The effects of aging on auditory cortical function

Age-related hearing loss is a prominent deficit, afflicting approximately half of the geriatric population.
In many cases, the person may have no deficits in detecting sounds, but nonetheless suffers from a
reduced ability to understand speech, particularly in a noisy environment. While rodent models have
shown that there are a variety of age-related changes throughout the auditory neuraxis, far fewer studies
have investigated the effects at the cortical level. Here I review recent evidence from a non-human
primate model of age-related hearing loss at the level of the core (primary auditory cortex, A1) and
belt (caudolateral field, CL) in young and aged animals with normal detection thresholds. The findings
are that there is an increase in both the spontaneous and driven activity, an increase in spatial tuning,
and a reduction in the temporal fidelity of the response in aged animals. These results are consistent with
an age-related imbalance of excitation and inhibition in the auditory cortex. These spatial and temporal
processing deficits could underlie the major complaint of geriatrics, that it is difficult to understand
speech in noise.