Effects of Age, Acoustic Challenge, and Verbal Working Memory on Recall of Narrative Speech

Abstract

Background A common goal during speech comprehension is to remember what we have heard. Encoding speech into long-term memory frequently requires processes such as verbal working memory that may also be involved in processing degraded speech. Here we tested whether young and older adult listeners’ memory for short stories was worse when the stories were acoustically degraded, or whether the additional contextual support provided by a narrative would protect against these effects. Methods We tested 30 young adults (aged 18–28 years) and 30 older adults (aged 65–79 years) with good self-reported hearing. Participants heard short stories that were presented as normal (unprocessed) speech, or acoustically degraded using a noise vocoding algorithm with 24 or 16 channels. The degraded stories were still fully intelligible. Following each story, participants were asked to repeat the story in as much detail as possible. Recall was scored using a modified idea unit scoring approach, which included separately scoring hierarchical levels of narrative detail. Results Memory for acoustically degraded stories was significantly worse than for normal stories at some levels of narrative detail. Older adults’ memory for the stories was significantly worse overall, but there was no interaction between age and acoustic clarity or level of narrative detail. Verbal working memory (assessed by reading span) significantly correlated with recall accuracy for both young and older adults, whereas hearing ability (better ear pure-tone average) did not. Conclusion Our findings are consistent with a framework in which the additional cognitive demands caused by a degraded acoustic signal use resources that would otherwise be available for memory encoding for both young and older adults. Verbal working memory is a likely candidate for supporting both of these processes.

The Neural Consequences of Age-Related Hearing Loss

“…For example, memory is typically poorer for acoustically degraded words [102-105] and stories [106,107] than for acoustically clear versions. Importantly, these memory deficits occur even when it can be demonstrated that the words themselves have been successfully recognized.…”

Efficacy of a newly developed auditory–cognitive training system on speech recognition, central auditory processing and cognitive ability among older adults with normal cognition and with neurocognitive impairment

“…There are three hypotheses to explain age‐related decline in speech understanding experienced by older adults: the peripheral hypothesis, the central–auditory hypothesis and the cognitive hypothesis . Although hearing acuity plays a primary role in speech recognition, cognition and central auditory function also contribute significantly, especially, in noisy environments …”

“…Verbal working memory is correlated with recall accuracy among older adults, and therefore, impacts their speech comprehension . Additionally, working memory capacity also affects the ability to suppress irrelevant information in order to handle multiple streams of information, and comprehend and store information extracted from speech for later recall …”

Cingulo-opercular activity affects incidental memory encoding for speech in noise

“…Poor recall of words occurs in difficult listening conditions, such as in background noise, even when those words were understood (Murphy et al, 2000; Pichora-Fuller et al, 1995; Rabbitt, 1968; Ward et al, 2016). One explanation for poor recall of speech in noise is that attention is diverted away from memory encoding to help extract the speech signal from noise, at least for serial recall tasks (Heinrich et al, 2008; Rabbitt, 1991, 1968; Tun et al, 2009; Wild et al, 2012).…”