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PubMed1998

Comparative review of the human bony labyrinth.

The bony labyrinth inside the petrous part of the temporal bone houses the organs of hearing and balance. Being functionally linked with sensory control of body movements and located in a part of the basicranium that is closely associated with the brain, this structure is of great interest in the study of human evolutionary history. However, few aspects of its morphology have been studied in nonhuman primates. This review compares the bony labyrinth of humans with that of the great apes and 37 other primate species based on data newly acquired with computed tomography combined with previous descriptions. With body mass taken into account, consistent differences are found between the size of the semicircular canals in humans, the great apes, and other primates. In particular, the arcs of the anterior and posterior canals are larger in humans than in the African apes. The functional implications of semicircular canal dimensions for registering angular head motion are evaluated in relation to locomotor behavior. Biophysical models, comparative studies, and some neurophysiological experiments all support a link between semicircular canal size and agility, or more specifically the frequency contents of natural head movements, but the evidence on the exact nature of this link is ambiguous. It is concluded that any link between the characteristic dimensions of the human canals and locomotion will be more complex than a simple association with the broad categories of quadrupedal vs. bipedal behavior. The functionally important planar orientations of the semicircular canals are similar in humans and the African apes as well as in many other species. In contrast, other aspects of the human labyrinth differ markedly in shape, following a pattern that seems to reflect the characteristic architecture of the human basicranium. Indeed, it is found that labyrinthine and basicranial shape are interspecifically correlated in the sample, and in most respects the human morphology is consistent with the general trend among primate species. Differences in brain growth and development are proposed as the predominant factor underlying both the unique shape of the human labyrinth as well as the interspecific labyrintho-basicranial correlations.

Anatomy, Comparative↗
PubMed2001

Remarks on the inner ear of elasmobranchs and its interpretation from skeletal labyrinth morphology.

The structure and function of the craniate inner ear is reviewed, with 33 apomorphic characters of the membranous labyrinth and associated structures identified in craniates, gnathostomes, and elasmobranchs. Elasmobranchs are capable of low-frequency semi-directional phonoreception, even in the absence of any pressure-to-displacement transducer such as ear ossicles. The endolymphatic (parietal) fossa, semicircular canals, and crista (macula) neglecta are all adapted toward phonoreception. Some (but not all) of the morphological features associated with phonoreception can be inferred from the elasmobranch skeletal labyrinth. Endocranial spaces such as the skeletal labyrinth also provide suites of morphological characters that may be incorporated into phylogenetic analyses, irrespective of how closely these spaces reflect underlying soft anatomy. The skeletal labyrinths of Squalus and Notorynchus are compared using silicone endocasts and high-resolution CT-scanning. The latter procedure offers several advantages over other techniques; it is more informative, nondestructive, preserves relationships of surrounding structures, and it can be applied both to modern and fossil material.

Animals↗
PubMed1990

Computer-aided three-dimensional reconstruction of the osseous and membranous labyrinths.

In order to obtain an adequate knowledge of the stereoscopic anatomy of the temporal bone, it is very useful to make three-dimensional reconstructions of the bone. By using the histological sections of a human temporal bone processed for routine evaluation, we have undertaken computer-aided reconstruction of the osseous and the membranous labyrinths, as well as the inner ear sensory organs. Reconstructions were done either separately or simultaneously. Owing to the "semitransparent display" function of the computer system, it was possible to observe the reconstructed membranous labyrinth through the simultaneously reconstructed osseous labyrinth, and the sensory organs through the membranous labyrinth. The results were satisfactory for understanding the spatial relationships among these structures. We also attempted computer-aided measurements of the reconstructed sensory organs and calculated the length of the organ of Corti and the angle between the saccular and the utricular maculae.

Computer Simulation↗
PubMed1985

Influence of Renshaw cells on the response gain of hindlimb extensor muscles to sinusoidal labyrinth stimulation.

