Leslie (Les) R. Bernstein - US grants

The purpose of the proposed research is to gain a broader understanding of the manner in which interaural temporal disparities (ITD's) and interaural intensitive disparities (IID's) ar processed within high- frequency, complex waveforms. One subset of experiments concerns the evaluation of the degree to which ITD's and/or IID's account for the rather large release from masking which can be obtained when dichotic as compared to diotic signals are employed (the high-frequency MLD). "Natural" as well as specially constructed digital stimuli will be employed which will allow for the variation and measurement of the interaural parameters in a controlled and predictable fashion. In addition, listeners' absolute sensitivities to the presence of such cues within high-frequency, complex waveforms will be measured. A second subset of experiments involves a parametric investigation of the conditions under which listeners' use of interaural disparities within a (target) stimulus at one spectral locus is affected by the presence of (interfering) stimuli at different spectral loci. The manner in which these interfering stimuli affect the lateral position (measured via an acoustic "pointing" task) of the target, sensitivity to the presence of interaural disparities within the target and detection of targets within a background of noise (the MLD) will be investigated. A third subset of experiments will assess to what degree processing of ITD's within the envelopes of high-frequency stimuli is analogous to the processing of ITD's within the fine-structure of low-frequency stimuli. Detection of ITD's and extent of laterality will be measured for bands of noise and sinusoidally amplitude modulated tones (SAM) with center frequencies between 4 kHz and 15 kHz. In addition, an investigation of the conditions under which an envelope-based "binaural beat" occurs with SAM tones and two-tone complexes will be conducted.

The objective of the proposed research is a comprehensive, systematic and parametric evaluation of and how well the binaural auditory system processes interaural temporal disparities (ITDs) and interaural insensitive disparities (IIDs). The experiments proposed are focused on two general topics: 1) the characterization of the binaural auditory system as a complex cross-correlator, with the interaural correlation derived from the fine-structure for lower frequencies (below 1200 Hz to 1500 Hz or so) and from the envelope for higher frequencies; 2) the ability of the binaural auditory system to utilize dynamically varying interaural information. By producing ITDs and IIDs within and across selected aspects of narrow-band and/or broadband noises, the goal is to extend greatly knowledge of how the human's ability to detect and to discriminate interaural disparities is affected by the spectral region and spectral compositions of sounds that are processed via binaural interactions. One subset of experiments concerns quantifying high-frequency, envelope- based binaural cross-correlation in a manner that is consistent with the listeners' actual processing of the auditory stimulus. The objective is to obtain decisive behavioral data that will determine which index of interaural correlation corresponds best with listeners' performance. A second large subset of experiments will be directed toward measuring sensitivity to dynamically-changing, interaural temporal disparities (ITDs) and interaural insensitive disparities (IIDs) presented within Gaussian, narrow-band noises as a function of their bandwidth and center- frequency. Specialized digital signal-processing techniques developed in our laboratory will permit measurements of sensitivity to dynamically- changing ITDs and IIDs that are independent of the bandwidth of the stimuli. A third subset of experiments will focus on how sensitive listeners' are to abrupt changes in the magnitude of interaural cues. The experiments have been designed to allow an independent, quantitative assessment of the time-constants that describe how well listeners can process changes in binaural information. The last subset of experiments concerns determining how well listeners can discriminate changes in patterns of activity across a putative, two-dimensional, cross- correlation surface whose axes are defined by frequency and interaural delay. The potential health benefits are a better understanding of how the ear and brain process information and the potential for "better" diagnostic procedures that may, eventually, have clinical significance.

DESCRIPTION: (Adapted from the Investigator's Abstract) The objectives of the proposed research are an evaluation, characterization, and comparison of how the binaural auditory system processes interaural temporal disparities (ITDs) at high and low frequencies. The principal aim of the research is to investigate whether and the degree to which well-known differences in binaural processing at low and high frequencies stem from true differences in the binaural mechanisms that mediate performance or stem from inherent differences in the monaural neural information that serves as input to the binaural system. The experiments involve "transposing" or heterodyning rectified and low-passed, low-frequency information to high frequencies. We will create high-frequency stimuli whose envelopes contain information that is like that normally available from the fine-structure of stimuli presented at low frequencies. The data obtained from detection and lateralization experiments will reveal 1) the relative sensitivity to ITDs at low and high frequencies and the degree to which information available to the putative internal cross-correlation mechanism is processed similarly, as a function o center frequency and 2) the degree to which the processing of interaural disparities conveyed by transposed, high-frequency stimuli is protected from binaural "interference" that typically occurs with "conventional" high-frequency stimuli.

B cell lymphoma; disease /therapy duration; interleukin 6; neoplasm /cancer epidemiology; neoplasm /cancer genetics; nonHodgkin's lymphoma; therapy design /development

[unreadable] DESCRIPTION (provided by applicant): The objectives of the proposed research continue to be an evaluation, characterization, and comparison of how the binaural auditory system processes interaural temporal disparities (ITDs), a major cue for the localization of sound. The program of research flows directly from our findings that the use of special "transposed" high-frequency stimuli can overcome the typically poor ability of listeners to process ITDs within high-frequency channels. Not only do transposed stimuli lead to more efficient ITD-processing, they also appear to be relatively "immune" to the degrading effects observed with conventional high-frequency stimuli, when other, "jamming" or "interfering," low-frequency information is present. The proposed program of research seeks to reveal and understand what specific aspects of the envelopes of high-frequency temporal waveforms are sufficient for the processing of ITDs to be enhanced and for "resistance" to binaural "interference" to occur. In order to provide answers, we propose to employ a multi-faceted, convergent, and, we believe, innovative approach that exploits the combination of 1) a number of sophisticated computer- based techniques for controlling and quantifying via specific metrics the temporal characteristics of the envelopes of high-frequency stimuli; 2) highly precise and repeatable behavioral measures of threshold-ITDs and ITD-based laterality; 3) a type of theoretical approach that yields specific quantitative predictions about the patterning of the behavioral data in terms of either variations in the external stimulus, per se, or in terms of variations in the stimuli as processed by both peripheral and central stages of auditory processing. The relevance of the proposed research to public health includes potential health benefits stemming from a better understanding of how the ear and brain process envelope-based information. The results of our investigations promise to provide direction to others about how they can manipulate specific temporal aspects of the envelopes of high-frequency waveforms to convey more efficiently monaural as well as binaural timing information via prosthetic devices such as cochlear implants and/or digital hearing aids.. [unreadable] [unreadable] [unreadable]