Head movement and its relation to hearing

Head position at any point in time plays a fundamental role in shaping the auditory information that reaches a listener, information that continuously changes as the head moves and reorients to different listening situations. The connection between hearing science and the kinesthetics of head movement has gained interest due to technological advances that have increased the feasibility of providing behavioral and biological feedback to assistive listening devices that can interpret movement patterns that reflect listening intent. Increasing evidence also shows that the negative impact of hearing deficits on mobility, gait, and balance may be mitigated by prosthetic hearing device intervention. Better understanding of the relationships between head movement, full body kinetics, and hearing health, should lead to improved signal processing strategies across a range of assistive and augmented hearing devices. The purpose of this review is to introduce the wider hearing community to the kinesiology of head movement and to place it in the context of hearing and communication with the goal of expanding the field of ecologically-specific listener behavior

GRM7 variants associated with age-related hearing loss based on auditory perception

Age-related hearing impairment (ARHI), or presbycusis, is a common condition of the elderly that results in significant communication difficulties in daily life. Clinically, it has been defined as a progressive loss of sensitivity to sound, starting at the high frequencies, inability to understand speech, lengthening of the minimum discernable temporal gap in sounds, and a decrease in the ability to filter out background noise. The causes of presbycusis are likely a combination of environmental and genetic factors. Previous research into the genetics of presbycusis has focused solely on hearing as measured by pure-tone thresholds. A few loci have been identified, based on a best ear pure-tone average phenotype, as having a likely role in susceptibility to this type of hearing loss; and GRM7 is the only gene that has achieved genome-wide significance. We examined the association of GRM7 variants identified from the previous study, which used an European cohort with Z-scores based on pure-tone thresholds, in a European–American population from Rochester, NY (N = 687), and used novel phenotypes of presbycusis. In the present study mixed modeling analyses were used to explore the relationship of GRM7 haplotype and SNP genotypes with various measures of auditory perception. Here we show that GRM7 alleles are associated primarily with peripheral measures of hearing loss, and particularly with speech detection in older adults

Pitch strength of normal and dysphonic voices

Two sounds with the same pitch may vary from each other based on saliency of their pitch sensation. This perceptual attribute is called “pitch strength.” The study of voice pitch strength may be important in quantifying of normal and pathological qualities. The present study investigated how pitch strength varies across normal and dysphonic voices. A set of voices (vowel /a/) selected from the Kay Elemetrics Disordered Voice Database served as the stimuli. These stimuli demonstrated a wide range of voice quality. Ten listeners judged the pitch strength of these stimuli in an anchored magnitude estimation task. On a given trial, listeners heard three different stimuli. The first stimulus represented very low pitch strength (wide-band noise), the second stimulus consisted of the target voice and the third stimulus represented very high pitch strength (pure tone). Listeners estimated pitch strength of the target voice by positioning a continuous slider labeled with values between 0 and 1, reflecting the two anchor stimuli. Results revealed that listeners can judge pitch strength reliably in dysphonic voices. Moderate to high correlations with perceptual judgments of voice quality suggest that pitch strength may contribute to voice quality judgments

Electrophysiological responses to lateral shifts are not consistent with opponent-channel processing of interaural level differences

Cortical encoding of auditory space relies on two major peripheral cues, interaural time difference (ITD) and interaural level difference (ILD) of the sounds arriving at a listener’s ears. In much of the precortical auditory pathway, ITD and ILD cues are processed independently, and it is assumed that cue integration is a higher order process. However, there remains debate on how ITDs and ILDs are encoded in the cortex and whether they share a common mechanism. The present study used electroencephalography (EEG) to measure evoked cortical potentials from narrowband noise stimuli with imposed binaural cue changes. Previous studies have similarly tested ITD shifts to demonstrate that neural populations broadly favor one spatial hemifield over the other, which is consistent with an opponent-channel model that computes the relative activity between broadly tuned neural populations. However, it is still a matter of debate whether the same coding scheme applies to ILDs and, if so, whether processing the two binaural cues is distributed across similar regions of the cortex. The results indicate that ITD and ILD cues have similar neural signatures with respect to the monotonic responses to shift magnitude; however, the direction of the shift did not elicit responses equally across cues. Specifically, ITD shifts evoked greater responses for outward than inward shifts, independently of the spatial hemifield of the shift, whereas ILD-shift responses were dependent on the hemifield in which the shift occurred. Active cortical structures showed only minor overlap between responses to cues, suggesting the two are not represented by the same pathway

