Effects of Hearing Loss and Cognitive Load on Speech Recognition with Competing Talkers

Factors that can affect divided speech intelligibility

Previous studies have shown that in challenging listening situations, people find it hard to equally divide their attention between two simultaneous talkers and tend to favor one talker over the other. The aim here was to investigate whether talker onset/offset, sex and location determine the favored talker. Fifteen people with normal hearing were asked to recognize as many words as possible from two sentences uttered by two talkers located at 45° and +45° azimuth, respectively. The sentences were from the same corpus, were time-centered and had equal sound level. In Conditions 1 and 2, the talkers had different sexes (male at +45°), sentence duration was not controlled for, and sentences were presented at 65 and 35 dB SPL, respectively. Listeners favored the male over the female talker, even more so at 35 dB SPL (62 % vs 43 % word recognition, respectively) than at 65 dB SPL (74 % vs 64 %, respectively). The greater asymmetry in intelligibility at the lower level supports that divided listening is harder and more 'asymmetric' in challenging acoustic scenarios. Listeners continued to favor the male talker when the experiment was repeated with sentences of equal average duration for the two talkers (Condition 3). This suggests that the earlier onset or later offset of male sentences (52 ms on average) was not the reason for the asymmetric intelligibility in Conditions 1 or 2. When the location of the talkers was switched (Condition 4) or the two talkers were the same woman (Condition 5), listeners continued to favor the talker to their right albeit non-significantly. Altogether, results confirm that in hard divided listening situations, listeners tend to favor the talker to their right. This preference is not affected by talker onset/offset delays less than 52 ms on average. Instead, the preference seems to be modulated by the voice characteristics of the talkers.

Inner ear therapeutics and the war on hearing loss: systemic barriers to success

Despite over 20 years of effort in academic research centers, start-up companies, and established pharmaceutical companies, there are no FDA-approved inner ear therapeutics for treatment of sensorineural hearing loss. There are a number of systemic barriers to creation of this new field of inner ear therapeutics. These include insufficient understanding of the particularity of different causes of hearing loss at the cellular and molecular level, lack of diagnostics of adequate sensitivity and specificity to discern these differences in vivo, a tendency for start-up biotech/pharma companies to prioritize competition over collaboration, and a drug development ecosystem that is really in the "pre-competitive" phase and a lack of infrastructure to develop, validate, gain regulatory approval, and successfully market an inner ear therapeutic. These issues will be discussed in this perspective article and a proposed remedy in the form of an inner ear therapeutics "moon shot" will be offered.

Lexical Effects on the Perceived Clarity of Noise-Vocoded Speech in Younger and Older Listeners

When listening to degraded speech, such as speech delivered by a cochlear implant (CI), listeners make use of top-down linguistic knowledge to facilitate speech recognition. Lexical knowledge supports speech recognition and enhances the perceived clarity of speech. Yet, the extent to which lexical knowledge can be used to effectively compensate for degraded input may depend on the degree of degradation and the listener's age. The current study investigated lexical effects in the compensation for speech that was degraded via noise-vocoding in younger and older listeners. In an online experiment, younger and older normal-hearing (NH) listeners rated the clarity of noise-vocoded sentences on a scale from 1 ("very unclear") to 7 ("completely clear"). Lexical information was provided by matching text primes and the lexical content of the target utterance. Half of the sentences were preceded by a matching text prime, while half were preceded by a non-matching prime. Each sentence also consisted of three key words of high or low lexical frequency and neighborhood density. Sentences were processed to simulate CI hearing, using an eight-channel noise vocoder with varying filter slopes. Results showed that lexical information impacted the perceived clarity of noise-vocoded speech. Noise-vocoded speech was perceived as clearer when preceded by a matching prime, and when sentences included key words with high lexical frequency and low neighborhood density. However, the strength of the lexical effects depended on the level of degradation. Matching text primes had a greater impact for speech with poorer spectral resolution, but lexical content had a smaller impact for speech with poorer spectral resolution. Finally, lexical information appeared to benefit both younger and older listeners. Findings demonstrate that lexical knowledge can be employed by younger and older listeners in cognitive compensation during the processing of noise-vocoded speech. However, lexical content may not be as reliable when the signal is highly degraded. Clinical implications are that for adult CI users, lexical knowledge might be used to compensate for the degraded speech signal, regardless of age, but some CI users may be hindered by a relatively poor signal.

