Kelly L. Whiteford

Using individual differences to test the role of temporal and place cues in coding frequency modulation

The question of how frequency is coded in the peripheral auditory system remains unresolved. Previous research has suggested that slow rates of frequency modulation (FM) of a low carrier frequency may be coded via phase-locked temporal information in the auditory nerve, whereas FM at higher rates and/or high carrier frequencies may be coded via a rate-place (tonotopic) code. This hypothesis was tested in a cohort of 100 young normal-hearing listeners by comparing individual sensitivity to slow-rate (1-Hz) and fast-rate (20-Hz) FM at a carrier frequency of 500 Hz with independent measures of phase-locking (using dynamic interaural time difference, ITD, discrimination), level coding (using amplitude modulation, AM, detection), and frequency selectivity (using forward-masking patterns). All FM and AM thresholds were highly correlated with each other. However, no evidence was obtained for stronger correlations between measures thought to reflect phase-locking (e.g., slow-rate FM and ITD sensitivity), or between measures thought to reflect tonotopic coding (fast-rate FM and forward-masking patterns). The results suggest that either psychoacoustic performance in young normal-hearing listeners is not limited by peripheral coding, or that similar peripheral mechanisms limit both high- and low-rate FM coding.

Musicians do not benefit from differences in fundamental frequency when listening to speech in competing speech backgrounds

Recent studies disagree on whether musicians have an advantage over non-musicians in understanding speech in noise. However, it has been suggested that musicians may be able to use differences in fundamental frequency (F0) to better understand target speech in the presence of interfering talkers. Here we studied a relatively large (N = 60) cohort of young adults, equally divided between non-musicians and highly trained musicians, to test whether the musicians were better able to understand speech either in noise or in a two-talker competing speech masker. The target speech and competing speech were presented with either their natural F0 contours or on a monotone F0, and the F0 difference between the target and masker was systematically varied. As expected, speech intelligibility improved with increasing F0 difference between the target and the two-talker masker for both natural and monotone speech. However, no significant intelligibility advantage was observed for musicians over non-musicians in any condition. Although F0 discrimination was significantly better for musicians than for non-musicians, it was not correlated with speech scores. Overall, the results do not support the hypothesis that musical training leads to improved speech intelligibility in complex speech or noise backgrounds.

Auditory deficits in amusia extend beyond poor pitch perception

ABSTRACT Congenital amusia is a music perception disorder believed to reflect a deficit in fine‐grained pitch perception and/or short‐term or working memory for pitch. Because most measures of pitch perception include memory and segmentation components, it has been difficult to determine the true extent of pitch processing deficits in amusia. It is also unclear whether pitch deficits persist at frequencies beyond the range of musical pitch. To address these questions, experiments were conducted with amusics and matched controls, manipulating both the stimuli and the task demands. First, we assessed pitch discrimination at low (500 Hz and 2000 Hz) and high (8000 Hz) frequencies using a three‐interval forced‐choice task. Amusics exhibited deficits even at the highest frequency, which lies beyond the existence region of musical pitch. Next, we assessed the extent to which frequency coding deficits persist in one‐ and two‐interval frequency‐modulation (FM) and amplitude‐modulation (AM) detection tasks at 500 Hz at slow (fm=4 Hz) and fast (fm=20 Hz) modulation rates. Amusics still exhibited deficits in one‐interval FM detection tasks that should not involve memory or segmentation. Surprisingly, amusics were also impaired on AM detection, which should not involve pitch processing. Finally, direct comparisons between the detection of continuous and discrete FM demonstrated that amusics suffer deficits in both coding and segmenting pitch information. Our results reveal auditory deficits in amusia extending beyond pitch perception that are subtle when controlling for memory and segmentation, and are likely exacerbated in more complex contexts such as musical listening. HIGHLIGHTSPoor pitch discrimination in amusia extends to high frequencies.Amusics have impaired frequency‐ and amplitude‐modulation detection.Memory and segmentation demands exacerbate underlying auditory deficits in amusia.