The contraction of limb extensor muscles during side-down roll tilt of the animal depends upon an increased discharge of excitatory vestibulospinal (VS) neurons (alpha-response) and a reduced discharge of inhibitory reticulospinal (RS) neurons of the medulla (beta-response), both acting on ipsilateral limb extensor motoneurons. In the decerebrate cat, a modulation of the multiunit EMG activity was clearly present in forelimb extensors, but was extremely weak or absent in hindlimb extensors. Experiments performed in decerebrate cats with the deefferented GS muscle fixed at a constant length have shown that Renshaw (R)-cells, monosynaptically coupled with gastrocnemius-soleus (GS) motoneurons, were either unresponsive or displayed only very weak, small amplitude alpha-responses to sinusoidal stimulation of labyrinth receptors elicited during slow head rotation after bilateral neck deafferentation. This effect was attributed to excitatory VS volleys acting on GS motoneurons and, through their recurrent collaterals, on the related R-cells. In these instances the recurrent inhibition of the GS motoneurons contributed to the very low gain of the EMG response of the corresponding muscles to labyrinth stimulation. Intravenous injection of an anticholinesterase (eserine sulphate, 0.05-0.1 mg/kg) at a dose that in previous experiments increased the firing rate of medullary RS neurons, while decreasing the decerebrate rigidity, slightly increased the discharge rate of R-cells linked with the GS motoneurons in the animal at rest; these findings suggest that the RS system inhibits the extensor motoneurons by exciting the related R-cells. All the R-cells, which prior to the injection were either unresponsive or showed an alpha-response to head rotation (at 0.026-0.15 Hz, +/- 10 degrees), after eserine sulphate showed a beta-response for the same parameters of labyrinth stimulation. In particular, a reduced discharge of the R-cells linked with the GS motoneurons occurred during side-down head rotation as shown for the majority of the RS neurons. It appears therefore that the same R-cells, which in the normal decerebrate cat responded to the excitatory VS volleys acting through the GS motoneurons, were now decoupled from their input motoneurons during head rotation, thus behaving as if they underwent the most efficient direct excitatory control of the RS system. The reduced discharge of the R-cells linked with the GS motoneurons during side-down head rotation would lead to disinhibition of these motoneurons, thus enhancing the response gain of the corresponding muscle to labyrinth stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1980

Labyrinth and neck reflex modification of the tonic vibration reflex in the decerebrate cat.

The interaction between tonic labyrinth or neck reflexes and the tonic vibration reflex acting on the medial head of triceps in the decerebrate cat is described. Medial triceps was isotonically loaded and reflex actions were measured as changes in muscle length. Natural stimulation of the receptors giving rise to tonic labyrinth or neck reflexes can either enhance or diminish the size of a pre-existing tonic vibration reflex. It is also shown that descending activity from either the labyrinth or neck reflex systems can completely suppress the tonic vibration reflex, whereas the tonic vibration reflex was never observed to suppress an established labyrinth or neck reflex.

Animals↗
PubMed1998

Three-dimensional reconstruction of the membranous vestibular labyrinth in the toadfish, Opsanus tau.

Membranous vestibular labyrinths from the oyster toadfish, Opsanus tau, were fixed, dissected from the animal, stained, and embedded in rectangular blocks of clear histological resin. Photomicrographs of complete embedded labyrinths were taken from six orthogonal directions and used to construct three-dimensional (3D) geometrical models of the semicircular canals, ampullae, utricular vestibule and common crus. Membraneous ducts and ampullae were modeled using a set of cross-sectional elliptical curves laced together to generate curved tubular models of each structure. The ensemble of these curved tubes was used to generate a complete 3D reconstruction of the outside surface of the membranous labyrinth. When viewed from six orthogonal directions, reconstructions closely matched the embedded tissue. Dimensions of the reconstruction and histological sections were compared to measurements of fresh tissue taken from the same animals prior to fixation and used to correct the reconstructions for tissue shrinkage. Results provide estimates of the endolymphatic volumes, local cross-sectional areas and elliptical eccentricities as well as 3D orientations of the geometric canal planes relative to the skull. Ten micrometer histological sections of the material were also prepared to measure wall thickness in various regions of the labyrinth.

Animals↗
PubMed2001

Development of the membranous labyrinth of human embryos and fetuses using computer aided 3D-reconstruction.

