Thesis (Ph.D.)--Indiana University, Dept. of Speech and Hearing Sciences, 2009. / Title from PDF t.p. (viewed on Jul 19, 2010). Source: Dissertation Abstracts International, Volume: 70-12, Section: B, page: 7467. Adviser: Larry Humes.

Abstract not available.

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No description available.

The objective of this study was to describe ways in which properties of human cochlear travelling waves may be manifested in characteristics of distortion-product otoacoustic emissions (DPOAEs). Four young adults served as subjects. DPOAE magnitude was studied for various frequency-ratio and intensity relationships of the primary stimuli. Results revealed complex relationships between stimulus level (L) and frequency ratios (f). The optimal f2/f1 ratios were highly dependent upon differences between L1 and L2. Maximum distortion product amplitudes were encountered when L2 was smaller than L1 for several stimulus conditions and when f2/f1 ratios were approximately 1.20 (range = 1.05 to 1.25). These observations replicate and extend the findings of prior investigations regarding the optimal parameters associated with the production of DPOAEs, and also provide evidence of the complex, nonlinear events leading to the creation of DPOAEs.

<p> There is an increasing amount of evidence indicating potentially devastating long-term effects of subconcussive impacts in the absence of clinical symptoms of concussion in high school football players.</p><p> <i>Purpose:</i> To determine whether subconcussive head impacts produce any immediate cognitive, postural, and physiological changes after athletic participation.</p><p> <i>Methods:</i> Fifty-nine interscholastic football (FB), soccer (SOC), and track (RUN) athletes provided baseline and post-participation data. Four cerebral acoustic response variables were examined using the Brain Acoustic Monitor (BAM) (Active Signal Technologies, Linthicum Heights, MD). Oculomotor function was assessed via the King-Devick (K-D) test. Balance was evaluated using a computerized version of the Balance Error Scoring System (BESS).</p><p> <i>Results:</i> Significant changes in left-brain ratio were observed in football players postgame (p = 0.023). Between-group analysis of baseline data for left- and right-brain divergence noted differences as well (FB vs. SOC, p = 0.012, p = 0.008, respectively; FB vs. RUN, p &lt; 0.001, p &lt; 0.001, respectively). There were no significant differences with either oculomotor or balance variables.</p><p> <i>Conclusions:</i> One game may not provide enough head impact exposure to elicit detectable changes with the utilized instrumentation. Unexpectedly, there were differences observed in football players' baseline BAM scores in the absence of significant differences in baseline and post-participation K-D test and BESS scores across all groups, possibly indicating that prior exposures to subconcussive impacts in this cohort of football players may be present.</p>

The auditory P3 response is thought to be related to stimulus evaluation time. It is typically elicited using an "oddball tonal paradigm" in which "rare" acoustic events (tones) are embedded in a stream of "frequent" tonal signals. The P3 is a cognitive response, generated when the subject consciously identifies a difference between the frequent and rare stimuli. Currently, data are available which suggest that P3 latency will vary as a function of the difficulty of the cognitive task. It is believed that the use of a more relevant stimulus (speech) may provide useful information regarding neurological functioning during speech processing. / The purpose of this study was to determine if differences exist in the P3 response (latency and amplitude) elicited by tonal and speech signals during competing and non-competing stimulus conditions. P3 responses were obtained from 61 normal hearing young adult subjects under the following conditions: tones in quiet; tones in noise; words in quiet; words in noise. Although waveform morphology was superior for the tonal conditions, eighty-five percent of the subjects who demonstrated the P3 response to tones also demonstrated the P3 to verbal stimuli. / The addition of competing noise resulted in decreases in certain wavepeak amplitudes and increases in P3 latencies. The choice of stimulus (tones versus words) had no effect on wavepeak amplitude. However, P3 latencies were significantly longer for words than for tones. P3 latency differences to tonal as compared to speech stimuli are believed to be related to longer stimulus evaluation time required for speech processing. The findings of this study demonstrate that the P3 response to speech stimuli can be reliably elicited in a large percentage of subjects who demonstrate the P3 response to tones. / Source: Dissertation Abstracts International, Volume: 51-12, Section: B, page: 5793. / Major Professor: Lloyd Price. / Thesis (Ph.D.)--The Florida State University, 1990.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3400. Adviser: Charissa Lansing. Includes bibliographical references (leaves 157-170) Available on microfilm from Pro Quest Information and Learning.