Complex frequency modulation detection and discrimination at low and high frequencies

Whether frequency modulation (FM) is represented by place (tonotopic) or temporal (phase-locking) information in the peripheral system may depend on the carrier frequency (fc) and the modulation rate (fm), with only fcs below 4 kHz and fms below 10 Hz thought to involve temporal coding. This study tested the role of temporal coding in harmonic complexes by measuring FM detection and discrimination for two F0s (200 Hz and 1400 Hz), modulated at slow (1 Hz) and fast (20 Hz) rates, for tones with lower (2-5) or upper (6-9) harmonics embedded in threshold equalizing noise. Pure-tone FM detection was measured for fcs between 200 and 12000 Hz at the same fms. In detection tasks, participants selected which of two intervals contained FM. In discrimination tasks, participants selected which of three FM complex tones was incoherently modulated. Preliminary results suggest better FM detection for slow than fast rates, even when all tones are above 4 kHz. However, this effect was stronger at lower frequencies, where...

Acoustics-related graduate programs at the University of Minnesota

The University of Minnesota offers a wide variety of graduate programs related to acoustics, primarily in the areas of Speech Communication, Psychological and Physiological Acoustics, and Animal Bioacoustics. Degree programs include Psychology (Ph.D.), Speech-Language-Hearing Sciences (M.A., Au.D., and Ph.D.), Biomedical Engineering (M.S. and Ph.D.), Ecology, Evolution, and Behavior (Ph.D.), and Neuroscience (Ph.D.). Faculty across departments have a shared interest in understanding how the ear and brain work together to process sound and in developing new technologies and approaches for improving hearing disorders. The university offers a number of resources for pursuing research related to these topics. The Center for Applied and Translational Sensory Science (CATSS) provides opportunities for utilizing interdisciplinary collaborations to better understand sensory-related impairments, including hearing loss and low vision. Within CATSS is the Multi-Sensory Perception Lab, which houses shared equipment, ...

Long-term maintenance for learning on pitch and melody discrimination in congenital amusia

Congenital amusia is described as a life-long disorder in melody discrimination, related to poor fine-grained pitch perception. A recent study in our lab found, however, that pitch and melody discrimination in amusia can improve with laboratory training. After training, over half of the amusics no longer met the standard diagnostic criterion for amusia, assessed via the Montreal Battery of Evaluation of Amusia (MBEA). The present study examined the durability of learning effects by re-examining frequency difference limens (FDLs) and melody discrimination in the same participants one year after post training. Pure-tone FDLs were measured at 500, 2000, and 8000 Hz using an adaptive three-interval forced-choice procedure, and melody discrimination was assessed via the MBEA. Preliminary results (n = 23; 11 amusics) showed no significant change in FDLs or melody discrimination between post training and one-year follow-up. Consistent with post-training results, there were significant main effects of group, with...

Effects of age and hearing loss on coding frequency and amplitude modulation

Is phase-locking to temporal fine structure (TFS) selectively affected by hearing loss or ageing? This question has clinical relevance because audiometric measures may be insensitive to TFS deficits linked to auditory neuropathy/dyssynchrony and synaptopathy (“hidden hearing loss”). Previous work has suggested that slow-rate FM is coded via phase-locking to TFS, whereas fast-rate FM is converted to amplitude modulation (AM) via cochlear filtering. This hypothesis was tested by correlating performance in slow- and fast-rate FM with performance in tasks known to reflect TFS coding (interaural-time-difference detection, ITD) and cochlear filtering (forward masking patterns). Subjects with clinically normal hearing at low frequencies between the ages of 20 and 80 years were tested, with approximately 10 subjects per decade. Effects of low- and high-frequency hearing loss were also examined, while controlling for age. Although correlations were found between all measures of FM and AM, no clear specific effect ...