How Do Age and Hearing Loss Impact Spectral Envelope Perception?

Purpose: The goal was to evaluate the potential effects of increasing hearing loss and advancing age on spectral envelope perception. Method: Spectral modulation detection was measured as a function of spectral modulation frequency from 0.5 to 8.0 cycles/octave. The spectral modulation task involved discrimination of a noise carrier (3 octaves wide from 400 to 3200 Hz) with a flat spectral envelope from a noise having a sinusoidal spectral envelope across a logarithmic audio frequency scale. Spectral modulation transfer functions (SMTFs; modulation threshold vs. modulation frequency) were computed and compared 4 listener groups: young normal hearing, older normal hearing, older with mild hearing loss, and older with moderate hearing loss. Estimates of the internal spectral contrast were obtained by computing excitation patterns. Results: SMTFs for young listeners with normal hearing were bandpass with a minimum modulation detection threshold at 2 cycles/octave, and older listeners with normal hearing were remarkably similar to those of the young listeners. SMTFs for older listeners with mild and moderate hearing loss had a low-pass rather than a bandpass shape. Excitation patterns revealed that limited spectral resolution dictated modulation detection thresholds at high but not low spectral modulation frequencies. Even when factoring out (presumed) differences in frequency resolution among groups, the spectral envelope perception was worse for the group with moderate hearing loss than the other 3 groups. Conclusions: The spectral envelope perception as measured by spectral modulation detection thresholds is compromised by hearing loss at higher spectral modulation frequencies, consistent with predictions of reduced spectral resolution known to accompany sensorineural hearing loss. Spectral envelope perception is not negatively impacted by advancing age at any spectral modulation frequency between 0.5 and 8.0 cycles/octave

How Aging Impacts the Encoding of Binaural Cues and the Perception of Auditory Space

Over the years, the effect of aging on auditory function has been investigated in animal models and humans in an effort to characterize age-related changes in both perception and physiology. Here, we review how aging may impact neural encoding and processing of binaural and spatial cues in human listeners with a focus on recent work by the authors as well as others. Age-related declines in monaural temporal processing, as estimated from measures of gap detection and temporal fine structure discrimination, have been associated with poorer performance on binaural tasks that require precise temporal processing. In lateralization and localization tasks, as well as in the detection of signals in noise, marked age-related changes have been demonstrated in both behavioral and electrophysiological measures and have been attributed to declines in neural synchrony and reduced central inhibition with advancing age. Evidence for such mechanisms, however, are influenced by the task (passive vs. attending) and the stimulus paradigm (e.g., static vs. continuous with dynamic change). That is, cortical auditory evoked potentials (CAEP) measured in response to static interaural time differences (ITDs) are larger in older versus younger listeners, consistent with reduced inhibition, while continuous stimuli with dynamic ITD changes lead to smaller responses in older compared to younger adults, suggestive of poorer neural synchrony. Additionally, the distribution of cortical activity is broader and less asymmetric in older than younger adults, consistent with the hemispheric asymmetry reduction in older adults model of cognitive aging. When older listeners attend to selected target locations in the free field, their CAEP components (N1, P2, P3) are again consistently smaller relative to younger listeners, and the reduced asymmetry in the distribution of cortical activity is maintained. As this research matures, proper neural biomarkers for changes in spatial hearing can provide objective evidence of impairment and targets for remediation. Future research should focus on the development and evaluation of effective approaches for remediating these spatial processing deficits associated with aging and hearing loss