The last detailed description of the development of the inner ear membranous labyrinth goes back to Streeter in 1918. This investigation can be regarded to be of outstanding scientific value. However, at that time no staging system of human embryos existed. In this respect, Streeter's work is outdated. It was the aim of this study to reinvestigate the development of the membranous labyrinth in human embryos and fetuses of which the developmental stages have been determined according to the Carnegie staging system and to compare the results with the literature. Serial histologic sections in the coronal or frontal plane of the heads of human embryos and fetuses of different developmental stages were used for computer aided 3D-reconstruction of the membranous labyrinth. From the obtained results, it is concluded that the endolymphatic duct develops earlier than previously described in the literature. The induction of the differentiation of the endolymphatic duct does not correspond with the superficial ectoderm because the endolymphatic duct develops medial of the otic vesicle. The membranous labyrinth determines the form of the petrosal bone as early as in stage 19 (47-48 days post conception).

Ear, Inner↗
PubMed1985

Radiation measurements in a labyrinth penetration at a high-energy proton accelerator.

The efficient design of access penetrations at high-energy proton accelerators is desirable for both economic and personnel protection reasons. This paper reports on a series of measurements made in a personnel access labyrinth which viewed an A1 target bombarded by 400-GeV protons from the Fermilab Tevatron. Measurements of absorbed dose in the labyrinth using tissue-equivalent ion chambers were consistent with theoretical predictions of both the relative attenuation through the penetration and the absolute magnitude near the target. The multisphere technique was used to determine the neutron energy spectrum in one section of the labyrinth. A recombination chamber was used to measure the quality factor of the radiation field in two sections of the labyrinth. Good agreement with the quality factor deduced from the multisphere result was obtained at the same measurement location.

Neutrons↗
PubMed2001

Chemical reaction-diffusion implementation of finding the shortest paths in a labyrinth.

An experimental technique for finding the shortest paths in a labyrinth is elaborated on based on chemical reaction-diffusion media. The system designed has hybrid architecture that combines an information-processing reaction-diffusion medium performing operations of high computational complexity with a digital computer carrying out supplementary operations. Two principal points are assumed as a basis for this design. They are the following: a light-sensitive Belousov-Zhabotinsky-type reagent chosen as a reaction-diffusion medium that offers the opportunity to simulate a labyrinth and spread wave evolution by its images stored in the medium; fast light-induced phase wave processes that spread through the labyrinth in seconds instead of the dozens of minutes typical of trigger waves inherent in reaction-diffusion media. Images of consecutive wave-spreading steps are stored in the memory of a digital computer. These images are used to determine the shortest paths based on the additional procedure of testing for the connectedness of labyrinth fragments.

Journal Article↗
PubMed2002

Example of a chaotic crystal: the labyrinth.

Labyrinthine structures often appear as the final steady state of pattern forming systems. Being disordered, they exhibit the same kind of short range positional order as the Newell-Pomeau turbulent crystal. Labyrinths can be seen as a limit case of the texture of disordered rolls with a coherence length of the same order as the wavelength. In the various two-dimensional model equations we looked at, labyrinths and parallel rolls are steady states for the same parameters, their occurrence depending on the initial conditions. Comparing the stability of these two structures, we find that in variational models their energy is very close, rolls always being more stable than labyrinths. For the nonvariational model we propose a numerical experiment which displays a well defined bifurcation from parallel rolls to labyrinths as the more stable state.

Journal Article↗
PubMed1967

The content and localization of catecholamines in the carotid labyrinths and aortic arches of Rana temporaria.

1. The catecholamine content of the carotid labyrinth of Rana temporaria was estimated by two different methods, and compared with that of the aortic arch. In both tissues adrenaline was found as the dominant amine, with traces of dopamine and noradrenaline detectable in the labyrinth only.2. Per gram of fresh tissue, the labyrinth usually contained more adrenaline than the aortic arch.3. On microscopic examination, the aortic arch was found to contain nerve fibres which fluoresced after treatment with formaldehyde, whereas within the carotid labyrinth the formaldehyde-induced fluorescence was localized in the cytoplasm of clusters of small cells. This fluorescence resembled that exhibited by glomus cells in the mammalian carotid body.

Animals↗
PubMed1981

The effect of cerebellectomy on the tonic labyrinth and neck reflexes in the decerebrate cat.

