Sid P. Bacon, Ph.D. - US grants

The proposed experiments have been designed to provide information on the dynamic characteristics of auditory processing. There are two separate but related lines of research. The first is motivated, in part, by recent evidence that simultaneous pure-tone masking is time-varying and, as a result, that psychophysical measures of frequency selectivity sharpen during the first 100 to 150 ms of stimulation. The goals of the first line of research are to further our understanding of the mechanisms responsible for the temporal effect, to determine whether sensorineural hearing loss affects those mechanisms, and to determine to what extent those temporal effects play a role in the auditory processing of complex signals such as speech. Specific projects include further studies of temporal effects in pure-tone masking in normal-hearing subjects and in subjects with sensorineural hearing loss, and studies of temporal effects in masking by complex (including vowel and consonant-vowel) maskers in normal-hearing subjects. Among the hypotheses to be tested is that the mechanisms responsible for enhancing frequency selectivity over time in normal-hearing subjects are damaged in subjects with sensorineural hearing loss. The second line of research is motivated by the fact that hearing- impaired individuals typically have difficulty understanding speech in noisy environments. The goal of this research is to evaluate the hypothesis that at least some of that difficulty is due to an inability to detect the slow (amplitude) modulations in speech in the presence of a background noise, such as speech from a competing source. This line of research involves studying the masking of an amplitude-modulated signal by an amplitude- modulated masker in normal-hearing and hearing-impaired subjects. It is hoped that the results from the proposed studies will further our understanding of the mechanisms involved in dynamic auditory processing; further our understanding of the peripheral mechanisms involved in the deterioration of frequency selectivity in subjects with sensorineural hearing loss; and further our understanding of processing of complex signals such as speech.

The long-range goals of the proposed research are to further our understanding of the mechanisms underlying the auditory processing of time-varying stimuli, and to determine how those mechanisms are affected by sensorineural hearing loss. There are three separate but related lines of research, and all focus to some extent on the potential role of peripheral compression in temporal processing. The influence of compression is evaluated by studying the effects of temporary, aspirin- induced hearing loss, permanent hearing loss, and model simulations. The first line of research focuses on the detection of brief signals as a function of prior masker stimulation. The underlying mechanisms could play an important role in enhancing newly arriving or intermittent signals, especially those in an on-going background. The general goal of this line of research is to test the hypothesis that the mechanisms underlying the temporal effect with off frequency tonal maskers differ from those underlying the effect with broadband noise maskers. The second line of research concentrates on phase effects in simultaneous masking, particularly on how the resulting temporal fluctuations influence the amount of masking. The general goal of this research is to gain a better understanding of the within- and across-channel mechanisms underlying these phase effects. This research should enhance our understanding of how the auditory system processes the temporal fluctuations inherent in many complex sounds, including speech, and could ultimately provide insight into why individuals with a sensorineural hearing loss have particular difficulties understanding speech in temporally complex backgrounds. The third line of research focuses on a recently described change in response growth from compressive to linear at high levels. This change, inferred from growth-of-masking functions, is responsible for a measured decline in temporal processing at high stimulus levels. The primary goal of this line of research is to gain a better understanding of the processing underlying this change in response growth.

In the Phoenix metropolitan area, high-need schools often experience on-going vacancies in the teaching staff and a high turnover rate of qualified teachers. This project attempts to identify and support up to 60 qualified secondary science teachers who will persist in high-need environments. Using different methods of recruitment, in conjunction with a marketing plan, science students are being identified and recruited to participate in undergraduate or post-baccalaureate programs that have extensive field experiences with diverse students, strong content knowledge requirements, and on-going opportunities to build their understanding of science as inquiry instruction. While students are completing their initial certification course work, field placements are being arranged in high need settings that consist of students who are Native American, Latina/o, or African American. Upon graduation, STARR Noyce teachers participate in science-focused induction programs, which specifically support their use of science as inquiry in diverse classrooms, their development as science teachers, and their socialization into the school community.
Ultimately, the dissemination of these findings is expected to direct future recruitment endeavors in this area.

[unreadable] DESCRIPTION (provided by applicant): Individuals with hearing restricted to the frequency region below about 500-750 Hz may benefit significantly from a combination of acoustic stimulation in the low-frequency region and electric stimulation in the higher frequency region. The advantage of electric-acoustic stimulation (EAS) is particularly apparent when listening to speech in the presence of competing speech, one of the most difficult listening situations for individuals with hearing loss. The often dramatic improvement in speech intelligibility when adding acoustic to electric stimulation occurs even though the acoustic stimulation alone often provides little or no intelligibility. The broad, long-term goal of the proposed research is to gain a better understanding of the acoustic cues and auditory processing underlying the benefits of EAS. In particular, the specific aims include identifying the acoustic cues in speech that are responsible for the benefits gained from low-frequency acoustic stimulation; determining the frequency extent and magnitude of low-frequency hearing that can support successful EAS; determining whether benefits similar to those seen with EAS can be observed in acoustic simulations of EAS by increasing the number of channels of stimulation in the low-frequency region; determining whether low-frequency acoustic stimulation helps the processing of interrupted speech; and determining whether low-frequency hearing in the implanted ear preserves important cues for understanding speech in the presence of spatially separated backgrounds. The research proposed here will include normal-hearing subjects listening to simulations of implant processing and cochlear implant patients with residual low-frequency hearing. This research should lead to a better understanding of EAS and could lead to improved speech reception for many current and potential patients and an increase in the number of individuals who might benefit from this relatively new and extremely promising technology. [unreadable] [unreadable] There are approximately 28 million individuals who suffer from hearing loss in the United States. A promising new approach to auditory rehabilitation for some of these includes a combination of acoustic stimulation and direct electrical stimulation of the auditory nerve. Additional research in this important new area is needed to broaden our theoretical understanding of electric-acoustic stimulation and to enhance its clinical efficacy.Recently, individuals fitted with cochlear implants have received a relatively short electrode array, intended to preserve their residual low-frequency hearing in the implanted ear. The addition of this low-frequency acoustic stimulation has been shown to dramatically improve speech reception both in real and simulated implant listening, particularly in background noise. The goal of this project is to gain a better understanding of the cues present in the low-frequency region that provide this benefit. [unreadable] [unreadable] [unreadable]