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Biomedical subjects

B Larsby

Publications and source records attributed to B Larsby.

At least 19 recordsLinked to original sources
PubMed2001

Cognitive effects in dichotic speech testing in elderly persons.

OBJECTIVE: To study the effect of chronologic age on central auditory functions using dichotic speech tests and to study whether and how the age effect in dichotic listening is related to cognitive ability. DESIGN: Dichotic speech tests and cognitive tests were performed on 30 bilaterally hearing-impaired subjects, with a pure-tone average better than 50 dB HL. They were between 42 and 84 yr of age and were divided into an older and a younger group comprising 15 subjects each. The dichotic test material were digits, low-redundancy sentences and consonant-vowel syllables. The subjects reported stimuli heard in both ears (free report) or in one ear (directed report to left or right ear). The cognitive test battery comprised tests focusing on short-term memory, verbal information-processing speed and phonologic processing. RESULTS: A decreased overall performance in all dichotic speech tests was observed in the older group. In the syllable test the older subjects showed poorer results when focusing on the stimuli heard in the left ear, as compared with when focusing on stimuli heard in the right ear, whereas the younger group showed almost equal results for left- and right ear-focusing conditions. An age effect was also seen in reaction times recorded in the cognitive tests and in the scores of the reading span test. These cognitive parameters correlate with the results of the dichotic test when focusing to the left, but not when focusing to the right in the directed report condition. In the free report condition the overall performance showed a high correlation with cognitive test parameters. CONCLUSIONS: Effects of chronologic age in dichotic speech tests in the elderly have been verified. The degree of effect is dependent on test material, way of reporting and focusing condition. The different listening tasks in dichotic tests put different demands on cognitive ability shown by a varying degree of correlations between cognitive function and dichotic test parameters. Also, the results indicate a strong connection between age-related cognitive decline in the elderly and problems to perceive stimuli presented to the left ear.

Adult↗
PubMed2000

A system for recording of auditory evoked responses.

A system for recording of evoked potentials from auditory stimulation was developed. The system consists of a PC equipped with an audio bandwidth board with analog input and output channels. The sound stimulus signal is generated in the computer, D/A converted, and via audio amplifier fed to earphones on the test subject. Auditory evoked potentials in response to sound stimuli are recorded via electrodes, amplified and filtered in an EEG recording system and fed to an A/D converter. The signal is analysed in the PC. The modular design of the program makes it a flexible system where stimulus and recording parameters can easily be modified and new applications can be added to standard clinical measurements. Three applications that are not possible with commercially available systems were developed and evaluated. a) A diagnostic procedure to verify hydrops in patients with Meniere's disease. b) Intraoperative recordings of auditory evoked potentials during neurootological surgery. c) Recording of mismatch negativity (MMN) potentials in evaluation of central auditory functions.

Audiometry, Evoked Response↗
PubMed1999

Auditory temporal and spectral resolution in normal and impaired hearing.

Temporal, spectral, and combined temporal-spectral resolution of hearing was assessed by recording masked hearing thresholds. The masker was an octave band noise. Spectral resolution was assessed by introducing a spectral gap of half an octave bandwidth in the masker. A 50-msec gap assessed temporal resolution. The spectral and temporal gaps were used separately or simultaneously. Normal-hearing and hearing-impaired subjects participated. For each masking condition, the subjects were tested at masker levels 50, 60, 70, and 80 dB SPL and at test-tone frequencies 0.5, 1, 2, and 4 kHz. Normal-hearing subjects showed reduced masking with spectral and temporal gaps. The combination of spectral and temporal gap reduced masking further. The release of masking was dependent upon the masker level. Hearing-impaired subjects showed less release of masking than normal-hearing subjects. The degree of hearing impairment was inversely related to release of masking. Reliability of the test procedure was assessed.

Adolescent↗
PubMed1998

A method for evaluating temporal, spectral and combined temporal-spectral resolution of hearing.

A method for evaluating the spectral, temporal and combined spectral temporal resolution of hearing is presented; it was used to obtain masked hearing thresholds using the fixed frequency Békéy technique. The masking noise was a broadband random noise with a 3 dB/octave roll off (pink noise). Spectral resolution was assessed by introducing a spectral gap in the masking noise centered at the test tone frequency. Temporal resolution was assessed by introducing temporal gaps, the centre of which coincided in time with the centre of the test tone-pulses. The spectral and temporal gaps were used either separately or simultaneously. Release of masking values were calculated from masked hearing thresholds. One test group comprised 16 normal-hearing subjects, a second group 16 elderly (age 55-75 years) subjects with normal hearing for their age. Temporal gaps were 20, 50 and 100 ms long. Spectral gaps had a bandwidth of 1/10, 1/3, and 1 octave. Each gap or combination of gaps was tested at the frequencies 0.5, 1, 2 and 4 kHz. Release of masking increased with increasing temporal or spectral gaps. If a temporal gap and a spectral gap were combined, the release of masking increased further. Maximum release of masking was obtained with the 100 ms temporal gap combined with the 1 octave notch filter. The overall difference in release of masking between the young and elderly normal-hearing group was 2 dB.

