Abstract
Prior research suggests that acoustical degradation impacts encoding of items into memory, especially in elderly subjects. We here aimed to investigate whether acoustically degraded items that are initially encoded into memory are more prone to forgetting as a function of age. Young and old participants were tested with a vocoded and unvocoded serial list learning task involving immediate and delayed free recall. We found that degraded auditory input increased forgetting of previously encoded items, especially in older participants. We further found that working memory capacity predicted forgetting of degraded information in young participants. In old participants, verbal IQ was the most important predictor for forgetting acoustically degraded information. Our data provide evidence that acoustically degraded information, even if encoded, is especially vulnerable to forgetting in old age.
Highlights
The richness of acoustic signals is an important factor that contributes to speech intelligibility
Four subjects in the older group and one subject in the younger group had to be excluded from the analysis for the following reasons: two subjects aborted the working memory task, one subject had a working memory score of 0, one subject did not succeed to learn the vocoded speech and another subject showed no learning of the vocoded word list in the verbal learning and memory test (VLMT, immediate recall score of 0)
To investigate our main hypothesis, that sensory degradation impacts consolidation of auditory information into long term memory, we focused on the proportion of remembered items after the delay as a function of degradation and age and performed a repeated measures analysis of variance (ANOVA) on this data with vocoded speech understanding and verbal IQ as covariates
Summary
The richness of acoustic signals is an important factor that contributes to speech intelligibility. Many everyday situations are characterized by factors that impact acoustic richness such as competing speakers, increased background noise or subject-specific factors like age-associated hearing loss, even if compensated with hearing aids. Despite this reduction in acoustic richness, listeners are usually able to extract information from degraded speech signals (Davis et al, 2005). It has been shown that immediate recall and associative memory decline in young adults presented with experimentally degraded stimuli. Poor hearing status increased dual task costs on immediate recall, an effect that was exacerbated in elderly subjects
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