The acoustic reflex system (AR) and the influence of the olivocochlear bundle (OCB) affect the ear's response to sound. Both systems are controlled by efferent neurons that originate in the superior olivary complex (SOC). The AR system affects middle ear function through its action on the stapedius muscle, and the OCB affects cochlear function through its action on outer hair cells (OHC). The AR is sensitive to the loudness of a stimulus; that is to say, changes in sound pressure level (SPL) and bandwidth of a stimulus affect the threshold and magnitude of stapedius muscle contraction. Investigators have shown that the magnitude of the OCB effect is influenced by changes in SPL. Transient evoked otoacoustic emissions (TEOAEs) were collected from 10 women in quiet and in the presence of three different contralateral noise bands centered at 2000 Hz. The NB (100 Hz bandwidth) and WB (2200 Hz bandwidth) noises were at 60 dB SPL. The SPL of the EQ (100 Hz bandwidth) noise was adjusted such that it was equal in loudness to the WB noise. The results of the present study indicate that an increase in loudness as associated by an increase in noise bandwidth affects the contralateral suppression of TEOAEs. Only the WB noise was associated with a reduction of TEOAE amplitudes. It is believed that this effect results because the WB noise has greater effective energy representation across frequency on the basilar membrane. Although the spectrum level of the WB noise is lower than that of the NB noise at the transducer, it receives more gain from the action of the cochlear amplifier than the NB noise and thus has greater energy representation on the cochlear partition. While the effective energy level on the basilar membrane may have been essentially the same for the WB and EQ noises as a result of the action of the cochlear amplifier, the WB noise was the more effective suppressor because its energy was summed across multiple critical bands. The energy in the EQ noise was confined to a single critical band.

<p> Does matching stimulation rates in bilateral cochlear implants (CI) really matter? When bilateral CI recipients are implanted sequentially, the first implant is likely to be mapped at a relatively slow stimulation rate, while the second may be capable of faster stimulation rates, due to the technology available at implantation. Ten sequential bilateral CI recipients were used to investigate this question. Prior to the experiment, all participants used slow rates in the first CI, ranging from 720-1856 Hz. Five used slow rates (900Hz) (matched) on the second CI, and five used high rates (2400-3867Hz) (mismatched). The stimulation rate in the first implanted CI was never changed (non-modified), but all participants were given at least four weeks experience with both low and high rates on the newer implant. </p><p> Speech perception in quiet (CNC) and in noise (CRISP) with the first CI alone (non-modified), the second CI alone (modified), and bilaterally was evaluated four times during the experiment. Phase 1) Baseline testing was conducted prior to any re-programming. The second implant was re-mapped with either a slow or high rate. Phase 2) Participants were tested and re-mapped with the alternative rate after four weeks experience with the new map. Phase 3) After four weeks experience with the alternative map, participants were retested then re-mapped with the original rates. Phase 4) Participants were given one week of additional experience before final testing. Participants were asked which mapping configuration they preferred and would like to continue using. Most (8/10) participants choose to leave with the mismatched configuration. </p><p> With bilateral stimulation, speech perception was better listening in quiet when they used a higher stimulation rate in one ear and a slow rate in the other ear than when they used slow rates in both ears, regardless of the program used before entering the study. There was no significant improvement in the CRISP (independent of noise source location) when participants were using both rate configurations with the modified CI alone, non-modified CI alone, or bilateral CIs. Clinicians programming bilateral CI patients who have internal equipment with different capabilities may find this information helpful when mapping this population.</p>