Phonological and semantic similarity of misperceived words in babble: Effects of sentence context, age, and hearing loss

This study investigated how age and hearing loss influence the misperceptions made when listening to sentences in babble. Open-set responses to final words in sentences with low and high context were analyzed for younger adults with normal hearing and older adults with normal or impaired hearing. All groups performed similarly in overall accuracy but differed in error type. Misperceptions for all groups were analyzed according to phonological and semantic properties. Comparisons between groups indicated that misperceptions for older adults were more influenced by phonological factors. Furthermore, older adults with hearing loss omitted more responses. Overall, across all groups, results suggest that phonological confusions most explain misperceptions in low context sentences. In high context sentences, the meaningful sentence context appears to provide predictive cues that reduce misperceptions. When misperceptions do occur, responses tend to have greater semantic similarity and lesser phonological similarity to the target, compared to low context sentences. In this way, semantic similarity may index a postdictive process by which ambiguities due to phonological confusions are resolved to conform to the semantic context of the sentence. These patterns demonstrate that context, age, and hearing loss affect the misperceptions, and potential sentence interpretation, made when listening to sentences in babble.

Ambient Noise Monitoring during Pure-Tone Audiometry

BACKGROUND

There is an increasing need to administer hearing tests outside of sound-attenuating rooms. Maximum permissible ambient noise levels (MPANLs) from published in standards (Occupational Health and Safety Administration [OSHA] 1983; American National Standards Institute [ANSI] S3.1-1999 (R2018)) can be modified to account for the additional attenuation provided by circumaural earphones (relative to supra-aural earphones) that are used for pure-tone audiometry. Ambient noise can influence the results of pure-tone audiometry by elevating thresholds by direct masking and by producing distractions that affect the accuracy of the test. The effects of these distractions have not been studied in relation to pure-tone audiometry in adult listeners.

PURPOSE

In Part I MPANLs provided by ANSI and OSHA standards are extended to account for the greater attenuation provided by circumaural earphones. Rules ("alerts") were developed taking into account the listeners' thresholds. In Part II effects of distracting noise on pure-tone thresholds are reported.

METHODS AND RESULTS

In Part I MPANLs two standards were modified for circumaural earphones by adding the additional attenuation provided by three circumaural earphones (relative to supra-aural earphones). A set of rules ("alerts") is provided for identifying masking effects from ambient noise in a variety of conditions (earphone type, threshold elevation, uncovered ear). In Part II the distracting effects of an industrial noise sample on thresholds obtained from five listeners with normal hearing are described. Pure-tone thresholds were measured in quiet and in distracting noise presented at various levels. The effects of the distracting noise on the following variables were measured: time per trial, number of trials required to measure threshold, threshold shift, and perceived distractibility of the noise. Time per trial was unaffected by distracting noise. Number of trials required for threshold, threshold shift, and perceived distractibility increased with distracting noise level.

CONCLUSION

Part I: The modified MPANLs provide more relevant determinations of the potential effects of ambient noise on pure-tone thresholds than the values in the standards. Part II: Distracting noise affects pure-tone threshold measurements in a manner that is different from direct masking. The potential contaminating effect of distracting noise can be measured and reported.

Hearing and dementia: from ears to brain

The association between hearing impairment and dementia has emerged as a major public health challenge, with significant opportunities for earlier diagnosis, treatment and prevention. However, the nature of this association has not been defined. We hear with our brains, particularly within the complex soundscapes of everyday life: neurodegenerative pathologies target the auditory brain, and are therefore predicted to damage hearing function early and profoundly. Here we present evidence for this proposition, based on structural and functional features of auditory brain organization that confer vulnerability to neurodegeneration, the extensive, reciprocal interplay between 'peripheral' and 'central' hearing dysfunction, and recently characterized auditory signatures of canonical neurodegenerative dementias (Alzheimer's disease, Lewy body disease and frontotemporal dementia). Moving beyond any simple dichotomy of ear and brain, we argue for a reappraisal of the role of auditory cognitive dysfunction and the critical coupling of brain to peripheral organs of hearing in the dementias. We call for a clinical assessment of real-world hearing in these diseases that moves beyond pure tone perception to the development of novel auditory 'cognitive stress tests' and proximity markers for the early diagnosis of dementia and management strategies that harness retained auditory plasticity.