1. Tonic labyrinth and neck reflexes were studied separately and in combination in the decerebrate cat before and after acute cerebellectomy. Reflex effects were observed as changes in the length of the medial head of triceps in both forelimbs. 2. In the decerebrate cat with an intact cerebellum the tonic labyrinth reflexes, elicited by side-up and side-down head rotations, produced asymmetric length changes in the medial head of triceps in both forelimbs, as described by Lindsay, Roberts & Rosenberg (1976). After cerebellectomy, head movements in either direction produced reflex shortenings in the medial triceps in both forelimbs, in contrast to the normal reciprocal reflex length changes. The presence of the cerebellum is thus required for the occurrence of the normal asymmetric labyrinth reflexes. 3. The direction of the neck reflexes remained unchanged by cerebellectomy. 4. It is suggested that the postural disturbances following cerebellar damage may partly result from the change in the form of the tonic labyrinth reflexes, which in combination with the tonic neck reflexes would no longer act in a stabilizing manner on the trunk.

Animals↗
PubMed1990

Labyrinth learning impairment in patients with early symptoms of presenile dementia.

21 patients (54 +/- 7 years old) with early cognitive deficit (ECD) during the presenile stage of presumptive primary degenerative dementia (mild stage) and 14 patients (54 +/- 4 years old) with early cognitive deficit with a background of cardiovascular disease (CVD) were examined in a labyrinth learning test of Milner (modified by Roth). 15 patients in the ECD group made 3 times more errors to negative fields (p less than 0.01), about 10 times more errors to positive fields (p less than 0.01) and needed treble the amount of time for passing through the labyrinth (p less than 0.01) compared with a healthy control group (51 +/- 4 years). A further 6 patients of the ECD group had no success in performing the labyrinth test. The CVD group was not different from the control group in making errors, but slower (p less than 0.05). The labyrinth test is found suitable for a more precise diagnosis of early cognitive deficit in the early stage of a primary degenerative dementia of the Alzheimer type.

Cognition Disorders↗
PubMed1997

The embryonic development of the human ethmoid labyrinth from 8-40 weeks.

The embryonic development of the human ethmoid labyrinth was studied in 24 fetal heads aged between 8 and 40 weeks of gestation under light microscopy. The uncinate process was identifiable at 8 weeks of gestation on the laterosuperior portion of the inferior turbinate; however, at this stage of development, the ethmoid bulla was not apparent. The ethmoid bulla developed on the lateral wall of the middle meatus by 12 weeks of gestation. By 14 weeks, the primordial ethmoid infundibulum and primordial maxillary sinus were seen developing between the uncinate process and the ethmoid bulla. It was obvious that the anterior and middle ethmoid cells developed from the ethmoid bulla. By 22 weeks of gestation, the first cell of the anterior ethmoid group was evident in the anterior-inferior portion of the ethmoid bulla. By 23 weeks of gestation, the first cell of the middle ethmoid group was visible in the superior portion of the ethmoid bulla. Pneumatization of the middle turbinate occurred as part of normal development of the ethmoid labyrinth. By 32 weeks of gestation, the ostium for the development of the middle turbinate cell was seen in the superior-interior portion of the middle turbinate. These observations provide new insight into the development of the ethmoid labyrinth and have important implications for the understanding of normal anatomy and developmental variants of the ethmoid labyrinth.

Embryonic and Fetal Development↗
PubMed2001

[Mathematic modeling of the shape and size of the ethmoidal labyrinth].

The present work was designed to study craniometric characteristics of ethmoidal labyrinths, facial and cerebral skeleton and to define mathematical correlation between the parameters of ethmoidal labyrinth and facial and cerebral skeleton. As a result average, minimal and maximal values of linear parameters and the parameters of the volume of ethmoidal labyrinths were calculated. Correlational, regressive and factor analyses of the craniometric characteristics studied were carried out. Significant regression equations for calculating width, height, length and volume of ethmoidal labyrinths for different types of cerebral skeleton were obtained.

Ethmoid Sinus↗
PubMed1976

EEG-studies on the phases of sleep and wakefulness after bilateral labyrinth destruction.