Adolescent↗
PubMed1998

Dichotic speech tests.

When central auditory dysfunction is present, ability to understand speech in difficult listening situations can be affected. To study this phenomenon, dichotic speech tests were performed with test material in the Swedish language. Digits, spondees, sentences and consonant-vowel syllables were used as stimuli and the reporting was free or directed. The test material was recorded on CD. The study includes a normal group of 30 people in three different age categories; 11 years, 23-27 years and 67-70 years. It also includes two different groups of subjects with suspected central auditory lesions; 11 children with reading and writing difficulties and 4 adults earlier exposed to organic solvents. The results from the normal group do not show any differences in performance due to age. The children with reading and writing difficulties show a significant deviation for one test with digits and one test with syllables. Three of the four adults exposed to solvents show a significant deviation from the normal group.

Adult↗
PubMed1996

The subjective horizontal in eccentric rotation influenced by peripheral vestibular lesion.

Peripheral vestibular equilibrium disorders may originate in various parts of the labyrinth or the vestibular nerve. Traditionally, the function of the lateral semicircular canals has been assessed with caloric irrigation, and sometimes falsely been interpreted as a vestibular nerve lesion. The vertical semicircular canals are not easily assessed. Caloric testing with the head in different positions is not very helpful, but the canals may pairwise be tested using specific rotational techniques. Often the otolithic organs, capable of detecting linear acceleration forces, are forgotten as a source of vertigo and dizziness. We have implemented horizontal rotatory testing with the subject seated eccentrically facing the direction of rotation as a means of assessing otolithic function. The subject experiences a lateral tilt and is instructed in darkness to put a short light bar in the position he thinks a water surface would have, which is identical to his perceived tilt. In 39 normal subjects, a theoretical tilt of 24 degrees was estimated as approximately 19.5 degrees, and the standard deviation was 6 degrees. A side difference index was proposed to be normal if below 25%. The preliminary findings in a few patients with known labyrinthine lesions are presented. We propose that otolithic as well as lateral semicircular canal functions are useful to monitor in patients with suspected peripheral equilibrium disorders.

Adult↗
PubMed1994

Effects of GABAB activation and inhibition on vestibulo-ocular and optokinetic responses in the pigmented rat.

The effects of the GABAB agonist baclofen and the GABAB antagonist CGP 35348, given separately or simultaneously, on the central vestibular system of pigmented rats have been evaluated. Drugs were administered either intramuscularly or intracerebroventricularly. Eye movements were recorded during vestibular, optokinetic and combined visual-vestibular stimulation. Activation of the GABAB receptors by baclofen caused a dose related disturbance of the system, manifested by (1) a decrease of the optokinetic gain, (2) a reduced ability to suppress nystagmus during conflicting vestibular and visual input, and (3) a disability to maintain the eccentric eye position upon a spontaneous saccade. All these effects could be inhibited in a dose-dependent fashion by CGP 35348, suggesting that the findings are specifically related to the GABAB receptor. Given separately, the antagonist did not affect the mentioned parameters. During horizontal acceleratory/deceleratory stimulation in darkness baclofen caused a biphasic pattern in the dose-response curves. Small amounts of baclofen caused an increase of the gain and of the duration of poststimulatory nystagmus, while high doses had a depressive action on the same parameters. The stimulating effect of baclofen could be inhibited or even reversed by CGP 35348, which has a depressive effect per se, similar to the effects of baclofen given in the upper range of doses.

Animals↗
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↗
PubMed1984

Vestibulo-ocular disturbances in rats exposed to organic solvents.

The influence of different kinds of industrial solvents on the vestibular function of rats has been studied by recording nystagmus, induced by accelerated rotation. The effect was related to the blood levels of the solvents. One group of solvents, including halogenated saturated hydrocarbons like dichloromethane, caused depression of the vestibulo-oculomotor reflex (VOR). Another group, including benzene compounds like xylene, toluene, styrene and cumene and halogenated unsaturated hydrocarbons like trichloroethylene caused an excitation of the VOR. The most striking chemical similarity between the different solvents in the last group is the occurrence of double-bonds. If the animals were exposed simultaneously to solvents from both groups the excitatory effect prevailed and was even potentiated. It is suggested that solvents cause depression or excitation of the VOR by interaction with central pathways in the reticular formation and the cerebellum.

Animals↗