on the tip of the long projecting basilar papilla. From observation of the locations of lagenae it is natural to speculate that there must have been some species of animal now extinct that had the evolving location of the lagena prior to that of chicks. In future it will be very interesting and useful to identify this extinct animal using DNA techniques.
Asunto(s)
Máculas Acústicas/anatomía & histología , Evolución Biológica , Membrana Otolítica/anatomía & histología , Animales , Pollos , Microscopía Electrónica de Rastreo , Perciformes , Ranidae , Salamandridae , Especificidad de la Especie , TortugasRESUMEN
To establish a link between otolith anatomy and function it is necessary to know the regions of the utricular and saccular maculae, which are stimulated by any arbitrary linear acceleration stimulus. That requires accurate information about the location and orientation of the spatially extended maculae in head-fixed coordinates and referred to head-fixed landmarks (such as Reid's line). New data showing the location of the otolithic maculae in the guinea pig with respect to head-fixed stereotaxic coordinates are presented. Guinea pigs were perfused with Karnovsky's fixative and the maculae were exposed while the head was held in a guinea pig stereotaxic device. An electrolytically sharpened fine wire held in a calibrated micromanipulator was touched to points all over the surface of each macula under visual observation with the aid of a high-power operating microscope. The x, y, z coordinates of these points were plotted using a three-dimensional plotting program. Both maculae have pronounced curvature so that dorsoventral shear forces will stimulate regions of both the utricular and saccular maculae.
Asunto(s)
Máculas Acústicas/anatomía & histología , Cobayas/anatomía & histología , Animales , Cabeza/anatomía & histología , Técnicas EstereotáxicasRESUMEN
Gamma-aminobutyric acid (GABA) is presumed to be a neurotransmitter candidate in the vestibular periphery of mammals. However, experimental reports about the localization of GABA in afferents or efferents of the vestibular systems are contradictory. It is an open question whether there are species differences in the amammalian vestibular system. The present study was designed to investigate the ultrastructural localization of GABA-like immunoreactivity in the vestibular periphery of the rat. A modified preembedding immunoelectron microscopy technique was applied using a polyclonal antibody to GABA as a marker. GABA-like immunoreactivity was revealed in the vestibular periphery of the rat, confined to the vesiculated nerve fibers and terminals of the rat vestibular neurosensory epithelia. Type I hair cells and type II hair cells as well as efferent chalices are devoid of GABA-like immunoreactive staining. These findings indicate that GABA is a neurotransmitter candidate of the efferent vestibular system of the rat.
Asunto(s)
Máculas Acústicas/anatomía & histología , Sáculo y Utrículo/anatomía & histología , Nervio Vestibular/anatomía & histología , Ácido gamma-Aminobutírico/análisis , Animales , Epitelio/ultraestructura , Femenino , Masculino , Microscopía Inmunoelectrónica , Fibras Nerviosas/ultraestructura , Ratas , Valores de ReferenciaRESUMEN
The globular substance, which occurs in the vestibular macula as a precursor of otoconia, was examined in aged mice in comparison with young adult mice. Dissected otoconial membrane from the utricular macula of C57BL/6J mice was loaded with fluo-3-AM, and directly observed under a confocal laser scanning microscope. Internal free Ca2+ concentration ([Ca2+]i) of the globular substance was determined through in situ calibration performed by superfusion with ionomycin and Mn2+. Total area of the otoconial membrane, average diameter of the globular substance, and [Ca2+]i showed no significant differences between young adult and aged groups. However, the number of globular substances in young adult mice was significantly larger than those of aged mice. These results suggest a reduced rate of otoconial formation in the aged vestibule, which would result in the sparseness of otoconia in the aged vestibule and lead to balance disorders commonly seen in elderly persons.