The dynamics of the state of wakefulness, slow and paradoxical sleep after labyrinth destruction was studied in chronic cats. The states were assessed according to the behaviour, EEG, myogram and eye movements. The labyrinth destruction was combined (chemical and mechanical). Bilateral labyrinth deafferentation results in a decrease in the duration of wakefulness from 30 to 17 per cent, p less than 0.001. At the same time paradoxical sleep increased from 4 to 8 per cent, p less than 0.001. This increase is due to both the greater average number of paradoxical sleep episodes and a higher average duration of the individual episode. The latency of the first appearance of a paradoxical sleep episode is considerably shortened after labyrinth destruction.

Animals↗
PubMed1988

Lesions in the mesencephalic reticular formation change open field and thirst motivated labyrinth behaviour of rats.

Open field behaviour and thirst motivated running through two labyrinth variants were compared before and after bilateral symmetric lesions of the anterior part of the dorsolateral parabrachial nucleus (PBl) and in the anterior mesencephalic area cuneiformis (CU), both n = 9, on 4-month-old male Long-Evans rats. CU-rats were characterized by abolished visual placing responses, aphagia or hypophagia which was limited up to the 15th postoperative day, ambulatory hyperactivity, reduced climbing and grooming, but enhanced rearing. Their preoperatively learnt thirst motivated labyrinth passage remained unimpaired but their drinking behaviour was persistently changed. They interrupted drinking several times and regularly did not empty the cups. Thirst motivation was evidently reduced after CU-lesions. PBl-rats were ambulatory hypoactive and slowed with accelerated habituation, reduced climbing and changed incline-plane behaviour. A slight hypophagia was generally overcome after the 5th postoperative day. Labyrinth performance of PBl-rats was evidently changed with significantly slower runs and impaired differentiation of the second labyrinth type in which passage duration, errors and even duration of licking were enhanced. Water intake was less reduced than in CU-rats. Both nuclei include parts of the "mesencephalic locomotor region", but contribute differently to the regulation of spontaneous and goal-directed behaviour.

Animals↗
PubMed1985

Tonic facilitatory influences of dorsal pontine reticular structures on the response gain of limb extensors to sinusoidal labyrinth and neck stimulations.

Experiments were performed to find out whether changes in resting discharge of the inhibitory reticulospinal (RS) neurons of the medulla, produced either by selective destruction or by cholinergic activation of a pontine tegmental reticular system, may modify the response gain of limb extensor muscles to given parameters of roll tilt of the animal or neck rotation. In precollicular decerebrate cats, an electrolytic lesion of the dorsal aspect of the pontine tegmentum, which slightly increased the tonic contraction of limb extensors, greatly decreased the amplitude of the multiunit EMG response of forelimb extensor muscles, i.e. of the medial head of the triceps brachii, to roll tilt of the animal and neck rotation (at 0.15 Hz, +/- 10 degrees), leading to selective stimulation of labyrinth or neck receptors. Correspondingly, the response gain of the forelimb extensors to labyrinth and neck stimulation decreased, but no change in the phase angle of the responses was observed. These findings did not depend on the increased postural activity, since they were still observed in the absence of any change in spontaneous EMG activity of the triceps brachii following the lesion. The changes in posture as well as in response gain of the forelimb extensors to labyrinth and neck stimulation produced by the pontine lesion appeared suddenly, and persisted for several hours throughout the survival period. Moreover, these changes involved mainly, but not exclusively, the limbs ipsilateral to the side of the lesion. Histological controls indicated that the structure responsible for the postural and reflex changes described above corresponded to the dorsal aspect of the pontine tegmentum located immediately ventral to the locus coeruleus (LC); this area corresponded to the peri-LC region as well as the surrounding pontine reticular formation (RF), including the dorsal aspect of the central tegmental field. This region closely corresponds to the area from which a tegmentoreticular tract, ending on the medullary inhibitory area, originates. It was previously shown that unilateral or bilateral lesion of the LC, which decreased the extensor tonus in the ipsilateral limbs, greatly enhanced the response gain of the triceps brachii to sinusoidal stimulation of labyrinth and neck receptors. These findings were attributed to suppression of an inhibitory influence that the LC exerts on the dorsal pontine reticular structures described above.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