1Neuroscience Institute, Carnegie Mellon University, Pittsburgh PA, United States
Everyday communication depends on an interplay between coding the auditory and visual signals reaching the ears and eyes and modulating the information contained in these signals through cortical networks for attention, working memory, and language processing. It is well established that aging affects both sensory coding and cognitive processes. However, teasing apart whether communication problems are due to sensory versus cognitive issues can be difficult. As an example, many middle-aged listeners have problems understanding speech in the presence of competing sound sources, even when they have no clinically quantifiable sensory deficits. Moreover, it is surprisingly difficult to identify simple psychophysical tasks that relate to difficulties understanding speech amidst competing sounds in middle-aged listeners without identifiable hearing loss. Together, this pattern of abilities seems to suggest that cognitive, rather than sensory, deficits are the root cause. We argue, however, that subtle sensory deficits (such as cochlear synaptopathy) may be to blame. Specifically, in naturalistic settings, sensory coding can impact how quickly a listener can focus on one sound source, extract information from that source, store meaning in memory, and switch attentional focus— all processes that are not exercised by simpler tasks. Thus, performance on “cognitive” tasks depends directly on sensory fidelity in complex, but not simple listening scenarios, a realization that has important implications for diagnosis of communication difficulties.