Biomedical subjects

V Honrubia

Publications and source records attributed to V Honrubia.

At least 91 records · Page 5Linked to original sources

PubMed1987

Eye movements in schizophrenia.

Smooth pursuit and other eye movements were quantitatively studied in patients with chronic schizophrenia to characterize the pattern and severity of eye movement abnormalities in this disorder. Twenty-one patients with schizophrenia, 13 patients with other psychiatric disorders (manic-depressive psychosis, schizoaffective disorder, depression and obsessive-compulsive disorder), and 19 normal subjects were studied. Horizontal eye movements were recorded with DC electro-oculography and analyzed by an online computer system. Eye velocity and closed-loop gain of pursuit, optokinetic nystagmus (OKN), vestibulo-ocular response (VOR) and visual-vestibular interactions were calculated. The latency, accuracy and peak velocity-amplitude relationships of voluntary saccades were measured. The group mean gains of pursuit and OKN of the schizophrenic patients were significantly lower than those of the normal subjects. Suppression of the VOR by fixation was impaired, and the latency of saccades was prolonged. However, the differences in group mean values were small in magnitude, and the frequencies of outliers among the schizophrenic patients were low. The patients with other psychiatric disorders had a similar pattern and severity of eye movement abnormalities. The frequency and severity of eye movement abnormalities in schizophrenic patients are lower than those indicated by previous studies that used different techniques of analysis.

Adolescent↗

PubMed1986

The effect of loop diuretics on the vestibular system. Assessment by recording the vestibular evoked response.

Whether or to what extent loop diuretics, e.g., ethacrynic acid and furosemide, affect the vestibular system is controversial. We studied this problem by recording in cats the short-latency vestibular evoked response (VsER) to acceleration stimuli by skin electrodes before and after local or systemic administration of loop diuretics. The effect on the VsER was minimal in contrast to the major changes that appeared in the auditory evoked response, in which, among the waves known to originate from the brain stem, the most affected was N1. These findings suggest that the vestibular end-organ function is minimally affected by loop diuretics and that the changes in the vestibulo-ocular reflex reported by several authors might be due to the effect of the drugs on the central nervous system. Thus, recording of the VsER in experimental animal models might serve as a useful tool for direct evaluation of the effect of certain drugs and conditions on the vestibular system.

Animals↗

PubMed1986

Vertical visual-vestibular interaction in normal human subjects.

Previous studies have described asymmetrical vertical eye movements when normal human subjects were rotated about a vertical inter-aural axis (with head rolled 90 degrees). We measured vertical eye movements induced by visual, vestibular and visual-vestibular stimuli with a magnetic scleral search coil technique while 10 normal subjects sat upright in a chair designed to rotate about the horizontal inter-aural axis at frequencies and amplitudes of natural head movements. Asymmetries in the gain of upward and downward pursuit and fixation-suppression of the VOR were found in individual subjects. However, there was no significant difference (p greater than 0.05) between the mean gain of up and down slow eye movements induced by vestibular, visual or visual-vestibular stimulation in the group of normal subjects. Systematic up-down asymmetries in vertical eye movements previously observed with testing about the vertical inter-aural axis were probably due to bias introduced by otolith stimulation and/or electro-oculographic eyelid artifact.

Adult↗

PubMed1986

Late cortical cerebellar atrophy. Clinical and oculographic features.

Ten patients with late cortical cerebellar atrophy documented with computerized tomography (CT) and magnetic resonance (MR) imaging presented a uniform pattern of oculomotor abnormalities. All had deficits in smooth pursuit and fixation suppression of the vestibulo-ocular reflex (VOR). The gain of the VOR was often increased but the dynamics of the VOR were not different from normals. Full-field optokinetic responses and visual-vestibular interaction mediated via the VOR velocity storage element were preserved. Just as in lower primates, the cerebellum in humans is a critical relay station for foveal pursuit and visual-vestibular interaction requiring foveal pursuit. Vestibular responses and visual-vestibular interaction mediated through the VOR velocity storage element are relatively independent of the cerebellum.

Adult↗

PubMed1986

Regeneration of the eight cranial nerve. I. Anatomic verification in the bullfrog.