Degree of Hearing Loss Affects Bilateral Hearing Aid Benefits in Ecologically Relevant Laboratory Conditions

Purpose Previous evidence supports benefits of bilateral hearing aids, relative to unilateral hearing aid use, in laboratory environments using audio-only (AO) stimuli and relatively simple tasks. The purpose of this study was to evaluate bilateral hearing aid benefits in ecologically relevant laboratory settings, with and without visual cues. In addition, we evaluated the relationship between bilateral benefit and clinically viable predictive variables. Method Participants included 32 adult listeners with hearing loss ranging from mild-moderate to severe-profound. Test conditions varied by hearing aid fitting type (unilateral, bilateral) and modality (AO, audiovisual). We tested participants in complex environments that evaluated the following domains: sentence recognition, word recognition, behavioral listening effort, gross localization, and subjective ratings of spatialization. Signal-to-noise ratio was adjusted to provide similar unilateral speech recognition performance in both modalities and across procedures. Results Significant and similar bilateral benefits were measured for both modalities on all tasks except listening effort, where bilateral benefits were not identified in either modality. Predictive variables were related to bilateral benefits in some conditions. With audiovisual stimuli, increasing hearing loss, unaided speech recognition in noise, and unaided subjective spatial ability were significantly correlated with increased benefits for many outcomes. With AO stimuli, these same predictive variables were not significantly correlated with outcomes. No predictive variables were correlated with bilateral benefits for sentence recognition in either modality. Conclusions Hearing aid users can expect significant bilateral hearing aid advantages for ecologically relevant, complex laboratory tests. Although future confirmatory work is necessary, these data indicate the presence of vision strengthens the relationship between bilateral benefits and degree of hearing loss.

[Hearing and cognition: neurocognitive test batteries in otorhinolaryngology]

BACKGROUND

Hearing and cognition are closely related to each other. Particularly in suboptimal listening situations, cognitive abilities become important to enable speech comprehension. Besides, studies have indicated that hearing impairment is associated with a more rapid mental decline compared to persons with normal hearing. However, hearing loss also has an impact on neurocognitive testing, which is generally based on auditive stimuli. With increasing age, the risk of sensory but also of cognitive impairments increases. So far this comorbidity receives little consideration in otorhinolaryngology.

MATERIALS AND METHODS

The paper presents an overview and evaluation of widely used German neurocognitive test batteries for older patients, with regard to the different test modalities and their focus.

RESULTS

A multitude of different neurocognitive screening tests and detailed test batteries are available, particularly in the field of dementia. So far, sensory deficits have not been considered in neurocognitive testing, neither concerning application nor interpretation. Normative data adapted to the hearing impaired are still missing.

CONCLUSION

With regard to demographic changes and the well-known bias between hearing and cognition, screening of neurocognitive functions should be implemented in basic otorhinolaryngologic diagnostics. More comprehensive test batteries might be useful for research purposes or speech therapy.

[Audiometric test battery for presbycusis]

Old people often complain that they can no longer sufficiently participate in communication with spoken language. The reasons for this lie in pathophysiological processes as well as in acoustic parameters and the decline in cognitive performance that frequently occurs in old age, which together severely limit the individual benefits of speech. Age-related hearing loss consists of a variety of pathophysiological and cognitive factors. Several audiometric procedures are necessary for profound diagnostics, planning and implementation of interventions for hearing improvement as well as interventions for the individual improvement of the benefits of hearing in everyday life. In a basic test battery, the subjective and objective procedures for the primary detailed quantification and differentiation of the pathophysiological effects of presbycusis are listed, which serve as a basis for interventions to improve hearing. If necessary, audiometric procedures for more in-depth pathophysiological analyses can be used as part of the extended test battery. They are mainly used to differentiate between peripheral and retrocochlear factors of age-related hearing loss. The aim of the methods in the test battery for the evaluation of communication impairment in everyday life is the quantitative and qualitative evaluation of the ability to participate in communication with spoken language under realistic acoustic everyday conditions. From the results, acoustic and cognitive factors can be identified which determine the limited benefits of speech. Thus, strategies and procedures for the improvement of speech communication can be derived which, despite the pathophysiological conditions, can lead to an improved participation in speech communication in the everyday life of the patients.

