Search PubMed⌕ Search

Biomedical subjects

B Larsby

Publications and source records attributed to B Larsby.

At least 19 recordsLinked to original sources
PubMed1992

Normal-hearing and hearing-impaired subjects' ability to just follow conversation in competing speech, reversed speech, and noise backgrounds.

The performance on a conversation-following task by 24 hearing-impaired persons was compared with that of 24 matched controls with normal hearing in the presence of three background noises: (a) speech-spectrum random noise, (b) a male voice, and (c) the male voice played in reverse. The subjects' task was to readjust the sound level of a female voice (signal), every time the signal voice was attenuated, to the subjective level at which it was just possible to understand what was being said. To assess the benefit of lipreading, half of the material was presented audiovisually and half auditorily only. It was predicted that background speech would have a greater masking effect than reversed speech, which would in turn have a lesser masking effect than random noise. It was predicted that hearing-impaired subjects would perform more poorly than the normal-hearing controls in a background of speech. The influence of lipreading was expected to be constant across groups and conditions. The results showed that the hearing-impaired subjects were equally affected by the three background noises and that normal-hearing persons were less affected by the background speech than by noise. The performance of the normal-hearing persons was superior to that of the hearing-impaired subjects. The prediction about lipreading was confirmed. The results were explained in terms of the reduced temporal resolution by the hearing-impaired subjects.

Audiometry↗
PubMed1991

Vestibular-oculomotor, opto-oculomotor and visual function in the rat after long-term inhalation exposure to toluene.

Pigmented rats were exposed to toluene (1000 ppm, 21 h/day) for 6 or 11 weeks. The function of the vestibulo- and opto-oculomotor systems was tested one month after the end of the exposure by recording of nystagmus, induced by vestibular or optokinetic stimuli. The eye movements were recorded by a magnetic search coil technique. The optokinetic gain in the exposed animals was reduced compared to a control group. There was also a slight reduction in gain during sinusoidal oscillatory vestibular stimulation. No effect of the toluene exposure on the gain or duration of nystagmus during acceleratory or deceleratory rotatory stimulation was demonstrated, nor was there any change in the duration of the optokinetic after-nystagmus. The function of the visual system was tested 2 to 5 days after exposure by recording the electroretinogram and the visual evoked response. The conduction velocity in peripheral nerve was also measured. No effect of the toluene exposure on these variables was seen. The results indicate that long-term inhalation of toluene causes a long-lasting, possibly permanent, lesion within the vestibulo-cerebellum. They gave no evidence that such exposure affects peripheral vestibular or visual function.

Administration, Inhalation↗
PubMed1990

Otoneurological findings in workers exposed to styrene.

An otoneurological test battery was administered to 18 workers with long-term exposure (6-15 years) to styrene at levels well below the current Swedish limit (110 mg/m3). The results were compared with those of a reference group. Disturbances were found in the central auditory pathways of seven workers. Tests reflecting central processing of impulses from different sensory equilibrium organs were abnormal for 16 workers. The most relevant tests seemed to be static posturography and the rotatory visual suppression test. In the posturography the styrene group had a significantly larger sway area than the reference group. In the visual suppression test, the styrene workers displayed a significantly poorer ability to suppress vestibular nystagmus than the reference group. It was concluded that styrene exposure in industrial environments at moderate or low levels causes central nervous system disturbances which are not always diagnosable with psychometric tests but can be apparent in special otoneurological tests.

Adult↗
PubMed1989

Visual suppression tests in acoustic neuroma patients.

Fifty-five patients with a unilateral acoustic neuroma were investigated preoperatively with visual suppression tests during rotatory oscillation and caloric irrigation. During a sinusoidal oscillation, 29% of the patients showed a reduced suppression compared to 9% during pseudo-random oscillation and 11% in the caloric test. In the sinusoidal and caloric tests the majority of the patients with deficient suppression had large or medium-sized tumors. In a few patients with small tumors, pathology was observed in both sinusoidal and randomized tests, presumably as a sign of unconcentration. The study shows that the sinusoidal visual suppression test and to a lesser degree suppression during caloric irrigation are of value for identification of brainstem-cerebellum compression of acoustic neuromas.

Adult↗
PubMed1988

Pursuit eye movements. Methodological aspects.