The regenerative capacity of the eight cranial nerve of the bullfrog, Rana catesbeiana, was investigated. The nerve was sectioned between the ganglion and the brain stem in 16 experimental animals. Horseradish peroxidase was extracellularly injected distal to the site of the nerve section five or more weeks postoperatively. Labeled fibers were identified histologically and their central nervous system projections studied. The findings were as follows: 1. The eight cranial nerve of the bullfrog regenerated after preganglionic axotomy. 2. Fibers of all sizes regenerated. The regenerated fibers in the nerve were disorderly at the site of nerve section. Most fibers entered the brain stem and formed a vestibuloauditory tract, although some "escaped" and coursed along the brain stem. 3. The regenerated vestibuloauditory tract was situated more laterally than normal, with thick and thin fibers intermixed. 4. Regenerated tertiary fibers were long and tortuous and had unusual trajectories. 5. All vestibuloauditory nuclei received thick and thin afferent fibers.

Animals↗

PubMed1985

Facial nerve evoked potentials.

Evoked potentials representing both intracranial and extracranial activity have been recorded from the canine scalp after retrograde stimulation of peripheral facial nerve branches. A negative electrode at the vertex and a positive electrode at the ipsilateral mastoid (grounded at the contralateral mastoid) show a monophasic negative stylomastoid evoked potential that appears to be generated from the facial nerve trunk at the stylomastoid foramen. When the positive electrode is moved from the mastoid to the posterior scalp (overlying the foramen magnum), a similar potential with a latency 1.5 msec greater is obtained. This brain stem evoked potential is generated from fibers in the vicinity of the root entry zone and the initial trajectory into the brain stem. A potential of similar latency but greater magnitude is recorded with the positive electrode in the cerebrospinal fluid of the posterior fossa.

Animals↗

PubMed1985

Rotational testing in patients with bilateral peripheral vestibular disease.

We performed quantitative low and high frequency rotational testing in 17 patients with bilateral peripheral vestibular deficits. A characteristic pattern of decreased gain and increased phase lead at low frequencies of sinusoidal stimulation and decreased time constant to impulsive stimulation was observed in most patients. The results of caloric testing correlated with the results of low frequency rotational testing but not with the results of high frequency testing. Only 2 patients complained of oscillopsia at the time of testing and both of these had decreased vestibulo-ocular reflex gain at low and high frequencies of sinusoidal rotation.

Adult↗

PubMed1985

Central projections of primary vestibular fibers in the bullfrog: I. The vestibular nuclei.

The central projections of the vestibular end organs in the bullfrog Rana calesbeiana were analyzed by using horseradish peroxidase labeling of the primary vestibular afferents. Separate extracellular injections were made of the anterior branch, the posterior branch, the ampullary nerve of each of the three semicircular canals, and the branch to the saccule. The anterior and posterior branches of the bullfrog eighth nerve, each containing both vestibular and auditory fibers, merge and enter the brain stem as a single nerve root. The thin caliber fibers of the anterior branch enter the brain stem on the ventral-posterior aspect of the nerve and immediately divide dichotomously into ascending (rostral) and descending (caudal) branches. The thick caliber fibers of the anterior branch enter the brain stem on the ventral-anterior aspect of the eighth nerve and traverse medially into the alar plate before dividing into ascending and descending branches. The primary afferent fibers of the vestibular nerve innervate an ipsilateral area of the brain stem which extends caudally from the rhombencephalon at the level of the twelfth nerve nucleus and rostrally up to and including the cerebellar nucleus and the cerebellum. The following vestibular nuclei can be identified by the fact that they receive primary vestibular afferents: the ventral vestibular nucleus, medial vestibular nucleus, descending vestibular nucleus, superior vestibular nucleus, and cerebellar nucleus. The dorsal (acoustic) nucleus, which receives primary auditory input, also receives afferents from the saccule. In addition to these nuclei, the cerebellum and the reticular formation receive significant primary input from the various vestibular receptors. The primary vestibulo-cerebellar fibers terminate mainly among the granular cells of the lobus auricularis and of the corpus cerebelli on the ipsilateral side. Each of the three semicircular canals projects into the cerebellum, while no such projection was observed in the saccular nerve preparations. Fibers from each of the three semicircular canals project to all of the vestibular nuclei. Heavily labeled large neurons, presumably vestibular efferents, are seen in the ipsilateral reticular formation, adjacent to the seventh motor nucleus.

Animals↗

PubMed1985

Central projections of primary vestibular fibers in the bullfrog. II. Nerve branches from individual receptors.

