Abstract
During hearing, acoustic signals travel up the ascending auditory pathway from the cochlea to auditory cortex; efferent connections provide descending feedback. In human listeners, although auditory and cognitive processing have sometimes been viewed as separate domains, a growing body of work suggests they are intimately coupled. Here, we review the effects of hearing loss on neural systems supporting spoken language comprehension, beginning with age-related physiological decline. We suggest that listeners recruit domain general executive systems to maintain successful communication when the auditory signal is degraded, but that this compensatory processing has behavioral consequences: even relatively mild levels of hearing loss can lead to cascading cognitive effects that impact perception, comprehension, and memory, leading to increased listening effort during speech comprehension.
Healthy aging is associated with neurophysiological changes at every stage of the human auditory system, including the cochlea, spiral ganglion neurons, cochlear nuclei, and other midbrain structures up through the auditory cortex.
Despite widespread declines in hearing ability, speech comprehension in older adulthood is generally good.
To maintain high levels of speech comprehension success, hearing-impaired listeners recruit systems outside the canonical speech-processing network to compensate for a poor auditory signal.
The additional cognitive effort required when listening to a degraded speech signal can impact other operations, such as remembering what has been heard.
