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Biomedical subjects

H S Colburn

Publications and source records attributed to H S Colburn.

13 recordsLinked to original sources
PubMed1992

Frequency dependence of binaural performance in listeners with impaired binaural hearing.

Binaural performance was measured as a function of stimulus frequency for four impaired listeners, each with bilaterally symmetric audiograms. The subjects had various degrees and configurations of audiometric losses: two had high-frequency, sensorineural losses; one had a flat sensorineural loss; and one had multiple sclerosis with normal audiometric thresholds. Just noticeable differences (jnd's) in interaural time, interaural intensity, and interaural correlation as well as detection thresholds for NoSo and NoS pi conditions were obtained for narrow-band noise stimuli at octave frequencies from 250-4000 Hz. Performance of the impaired listeners was generally poorer than that of normal-hearing listeners, although it was comparable to normal in a few instances. The patterns of binaural performance showed no apparent relation to the audiometric patterns; even the two subjects with similar degree and configuration of hearing loss have very different binaural performance, both in the level and frequency dependence of their performance. The frequency dependence of performance on individual tests is irregular enough that one cannot confidently interpolate between octaves. In addition, it appears that no subset of the measurements is adequate to characterize the performance in the rest of the measurements with the exception that, within limits, interaural correlation discrimination and NoS pi detection performance are related.

Acoustic Stimulation↗
PubMed1992

Test of a model of auditory object formation using intensity and interaural time difference discrimination.

A model of auditory object formation and an experimental evaluation of the model are described. Specifically, predictions for intensity discrimination and interaural time difference discrimination for the central component of a three-component harmonic complex are evaluated empirically. The onset time of the central, target component is varied relative to the onset times of the remaining, interferer components in order to vary the degree of fusion (versus perceptual segregation) of the target and the interferers. The model, which is based on the idea of attenuation of the components in the nonattended auditory image (in the case of segregated images), predicts lower sensitivity to information at the target component for the fused versus segregated target, and equal sensitivities for completely segregated targets and targets presented in isolation. Results are presented for four subjects with component frequencies of 400, 600, and 800 Hz and with onset time differences of 0 or 250 ms. The target duration was always 100 ms and offset times were the same for all components. The subjective results were as expected, with synchronous onsets yielding one sound object, and asynchrony of the central component yielding two sound objects. Also, the empirical results on interference in the synchronous case were in qualitative agreement with the above predictions. However, significantly more interference was found than was predicted for both synchronous and asynchronous conditions. In fact, the amount of interference found contradicts the simple attenuation model of object formation.

Adult↗
PubMed1991

Detection of tones in reproducible narrow-band noise.

Hit and false-alarm rates were measured for detection of a 500-Hz tone target in each of ten reproducible samples of 1/3-oct bandwidth noise centered at 500 Hz for both NoS pi and NoSo conditions. The effects on hit rates of the starting phase of the target relative to individual noise samples were investigated with two target phase angles for three subjects. The major results are: (1) performance varies significantly over masker waveforms; (2) for NoS pi conditions, the effect of target-to-marker phase angle on hit rates is not significant for these narrow-band maskers; (3) for NoSo conditions, the target-to-masker phase angle has a large effect; (4) no significant correlation between NoSo performance and NoS pi performance is seen across masker waveforms. These results are generally consistent wuth previously reported results for wideband maskers [R.H. Gilkey, D.E. Robinson, and T.E. Hanna, "Effects of masker waveform and signal-to-masker phase relation on diotic and dichotic masking by reproducible noise," J. Acoust. Soc. Am. 78, 1207-1219 (1985)] with an important exception. Specifically, in the wideband experiment, significant correlation between NoSo and NoS pi performance across noise samples was found. In addition, in the wideband experiment, a small yet statistically significant effect of target-to-masker phase was observed in the NoS pi condition.

Adult↗
PubMed1991

Fringed correlation discrimination and binaural detection.

Results are reported from a series of binaural detection and interaural correlation discrimination experiments at 500 Hz. The experiments include fringed correlation discrimination in which the correlation change is restricted to a narrow (38 Hz) target band of frequencies and the reference correlation is maintained in a fringe band of frequencies. This experiment is designed to be analogous to a detection experiment with a narrow-band target; in both cases the correlation changes only inside the target band. A simplified theoretical framework is used to compare the results of the detection and correlation discrimination experiments. Results are consistent with the notion that binaural detection and interaural correlation discrimination are effected by a common mechanism when the reference correlation is unity (as in the NoS pi case). When the reference correlation is zero (as in the NuSo case), detection performance is significantly better than predicted from the measured ability to discriminate interaural correlation.

