Abstract

It has been proposed in the literature that if too many processing resources need to be devoted to perception then higher-order cognitive functions, such as working memory (WM), may suffer. This effect may be particularly evident in individuals who have restricted processing resources, such as older adults (OA) suffering from hearing loss or cognitive impairment. One possibility to facilitate perception during speech processing is through the auditory-visual (AV) modality. The current research examined whether AV speech perception helps to facilitate perceptual and WM processing in OAs with restricted processing resources. In both studies, participants completed a WM n-back task under different speech modalities: AV, auditory-only, or visual-only (Study 1). Both behavioural and event-related potentials (ERPs) measures were collected during the task.
Study 1 examined the effect of AV speech on WM in OAs with hearing impairment compared to normal-hearing OAs. The results showed that AV speech in comparison to auditory-only speech led to facilitated perceptual processing in OAs with hearing impairment, as indicated by ERP responses. The AV modality also led to facilitated WM functioning in both groups, as suggested by ERP responses and behavioural reaction time. A few measures indicated that visual speech cues may have helped OAs with hearing impairment to counteract the demanding auditory processing.
Study 2 examined the effect of AV speech on WM in OAs suffering from mild cognitive impairment (MCI) or Alzheimer disease (AD) compared to cognitively healthy OAs. The ERP responses showed that the AV modality compared to the auditory-only modality led to facilitated perceptual and WM processing in both groups. In addition, the behavioural results showed improved accuracy during the WM task for the patient group, and faster reaction time for both the patient group and the cognitively healthy control group.
Overall, the results showed that OAs with hearing or cognitive impairment benefit from AV speech in terms of improved WM performance. In fact, there were a few indications that the AV benefit may be even more robust in these groups than in cognitively healthy OAs. The theoretical and practical implications of these findings and directions for future research are discussed.