[Hearing rehabilitation with cochlear implants and cognitive abilities]

The relevance of assessing cognitive functioning is increasing against the background of the continuing demographic changes. Up to a few years ago the focus was on the effects of cochlear implantation in children born deaf in comparison to healthy individuals. Currently, the question arises whether hearing rehabilitation in the elderly, e.g. by postlingual cochlear implantation, has a protective effect on cognitive functioning and therefore on the risk of onset of dementia. This review describes the association of cognitive functioning with hearing disorders and cochlear implantation. Historical aspects of intelligence testing are illustrated. Knowledge on cognitive aspects in elderly persons with hearing disorders and cochlear implants is rare in the currently available literature. Initial findings indicate a positive correlation between hearing improvement and cognitive functioning. Further studies are urgently required in order to elucidate appropriate guidelines for the treatment of patients with cognitive deficits and hearing impairment.

Discrepancies between self-reported hearing difficulty and hearing loss diagnosed by audiometry: prevalence and associated factors in a national survey

OBJECTIVE

To evaluate discrepancies prevalent between self-reported hearing difficulty (SHD) and audiometrically measured hearing loss (AHL) and factors associated with such discrepancies.

DESIGN

Nationwide cross-sectional survey.

SETTING

Data from 2010 to 2012 Korea National Health and Nutrition Examination Survey conducted by the Korea Centers for Disease Control and Prevention.

PARTICIPANTS

We included 14 345 participants aged ≥19 years who had normal tympanic membranes (mean age of 49 years).

MEASURES

Self-reported hearing was assessed by asking participants whether they had difficulty in hearing. AHL was defined as >25 dB of mean hearing thresholds measured at 0.5, 1, 2 and 4 kHz in better ear. Underestimated hearing impairment (HI) was defined as having AHL without SHD. Likewise, overestimated HI was defined as having SHD without AHL. Prevalence of underestimated and overestimated HIs was determined. Univariable and multivariable analyses were performed to examine factors associated with such discrepancies compared with concordant HL.

RESULTS

Among 14 345 participants, 1876 (13.1%) had underestimated HI while 733 (5.1%) had overestimated HI. Multivariable models revealed that participants who had discrepancies between SHD and AHL were less likely to have older age (OR: 0.979, 95% CI: 0.967 to 0.991 for the underestimated HI, OR: 0.905, 95% CI: 0.890 to 0.921 for the overestimated HI) and tinnitus (OR: 0.425, 95% CI: 0.344 to 0.525 for the underestimated HI and OR 0.523, 95% CI: 0.391 to 0.699 for the overestimated HI) compared with those who had concordant HI. Exposure to occupational noise (OR: 0.566, 95% CI: 0.423 to 0.758) was associated with underestimated HI, and medical history of hypertension (OR: 1.501, 95% CI: 1.061 to 2.123) and depression (OR: 1.771, 95% CI: 1.041 to 3.016) was associated with overestimated HI.

CONCLUSION

Age, tinnitus, occupational noise exposure, hypertension and depression should be incorporated into evaluation of hearing loss in clinical practice.

Extrinsic Cognitive Load Impairs Spoken Word Recognition in High- and Low-Predictability Sentences

OBJECTIVES

Listening effort (LE) induced by speech degradation reduces performance on concurrent cognitive tasks. However, a converse effect of extrinsic cognitive load on recognition of spoken words in sentences has not been shown. The aims of the present study were to (a) examine the impact of extrinsic cognitive load on spoken word recognition in a sentence recognition task and (b) determine whether cognitive load and/or LE needed to understand spectrally degraded speech would differentially affect word recognition in high- and low-predictability sentences. Downstream effects of speech degradation and sentence predictability on the cognitive load task were also examined.

