The high incidence of ear disease and hearing loss in Australian Indigenous children is well documented. This study aims to consider the effect of hearing loss and native-language phonology on learning English by Australian Indigenous children. Twenty-one standard Australian English consonants were considered in a consonant-vowel (CV) context. Each consonant was paired with each other to yield 'same' and 'different' consonant pairs. The participants were classified into three groups: (1) English speaking, non-Indigenous children without history of hearing loss and otitis media (three males, four females, mean age 13.7 years); (2) Indigenous children speaking Tiwi as their native language, without history of hearing loss and otitis media and learning English as a second language (two males, three females, mean age 12.1 yrs) and (3) Indigenous children speaking Tiwi as their native language, with a history of hearing loss and otitis media since childhood (six females, mean age 13.1 years). The reaction time from the onset of the second word of the pair to the pressing of a 'same' or 'different' button was measured. The results demonstrated that discrimination of consonants was differentially affected by differences in language. Hearing loss further complicated the difficulties that a child was already having with English. Hearing loss tended to affect discrimination of English consonants more than those in the native language. The study suggests that amplification alone does not suffice and recommended that phonological awareness programs, with or without amplification, need to be part of a reading program from preschool with Indigenous children learning English as a 'school' language.

An antimicrobial agent, kanamycin, has been shown to produce as an untoward effect, ototoxicity. The purpose of this study was to investigate differential effects of kanamycin ototoxicity as a function of Rx timing with regard to circadian rhythms. Four groups of comparable weight Sprague-Dawley rats received a daily subcutaneous dosage of 225 mg/kg kanamycin sulfate with each receiving the antibiotic at a different time: 8 AM (8A), 2 PM (2P), 8 PM (8P), and 2 AM (2A). The rats were housed in separate cages, in a room on a light-dark (12:12) illumination cycle with light between 6 AM and 6 PM. Hearing loss was assessed with the auditory brainstem response (ABR) using pure tone stimuli at 8, 16, 24, and 32 kHz. ABR measures were obtained before dosing began and 2, 4, and 6 weeks after the initial dosing. Kanamycin produced a hearing loss which reflected the total dosage given to each group. Significant differences in physiologic thresholds were observed for both timing of the daily dosage (p less than 0.05), and the 2, 4 and 6 week testings (p less than 0.001). After 2 weeks, the 8A group showed an average hearing loss of 11.5 dB at 32 kHz, with the other timed treatment groups exhibiting minimal effects (3.0-6.5 dB). For the 8A group at this frequency, the loss progressed at 4 (19.5 dB) and 6 (22.5 dB) weeks. The 2P group after 4 weeks exhibited similar losses as the 8A group for this frequency, with the loss at 6 weeks being even greater (34.0 dB). The 8P and 2A groups exhibited only slight losses over all frequencies.(ABSTRACT TRUNCATED AT 250 WORDS)

The relationships between each of seven predictor variables and the relative degree to which 84 normal and hearing-impaired children used audition or vision in their perception of word stimuli were investigated. The children's relative use of audition or vision was assessed by the auditory-visual presentation of monosyllabic word stimuli in which the visual word stimuli were in conflict with those presented acoustically. Six of the seven predictor variables were significantly correlated with the performance scores obtained within the auditory-visual conflict condition. Only pure-tone average hearing level and auditory word identification performance, however, made unique contributions toward predicting the degree to which audition or vision was used in the perception of the word stimuli. We concluded that the relative use of audition or vision was almost completely related to their auditory capabilities as represented by the children's unaided threshold sensitivity and aided speech reception performance.

Mice of the C57 B1/6 strain were used to assess auditory deficits due to methyl mercury chloride intoxication. Auditory Brainstem Responses were obtained to pure-tone stimuli from 4 to 78 kHz. Physiologic thresholds were compared with behavioral methods for determining audibility in mice. Two dosage levels were studied; 4 and 8 mg/kg. Recordings were taken weekly, for each mouse, for 3 consecutive weeks after initial injection. Analysis of physiologic threshold and latency indicated that methyl mercury chloride causes auditory deficits at all frequencies tested with the greater effect in the higher frequencies. Additionally, latencies indicated nerve conduction hypersensitivity in the brainstem.

The aminoglycoside antibiotic gentamicin can cause both ototoxicity and nephrotoxicity, the severity of which varies with circadian time of daily treatment. However, it is not yet resolved if such drug-induced adverse effects are independent or dependent phenomena. Two groups of 9 female Sprague-Dawley rats (200-250 g), each housed separately, entrained to a 12h light (06:00 to 18:00h)-12h dark cycle, received a daily subcutaneous injection of 100 mg/kg gentamicin. One group was treated at the beginning of the activity span, 2 HALO (Hours After Lights On), and the other at the beginning of the rest span, 14 HALO. Global toxicity was gauged both by body weight loss relative to the pre-treatment baseline and number of deaths. Ototoxicity, i.e., hearing loss, was assessed by changes in Auditory Brainstem Responses (ABR) for pure tone stimuli of 8, 16, 24, and 32 kHz before and after 2 and 4 weeks of gentamicin treatment. Renal toxicity was evaluated by changes in urinary N-acetyl-β-glucosaminidase (NAG)/creatinine (CR) concentration ratio before and after each week of treatment. In a complementary substudy of separate but comparable 2 and 14 HALO groups of rats, blood samples were obtained before and 30, 60, 120, and 240-mins post-subcutaneous injection of 100 mg/kg gentamicin. Number of animal deaths was greater in the 2 (4 deaths) than 14 HALO (1 death) group, mirroring more severe initial (1st 2 weeks of treatment) body weight losses from baseline, being more than 2-fold greater in animals of the 2 than 14 HALO group. Ototoxicity progressively worsened during treatment; although, the extent of hearing loss varied according to circadian time of treatment across all frequencies (p<0.05), particularly the 24 and 32 kHz ones (both p<0.005), both at the 2 and 4 week assessments. At 32 kHz after 4 weeks of gentamicin dosing, the 2 HALO group showed an average 42 dB hearing loss, while the 14 HALO group exhibited only an average 10 dB loss. ABR response latencies were longer for the 2 than 14 HALO rats. The time course of nephrotoxicity differed from that of ototoxicity. The mean urinary NAG/CR ratio peaked after the 1st week of treatment, averaging 13.64-fold greater than baseline for the 2 HALO-treated animals compared to 7.38-fold greater than baseline for the 14 HALO-treated ones. Ratio values declined thereafter; although even after the 2nd week of dosing, they remained greater in the 2 than 14 HALO group (averaging 8.15-fold greater and 2.23-fold greater than baseline, respectively). Pharmacokinetic analysis of the blood gentamicin values revealed slower clearance, on average by ∼25% (p<0.001), in the rats of the 14 than 2 HALO group (x̄ ± S.E.: 3.22 ± 0.49 and 4.53 ± 0.63 mL/min/kg, respectively). The study findings indicate robust difference of the time course in rats of both treatment groups of gentamicin-induced ototoxicity and nephrotoxicity, supporting the hypothesis these organ toxicities are independent of one another, and further suggest the observed treatment-time differences in gentamicin adverse effec...