Complaints of vertigo from people who are exposed to industrial solvents have focused interest on their toxic effect on the nervous system. In order to evaluate the influence of an organic solvent, xylene, on the mammalian vestibular system, a series of rabbit experiments were performed. To achieve a constant concentration, the xylene was infused as a lipid emulsion. Blood concentrations were estimated by gas chromatography. Elec-tronystagmography in darkness revealed that at blood xylene concentrations of 30 ppm all rabbits had a positional nystagmus. The beat direction was the opposite of positional alcohol nystagmus. Another difference between the alcohol and the xylene reaction was that rotatory nystagmus responses were exaggerated. The relations between the present findings and the reactions and blood concentrations in people exposed to industrial solvents are discussed.
The Swedish reading span test (Rönnberg, Lyxell, Arlinger, & Kinnefors, 1989) is often used to assess working memory capacity (WMC) in the field of cognitive hearing science. The test has proven useful as a predictor of speech recognition in noise in adverse conditions. It has been used in a wide range of experimental studies and has been translated to several languages. The purpose of this paper was to provide reference data for the Swedish reading span test (Rönnberg et al., 1989) in a large sample of adults with hearing impairment aged 50-89 years that are representative of patients seeking rehabilitation at audiological clinics. Data from finished and ongoing projects were collated and reanalyzed for this purpose. The original full version and a shortened version of the test were compared, in terms of percentage correct. In addition, performance on the full version was compared across two different age-cohorts, 50-69 year olds and 70-89 year olds. Frequency distributions and percentile scores are reported, as well as relations with demographic variables, and speech recognition in noise. Results showed that reading span performance was related to age, but not sex, with lower scores in older participants. Pure tone hearing thresholds accounted for a small but significant amount of the variance such that higher reading span scores were related to better hearing. The frequency distributions of scores did not differ across the two versions of the test, but the long version seemed to be more sensitive to age. Performance in both versions was significantly correlated with speech recognition in noise. Regression analyses however showed that reading span explained additional variance in speech in noise recognition, after the effects of age and pure tone hearing thresholds were accounted for, only in the 50-69 year olds. These findings are discussed in relation to age-related differences in the ability to recruit cognitive resources in the service of speech communication.
This paper describes a new approach to auditory diagnostics, which is one of the central themes of the EU-project HEARCOM. For this purpose we defined a so-called "Auditory Profile" that can be assessed for each individual listener using a standardized battery of audiological tests that - in addition to the pure-tone audiogram - focus on loudness perception, frequency resolution, temporal acuity, speech perception, binaural functioning, listening effort, subjective hearing abilities, and cognition. For the sake of testing time only summary tests are included from each of these areas, but the broad approach of characterizing auditory communication problems by means of standardized test is expected to have an added value above traditional testing in understanding the reasons for poor speech reception. The Auditory profile may also be relevant in the field of auditory rehabilitation and for design of acoustical environments. The results of an international 5-center study (in 4 countries and in 4 languages) will be presented and the relevance of a broad but well-standardized approach will be discussed.
Twenty-eight partners participated in the FP6 EU-funded project HearCom, with the goal to improve hearing in our communication society. One of the main achievements has been the provision of advanced hearing screening tests by telephone and Internet. For hearing diagnostics it was aimed at the harmonization of hearing diagnostic tests within Europe. For this the concept of the Auditory Profile has been developed with several tests for various languages. Hearing problems are also a result of adverse acoustical circumstances for which the effects have been studied, modelled and evaluated for hearing impaired. For hearing rehabilitation a large scale comparison study was performed on signal enhancement techniques (algorithms) for hearing devices. Modern technology may assist on hearing and communication by the use of wireless technology and automatic speech transcription. On this it is shown that improvements for auditory communication can be obtained, but that technology should develop further. An overview is given on the HearCom portal with sections for screening diagnostics, hearing information for the public and professionals, and a new service called HearCompanion that provides step-by-step support for the hearing rehabilitation process.
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.
A broad frequency-band rotatory test has been used to quantify compensatory eye movements in 13 healthy subjects during light and darkness conditions. Eye movements were recorded by EOG. Head movements were recorded either by a potentiometer attached to the chair's axis of rotation or by an angular rate sensor attached to a bite-board. Gain and phase values between eye and head velocity were calculated. A systematic error in the higher frequency range is introduced in the results by assuming head movement equal to chair movement. Different instructions in the dark can alter the gain values at lower frequencies (up to 2 Hz) during sinusoidal stimulation. During pseudorandom stimulation no such differences can be obtained. During all test conditions with the rate sensor the gain values approach unity at about 3 Hz.
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.
15 healthy volunteers were investigated in a vestibulo-oculomotor test battery during toluene exposure. The concentration was comparable to the threshold limit value. The results were compared to an identical air experiment. The intoxication caused an impaired visual suppression during a pseudo-random oscillatory swing test and also an increased saccade speed. Other vestibular-oculomotor parameters were normal. The findings are in accordance with our earlier study on styrene in humans, showing that the visual suppression test and the saccade test are sensitive parameters assessing neurotoxic influences by organic solvents.