Behavioral effects of aluminum ingestion on animal and human subjects.

Abnormally high brain aluminum concentrations have been detected in hemodialysis patients who died of an unexplained encephalopathy. As a result, this study was undertaken to examine whether the ingestion of aluminum produces behavioral aberrations in non-dialysed human subjects and rats with ostensibly normal renal function. Rats were fed AlCl3 by intubation in varying doses, and tests measuring learning ability, visual temporal acuity, motor coordination and activity were administered. It was found that orally ingested aluminum is absorbed by rats and deposited in the brain. High brain aluminum levels are associated with rapid general activity, decreased ability to maintain roto-rod activity, and increased sensitivity to flicker. Behavioral tests were also given to elderly human subjects and performance correlated with serum aluminum level. High serum levels of aluminum in elderly humans are associated with impaired visuo-motor coordination, poor long-term memory, and increased sensitivity to flicker.

Verbal coding strategies used by hearing-impaired individuals.

A paired-associate verbal learning task was used to determine the type of perceptual coding strategies hearing-impaired persons use in auditory perceptual processing of language. Four lists of word pairs were devised, whereby the word pairs in each list were characterized as sharing either similar sign-similar meaning, dissimilar sign-similar meaning, similar sign-dissimilar meaning, or dissimilar sign-dissimilar meaning. Severely hearing-impaired subjects were required to replace the missing word associated with the word pairs. The results showed that, while the subjects were able to code the verbal material on both a sign basis and a semantic basis, the semantic coding strategy appeared to be more efficient than the sign coding strategy. The findings are related to earlier investigations and are explained according to a theoretical model of perception.

Oral stereognosis: effect of varying form set, answer type, and retention time.

The oral stereognosis abilities of 40 young adults were investigated as a function of oral stereognosis form sets (four sets), retention time (unlimited and 5 sec), and response type (oral discrimination and visual recognition). Results showed that the Penn State forms were the easiest for the subjects under all conditions and that the Ringel form set was the most difficult under all conditions. A significant interaction between oral form sets and answer type indicated that the visual recognition task, rather than the discrimination task, was primarily responsible for the differences between the oral form sets. A three-way interaction revealed that the retention times had a significant effect on the two form sets of medium difficulty (NIDR-10 and NIDR-20) for the visual recognition condition. The results are discussed in view of their research and clinical implications.

Discrimination of time-altered sentential approximations and monosyllables by children with reading problems.

This study compared the performance of normal-reading and reading-impaired children using time-compressed three- and five-word sentential approximations to full grammaticality, and the Word Intelligibility by Picture Identification (WIPI) test presented with and without pictures. Results suggested that reading-impaired children could be differentiated from normal readers by scores on these measures and by types of errors made. Theoretical and pragmatic implications are discussed.

Lead and lag effects associated with the staggered spondaic word test.

This study was designed to determine to what extent onset times of overlapping spondaic words were controlled in the development of the Staggered Spondaic Word Test (SSW) (List EC), a measure which is used to detect central auditory dysfunction. The results showed that the SSW (List EC) was not well controlled relative to onset times. Further, the scores of 10 normal-hearing listeners who were administered the SSW were found not to suffer when the onset times were closely matched. The results were related to thn of dichotically presented stimuli.

Intelligibility of time-altered speech in relation to chronological aging.

The Northwestern University Auditory Test Number 6 (NU-6) measure of speech discrimination was time compressed and presented to four age groups ranging from 54 to 84 years of age. Experimental stimuli were presented at sensation levels of 24, 32, and 40 dB to an equal number of right and left ears and male and female subjects. Results indicated that intelligibility decreased as a function of increasing time compression and age and decreasing sensation level. Changes in speech intelligibility associated with the aging process appear to be closely allied to changes in the temporal resolving power of the central auditory processing system.

Time-compressed spondaic words as a measure of speech reception threshold.

Lists A and B of the C.I.D. W-1 spondees were time-compressed with a Lexicon Varispeech I unit. SRTs were collected from one ear of each of 60 normal-hearing young adults. No list differences were found. The R ears of 30 Ss were superior to the L ears of 30 Ss by 0.8 db. Mean SRTs collapsed across lists and ears were 9.3-10.7-13.2 db for the compressions in the order 0-40-60%. The differences were judged clinically insignificant, nevertheless when considered with earlier data it may be concluded that time-compressed spondees may come to have use as a clinical device.

Intelligibility of time-compressed sentential stimuli.

Time-compressed monosyllables have been studied relative to the assessment of central auditory disorders. In certain instances, sentential stimuli may be more useful than word lists in central auditory testing, particularly when results may be contaminated by concomitant peripheral hearing losses. Central Institute for the Deaf (CID) and Revised CID sentence lists and a contrived sentential approximation task were presented to 96 normal hearing young adults at time-compression ratios of 0%, 40%, 60%, and 70%, under sensation levels of 24 and 40 dB. The CID and RCID stimuli were more intelligible than the sentential approximations. The results are presented and discussed as they pertain to central auditory testing and are compared to earlier data using consonant-nucleus-consonant monosyllabic stimuli.

Adults' item and order errors on sequences of time-compressed rhyming words.