DESIGN

One hundred twenty young adults identified sentence-final spoken words in high- and low-predictability Speech Perception in Noise sentences. Cognitive load consisted of a preload of short (low-load) or long (high-load) sequences of digits, presented visually before each spoken sentence and reported either before or after identification of the sentence-final word. LE was varied by spectrally degrading sentences with four-, six-, or eight-channel noise vocoding. Level of spectral degradation and order of report (digits first or words first) were between-participants variables. Effects of cognitive load, sentence predictability, and speech degradation on accuracy of sentence-final word identification as well as recall of preload digit sequences were examined.

RESULTS

In addition to anticipated main effects of sentence predictability and spectral degradation on word recognition, we found an effect of cognitive load, such that words were identified more accurately under low load than high load. However, load differentially affected word identification in high- and low-predictability sentences depending on the level of sentence degradation. Under severe spectral degradation (four-channel vocoding), the effect of cognitive load on word identification was present for high-predictability sentences but not for low-predictability sentences. Under mild spectral degradation (eight-channel vocoding), the effect of load was present for low-predictability sentences but not for high-predictability sentences. There were also reliable downstream effects of speech degradation and sentence predictability on recall of the preload digit sequences. Long digit sequences were more easily recalled following spoken sentences that were less spectrally degraded. When digits were reported after identification of sentence-final words, short digit sequences were recalled more accurately when the spoken sentences were predictable.

CONCLUSIONS

Extrinsic cognitive load can impair recognition of spectrally degraded spoken words in a sentence recognition task. Cognitive load affected word identification in both high- and low-predictability sentences, suggesting that load may impact both context use and lower-level perceptual processes. Consistent with prior work, LE also had downstream effects on memory for visual digit sequences. Results support the proposal that extrinsic cognitive load and LE induced by signal degradation both draw on a central, limited pool of cognitive resources that is used to recognize spoken words in sentences under adverse listening conditions.

Exploring the Link Between Cognitive Abilities and Speech Recognition in the Elderly Under Different Listening Conditions

Elderly listeners are known to differ considerably in their ability to understand speech in noise. Several studies have addressed the underlying factors that contribute to these differences. These factors include audibility, and age-related changes in supra-threshold auditory processing abilities, and it has been suggested that differences in cognitive abilities may also be important. The objective of this study was to investigate associations between performance in cognitive tasks and speech recognition under different listening conditions in older adults with either age appropriate hearing or hearing-impairment. To that end, speech recognition threshold (SRT) measurements were performed under several masking conditions that varied along the perceptual dimensions of dip listening, spatial separation, and informational masking. In addition, a neuropsychological test battery was administered, which included measures of verbal working and short-term memory, executive functioning, selective and divided attention, and lexical and semantic abilities. Age-matched groups of older adults with either age-appropriate hearing (ENH, n = 20) or aided hearing impairment (EHI, n = 21) participated. In repeated linear regression analyses, composite scores of cognitive test outcomes (evaluated using PCA) were included to predict SRTs. These associations were different for the two groups. When hearing thresholds were controlled for, composed cognitive factors were significantly associated with the SRTs for the ENH listeners. Whereas better lexical and semantic abilities were associated with lower (better) SRTs in this group, there was a negative association between attentional abilities and speech recognition in the presence of spatially separated speech-like maskers. For the EHI group, the pure-tone thresholds (averaged across 0.5, 1, 2, and 4 kHz) were significantly associated with the SRTs, despite the fact that all signals were amplified and therefore in principle audible.

Speech understanding in noise in elderly adults: the effect of inhibitory control and syntactic complexity

BACKGROUND

Previous research has suggested that speech perception in elderly adults is influenced not only by age-related hearing loss or presbycusis but also by declines in cognitive abilities, by background noise and by the syntactic complexity of the message.

AIMS

To gain further insight into the influence of these cognitive as well as acoustic and linguistic factors on speech perception in elderly adults by investigating inhibitory control as a listener characteristic and background noise type and syntactic complexity as input characteristics.

