Using statistical decision theory to predict speech intelligibility. II. Measurement and prediction of consonant-discrimination performance.

The speech recognition sensitivity (SRS) model [H. Müsch and S. Buus, J. Acoust. Soc. Am. 109, 2896-2909 (2001)] was tested by applying it to consonant-discrimination data collected in this study. Normally hearing listeners' abilities to discriminate among 18 consonants were measured in 58 filter conditions using two test paradigms. In one paradigm, listeners chose among all 18 stimuli. In the other, response alternatives were restricted to the correct response and eight consonants that were randomly selected among the 17 incorrect response alternatives. The effect of the number of response alternatives on performance can be described by statistical decision theory. Most filter conditions included one or more sharply filtered narrow bands of speech. Depending on the selection of bands, listeners' performance in multi-band conditions falls short of, equals, or exceeds the performance expected from multiplication of the error rates in the individual bands. The performance advantage in multi-band conditions increases with average band separation. The SRS model provides a good fit to the data and predicts the data more accurately than does the speech intelligibility index.

Using statistical decision theory to predict speech intelligibility. I. Model structure.

This article introduces a new model that predicts speech intelligibility based on statistical decision theory. This model, which we call the speech recognition sensitivity (SRS) model, aims to predict speech-recognition performance from the long-term average speech spectrum, the masking excitation in the listener's ear, the linguistic entropy of the speech material, and the number of response alternatives available to the listener. A major difference between the SRS model and other models with similar aims, such as the articulation index, is this model's ability to account for synergetic and redundant interactions among spectral bands of speech. In the SRS model, linguistic entropy affects intelligibility by modifying the listener's identification sensitivity to the speech. The effect of the number of response alternatives on the test score is a direct consequence of the model structure. The SRS model also appears to predict the differential effect of linguistic entropy on filter condition and the interaction between linguistic entropy, signal-to-noise ratio, and language proficiency.

On loudness at threshold.

Absolute thresholds for and loudness matches between pure tones and four- and ten-tone complexes were used to assess the form of the function relating loudness to sensation level, SL, at low and moderate levels. The components of the tone complexes had equal SLs and were separated by one, two, four, or six critical bands. Six listeners with normal hearing were tested. The thresholds for the multitone complexes indicate that they generally can be detected even when the level of a single component is a few dB below the threshold. The average detection advantage is consistent with predictions for multiple observations in independent, frequency-selective auditory channels, but differences among listeners are apparent. The loudness matches also vary somewhat among listeners. Five of the six listeners matched tone complexes composed of subthreshold components to a pure tone a few dB above threshold. This indicates that the loudness of tones at or even below threshold is greater than zero for these five listeners. A simple model of loudness summation was used to obtain loudness functions from the individual listeners' loudness matches. The slopes of the loudness functions [log(loudness) plotted as a function of log(intensity)] generally exceed unity at low levels and are near 0.2 at 40 dB SL. This shallow slope at moderate levels agrees with loudness functions derived from data on temporal integration of loudness. The average loudness function derived from the present data also is in good agreement with a variety of previous data obtained by magnitude estimation, magnitude production, ratio production, and measurements of binaural loudness summation.

CA 125 in normal tissues and carcinomas of the uterine cervix, endometrium and fallopian tube. I. Immunohistochemical detection.

The distribution of cancer antigen 125 (CA 125) has been investigated in normal tissues and carcinomas of the Müllerian duct by immunohistochemical methods using the monoclonal antibody OC 125. Detection of CA 125 was most intense in cryostat sections and decreased in formalin fixed and paraffin embedded tissues according to the duration of fixation. Enzymatic digestion with neuraminidase or alkaline hydrolysis abolished specific staining suggesting the antigen is a sialylsaccharide bound to protein by alkali-labile linkage. Immunohistochemical staining demonstrated the presence of CA 125 in all normal glandular epithelia of the endocervix, endometrium and fallopian tube in different distribution patterns. In normal endometrium the cellular distribution pattern was related to the menstrual cycle. In endocervical, endometrial and tubal adenocarcinomas CA 125 was found in 73% of cases. In glandular structures the antigen was concentrated at the luminal surface of the tumour cells, in solid tumour areas it was spread throughout the cytoplasm or concentrated in large cytoplasmic vacuoles. The expression of CA 125 was considerably lower in solid tumour areas. These data show that CA 125 is not a true "tumour marker", but a product of female genital mucosae and of their cancerous derivates provided their synthesizing ability is not lost in the course of pathologic differentiation.

Methylmercury chloride induces learning deficits in prenatally treated rats.

Methylmercury chloride (MMC) was given to pregnant rats on the 6th, 7th, 8th, and 9th day after conception in doses of 0.05 and 2.0 mg/kg/day. The female offspring of these animals were tested 90 days after birth for learning ability using operant conditioning procedures. The rats were kept at 90% of their normal body weight and trained in a lever-box to press a bar in order to obtain a food pellet. Significant differences in the acquisition speed became apparent when the ratio of bar presses to reward was increased in a classical contingency of differential reinforcement of high rates even at MMC-doses of 4 X 0.05 mg/kg. These differences were not found in the general motility level nor in motor coordination.