Electrophysiological responses to lateral shifts are not consistent with opponent-channel processing of interaural level differences

Cortical encoding of auditory space relies on two major peripheral cues, interaural time difference (ITD) and interaural level difference (ILD) of the sounds arriving at a listener’s ears. In much of the precortical auditory pathway, ITD and ILD cues are processed independently, and it is assumed that cue integration is a higher order process. However, there remains debate on how ITDs and ILDs are encoded in the cortex and whether they share a common mechanism. The present study used electroencephalography (EEG) to measure evoked cortical potentials from narrowband noise stimuli with imposed binaural cue changes. Previous studies have similarly tested ITD shifts to demonstrate that neural populations broadly favor one spatial hemifield over the other, which is consistent with an opponent-channel model that computes the relative activity between broadly tuned neural populations. However, it is still a matter of debate whether the same coding scheme applies to ILDs and, if so, whether processing the two binaural cues is distributed across similar regions of the cortex. The results indicate that ITD and ILD cues have similar neural signatures with respect to the monotonic responses to shift magnitude; however, the direction of the shift did not elicit responses equally across cues. Specifically, ITD shifts evoked greater responses for outward than inward shifts, independently of the spatial hemifield of the shift, whereas ILD-shift responses were dependent on the hemifield in which the shift occurred. Active cortical structures showed only minor overlap between responses to cues, suggesting the two are not represented by the same pathway

How Do Age and Hearing Loss Impact Spectral Envelope Perception?

Purpose: The goal was to evaluate the potential effects of increasing hearing loss and advancing age on spectral envelope perception. Method: Spectral modulation detection was measured as a function of spectral modulation frequency from 0.5 to 8.0 cycles/octave. The spectral modulation task involved discrimination of a noise carrier (3 octaves wide from 400 to 3200 Hz) with a flat spectral envelope from a noise having a sinusoidal spectral envelope across a logarithmic audio frequency scale. Spectral modulation transfer functions (SMTFs; modulation threshold vs. modulation frequency) were computed and compared 4 listener groups: young normal hearing, older normal hearing, older with mild hearing loss, and older with moderate hearing loss. Estimates of the internal spectral contrast were obtained by computing excitation patterns. Results: SMTFs for young listeners with normal hearing were bandpass with a minimum modulation detection threshold at 2 cycles/octave, and older listeners with normal hearing were remarkably similar to those of the young listeners. SMTFs for older listeners with mild and moderate hearing loss had a low-pass rather than a bandpass shape. Excitation patterns revealed that limited spectral resolution dictated modulation detection thresholds at high but not low spectral modulation frequencies. Even when factoring out (presumed) differences in frequency resolution among groups, the spectral envelope perception was worse for the group with moderate hearing loss than the other 3 groups. Conclusions: The spectral envelope perception as measured by spectral modulation detection thresholds is compromised by hearing loss at higher spectral modulation frequencies, consistent with predictions of reduced spectral resolution known to accompany sensorineural hearing loss. Spectral envelope perception is not negatively impacted by advancing age at any spectral modulation frequency between 0.5 and 8.0 cycles/octave

Distribution of Spectral Modulation Transfer Functions in a Young, Normal-hearing Population

Spectral modulation transfer functions (SMTFs) were measured in 49 young (18–35 years of age) normal-hearing listeners. Noise carriers spanned six octaves from 200 to 12 800 Hz. Sinusoidal (on a log-amplitude scale) spectral modulation with random starting phase was superimposed on the carrier at spectral modulation frequencies of 0.25, 0.5, 1.0, 2.0, 4.0, and 8.0 cycles/octave. Modulation detection thresholds (in dB) yielded SMTFs that were bandpass in nature, consistent with previous investigations reporting data for only a few subjects. Thresholds were notably consistent across subjects despite minimal practice. Population statistics are reported that may serve as reference data for future studies