Brainstem Monaural and Binaural Responses to Phase-locked and Free Running Auditory Stimuli at Various Intensities and Rise/fall Times PDF Download
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Author: Elizabeth Van Allen
Publisher:
ISBN:
Category : Audiometry, Evoked response
Languages : en
Pages : 90
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Author: Elizabeth Van Allen
Publisher:
ISBN:
Category : Audiometry, Evoked response
Languages : en
Pages : 90
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Understanding speech in the presence of background noise is a common complaint of middle-aged and older listeners with clinically normal audiograms. There is great interest in understanding how age-related changes in auditory physiology make it harder for older adults to understand speech in difficult listening situations, compared to young listeners. It was recently reported that middle-aged and older normal-hearing listeners showed frequency-dependent, age-related declines in the behavioral and physiological detection of interaural phase differences (Grose & Mamo, 2010; Ross et al, 2007). There is also evidence of an age-related, frequency-dependent decline in the frequency-following response (FFR) (Clinard et al., 2010), an auditory evoked potential dependent on phase-locked neural activity (Worden & Marsh, 1968). Age-related declines in binaural processing may be related to age-related declines in phase locking. This study used the frequency-following response (FFR) to examine monaural and binaural phase locking in subjects of two groups; younger and middle-aged. Responses were obtained from 300 ms toneburst stimuli at four frequencies (500, 750, 1000, and 1125 Hz) at an intensity of 80 dB SPL. FFRs were analyzed for response amplitude, binaural amplitude differences, and stimulus-to-response cross-correlations. Results showed FFR amplitude decreased as frequency increases and, at 500 Hz, the summed left and right monaural FFR amplitudes were smaller than the binaural FFR amplitude, which is in contrast to previous literature (Clinard, 2010; Fowler, 2004; Krishnan & McDaniel, 1998). Results further indicated that the stimulus-to-response correlation coefficient is greatest for 500 Hz and declines as frequency increases. There was no significant difference between the age groups but perhaps a broader age range including older adults would show the hypothesized amplitude differences between groups. Further, results may be different than expected due to minimal difference between summed monaural and binaural processing at 750, 1000, and 1125 Hz. When looking at the data there is a larger difference between groups at 1125 Hz and, while it is not significantly different, it may be that a broader frequency range (e.g., 1250 Hz or above) and age range (e.g. 0 to 100), may be more effective at revealing a group x frequency interaction.
Author: Melissa A. Koberg
Publisher:
ISBN:
Category :
Languages : en
Pages : 76
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Author: Paul Alfred Lobaugh
Publisher:
ISBN:
Category : Auditory evoked response
Languages : en
Pages : 272
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Author: Yoojin Chung
Publisher:
ISBN:
Category :
Languages : en
Pages : 320
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Abstract: Bilateral cochlear implants (BiCIs) are becoming more common recently and have been proven to provide improvements in speech perception in noise and sound localization. However, benefits to sound localization for BiCI listening are mainly from the perception of interaural level differences while interaural time difference (ITD) sensitivity is very limited. To help understand this, the current modeling study focused on the following characteristics of neurophysiological data from ITD-sensitive neurons in acutely deafened animal models with BiCIs: (1) rate-limitation of ITD sensitivity to constant-amplitude pulse trains, (2) intensity dependence of ITD sensitivity, and (3) effect of amplitude modulation on ITD sensitivity with high-rate stimulation. A network of model neurons was used to study binaural responses to electrical stimulation. Our working hypothesis was that central auditory processing is normal so that the abnormality in the response to the electric stimulation at the level of the auditory nerve fibers (ANFs) is the source of the limited binaural response. A descriptive model of ANF response to electric stimulation was implemented and used as an input to a network of model neurons in the ascending auditory pathway, up to the inferior colliculus (IC). The result shows that ITD sensitivity depends strongly on the specific configurations of membrane and synaptic parameters for different input stimulation rates. Stronger excitatory synaptic inputs and a faster membrane response are required for the model neurons to be ITD-sensitive at high stimulation rates, both in electric and acoustic stimulation. This raises the possibility of frequency-dependent differences in neural mechanisms of binaural processing; limitations in ITD sensitivity may be due to the mismatch between stimulation rate and cell parameters in ITD-sensitive neurons. The high spike rate and phase-locking at the ANF to electric stimulation changes the rate-ITD tuning at the IC. Amplitude modulation of the high-rate stimulation restores the ongoing ITD sensitivity by effectively reducing the spike rate in the ANF. ITD sensitivity to temporal fine-structure is restored in the model with amplitude-modulated high-rate stimulation, consistent with physiological results. Overall, this study suggests that fine-structure ITD can be delivered to BiCI users with proper processing strategies.
Author: Joan Lynch Luckett
Publisher:
ISBN:
Category :
Languages : en
Pages : 114
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Author:
Publisher:
ISBN:
Category : Audiology
Languages : en
Pages : 234
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Author: Ballachanda Belliappa Bopanna
Publisher:
ISBN:
Category : Auditory perception
Languages : en
Pages : 322
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Author: Jacqueline Robyn Dzau
Publisher:
ISBN:
Category :
Languages : en
Pages : 96
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Author: Mary Jennifer Vaughan
Publisher:
ISBN:
Category :
Languages : en
Pages : 122
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