Asunto(s)
Envejecimiento/patología , Membrana Otolítica/anatomía & histología , Máculas Acústicas/anatomía & histología , Máculas Acústicas/metabolismo , Envejecimiento/metabolismo , Compuestos de Anilina , Animales , Calcio/metabolismo , Colorantes Fluorescentes , Células Ciliadas Vestibulares/anatomía & histología , Células Ciliadas Vestibulares/metabolismo , Ionomicina , Ionóforos , Manganeso , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos , Microscopía Confocal , Membrana Otolítica/metabolismo , Equilibrio Postural , Sáculo y Utrículo/anatomía & histología , Sáculo y Utrículo/metabolismo , Trastornos de la Sensación/etiología , Vestíbulo del Laberinto/anatomía & histología , Vestíbulo del Laberinto/metabolismo , XantenosRESUMEN
The calcium ion turnover into otoconia of adult guinea pigs was investigated by the use of different fluorochromes, i.e. tetracycline (TC), calcein (Cal) and alizarin complexone (AC). The administration of all fluorochromes induced yellow (TC), green (Cal) and red (AC) fluorescence on the outer surface of otoconia, respectively. Sequential polychromatic labeling with AC followed by TC induced only red fluorescence after 1 week administration of TC, combined fluorescence after 2 weeks administration of TC and only yellow fluorescence after more than 3 weeks of administration of TC. The otoconia labeled with both AC and TC showed red fluorescence on the side faces of otoconia and yellow fluorescence on the terminal faces. These results may indicate the existence of a dynamic exchange of calcium ions in the otoconia and this exchange is mainly restricted to the terminal faces. The sequential polychromatic labeling may thus be of great use for the further investigation of the calcium dynamics of otoconia.
Asunto(s)
Calcio/metabolismo , Colorantes Fluorescentes , Membrana Otolítica/metabolismo , Máculas Acústicas/anatomía & histología , Máculas Acústicas/metabolismo , Administración Oral , Animales , Antraquinonas/administración & dosificación , Quelantes/administración & dosificación , Color , Femenino , Fluoresceínas/administración & dosificación , Fluorescencia , Colorantes Fluorescentes/administración & dosificación , Cobayas , Indicadores y Reactivos/administración & dosificación , Inyecciones Subcutáneas , Masculino , Membrana Otolítica/anatomía & histología , Sáculo y Utrículo/anatomía & histología , Sáculo y Utrículo/metabolismo , Tetraciclina/administración & dosificaciónRESUMEN
The distribution of microtubule-associated proteins MAP-1 and MAP-2 was analysed with immunomorphological techniques in the serially sectioned adult human membranous labyrinth. In the organ of Corti, monoclonal antibodies to MAP-1 did not stain. Positivity for MAP-2 occurred in the entire outer hair cell cytoplasm, in the inner hair cells (?), in the nerve fibres and in the cytoplasm of epithelial cells of the spiral prominence. In addition, staining for MAP-2 was identified in many (but not all) cells or Reissner's membrane. Immunofluorescence for MAP-1 occurred in the supporting cells of the cristae and maculae interpreted to be localized in the apical region adjacent to the sensory cells. Thus, the distribution of MAP-1 and MAP-2 in the adult human membranous labyrinth was the same as described for several animal species with regard to the cochlea. In contrast to such a pattern, both MAP-1 and MAP-2 were identified in the human vestibular organs, thus identifying a subpopulation of centrally located nerve calyces and possibly also the apical portion of vestibular hair cells.
