Exploring Differences in Speech Processing Among Older Hearing-Impaired Listeners With or Without Hearing Aid Experience: Eye-Tracking and fMRI Measurements

Abstract

Recently, evidence has been accumulating that untreated hearing loss can lead to neurophysiological changes that affect speech processing abilities in noise. To shed more light on how aiding may impact these effects, this study explored the influence of hearing aid (HA) experience on the cognitive processes underlying speech comprehension. Eye-tracking and functional magnetic resonance imaging (fMRI) measurements were carried out with acoustic sentence-in-noise (SiN) stimuli complemented by pairs of pictures that either correctly (target picture) or incorrectly (competitor picture) depicted the sentence meanings. For the eye-tracking measurements, the time taken by the participants to start fixating the target picture (the ‘processing time’) was measured. For the fMRI measurements, brain activation inferred from blood-oxygen-level dependent responses following sentence comprehension was measured. A noise-only condition was also included. Groups of older hearing-impaired individuals matched in terms of age, hearing loss, and working memory capacity with (eHA; N = 13) or without (iHA; N = 14) HA experience participated. All acoustic stimuli were presented via earphones with individual linear amplification to ensure audibility. Consistent with previous findings, the iHA group had significantly longer (poorer) processing times than the eHA group, despite no differences in speech recognition performance. Concerning the fMRI measurements, there were indications of less brain activation in some right frontal areas for SiN relative to noise-only stimuli in the eHA group compared to the iHA group. Together, these results suggest that HA experience leads to faster speech-in-noise processing, possibly related to less recruitment of brain regions outside the core sentence-comprehension network. Follow-up research is needed to substantiate the findings related to changes in cortical speech processing with HA use.

Effects of age-related hearing loss and hearing aid experience on sentence processing

“…Using fMRI measures, they found decreased activity-compared to a baseline measure before hearing aid fitting-in the superior temporal gyrus following the presentation of speech sounds to the unaided ear as well as the aided ear. Finally, Habicht et al 28 used fMRI measures and found decreased activity in superior and middle frontal regions outside of the speech processing network in hearing aid users compared to hard-of-hearing unaided listeners when processing speech in noise. In addition, they found increased activity in the lingual gyri and the left precuneus with longer hearing aid use when processing complex sentences.…”

“…In addition, they found increased activity in the lingual gyri and the left precuneus with longer hearing aid use when processing complex sentences. Since decreased activity in frontal regions has been found when hearing aid use was used as a grouping factor 27,28 , but increased activity in other regions has been found to correlate with length of hearing aid use 28 , both the location and the direction of the influence of hearing aid use on neural processing remain unclear. In addition, many of these studies had small sample sizes (e.g., groups of 8 27 or 13 28 participants) and in Habicht et al 28 the significance thresholds were not corrected for multiple comparisons.…”

“…Since decreased activity in frontal regions has been found when hearing aid use was used as a grouping factor 27,28 , but increased activity in other regions has been found to correlate with length of hearing aid use 28 , both the location and the direction of the influence of hearing aid use on neural processing remain unclear. In addition, many of these studies had small sample sizes (e.g., groups of 8 27 or 13 28 participants) and in Habicht et al 28 the significance thresholds were not corrected for multiple comparisons. As the authors 28 acknowledge the accompanying higher risk of false positives and the need for follow-up studies, it is clear that more research on hearing aid use in relation to sentence processing is needed.…”

“…In addition, many of these studies had small sample sizes (e.g., groups of 8 27 or 13 28 participants) and in Habicht et al 28 the significance thresholds were not corrected for multiple comparisons. As the authors 28 acknowledge the accompanying higher risk of false positives and the need for follow-up studies, it is clear that more research on hearing aid use in relation to sentence processing is needed. Thus, even though there are some indications of behavioral as well as neural effects of hearing aid use, the relationship between hearing loss, the use of hearing aids, and their effects on higher-level language processes in relation to neural changes is not well understood yet.…”

“…Also, some effects of hearing loss or hearing aid use might only emerge when a task is sufficiently difficult, such as the processing of complex sentences [e.g., 18,31,32 ]. Thus, effects of these hearing-related measures may be found during the processing of complex sentences but not during the processing of simple sentences (as in 28 ). Individual measures of hearing loss and the duration of hearing aid use (hearing aid experience) were obtained from each participant, so that their associations with sentence processing could be investigated.…”