METHODS & PROCEDURES

Phoneme identification was measured in different noise conditions and in different linguistic contexts (single words, sentences with varying syntactic complexity). Additionally, inhibitory control was measured using a visual stimulus-response matching task. Fifty-one adults participated in this study, including elderly adults with age-related hearing loss (n = 9) and with normal hearing (n = 17), and a control group of normal hearing younger adults (n = 25).

OUTCOMES & RESULTS

The analysis revealed that elderly adults with normal hearing and with hearing loss were less likely to identify successfully phonemes in single words than younger normal hearing controls. In the context of sentences, only elderly adults with hearing loss had a lower odds of correct phoneme perception than the control group. Additionally, in elderly adults with hearing loss, phoneme-in-sentence perception was linked to age-related declines in inhibitory control. In all participants, phoneme identification in sentences was influenced by both noise type and syntactic complexity.

CONCLUSIONS & IMPLICATIONS

Inhibitory control and syntactic complexity might play a significant role in speech perception, especially in elderly listeners. These factors might also influence the results of clinical assessments of speech perception. Testing procedures thus need to be selected and their results interpreted carefully with these influences in mind.

Effects of hearing loss on maintaining and switching attention

The ability to intentionally control attention based on task goals and stimulus properties is critical to communication in many environments. However, when a person has a damaged auditory system, such as with hearing loss, perceptual organization may also be impaired, making it more difficult to direct attention to different auditory objects in the environment. Here we examined the behavioral cost associated with maintaining and switching attention in people with hearing loss compared to the normal hearing population, and found a cost associated with attending to a target stream in a multi-talker environment that cannot solely be attributed to audibility issues.

[Speech audiometry, speech perception and cognitive functions. German version]

Examination of cognitive functions in the framework of speech perception has recently gained increasing scientific and clinical interest. Especially against the background of age-related hearing impairment and cognitive decline potential new perspectives in terms of better individualisation of auditory diagnosis and rehabilitation might arise. This review addresses the relationships of speech audiometry, speech perception and cognitive functions. It presents models of speech perception, discusses associations of neuropsychological with audiometric outcomes and shows recent efforts to consider cognitive functions with speech audiometry.

Hearing impairment, cognition and speech understanding: exploratory factor analyses of a comprehensive test battery for a group of hearing aid users, the n200 study

OBJECTIVE

The aims of the current n200 study were to assess the structural relations between three classes of test variables (i.e. HEARING, COGNITION and aided speech-in-noise OUTCOMES) and to describe the theoretical implications of these relations for the Ease of Language Understanding (ELU) model.

STUDY SAMPLE

Participants were 200 hard-of-hearing hearing-aid users, with a mean age of 60.8 years. Forty-three percent were females and the mean hearing threshold in the better ear was 37.4 dB HL.

DESIGN

LEVEL1 factor analyses extracted one factor per test and/or cognitive function based on a priori conceptualizations. The more abstract LEVEL 2 factor analyses were performed separately for the three classes of test variables.

RESULTS

The HEARING test variables resulted in two LEVEL 2 factors, which we labelled SENSITIVITY and TEMPORAL FINE STRUCTURE; the COGNITIVE variables in one COGNITION factor only, and OUTCOMES in two factors, NO CONTEXT and CONTEXT. COGNITION predicted the NO CONTEXT factor to a stronger extent than the CONTEXT outcome factor. TEMPORAL FINE STRUCTURE and SENSITIVITY were associated with COGNITION and all three contributed significantly and independently to especially the NO CONTEXT outcome scores (R(2) = 0.40).

CONCLUSIONS

All LEVEL 2 factors are important theoretically as well as for clinical assessment.

Speech audiometry, speech perception, and cognitive functions : English version

Examination of cognitive functions in the framework of speech perception has recently gained increasing scientific and clinical interest. Especially against the background of age-related hearing impairment and cognitive decline, potential new perspectives in terms of a better individualization of auditory diagnosis and rehabilitation might arise. This review addresses the relationships between speech audiometry, speech perception, and cognitive functions. It presents models of speech perception, discusses associations of neuropsychological and audiometric outcomes, and shows examples of recent efforts undertaken in Germany to consider cognitive functions with speech audiometry.