A reduced smooth pursuit ability is often a sign of central vestibular pathology. Methodological aspects of stimulation, recording of eye movements and analysis of results in the evaluation of the smooth pursuit function are discussed. A method for evaluation of the smooth pursuit function over a broad frequency range is presented and the effects of target predictability and age on recorded parameters are shown.

Adult↗
PubMed1988

Broad-frequency rotatory testing.

The method of broad-frequency-band rotatory testing with results from normal subjects and patients with peripheral uni- and bilateral loss as well as central vestibular disorders are reviewed. The following conclusions are drawn: adequate testing of the vestibulo-ocular reflex including side detection of unilateral loss in light or in darkness can only be done with either random or high-frequency (2.5-3 Hz) sinusoidal stimulation. Measurements of compensatory eye movements at lower frequencies where vestibular and non-vestibular signals interact are of interest for central vestibular diagnosis. A decreased ability to suppress vestibular nystagmus is not an uncommon finding in patients with large acoustic neuromas or pathology in the brainstem or cerebellum.

Central Nervous System Diseases↗
PubMed1988

Vestibular and audiologic functions in gentamicin-treated Menière's disease.

Fifteen patients with disabling Meniere's disease were treated with local intratympanic administration of gentamicin once daily. They had suffered from frequent attacks of vertigo and vomiting, the hearing in the affected ears was decreased permanently, and spontaneous nystagmus was observed. The number of treatment days ranged between 3 and 11. Follow-up time was 1 to 6 years. For evaluation of the treatment, audiologic and vestibular examinations were used, including the broad frequency-band rotatory test (0.4-4.5 Hz). Fourteen patients were free from vertigo after treatment. In 5 patients, there was an increased hearing loss, and in 10 it remained unchanged. Tinnitus and fullness sensations were diminished. After treatment, all ears were unresponsive to caloric stimulation. The clinical examination and rotatory testing in light with sinusoidal stimulation revealed good central compensation of the vestibular loss. However, with pseudorandomized oscillations in darkness, the broad frequency-band rotatory test quantified the loss of peripheral vestibular function and was able to detect the side of the lesion in eight of nine patients.

Administration, Topical↗
PubMed1987

Audiological and vestibulo-oculomotor findings in workers exposed to solvents and jet fuel.

Three groups of subjects with long-term (5-41 years) occupational exposure to industrial solvents have been evaluated with extensive audiological and vestibular test batteries. Group A comprised 16 subjects with a confirmed diagnosis of psycho-organic syndrome (POS), while group B consisted of 7 subjects with suspected POS. Both groups had been exposed to mixtures of aliphatic and aromatic solvents. Eight subjects with long-term exposure to jet fuel constituted group C. In the audiological test battery, discrimination of interrupted speech and evoked cortical potentials in response to frequency glides were the tests that yielded significantly abnormal results. In the vestibular test battery, considerable pathology was seen in electronystagmography, and in addition, visual suppression test and saccade test indicated CNS disturbance. In general, when a test yielded pathological results, the incidence of pathology was highest in group A and lowest in group C.

Adult↗
PubMed1979

The influence of trichloroethylene and related drugs on the vestibular system.

A previously described experimental model for studying the effect of industrial solvents on the vestibular system of rabbits has been applied to trichloroethylene. Estimation of trichloroethylene and its metabolites in blood and cerebrospinal fluid was performed by gas chromatography. Vestibular function was studied by recording nystagmus, induced by positional changes or accelerated rotation. At blood levels of trichloroethylene above 30 p.p.m. "positional nystagmus" develops. Two metabolites of trichloroethylene, chloral hydrate and trichloroethanol, which are known as central nervous system (CNS) depressants, did not induce this abnormal nystagmus. However, alpha-chloralose, a derivative of chloral hydrate, induced positional nystagmus and also a markedly exaggerated nystagmus developed during rotatory acceleration. It is suggested that solvents like trichloroethylene elicit vestibular disturbances by stimulation of central subcortical vestibulo-oculomotor connections. The stimulation may be caused by a blockage of inhibitory systems.

Animals↗
PubMed1979

On the mechanism of vestibular disturbances caused by industrial solvents.