This investigation provided normative data for the intelligibility of time-compressed (TC) phonemes in 40 normal-hearing adults aged 18-26 yrs. Individual Ss were presented with 5-word rhyming sequences from the Fairbanks Rhyme Test (e.g., cat-bat-hat-mat-rat) sent to a monaural earphone at 40 db re SRT, and required to write the initial phonemes in the order as heard. Sequences were either at normal speed or at 60% TC, either unmasked or under contralateral multitalker masking at 65 db re SRT, counterbalanced for ear (R,L) and presentation order (R-L, L-R). Significant effects for both TC and masking were obtained with separate analyses of item and order errors. The findings support the diagnostic potential of these stimuli in detecting and documenting subtle auditory perceptual problems in adults, since they were consistent with findings for other stimuli known to be diagnostically effective and have the further property of tapping memory and sequencing abilities. Significant interactions with the factor of ear (R vs L) suggest that the stimuli may be especially sensitive to ear differences. Similar studies with groups such as those with high-level aphasia, sickle cell anemia, repeated strokes, etc., should be forthcoming to determine the clinical utility of these materials and procedures.

The performance of children with auditory perceptual disorders on a time-compressed speech discrimination measure.

A time-compressed version of the PB-K 50 speech discrimination measure was administered to 20 children diagnosed as displaying auditory perceptual disorders. Results indicated that these children performed equally well at both 0 and 30% time compression. Performance decreased significantly at 60% time compression. Comparison of the results with normative data indicated that performance of the two groups of children was similar at the 30% time compression condition but that children with auditory perceptual disorders performed poorer at both 0 and 60% time compression. The results were discussed relative to short-term memory abilities.

Children's performance on a binaural fusion task.

Binaural auditory fusion of 108 children (4, 6, and 8 years old) was studied using three lists of monosyllable words (WIPI) presented at two sensation levels (30 and 40 dB). The words were processed to produce three bandwidth conditions (100, 300, 600 Hz) and were administered via three presentation modes (binaural fusion 1, diotic, binaural fusion 2). Results showed improved discrimination scores with increasing age, sensation level, and filter bandwidth. Diotic scores were better than the widest bandwidth (600 Hz) condition. The results confirmed the contention that prior research results were equivocal due, in large measure, to procedural variability. Methods for reducing such variability and enhancing the clinical viability of binaural fusion tasks are suggested.

Children's perception of temporally distorted sentential approximations of varying length.

The purpose of this study was to investigate the abilities of second-grade and fourth-grade children to auditorially process three orders of three- and five-word sentential approximations, which had normal interstimulus intervals (ISI) and ISIs of 200 and 400 ms. Results showed that percent correct scores decreased as a function of increasing sentence length and ISI, and decreasing order of sentential approximation and grade level. The results are discussed relative to theoretical notions of short-term memory and auditory perceptual processing as well as potential clinical applications.

Children's perception of time-compressed speech on two measures of speech discrimination.

Time-compressed versions of the WIPI and PB-K 50 speech discrimination measures were presented at two sensation levels to 60 children divided into three age-groups of 20 each. Results showed that average intelligibility scores increased as a function of increasing age and sensation level and decreased with increasing amounts of time compression. The PB-K 50 measure was found to be more difficult than the WIPI for each age-group under each condition of time compression and sensation level. The several factors under study were found to interact. The results are discussed relative to open- versus closed-message set response tasks and the implications for audiological diagnoses of children with central auditory processing problems.

Performance of noise-induced hearing-impaired listeners on time-compressed consonant-nucleus-consonant monosyllables.

The effects of time compression on the intelligibility of consonant-nucleus-consonant (CNC) monosyllables was investigated by presenting six conditions of a time-compressed versions of the Northwestern University Auditory Test no. 6; at four sensation levels, to nine subjects with noise-induced sensorineural hearing impairments. Results indicated that intelligibility gradually decreased as the ratio of time compression increased, with a dramatic breakdown at the highest ratio of time compression. A typical roll-over phenomenon was also found. Results are related to data on normal listeners.

Perception of time-compressed consonant-nucleus-consonant monosyllables by non-native speaker/listeners of English.

Recent investigations of time-altered speech have dealt with the effect of time compression and sensation level on intelligibility scores of native speaker/listeners of English. In the present investigation, the intelligibility of time-compressed consonant-nucleus-consonant monosyllables was studied using English speaker/listeners whose native languages are Spanish or Indo-Dravidian. Results supported earlier findings in that intelligibility decreased as a function of increasing percentage of time compression and decreasing sensation level. This effect was more prominent for the Indo-Dravidian than for Spanish speaker/listeners. The Spanish group of subjects showed generally lower difference scores than did the Indo-Dravidian group when compared to native English speaker/listeners.

Use of frequency-shifted/time-compressed speech with hearing-impaired children.

Several electromechanical aids to education for hearing-impaired children have been studied. One method that has received minimal attention is that of frequency-shifted/time-compressed (FS/TC) speech. This study was designed to determine if intelligibility scores on a standard intelligibility measure for children, whereby the words on the test was modified by 35% FS/TC, would show improvement from a pre- to a post-testing session. Nine hearing-impaired children were presented a 0 and 35% FS/TC speech pretest, then trained for 15 days using 35% FS/TC speech signals, and subsequently were presented a 0 and 35% FS/TC speech post-test. A second group of 9 hearing-impaired children were presented similar pre- and post-tests, but were trained under a 0% FS/TC speech condition. The group trained under the 35% FS/TC speech condition showed score gains from the pre- to post-test session, whereas the 0% FS/TC speech group showed essentially no gains from the pre- to the post-test session. The potential application of FS/TC speech to the education of hearing-impaired children were discussed.

Age and sex differences on preferred listening rates for speech.

The preferred listening rate of speech was investigated in 30 men and 30 women aged 18--87 yrs. Ss were presented auditorially a reading of a standard prose passage and themselves adjusted a Varispeech I time compressor/expander to yield preferred listening rate. Differences in rate preference were significant for age but not for sex differences. Results support previous reports of auditory perceptual differences with increasing age and suggest that variability in previous reports of preferred listening rates may have been due in part to age differences of the Ss.