Aging in the Primary Auditory Cortex.

Age-related auditory dysfunction affects half of all individuals 60 years and older, yet its causes are poorly understood. While commonly associated with cochlear dysfunction, a growing body of literature suggests that dysfunction originating in the auditory cortex itself is also a major contributor. Here, we review recent literature that describes the effects of aging on the primary auditory cortex in humans, non-human primates, rodents, and a variety of other species. During aging, individuals with auditory cortical dysfunction experience deficits in spectral and temporal processing of sounds, resulting not only from a loss of inhibition but also from an extensive restructuring of cortical circuits. Importantly, aging in the auditory cortex is sex-dependent, yet few studies account for this variable. A lack of comprehensive knowledge on aging in the auditory cortex hinders the path toward restoring cortical function through auditory training or broader cortical rehabilitation paradigms. Thus, we propose a cohesive mechanism of aging in the primary auditory cortex that involves a complex interaction between excitatory and inhibitory neurons, which several factors can modify. These factors include input from higher-order cortical areas, such as the orbitofrontal cortex, as well as the wide-ranging effects of neuromodulators and the external sensory environment, which must be accounted for in a sex-dependent manner.