The fibers from the nerves innervating each of the three semicircular canals and the saccule were labeled by injecting horseradish peroxidase extracellularly into these nerves. The projections into the various vestibular nuclei of each receptor were studied in transverse sections of the brain stem throughout the vestibular nuclear area. All five vestibular nuclei receive primary afferents throughout their areas. There are differences in the projection patterns of the canals. In the superior and ventral vestibular nuclei, the location of the projections depends on the crista injected. The anterior canal projects ventrally, the horizontal canal centrally, and the posterior canal more dorsally. Each canal, however, sends fibers to all areas, with overlap of fibers from the different cristae. The cerebellar nucleus receives uniform innervation from the three canals. The medial vestibular nucleus in the rostral and caudal areas receives only thin fibers from each canal, with considerable overlap. The descending nucleus in the rostral and caudal areas receives innervation from the cristae, also with considerable overlap, but with greater intensity in the ventral part of the caudal portion of the nucleus. Each crista sends fibers to the cerebellar granular layer and to the base of the cerebellar Purkinje cell layer. These fibers also innervate the reticular formation below the entry zone of the eighth nerve. The saccule innervates both the dorsal (acoustic) and the ventral nuclei, the latter in the most dorsal position. The innervation of the utricle could be ascertained only in the middle section of the descending and the medial nuclei, an area which does not receive significant innervation from the cristae. Primary afferent fibers course in the vestibular tract, forming a longitudinal bundle lateral to the vestibular nuclei. In the bundle the larger fibers are medially situated.

Afferent Pathways↗

PubMed1985

Central projections of primary vestibular fibers in the bullfrog. III. The anterior semicircular canal afferents.

A study was made of the projection patterns in the vestibular nuclei of primary afferent fibers innervating the crista of the anterior semicircular canal (ASC) of the bullfrog. Individual neurons were intracellularly recorded to characterize their spontaneous activity and injected with horseradish peroxidase to visualize their central and peripheral projections. A quantitative evaluation was made of the lengths of the central projections of primary afferents in the various vestibular nuclei and of the number of branch terminals and their precise locations in each of the major vestibular projection areas in the brain stem. The differences between the central projection patterns of the two types of primary afferent fibers were documented: the thick fibers with their irregular spontaneous activity and the thin fibers with their more regular spontaneous activity. Each neuron sends many terminals to various vestibular nuclei. The ventral part of the ventral nucleus receives the greatest number of terminals from fibers of all sizes. The medial nucleus receives terminals from the thin fibers only, while the reticular formation receives terminals exclusively from the thick fibers. All the vestibular nuclei receive innervation from ASC afferents, with considerable overlap in areas of innervation between fibers of different caliber. Differences were found between the thick and thin fibers in their locations, their patterns of branching, and the appearance of their terminal boutons. These anatomic characteristics are interpreted to represent physiologic differences in the production of reflexes by thick and thin neurons. It is also postulated that these different neurons play different roles in vestibular system function: thick neurons contribute to the maintenance of equilibrium during movement while thin neurons participate in the maintenance of posture and vestibular tonus.

Animals↗

PubMed1985

Velocities of vertical saccades with different eye movement recording methods.

Voluntary vertical saccades were recorded in five normal human subjects with electro-oculography (EOG), an infrared, limbus tracking system (IR), and a magnetic scleral search coil method. The peak velocity-amplitude relationships of up and down saccades were measured during refixations across the center of the orbit and within the upper and lower fields of the orbit. The search coil was the most accurate method and did not reveal significant differences between the group mean velocities of up and down saccades in the different fields of the orbit. However, subjects can have idiosyncratic differences in velocities between up and down saccades. EOG overestimated the velocities of up saccades. IR underestimated the velocities of up saccades. The search coil was used to record vertical saccades in adduction and abduction. Horizontal eccentric gaze did not significantly affect the velocities of vertical saccades.

Adult↗

PubMed1984

Episodic vertical oscillopsia and downbeat nystagmus in a Chiari malformation.

A 36-year-old woman had intermittent downbeat nystagmus. Between episodes of downbeat nystagmus, eye movements were normal, except for stationary positional nystagmus and decreased vestibulo-ocular responses (VOR) to rotation. Smooth pursuit, optokinetic nystagmus, and visual-VOR interactions, which are usually impaired in patients with downbeat nystagmus and cerebellar dysfunction, were normal. Computed tomography and findings during a suboccipital craniotomy demonstrated a mild Chiari malformation, type 1. Episodic downbeat nystagmus that is not associated with other ocular motor abnormalities due to cerebellar dysfunction can be an initial sign of a Chiari malformation.

Adult↗

PubMed1984

Changes in the human vestibulo-ocular reflex after loss of peripheral sensitivity.