Asunto(s)
Oído Interno/anatomía & histología , Proteínas Asociadas a Microtúbulos/metabolismo , Máculas Acústicas/anatomía & histología , Máculas Acústicas/metabolismo , Adolescente , Adulto , Anciano , Animales , Conducto Coclear/anatomía & histología , Conducto Coclear/metabolismo , Citoplasma/metabolismo , Citoplasma/ultraestructura , Oído Interno/metabolismo , Epitelio/anatomía & histología , Epitelio/metabolismo , Células Ciliadas Auditivas Internas/anatomía & histología , Células Ciliadas Auditivas Internas/metabolismo , Células Ciliadas Auditivas Externas/anatomía & histología , Células Ciliadas Auditivas Externas/metabolismo , Células Ciliadas Vestibulares/anatomía & histología , Células Ciliadas Vestibulares/metabolismo , Humanos , Persona de Mediana Edad , Fibras Nerviosas/metabolismo , Fibras Nerviosas/ultraestructura , Órgano Espiral/anatomía & histología , Órgano Espiral/metabolismo , Canales Semicirculares/anatomía & histología , Canales Semicirculares/metabolismo , Lámina Espiral/anatomía & histología , Lámina Espiral/metabolismoRESUMEN
The macular neuroepithelium is morphologically organized as a weighted neural network for parallel distributed processing of information. The network is continuous across the striola, where some type II hair cells synapse with calyces containing type I cells with tufts of opposite directional polarities. Whether other hair cell to calyx appositions that lack synapses interact because of intercellular potassium accumulation remains an open question. A functionally important inference of macular organization is that just as arrays of hair cells communicate an entire piece of information to a nerve fiber, so do macular subarrays of nerve fibers (not single units) carry the whole coded message to the brain stem. Moreover, the size of the network subarray can expand or become more limited depending upon the strength and/or duration of the input. It is the functioning of the network and its subarrays that must be understood if we are to learn how maculas carry out their work and adapt to new environments. Simulations of functioning maculas, or subparts, based on precise morphology and known physiology are useful tools to gain insights into macular information processing. The current simulations of afferent collateral electrical activity are a prelude to development of a 3-D model. The simulations demonstrate a relationship between geometry and function, with the diameter of the stem apparently being a major determinant of electrical activity transmitted to the base in the case of collaterals with short stems. Thus, while changes in synaptic number and/or size may be an important adaptive mechanism in an altered g environment, changes in diameter of the stem is another means of altering outflow. Research on the effects of microgravity should be extremely useful in examining the validity of this and other concepts of neural adaptation, since maculas are biological linear accelerometers ideally suited to the task. Maculas are also extremely interesting to study in detail because of the richness of connectivities and submicroscopic organization they present. Many of their features are common with more complex parts of the brain. It seems possible that knowledge of the three-dimensional geometric relationships operative in a functioning macula will contribute much to the understanding of the dynamics underlying more complex behavior. Computerized approaches greatly facilitate this task and provide an objective method of analysis. It is likely that, in the end, simple rules will be found to govern optimal neural architectural organization, even at higher cognitive levels. The architecture only appears complex because we do not yet grasp its meaning.(ABSTRACT TRUNCATED AT 400 WORDS)
Asunto(s)
Máculas Acústicas/anatomía & histología , Máculas Acústicas/fisiología , Simulación por Computador , Modelos Anatómicos , Red Nerviosa/anatomía & histología , Máculas Acústicas/inervación , Animales , Gráficos por Computador , Fibras Nerviosas/fisiología , Fibras Nerviosas/ultraestructura , Red Nerviosa/fisiologíaRESUMEN
The cupula of the supraorbital neuromast in the lateral line canal of the clown knifefish contains vertical columns. In the central region of the cupula overlying the macula, these columns are densely packed, are relatively constant in size, and run from the base of the cupula to the surface of the cupula which is exposed to canal fluid. There are two types of columns, dark and light, which form elliptical compartments in planes of section that cut across the columns; the cupula therefore has the appearance of mosaic tile in such sections. The dark compartments contain tubules that extend from the base of the cupula at the junction with the macula to the top of the cupula. Each tubule is associated with the kinocilium of a single hair cell. The lateral parts of the cupula, not overlying the macula, also contain compartments, but these compartments differ in size and structure from those in the central region. In addition to the compartments, the central region of the cupula also contains spherical aggregates of droplets. These small aggregates, termed mora, are found principally in a layer within the central region of the cupula, but are also found outside this layer. Because of their light-reflecting properties, the mora can be used for noninvasive optical measurements in vivo of the motion of the cupula.