Attention↗
PubMed1990

Coincidence model of MSO responses.

A simple coincidence model of MSO responses is presented. The model is notable in that it contains no inhibition beyond the synchronization to the fine structure of the stimulus as seen in auditory nerve firing patterns. Output patterns for model cells are simulated and compared with patterns observed in available recordings from EE cells in the MSO. Patterns are compared in terms of discharge rate, vector strength, and period histograms. The patterns generated by the model are found to provide an adequate representation of the data, and it is concluded that a more complex model is not required at this tme to describe available data on MSO firing patterns.

Algorithms↗
PubMed1989

Binaural processing of noisy stimuli: internal/external noise ratios for diotic and dichotic stimuli.

A set of ten digitized statistically similar Gaussian maskers was used in one-internal tone-in-noise detection experiments under diotic (NoSo) and dichotic (NoS pi) interaural conditions. Stimulus/response matrices were generated for each masker in the presence or absence of a target 500-Hz tone. For both NoSo and NoS pi, nonparametric analyses show that response probabilities and sensitivities vary significantly across noise waveforms, indicating a considerable external noise component in subject response variability. A parametric model is developed that maps individual stimulus waveforms onto a decision axis, facilitating evaluation of internal/external noise variance ratios. For both NoSo and NoS pi, internal and external noise variance are of similar magnitude.

Acoustic Stimulation↗
PubMed1979

Discrimination of symmetric time-intensity traded binaural stimuli.

Experiments were conducted to determine the extent to which listeners can discriminate between different combinations of interaural time and intensity for binaural stimulus configurations which eliminate loudness, lateralization, and image-diffuseness cues. A two-interval forced choice paradigm was used, and the task of the subject was to determine the order of two stimuli, each of which was a slowly gated 500-Hz tone with a combination of interaural time and intensity differences that resulted in a centered primary spatial image. The two stimuli to be discriminated were symmetric in that they differed only in the polarity of their interaural differences. Also, in order to reduce artifacts introduced by variations in the coupling of the earphones to the head, acoustic monitoring and compensation was performed both before and after each experimental run. The performance of the two most highly trained subjects is consistent with previous experimental results that indicate an incomplete trading of interaural time and intensity information. The subjective perceptions of these observers are not consistent with previous studies that describe a "time image" and a "time-intensity traded" spatial image.

Acoustic Stimulation↗
PubMed1978

Theory of binaural interaction based on auditory-nerve data. III. Joint dependence on interaural time and amplitude differences in discrimination and detection.

This paper is primarily concerned with issues of symmetry-asymmetry in the joint dependence of binaural performance on interaural time delay and interaural amplitude ratio. The predictions of our model based on auditory-nerve data are shown to be inadequate for available data showing asymmetries in interaural time discrimination. Measured detection thresholds for a 500-Hz tone burst masked by wide-band noise are reported for nonunity amplitude ratios and both polarities of delays in order to test for asymmetries analogous to those observed in the time discrimination case. The detection results show only small asymmetries and are not inconsistent with the model. A general discussion of our model and the implications of available empirical results leads to a suggested modification of the model. We show by an example that modifications of the type we are suggesting are capable of describing the detection data and at least the gross trends of the discrimination data.

Auditory Perception↗
PubMed1978

Theory of binaural interaction based in auditory-nerve data. IV. A model for subjective lateral position.

A model for the subjective lateral position of 500-Hz tones is presented and compared with experimental lateralization data. Previous papers in this series have explicitly described the auditory-nerve response to these stimuli and proposed a binaural displayer that interaurally compares the auditory-nerve firing times. The outputs of the displayer are postulated to represent the only information about detailed firing times that is available to the brain. In the present paper, lateral-position predictions are obtained by a central nonoptimal weighting of these outputs that depends on the interaural intensity difference of the tone. These predictions describe the results of lateralization-matching experiments more accurately and over a wider range of stimulus conditions than previous theories, except for those results which suggest that low-frequency binaural tones can generate multiple perceptual images. The predictions of our model are also consistent with the results of centering and laterality-comparison experiments. It is argued that the data discussed in this paper are generally incompatible with theories that propose a peripheral interaction of interaural timing and intensity information such as the latency hypothesis.

Action Potentials↗