Quantitative rotational testing was used to study changes in the vestibulo-ocular reflex of patients with unilateral and bilateral peripheral vestibular lesions. Compared with normal subjects, the patients exhibited a characteristic pattern of decreased gain and increased phase lead at low frequencies of sinusoidal stimulation and decreased time constants on impulsive stimulation. By contrast, gain and phase measurements on high-frequency-low-amplitude sinusoidal stimulation were often normal. In the patients with bilateral lesions, the results of caloric testing correlated with the results of low-frequency rotational testing but not with the results of high-frequency testing. There are two main clinical implications of these findings. First, patients with absent response to caloric stimulation (unilateral or bilateral) may have a normal response to high-frequency sinusoidal rotation (i.e., the frequencies that constitute most natural head movements). This probably explains why such patients do not report oscillopsia. Second, low-frequency sinusoidal rotational testing and caloric testing are more sensitive than high-frequency sinusoidal or impulsive rotational testing for detecting early loss of vestibular sensitivity due, for example, to ototoxic drugs.

Adult↗

PubMed1984

Quantitative vestibular testing.

Our standard rotational test battery includes tests of optokinetic nystagmus (OKN), the vestibulo-ocular reflex (VOR), and visual-vestibular interaction. Lesions of the peripheral vestibular system characteristically impair only the VOR, whereas lesions of the central system impair OKN and visual-vestibular interaction. The pattern of abnormal responses can help localize lesions within the central vestibular pathways.

Electronystagmography↗

PubMed1984

Anatomical characteristics of the anterior vestibular nerve of the bullfrog.

Study was made of the dimensions of the nerves to the receptor organs in the anterior branch of the bullfrog vestibular nerve. The number of fibers and their diameters and trajectories in the nerve and Scarpa's ganglion were studied. A correlation was made between the anatomical and physiological properties of neurons identified with intracellular injections of horseradish peroxidase. The data suggest a specific pattern of innervation of the organs, organization of fibers and cells in the vestibular nerve, and significant correlation between the anatomical and physiological properties of individual neurons. A comparison was made between the information obtained from the bullfrog and that from other animals, which suggests a similarity between species and supports the hypothesis of a differential physiological role of the neurons in each vestibular organ according to anatomical characteristics.

Animals↗

PubMed1984

Low and high frequency sinusoidal rotational testing in patients with peripheral vestibular lesions.

We found a consistent pattern of response to low and high frequency sinusoidal rotational testing in patients with chronic compensated unilateral and bilateral peripheral vestibular lesions. Gain (peak slow phase eye velocity/peak chair velocity) was decreased and phase lead increased at low frequencies but both measurements approached normal at high frequencies. Asymmetries in gain, when present, were approximately the same in the low and high frequency range. These changes can be explained by a simple first order linear model of the vestibulo-ocular reflex if one assumes that the goal of the compensation process is to maintain gain in the high frequency range.

Electrooculography↗

PubMed1983

Influence of vestibulo-ocular reflex gain on human optokinetic responses.

In 15 patients with severe bilateral vestibular impairment (mean vestibulo-ocular reflex (VOR) gain less than 0.05), constant velocity optokinetic nystagmus (OKN) gain, optokinetic after nystagmus (OKAN) initial velocity, and OKAN duration were significantly (p less than 0.0025) lower than in 20 normal subjects of similar age. In the normal subjects VOR gain was significantly correlated (p less than 0.05) with OKAN initial velocity but not with OKAN duration or OKN gain. The results of this study provide additional evidence for the existence in human subjects of an optokinetic pathway whose function, like that of the subcortical optokinetic pathway in animals, varies with VOR gain.

Adult↗

PubMed1983

The dynamics of vertical eye movements in normal human subjects.

We studied the dynamics of horizontal and vertical slow eye movements (vestibular, optokinetic, pursuit, and visual-vestibular) in 10 normal human subjects. Several differences between horizontal and vertical eye movements were found. The time constant (time required for the slow-phase eye velocity to decay to 37% of the peak value) of vertical postrotatory nystagmus (PRN) was, on average, 50% as long as the time constant of horizontal PRN; the mean phase lead of per-rotatory nystagmus during low-frequency sinusoidal rotation in the vertical plane was approximately twice the mean phase lead of per-rotatory nystagmus at the same frequency in the horizontal plane. Vertical optokinetic after-nystagmus (OKAN) was minimal compared to horizontal OKAN. Asymmetries in the dynamics of vertical eye movements were also noted. The mean time constant of PRN with upward slow phases was consistently longer than the mean time constant of PRN with downward slow phases and vertical OKAN only occurred when the optokinetic stimulus moved upward. Upward pursuit was better than downward pursuit and upward slow phases of vestibular nystagmus were poorly inhibited with fixation while downward slow phases were normally inhibited.

Electrooculography↗