The industrial solvents xylene, styrene, trichloroethylene and methylchloroform administered to rabbits caused a positional nystagmus and disturbances in the nystagmus response to rotatory acceleration. The positional nystagmus had a beat direction the opposite to positional alcohol nystagmus, which was in similar experiments elicited by methanol, ethanol and propanol. The three alcohols needed a ten times higher blood concentration to cause a nystagmus than the solvents did.

1-Propanol↗
PubMed1978

Exposure of rabbits to styrene. Electronystagmographic findings correlated to the styrene level in blood and cerebrospinal fluid.

Objective methods for critically evaluating the toxic effect of industrial solvents are highly desirable. As many of these solvents are suspected to cause vertigo, an animal experimental model was set up for studying the effects of solvents on the vestibular systems. The vestibular function was studied by registration of involuntary eye movements--nystagmus--which are elicited via central vestibulo-oculomotor connections. During exposure to styrene a so-called positional nystagmus was demonstrated that indicated vestibular disturbances. Nystagmus is normally elicited by rotatory acceleration. During exposure to styrene the direction of this rotatory nystagmus was reversed. The incidence of the positional nystagmus correlated well with the blood level of the solvent, measured by gas chromatography. Kinetic studies also demonstrated a rapid equilibration between the level of the solvent in arterial blood and cerebrospinal fluid, and therefore suggested that estimation of the arterial level reliably indicates the level in the central nervous system.

Animals↗
PubMed1976

Projection of thalamic neurons to cat primary vestibular cortical fields studied by means of retrograde axonal transport of horseradish peroxidase.

The two vestibular cortical projection areas in the anterior suprasylvian sulcus and post-cruciate dimple regions were defined by evoked potential technique in anaesthetized cats. The thalamic location of neurons with axon terminals in these fields was determined using the method of retrograde axonal transport of horseradish peroxidase. The ascending vestibular pathway appeared to be separated also at the thalamic level, where cells in the ventroposterolateral nucleus were found to project to the post cruciate dimple and cells in the posterior nuclear group to the anterior suprasylvian vestibular cortical fields.

Afferent Pathways↗
PubMed1975

Vestibular and somatosensory inflow to the vestibular projection area in the post cruciate dimple region of the cat cerebral cortex.

In anesthetized cats 251 cells within the cortical vestibular projection area, adjacent to the post-cruciate dimple, were analyzed as to their input characteristics employing extracellular recording techniques. The post cruciate dimple vestibular field, which is located in area 3a, has a high degree of convergence between vestibular and peripheral somatosensory input. The latter is not restricted to muscle afferents but includes cutaneous modalities. The functional significance of this vestibular cortical projection field is discussed.

Animals↗
PubMedDate not supplied

The effect of toluene on the vestibulo- and opto-oculomotor system in rats, pretreated with GABAergic drugs.

Toluene, an aromatic solvent, prolongs the duration of nystagmus induced by a rotatory acceleration or by an optokinetic stimulation in the pigmented rat. Baclofen, an agonist of GABAB receptors, and 4,5,6,7-tetrahydroisoxazolo[5,4-c]-pyridin-3-ol (THIP), an agonist of GABAA receptors are able to block this toluene effect on the vestibular system. On the contrary diazepam, which by itself causes an evident reduction of the duration of acceleratory nystagmus, is not able to block the toluene effect. The results indicate that the toluene effect is related to GABA transmission and that the solvent interacts by a rather receptor specific mechanism of action.

Animals↗
PubMedDate not supplied

Projection of the vestibular nerve to the SI arm field in the cerebral cortex of the cat.

Evoked cortical focal potentials from electrical vestibular nerve stimulation were recorded in the Pcd-area in cats anaesthetized with Chloralose or Nembutal. For comparison, additional cortical projections were located for n. rad. superficialis and group Ia muscle afferents from n. rad. prof., n. fibularis prof., n. femuralis ramus muscularis and the motor nerve to the trapezoid muscle. Surface positive potentials, which reversed to negativity in middle cortical layers, were for vestibular nerve stimulation recorded in the S I forelimb field in a small area close to Pcd in the posterior medial part of the deep radial nerve projection field. The location of this field is compared with the vestibulo-cortical projections described earlier for rodents, squirrel monkey, and rhesus monkey. The histology shows that the field was within the cytoarchitectonic 3a area.

Animals↗