The reliability of the SCAN test: results from a primary school population in the UK.

The SCAN test utilizes a pre-recorded tape, with carrier phrase and target words spoken by an American English speaker, to screen for central auditory processing disorders in children. The aim of the present study was to establish whether the normative data, derived from American school children, are applicable to a UK primary school population. The SCAN test was administered to 133 British primary school children with normal hearing, stratified into one-year age bands. Mean scores from the UK sample were found to be significantly lower than US mean scores for the most of the age bands. Analysis of word errors indicates accent and word familiarity effects. This evaluation of the SCAN indicates that the test is not directly applicable to British children as currently normalized. The present study provides interim norms for the American recording for age bands six to 11 years. It is recommended that the test material is recorded by a UK English speaker, with substitution of high error-rate target words, followed by normative data collection for the new test material.

Detection and intensity discrimination of brief tones as a function of duration by hearing-impaired listeners.

For normal listeners, difference limens for intensity (DLs) for Gaussian-shaped tone pulses are largest at medium pulse durations (corresponding to about five cycles of the tonal carrier) when the pedestals are 10 dB above threshold, either in quiet or in a pink noise background. One explanation for this is that worst performance occurs when the internal representation of the tone pulses is most compact in time and frequency, affording minimal opportunity for 'multiple looks' (Van Schijndel et al., J. Acoust. Soc. Am. 105 (1999) 3425-3435). However, the mid-duration worsening is largest for medium overall levels, suggesting an involvement of compression on the basilar membrane (BM), which is also greatest at medium levels (Baer et al., J. Acoust. Soc. Am. 106 (1999) 1907-1916). If this is so, the mid-duration worsening should be reduced when BM compression is reduced by outer hair cell damage. To test this, subjects with sensorineural hearing losses were tested using 1-kHz or 4-kHz Gaussian-shaped tone pulses, in quiet or in pink noise that raised thresholds by 10-20 dB. For subjects with mild losses, poorest performance was sometimes found for medium durations. For more severe losses, intensity DLs tended to improve monotonically or remain roughly constant with increasing duration. Performance overall tended to be better for subjects with greater hearing losses. The results are more consistent with an explanation based on BM compression than with an explanation based on multiple looks.

Comparison of three procedures for initial fitting of compression hearing aids. I. Experienced users, fitted bilaterally.

We compared the effectiveness of three procedures for the initial fitting of hearing aids with multi-band compression: (1) CAMEQ, which aims to amplify speech so as to give equal loudness per critical band over the frequency range important for speech intelligibility, and to give similar overall loudness to 'normal': (2) CAMREST, which aims to amplify speech so as to restore 'normal' specific loudness patterns, over a wide range of speech levels; (3) DSL I/O, which aims to map the dynamic range of normally hearing people into the reduced dynamic range of hearing-impaired people, with 'full' restoration of audibility. Ten experienced hearing aid users with moderate sensorineural loss were fitted bilaterally with Danalogic 163D digital hearing aids, using each procedure in turn; the order was counterbalanced across subjects. The fitting required specification of gains for input levels of 55 and 80 dB SPL at six centre frequencies. Real-ear measurements were made to ensure that target gains were reached (+/-3 dB). Immediately after fitting with a given procedure, and one week after fitting, the gains were adjusted when required by the minimum amount necessary to achieve acceptable fittings. The amount of adjustment required provides one measure of the adequacy of the initial fitting. On average, the adjustments were smallest for the CAMEQ procedure. The gain changes were slightly larger for the CAMREST procedure and were largest of all for DSL I/O. For the latter, the gain changes were mostly negative, especially for high frequencies and the higher input level. This indicates that the DSL I/O procedure prescribes more high-frequency gain than is preferred by adult users. After these gain adjustments, users wore the aids for at least three weeks before filling out the APHAB questionnaire and taking part in laboratory measurements of the speech reception threshold (SRT) for sentences in quiet and in steady and fluctuating background noise at levels of 60 and 75 dB SPL. Following these tests, the hearing aids were re-fitted with the next procedure. The scores on the APHAB test and the SRTs did not differ significantly for the three procedures. We conclude that the CAMEQ and CAMREST procedures provide more appropriate initial fittings than DSL I/O.

Use of the distraction hearing test in children with congenital ocular motor apraxia.

Five of the 14 children with congenital ocular motor apraxia under Addenbrooke's Hospital Ophthalmology Department were assessed in tertiary audiology clinics. These referrals had been made after the children had failed to pass the 8-month hearing screen and second tier community-based assessment using distraction testing. In all cases they were found to have normal hearing on further assessment. The false positive response with the distraction test is likely to be due to the child's inability to initiate appropriate head and eye movements. We present a case report on a child with congenital ocular motor apraxia (COMA) at tertiary hearing assessment.

Is central hyperacusis a symptom of 5-hydroxytryptamine (5-HT) dysfunction?

The subjective symptom of hyperacusis is described. The terms 'hyperacusis' and 'phonophobia' are considered to be synonymous as there is no recognized distinction between these two descriptions. Peripheral auditory pathologies with associated hearing sensitivity are reviewed and the likely mechanisms underlying the hyperacusis are listed. The neurological conditions, which have been reported to occur with hyperacusis, are reviewed. A separate aetiology of central hyperacusis is therefore proposed, with a symptom profile distinct from the peripheral hyperacusis. A common factor to neurological conditions with hyperacusis, is disturbance of 5-HT (5-hydroxytryptamine) or serotonin function. The research literature on the role of 5-HT in sensory modulation (specifically auditory startle) in animals is presented. It is proposed that 5-HT dysfunction is a probable cause of increased auditory sensitivity manifested as central hyperacusis or phonophobia.

Observations bearing upon semi-circular canal dynamics.

It can be shown that following an angular velocity step stimulus delivered in darkness, the nystagmic responses can be effectively 'dumped' after any interval in time by the application of an appropriate step decrement in velocity. In practise the null velocity is bracketed between those step decrements inducing just detectable nystagmus to left and right and can be determined within a range of +/- 1.5 degrees s-1. With test stimuli of 22, 44, and 64 degrees s-1 the 'dump' velocities have been established at varying intervals in time on four normal subjects. Contrary to expectations the dump velocity/time relations for all three test stimuli follow a convergent linear course. The dump velocities are unaffected by fixation suppression of the nystagmus induced by the test stimuli. The seeming irrelevance of nystagmus generation to dump velocity values is confirmed by the good correspondence with the results of a separate study using the oculogyral illusion as a guide in place of nystagmus. These findings are difficult to relate to conventional concepts of cupular dynamics.